draft-ietf-ospf-ara-00.txt   draft-ietf-ospf-ara-01.txt 
Expiration Date: February 1998 Expiration Date: May 1998
File name: draft-ietf-ospf-ara-00.txt File name: draft-ietf-ospf-ara-01.txt
The OSPF Address Resolution Advertisement Option The OSPF Address Resolution Advertisement Option
Rob Coltun Rob Coltun
FORE Systems FORE Systems
(301) 571-2521 (301) 571-2521
rcoltun@fore.com rcoltun@fore.com
Juha Heinanen Juha Heinanen
Telecom Finland Telecom Finland
skipping to change at page 3, line 5 skipping to change at page 36, line ?
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Coltun, Heinanen [Page 1]
Table Of Contents Table Of Contents
1.0 Abstract ................................................. 5 1.0 Abstract ................................................. 4
2.0 Overview ................................................. 5 2.0 Overview ................................................. 4
2.1 Acknowledgments .......................................... 5 2.1 Address Resolution Advertisements ........................ 5
3.0 A Brief Comparison Of Address Resolution Models .......... 6 2.2 ARA Association Table .................................... 5
4.0 ARA Associations ......................................... 7 2.3 Logical Network ID List .................................. 5
5.0 Examples ................................................. 8 2.4 Routing Table Extensions ................................. 5
5.1 Example 1: Intra-Area .................................... 8 2.5 Restricting Shortcut Connectivity ........................ 6
5.2 Example 2: Inter-Area .................................... 9 2.6 Acknowledgments .......................................... 6
6.0 Description Of ARA Packet Formats ........................ 10 3.0 A Brief Comparison Of Address Resolution Models .......... 7
6.1 Vertex Types And Vertex Identifiers ...................... 11 4.0 ARA Associations ......................................... 8
7.0 Distribution Of ARA Information .......................... 11 5.0 Examples ................................................. 9
8.0 ARA Routing Table Extensions ............................. 13 5.1 Example 1: Intra-Area .................................... 9
8.1 Adding ARA Routing Table Extensions ...................... 13 5.2 Example 2: Inter-Area .................................... 10
8.1.1 Modifications To The Intra-Area Route Calculation ...... 14 5.3 Example 3: Multiple Logical Networks ..................... 11
8.1.2 Modifications To The Inter-Area Route Calculations ..... 15 6.0 Description Of ARA Packet Formats ........................ 12
8.1.3 Modifications To The AS External Route Calculations .... 15 6.1 Vertex Types And Vertex Identifiers ...................... 13
9.0 Receiving ARAs ........................................... 16 7.0 Distribution Of ARA Information .......................... 14
10.0 Additional Data Structures And APIs ..................... 17 7.1 Originating Inter-Area ARAs .............................. 15
Appendix A: ARA Data Formats ................................. 17 8.0 ARA Routing Table Extensions ............................. 17
A.1 ARA Formats .............................................. 17 8.1 Adding ARA Routing Table Extensions ...................... 18
A.1.1 The ARA Header ......................................... 18 8.1.1 Modifications To The Intra-Area Route Calculation ...... 18
A.1.2 Router ARAs ............................................ 20 8.1.2 Modifications To The Inter-Area Route Calculation ...... 19
A.1.3 Network ARAs ........................................... 20 8.1.3 Modifications To The AS External Route Calculation ..... 20
A.1.4 Vertex Association ..................................... 22
A.1.5 Resolution Information ................................. 23 Coltun, Heinanen [Page 2]
9.0 Receiving ARAs ........................................... 21
A.1.6 ATM Address ............................................ 24 10.0 Additional Data Structures And APIs ..................... 21
References ................................................... 26 Appendix A: ARA Packet Formats ............................... 23
A.1 The ARA Header ........................................... 23
A.2 Intra-Area Router ARA .................................... 26
A.3 Intra-Area Network ARA ................................... 27
A.4 Inter-Area Router ARA .................................... 28
A.5 Inter-Area Network ARA ................................... 30
A.6 Vertex Association ....................................... 31
A.7 Resolution Information ................................... 32
A.7.1 ATM Address ............................................ 34
A.7.2 ATM LIJ Call Identification ............................ 35
References ................................................... 35
Coltun, Heinanen [Page 3]
1.0 Abstract 1.0 Abstract
This document defines an OSPF option which enables routers to distri- This document defines an OSPF option to enable routers to distribute
bute IP to link-layer address resolution information. An OSPF Address IP to link-layer address resolution information. An OSPF Address
Resolution Advertisement (ARA) may include link-layer specific func- Resolution Advertisement (ARA) may include media-specific information
tionality such as a multipoint-to-point connection identifier along such as a multipoint-to-point connection identifier along with the
with the address resolution information. The ARA option can be used address resolution information to support media-specific functions.
to support router-to-router inter-subnet shortcut architectures such The ARA option can be used to support router-to-router inter-subnet
as those described in [HEIN] shortcut architectures such as those described in [HEIN].
2.0 Overview 2.0 Overview
Along with the evolution of switched layer 2 technologies comes the Along with the evolution of switched layer 2 technologies comes the
ability to provide inter-subnet shortcut and cut-through data switch- ability to provide inter-subnet shortcut data switching (bypassing
ing (bypassing router intervention). Before the ingress devices is router intervention). Before the ingress devices is able to dynami-
able to dynamically set up the switched path it must have the link- cally set up the switched path it must have the link-layer address of
layer address of the egress device. Acquisition of the egress the egress device. Acquisition of the egress device's link-layer
device's link-layer address may be through configuration or through a address may be through configuration or through a dynamic mechanism
discovery mechanism which resolves an IP address (or an IP end-point which resolves an IP address (or an IP end-point identifier) to a
identifier) to a link-layer address. link-layer address.
This document introduces a method for IP to link-layer address resolu- This document introduces a method for IP to link-layer address resolu-
tion to support router-to-router and router-to-network inter-subnet tion to support router-to-router and router-to-network inter-subnet
shortcuts. The ARA option supports both topology-derived and data- shortcuts. The ARA option supports both topology-derived and data-
driven shortcuts architectures with simple extensions to OSPF. Dis- driven shortcuts architectures with simple extensions to OSPF. Dis-
tribution of address resolution information is performed using stan- tribution of address resolution information is performed using stan-
dard OSPF flooding mechanisms. This document does not define an dard OSPF flooding mechanisms. This document does not define an
architecture but is meant to be used with architectures such as those architecture but is meant to be used with architectures such as those
defined in [HEIN]. The ARA option is designed to support the follow- defined in [HEIN]. The ARA option is designed to support the follow-
ing operations. ing operations.
Shortcuts between core or access routers within ISP Backbones. Shortcuts between core or access routers within ISP Backbones.
Shortcuts in enterprise networks between routers in the same OSPF Shortcuts in enterprise networks between routers in the same OSPF
area, between OSPF internal routers and autonomous system border autonomous system, between OSPF internal routers and autonomous
routers (ASBR) and between routers and servers. system border routers (ASBR) or between routers and servers.
Distributed router architectures. Distributed router architectures.
Interoperation with ION NHRP and MPOA. Interoperation with ION NHRP and ATMF MPOA.
Inter-subnet multicast shortcuts using LIJ or Point-to-MultiPoint Inter-subnet multicast shortcuts using LIJ or Point-to-MultiPoint
procedures. procedures.
2.1 Acknowledgments Coltun, Heinanen [Page 4]
The author would like to thank Lou Berger, John Moy and Yiqun Cai, and
the rest of the OSPF Working Group for the ideas and support they have 2.1 Address Resolution Advertisements
given to this project.
The ARA option defines a set of link-state advertisements called
address resolution advertisements (ARAs). ARAs are used to distribute
link-layer information of routers and their directly connected net-
works within and between OSPF areas. ARA information is encapsulated
in Opaque LSAs (see [OPAQ] for a further description of Opaque LSAs).
Three LS Types (LS Type 9, 10 and 11) constitute the Opaque class of
link-state advertisements. Each of the three Opaque link-state types
have a scope associated with them so that distribution of the informa-
tion may be limited appropriately by the originator of the LSA.
Because the flooding scope for ARAs is always area local, ARAs are
encapsulated in LS Type 10 LSAs. Opaque LSAs have a sub-type which
identifies the specific information that is carried within the LSA.
ARA uses Opaque-types 1, 2, 3 and 4. See section 6.0 for a further
description of the ARA packet formats.
2.2 ARA Association Table
A router implementing the ARA option maintains a table of link-layer
associations for each of its OSPF areas. The ARA Association Table is
used in calculating the ARA routing table extensions and by area
border routers in the inter-area ARA origination process. The indexes
for an entry in this table entry are the Vertex Type, Vertex ID and
the Vertex Originator. The Vertex Type identifies the type of IP
topology element that the link-layer information is being associated
with (i.e., a router or a network). The Vertex ID identifies a piece
of the OSPF topology (i.e., a router ID or an IP network number). The
Vertex Originator is the ARA originator's Router ID.
2.3 Logical Network ID List
An ARA capable router maintains a configured list of logical networks
IDs. This list represents the logical networks that a router is con-
nected to and may be used to restrict the set of devices that the
router may setup shortcuts to (see section 2.5 "Restricting Shortcut
Connectivity"). The absence of entries in the router's list of Logi-
cal Network IDs means that the router will only activate ARA Associa-
tion Table entries with the default Logical Network ID (Logical Net-
work ID 0).
2.4 Routing Table Extensions
Associations are added to the routing table during the OSPF routing
table calculation (see section 8.1 entitled "Adding ARA Routing Table
Coltun, Heinanen [Page 5]
Extensions"). That is, in addition to the standard information fields
contained in the routing table (IP network number, IP mask, next-hop
interface, etc.), the routing table is extended to contain link-layer
associations. However, only 'active' link-layer associations are
added to the routing table. Associations containing a logical network
ID that matches a currently enabled entry in the router's list of log-
ical network IDs are considered to be active. Both active and non-
active link-layer associations may be included in inter-area ARAs that
are originated by an ABR.
The routing table (and its ARA routing table extensions) must be
recalculated if 1) there is a change to the OSPF topology, 2) there is
a change to the components in the ARA Association Table (see section
9.0 "Receiving ARAs"), or 3) the router's logical network connectivity
has changed (e.g., the logical network ID list is modified or the
status of the router's connections to one of its logical networks has
changed).
The use of the routing table extensions are application specific and
beyond the scope of this document. See [HEIN] for an example of an
ARA user application.
2.5 Restricting Shortcut Connectivity
As a result of setting up shortcuts in an OSPF topology between ARA-
capable routers, the shortcut connectivity may become fully meshed.
In many environments this may be desirable whereas in in others this
may be undesirable. The ARA option allows for several methods to be
used which can limit shortcut connectivity.
o [HEIN] proposes that shortcuts are setup by ingress routers
only after the sending data rate has passed a configured thres-
hold.
o ARA-capable routers may choose not to advertise their resolu-
tion information until some event has occured.
o Routers may be associated with "closed user shortcut groups" so
that only routers that are within the same shortcut group may
set-up shortcuts to each other. This is done by coordinating the
configuration of a router's logical network ID list with the log-
ical network ID advertised in ARA associations.
2.6 Acknowledgments
The author would like to thank Atul Bansal, Lou Berger, Yiqun Cai,
Coltun, Heinanen [Page 6]
John Moy and the rest of the OSPF Working Group for the ideas and sup-
port they have given to this project.
3.0 A Brief Comparison Of Address Resolution Models 3.0 A Brief Comparison Of Address Resolution Models
Current models of inter-subnet address resolution have taken the form Current models of inter-subnet address resolution have taken the form
of a query/response protocol as in the case of [NHRP]. In this model of a query/response protocol as in the case of [NHRP]. In this model
the ingress device originates a resolution request which is forwarded the ingress device originates a resolution request which is forwarded
hop-by-hop through a series of NHRP servers towards the destination IP hop-by-hop through a series of NHRP servers towards the destination IP
address contained in the request. The the last-hop server (the one address contained in the request. The the last-hop server (the one
that is closest to the destination) responds to the request with the that is closest to the destination) responds to the request with the
link-layer address that it associates with the requested IP address. link-layer address that it associates with the requested IP address.
The returned address may be the address of the requested host system The address that is returned may be the address of the requested host
or the address of a router which is on the path to the destination. system or the address of a router which is on the path to the destina-
Upon receiving a response to its request, the ingress device sets up a tion. Upon receiving a response to its request, the ingress device
shortcut path to be used for data transfer. The resolution request sets up a shortcut path to be used for data transfer. The resolution
mechanism has the following characteristics. request mechanism has the following characteristics.
o Routers and hosts may participate in the request mechanism. The o Routers and hosts may participate in the request mechanism.
participating devices are discovered through polling. The participating devices are discovered through polling.
o The request mechanism requires polling by the ingress device to o The request mechanism requires polling by the ingress device to
detect topology and reachability changes. Changes in the topology detect topology and reachability changes. Changes in the topology
could result in packet loss for the polling interval. Stable routing could result in packet loss for the polling interval. Stable
loops may form as a result of topology changes (given a limited set of routing loops may form as a result of topology changes (given a
failure conditions and topologies). limited set of failure conditions and topologies).
o Requests are unreliable and are subject to packet loss. o Requests are unreliable and are subject to packet loss.
o It is recommended that the request mechanism be limited to intra- o It is recommended that the request mechanism be limited to
area shortcuts (although with correctly designed topologies this limi- intra-area shortcuts (although with correctly designed topologies
tation may be over restrictive). this limitation may be over restrictive).
o The target of a request may be a host or network addresses (exclud- o The target of a request may be a host or network addresses
ing class D (multicast) networks). (excluding class D (multicast) networks).
o The response to the request allows the requesting entity to set up a o The response to the request allows the requesting entity to set
point-to-point shortcut. up a point-to-point shortcut.
Given the above characteristics, the query-response protocol may not Given the above characteristics, the query-response protocol may not
be the optimal mechanism for particular applications such as the one be the optimal mechanism for particular applications such as the one
described in [HEIN]. The ARA option has the following characteristics. described in [HEIN]. The ARA option has the following characteristics.
o Only routers participate in the ARA option. Participation in the o Only routers participate in the ARA option. A router's
ARA option is discovered through address resolution advertisements.
o The ARA option does not require polling by the ingress device to Coltun, Heinanen [Page 7]
detect topology and reachability changes. Changes in the topology and participation in the ARA option is discovered through its address
system reachability may result in packet loss (or transient loops) for resolution advertisements.
the OSPF convergence time. Additionally, since topology changes are
determined as a result of OSPF's SPF calculation (which results in
loop-free paths), shortcuts derived from the ARA option will never
result in stable routing loops.
o Address resolution distribution is reliable and is not subject to o The ARA option does not require polling by the ingress device
packet loss. to detect topology and reachability changes. Changes in the
topology and system reachability may result in packet loss (or
transient loops) for the OSPF convergence time. Additionally,
since topology changes are determined as a result of OSPF's SPF
calculation (which results in loop-free paths), shortcuts derived
from the ARA option can never result in stable routing loops.
o The target of ARA derived shortcuts may be routers and and their o Address resolution distribution is reliable and is not subject
connected networks within an OSPF area. Inter-area shortcuts are sup- to packet loss.
ported when the destination is associated with an OSPF AS boundary
router advertisement (e.g., networks external to the OSPF autonomous
system).
o The ARA option allows the requesting entity to set up point-to-point o The target of ARA derived shortcuts may be routers and and
shortcuts as well as shortcuts that join point-to-multipoint and their connected networks within the OSPF autonomous system.
multipoint-to-point trees. Shortcuts are also supported when the destination is associated
with an OSPF AS boundary router advertisement (e.g., networks
external to the OSPF autonomous system).
o Routers that run the ARA option can interoperate with systems run- o The ARA option allows the requesting entity to set up point-
ning NHRP. to-point shortcuts as well as shortcuts that join point-to-
multipoint and multipoint-to-point trees.
o The ARA option may easily be extended to support inter-subnet multi- o Routers that run the ARA option can interoperate with systems
cast shortcuts. running NHRP.
o The ARA option may easily be extended to support inter-subnet
multicast shortcuts.
4.0 ARA Associations 4.0 ARA Associations
The ARA option defines three types of advertisements. These include The ARA option defines four types of advertisements. These include 1)
1) intra-area router associations, 2) intra-area network associations, intra-area router associations, 2) intra-area network associations, 3)
and 3) inter-area ASBR associations. Associations correspond to a inter-area network associations and 3) inter-area autonomous system
boundary router (ASBR) associations. Associations correspond to a
piece of the OSPF topology. Intra-area router associations correspond piece of the OSPF topology. Intra-area router associations correspond
to link-layer reachability of a router within the local area, intra- to link-layer reachability of a router within the local area, intra-
area network associations correspond to link-layer reachability of a area network associations correspond to the link-layer reachability of
router's directly connected networks (also within the local area), and a router's directly connected network (also within the local area),
inter-area ASBR associations correspond to ASBRs that may be in the inter-area network associations correspond to the link-layer reacha-
local or in a remote area. An ingress router can use these associa- bility of a remote area router's directly connected network, and
tions as follows. inter-area ASBR associations correspond to ASBRs that are in remote
OSPF areas. Note that an inter-area network association may be ori-
ginated by an area border router (ABR) only if the network is not a
component of a configured net range. An ingress router can use these
associations as follows.
Coltun, Heinanen [Page 8]
Intra-area router associations are used to setup shortcuts to Intra-area router associations are used to setup shortcuts to
routers within the local area. Data sent over the shortcut will routers within the local area. Data sent over the shortcut will
be forwarded to destinations local to and beyond the router be forwarded to destinations local to and beyond the router
including ones that are in the local area, in a remote area or including ones that are in the local area, in a remote area or
external to the autonomous system. A destination that is "beyond external to the autonomous system. Destinations that are "beyond
the router" is determined by the OSPF topology map. the router" are determined by the OSPF topology map.
Intra-area network associations (which may advertise a host, net-
work or IP multicast address) are used to setup a shortcuts to
systems whose address fall within the range of the advertised
network.
Inter-area ASBR associations are used to setup shortcuts to ASBRs Intra-area network associations (which may advertise hosts or
that are in the local or remote area. These shortcuts are used networks) are used to setup intra-area shortcuts to systems whose
to send data to destinations that are external to the autonomous addresses fall within the range of the advertised network.
system and reachable via the ASBR.
The ARA option maintains a list of all association for a specific ver- Inter-area network associations (which may advertise a host or
tex and vertex type in an ARA Association Table. The lookup keys to network address) are used to setup inter-area shortcuts to sys-
an entry in the table include the vertex type, vertex ID and, if the tems whose address fall within the range of the advertised net-
scope is area-local, the area ID. work.
Associations are added to the routing table during the OSPF routing Inter-area ASBR associations are used to setup shortcuts to ASBRs
table calculation (see the section entitled Adding ARA Routing Table that are in a remote area. These shortcuts are used to send data
Extensions below). So, in addition to the standard information fields to destinations that are external to the autonomous system and
contained in the routing table (i.e., IP network number, IP mask, reachable via the ASBR.
next-hop interface, etc.), the routing table is extended to contain
link-layer associations (via a reference to the ARA Association
Table). The use of the extensions are ARA user application specific
and beyond the scope of this document. See [HEIN] for an example of
an ARA user application.
5.0 Examples 5.0 Examples
5.1 Example 1: Intra-Area 5.1 Example 1: Intra-Area
Consider the sample single-area topology in Figure 1 below. In this Consider the sample single-area topology in Figure 1 below. In this
example RT1, RT2 and RT5 support the ARA option (by definition they example RT1, RT2 and RT5 support the ARA option (by definition they
also support the Opaque LSA option) and RT4 supports the Opaque LSA also support the Opaque LSA option) and RT4 supports the Opaque LSA
option only (this is necessary so that RT4 redistributes the ARAs ori- option only (this is necessary so that RT4 redistributes the ARAs ori-
ginated by RT1, RT2 and RT5). RT2 and RT5 have each originated an ARA ginated by RT1, RT2 and RT5). RT2 and RT5 have each originated a R-
with an intra-area router association and RT5 has originated an ARA ARA with an intra-area router association and RT5 has originated a N-
with an intra-area network association for N5. ARA with an intra-area network association for N5.
As a result of running the routing table calculation, RT1 would have As a result of running the routing table calculation, RT1 has entries
entries for N1-N8 in its routing table. The entry for N2 would refer- for N1-N8 in its routing table. The entry for N2 references the
ence the link-layer associations distributed in RT2's R-ARA, the link-layer associations distributed in RT2's R-ARA, the entries for
entries for N3, N4, N6, N7, N8 would reference the link-layer associa- N3, N4, N6, N7, N8 references the link-layer associations distributed
tions distributed in RT5's R-ARA and the entry for N5 would reference in RT5's R-ARA and the entry for N5 references the link-layer associa-
the link-layer associations distributed in RT5's intra-area N-ARA. tions distributed in RT5's intra-area N-ARA.
Coltun, Heinanen [Page 9]
+ ARA + ARA
| +---+ N3 N5 | +---+ N3 N5 (ARA)
N1|--|RT1|\ \ N4 / N1|--|RT1|\ \ N4 /
| +---+ \ \ | / | +---+ \ \ | /
+ \ \|/ + \ \|/
\+---+ +---+ \+---+ +---+
|RT4|------------|RT5|ARA |RT4|------------|RT5|ARA
+---+ +---+ +---+ +---+
+ ARA / | N7 + ARA / | N7
| +---+ / | / | +---+ / | /
N2|--|RT2|/ | / N2|--|RT2|/ | /
| +---+ +---+ +---+/ | +---+ +---+ +---+/
skipping to change at page 9, line 29 skipping to change at page 36, line ?
| |
| |
+---------+ +---------+
N6 N6
Figure 1: Sample Single-Area Toplogy Figure 1: Sample Single-Area Toplogy
5.2 Example 2: Inter-Area 5.2 Example 2: Inter-Area
Consider the sample 2-area topology in Figure 2 below. In this exam- Consider the sample 2-area topology in Figure 2 below. In this exam-
ple RT1, RT2, RT3, RT4 and RT6 support the ARA option and RT5 supports ple RT1, RT2, RT3, RT4, RT6 and RT7 support the ARA option, and RT5
the Opaque option. N3-N7 are AS external routes and RT5 and RT6 are supports the Opaque option. N4 is an AS external route (which is
ASBRs. RT4 is an area-border router and originates LS Type-4 LSAs on flooded to all areas) and RT6 is an ASBR. RT4 is an area-border
behalf of RT5 and RT6 and a LS Type-3 LSA for N8 into area 1.1.1.1. router and originates an LS Type-4 LSA on behalf of RT6 and a LS
Type-3 LSA for N5 into area 1.1.1.1.
RT1, RT2, RT3 and RT4 have originated intra-area R-ARAs, and RT6 has Within area 1.1.1.1, RT1, RT2, RT3 and RT4 originate intra-area R-
originated an inter-area R-ARA. ARAs. Within the backbone RT6 and RT7 originate intra-area R-ARAs and
R7 originates a N-ARA for N5. All backbone ARAs of have their the P-
bit set (this bit informs ABRs that the ARA may be propagated between
areas). RT4 originates an inter-area R-ARA for RT6 (which is an ASBR)
as well as an inter-area N-ARA for N5 into area 1.1.1.1 RT4 does not
originate an inter-area R-ARA for RT7 because it is not an ASBR.
As a result of running the routing table calculation, RT1 would have As a result of running the routing table calculation, RT1 has entries
entries for N1-N8 in its routing table. The entry for N2 would refer- for N1-N5 in its routing table. The entry for N2 references the
ence the link-layer associations distributed in RT3's R-ARA, the link-layer associations distributed in RT3's R-ARA, the entry for N3
entries for N3, N4, N5 and N8 would reference the link-layer associa- references the link-layer associations distributed in RT4's intra-area
tions distributed in RT4's intra-area R-ARA (i.e., R1 can't see link- R-ARA, the entry for N4 references the link-layer associations distri-
layer information beyond the area border router) and the entries for buted in RT4's inter-area R-ARA (indirectly referencing RT6's R-ARA)
N6 and N7 would reference the link-layer associations distributed in and the entry for N5 references the link-layer associations
RT6's inter-area R-ARA.
Coltun, Heinanen [Page 10]
distributed in RT4's inter-area N5 N-ARA.
|
+ ARA ARA | + ARA ARA |
| +---+ +---+ | N3 N5 | +---+ +---+ |
N1|--|RT1|----|RT2|\ | \ N4 / N1|--|RT1|----|RT2|\ | N3 N4<ASE
| +---+ +---+ \ | \ | / | +---+ +---+ \ | +-----+ /
+ \ ARA \|/ + \ ARA | ARA /
\+---+ +---+ +---+
|RT4|----|RT5|---|RT6|<ASBR
+---+ +---+ +---+
+ ARA / | |
| +---+ / | ARA +
N2|--|RT3|/ | +---+ |
| +---+ | |RT7|---|N5(ARA)
+ | +---+ |
------------------------|-------------------- +
Area 1.1.1.1 | OSPF Backbone
Figure 2: Sample Area Toplogy
5.3 Example 3: Multiple Logical Networks
The ARA option supports the existence of disjoint switched networks
within an OSPF domain. To accomplish this, an ARA may include an iden-
tifier (the logical network ID) for a specific switched network. When
associations are added to the routing table during the OSPF routing
table calculation (see the section 8.1 "Adding ARA Routing Table
Extensions") only the associations that include a logical network ID
that matches one of the router's configured logical network IDs are
added to the routing table. This function may also be used to support
a variation of closed user groups so that shortcuts are limited to
those routers that are configured to be in the same logical network.
The single-area topology described in Figure 3 below divides an OSPF
area into logical networks X and Y. In this example RT1, RT2 and RT4
support the ARA option and RT3 supports the Opaque LSA option only.
RT1 is connected to logical network (LN) X, RT2 is connected LN Y and
RT4 is connected to both LN X and LN Y. RT1, RT2 and RT4 all ori-
ginate R-ARAs.
As a result of running their routing table calculation, RT1 and RT2
have entries for N1-N5 in their routing table. In both routing
tables, the N3-N5 entries reference the link-layer associations dis-
tributed in RT4's R-ARA. However, RT1's routing table does not refer-
ence RT2's link-layer associations for N2 and RT2's routing table does
Coltun, Heinanen [Page 11]
not reference RT1's link-layer associations for N1 (i.e., they would
not be able to set up shortcuts to each other and would be forced to
use a hop-by-hop path to communicate).
+ ARA (LN=X)
| +---+ N3 N5
N1|--|RT1|\ \ N4 /
| +---+ \ \ | /
+ \ \|/
\+---+ +---+ \+---+ +---+
|RT4|------|RT5| |RT3|------------|RT4| ARA (LN=X,Y)
+---+ +---+ +---+ +---+
+ ARA / | | N6 /
| +---+ / | | / + ARA (LN=Y)
N2|--|RT3|/ | ARA / | +---+ /
| +---+ | +---+/ N2|--|RT2|/
+ | |RT6|----N7
| +---+
| |
| |
| +---+
| |RT7|
| +---+ | +---+
| | +
| +-----+
| N8
|
|
|
Area 1.1.1.1 | OSPF Backbone
------------------------|-------------------------
Figure 2: Sample Area Toplogy Figure 3: Sample Toplogy With Logical Networks
6.0 Description Of ARA Packet Formats 6.0 Description Of ARA Packet Formats
ARA LSAs (ARAs) include the information necessary to associate an IP ARA LSAs (ARAs) include the information necessary to associate an IP
entity (i.e., a router, network or host) with a link-layer address. entity (i.e., a router, network or host) with a link-layer address.
The ARA option allows further refinement so that an association may The ARA option allows further refinement so that an association may
additionally include information about QoS control services and link- additionally include information about QoS control services and link-
layer functionality (e.g., for Point-to-MultiPoint and MultiPoint-to- layer functionality (e.g., for Point-to-MultiPoint and MultiPoint-to-
point connections). ARA advertisements may also include a logical point connections). ARA advertisements may also include a logical
network identifier field, which is to be used when more than one vir- network identifier field, which is used when multiple switched net-
tual overlay network is present within the OSPF domain. works are present within the OSPF domain.
The ARA format allows more than one equivalent association to been The ARA format allows more than one equivalent association to been
advertised by a router for a specific vertex. The association can advertised by a router for a specific vertex. Equivalent associations
include a preference which identifies the advertising router's are ones that have identical link service type, integrated service
relative preference for the equivalent associations. Equivalent asso- type and logical network identifier fields, but have different resolu-
ciations are ones that have identical link service type, integrated tion information. Associations can include a preference which identi-
service type and logical network identifier fields. fies the advertising router's relative preference for the equivalent
associations.
ARA information is encapsulated in Opaque LSAs. Three LS Types (LS ARA information is encapsulated in Opaque LSAs. Three LS Types (LS
Type 9, 10 and 11) constitute the Opaque class of link-state adver- Type 9, 10 and 11) constitute the Opaque class of link-state adver-
tisements. Each of the three Opaque link-state types have a scope tisements. Each of the three Opaque link-state types have a scope
associated with them so that distribution of the information may be associated with them so that distribution may be limited appropriately
limited appropriately by the originator of the LSA. Opaque LSAs have
a sub-type which identifies the specific information that is carried Coltun, Heinanen [Page 12]
within the LSA. The ARA Opaque types are Opaque-type 1 and 2. The by the originator of the LSA. Opaque LSAs have a sub-type which iden-
flooding scope for specific vertex types is realized by embedding the tifies the specific information that is carried within the LSA. The
association in the appropriate Opaque LSA type. ARA Opaque types are Opaque-type 1 - 4. Because the flooding scope
for ARAs is always area local, ARAs are encapsulated in LS Type 10
LSAs.
6.1 Vertex Types And Vertex Identifiers 6.1 Vertex Types And Vertex Identifiers
The Vertex Type identifies the piece of IP topology that the link- The Vertex Type identifies the piece of IP topology that the link-
layer information is being associated with. The Vertex Type may be a layer information is being associated with. The Vertex Type may be a
router or a network (a host is considered a network with a mask of router or a network (a host is considered a network with a mask of
255.255.255.255). 255.255.255.255).
Vertex type 1 ARAs advertise router address resolution associations. Vertex Type 1 ARAs advertise intra-area router resolution associa-
These associations are used to advertise the router's link-layer tions. These associations distribute the router's link-layer attach-
attachments. A Vertex Type of 1 is identified by an Opaque type of 1. ments. A Vertex Type of 1 is identified by an Opaque type of 1. The
The vertex identifier for a Router ARA (R-ARA) is the advertising Vertex Identifier for a R-ARA is the advertising router field in the
router field of the ARA header. Intra-area vertex type-1 advertise- ARA header.
ments are included in Opaque Type-10 LSAs (their flooding scope is
area-local). Inter-area vertex type-1 advertisements are included in
Opaque Type-11 LSAs (their flooding scope is domain-wide). Inter-area
vertex type-1 advertisements are originated by as AS boundary routers.
Vertex type 2 ARAs advertise IP network address resolution associa- Vertex Type 2 ARAs advertise intra-area IP network address resolution
tions (the network may be a IP multicast (class D) network). These associations. These associations distribute the link-layer associa-
associations are used to advertise the link-layer associations for a tions for a router's directly connected network. A Vertex Type of 2
router's directly connected network. Vertex Type 2 advertisements are is identified by an Opaque type of 2. The Vertex Identifier (the net-
be included in area-local (LS Type 10) advertisements. A Vertex Type work and mask) for a N-ARA is contained in the body of the advertise-
of 2 is identified by an Opaque type of 2. The vertex identifier (the ment. N-ARAs may only contain a single network (i.e., lists of net-
network and mask) for a Network ARA (N-ARA) is contained in the body works are not permitted).
of the advertisement. A N-ARA may only identify a single network
(i.e., lists of networks are not permitted). Vertex Type 3 ARAs advertise inter-area IP network address resolution
associations. These associations are used to distribute link-layer
associations for networks into remote areas. A Vertex Type of 3 is
identified by an Opaque type of 3. The Vertex Identifier (the network
and mask) for a inter-area N-ARA is contained in the body of the
advertisement. N-ARAs may only identify a single network (i.e., lists
of networks are not permitted). Vertex Type 3 N-ARAs are originated
by an area border router (ABR) into an area when 1) the ABR originates
a type-3 LSA for the network into the target area, 2) the network is
not included in any of the area border router's configured area
ranges, 3) there is a N-ARA for the network in the source area, 4) the
source N-ARA may be an intra or inter-area N-ARA. If it is an intra-
area N-ARA the P-bit must be set in its options field. The setting of
the P-bit by the originator denotes that the associations contained in
the N-ARA are allowed to be propagated into other areas.
Vertex Type 4 ARAs advertise inter-area router address resolution
associations. These R-ARAs redistribute associations for ASBRs into
remote areas. A Vertex Type of 4 is identified by an Opaque type of
4. The Vertex Identifiers for an inter-area R-ARA are the advertising
router field of the ARA header and the ASBR Router ID found in the
Coltun, Heinanen [Page 13]
body of the ARA. Vertex Type 4 R-ARAs are originated by an area
border router (ABR) into a target area when 1) the ABR originates a
type-4 LSA for the ASBR into the target area, 2) there is a R-ARA for
the network in the source area, 3) the source R-ARA may be an intra or
inter-area R-ARA. If the source R-ARA is an intra-area R-ARA its P-
bit must be set in the options field. The setting of the P-bit by the
originator denotes that the associations contained in the R-ARA are
allowed to be propagated into other areas.
If a router wishes to advertise several associations for a single ver- If a router wishes to advertise several associations for a single ver-
tex it has two options. It may originate multiple (N or R) ARAs each tex it has two options. It may originate multiple (N or R) ARAs each
containing different associations or it may originate a single (N or containing different associations or it may originate a single (N or
R) ARA containing a list of associations. R) ARA containing a list of associations. An implementation must not
include identical associations in more than one ARA.
7.0 Distribution Of ARA Information 7.0 Distribution Of ARA Information
In general, OSPF is composed of two components. It's transport com- In general, OSPF is composed of two components. It's transport com-
ponent deals with adjacency formation and reliable distribution of ponent handles adjacency formation and reliable distribution of topol-
topology information. The second component tracks topology informa- ogy information. The second component tracks topology changes and
tion changes and organizes the topology information that has gathered organizes the topology information that has been gathered from other
from other routers into to a topology map which is used to build the routers into to a topology map. This map is used to build the router's
router's routing table. The ARA option uses both the OSPF transport routing table. The ARA option uses both the OSPF transport component
component and of the topology map component. and of the topology map component.
ARA uses the OSPF Opaque LSA as defined in [OPAQ] for distribution of ARA uses the OSPF Opaque LSA as defined in [OPAQ] for distribution of
resolution information. The Opaque LSA is an optional mechanism to resolution information. The Opaque LSA is an optional mechanism to
allow for distribution of information. This information may be used allow for distribution of opaque information which may be used
directly by OSPF or by other protocols and mechanisms such as the ARA directly by OSPF or by other protocols and mechanisms. Opaque LSAs
option. Opaque LSAs use standard OSPF link-state database flooding use the standard OSPF link-state database flooding mechanisms for dis-
mechanisms for distribution. Each of the three Opaque types (LS Types tribution. Each of the three Opaque types (LS Types 9, 10 and 11)
9, 10 and 11) have a scope associated with them so that distribution have a scope associated with them (link-local, area-local or domain-
of the information throughout the OSPF topology may be limited if wide, respectively). Scoping provides an application with a method to
appropriate. ARA information has topology-specific scopes (i.e., dif- limit the range of information distribution. ARA information is dis-
ferent Opaque types) depending on the ARA vertex type (see the section tributed with area-local scope (i.e., ARA information is encapsulated
entitled Vertex Types and Vertex Identifiers). in LS Type 10 LSAs).
The ARA option uses the topology map component of OSPF to validate the The ARA option uses the topology map component of OSPF to validate the
information that is received by the distribution mechanism and to information that is received by the distribution mechanism and to
install the associations into the routing table. Validation is needed install the associations into the ARA routing table extensions. Vali-
because topology information contained in the OSPF link-state database dation is necessary because topology information contained in the OSPF
may be stale (i.e., the originator of the information is no longer link-state database may be stale (e.g., the originator of the informa-
reachable). tion is no longer reachable).
It is envisioned that an implementor designs an ARA user application It is envisioned that an implementor designs an ARA user application
interface to which facilitates 1) flooding of ARA information to other interface which facilitates 1) flooding of ARA information to other
routers in the OSPF network, 2) receiving ARA information from other routers in the OSPF network, 2) receiving ARA information from other
routers in the OSPF network and 3) determining the validity (and
change of validity) of ARA information. Coltun, Heinanen [Page 14]
routers in the OSPF network and 3) determines the validity (and change
of validity) of ARA information.
For the realization of 1 above, an implementation must provide an API For the realization of 1 above, an implementation must provide an API
which allows the ARA user application to have its local OSPF entity to facilitate the ARA user application's "hand off" of resolution
distribute resolution information in the ARA defined format (if the information to its local OSPF entity which will then be distributed
scope is area-local, the area must also be supplied). In addition, throughout the OSPF topology. In addition, the API must support the
the API must support the purging of associations that were previously purging of associations that were previously originated by the router
originated by the router if they are no longer valid and send out new if they are no longer valid and send out new versions when the associ-
versions when the association information has changed. ation information has changed.
For the realization of 2 and 3 above, this document extends the rout- For the realization of 2 and 3 above, this document extends the rout-
ing table to include the associations that have been advertised by the ing table to include the associations that have been advertised by the
ARA capable routers. (i.e,. the routing table provides the API for ARA capable routers (i.e,. the routing table provides the API for the
the ARA user application). That is, in addition to the standard ARA user application). That is, in addition to the standard informa-
information fields contained in the routing table (i.e., IP network tion fields contained in the routing table (i.e., IP network number,
number, IP mask, next-hop interface, etc.), the routing table is IP mask, next-hop interface, etc.), the routing table is extended to
extended to contain link-layer associations. The associations are contain link-layer associations. The associations are added to the
added to the routing table during the OSPF routing table calculation routing table during the OSPF routing table calculation. Section 8.0
(see the section on Adding ARA Routing Table Extensions below). The defines the mechanism to calculate the ARA routing table extensions.
use of the extensions are ARA user application specific and beyond the The use of the extensions are ARA user application specific and beyond
scope of this document. See [HEIN] for an example of an ARA user the scope of this document. See [HEIN] for an example of an ARA user
application. application.
The following section defines the mechanism to calculate the ARA rout- 7.1 Originating Inter-Area ARAs
ing table extensions.
Inter-area ARAs provide a mechanism to distribute link-layer associa-
tions to other areas. Inter-area ARAs (consisting of Vertex Type-3
and Type-4 ARAs) have a one-to-one correspondence to Summary LSAs (LS
type-3 and type-4 LSAs). Vertex Type-3 ARAs advertise the link-layer
associations of IP networks whereas Vertex Type-4 ARAs advertise the
link-layer associations of autonomous system boundary routers (ASBR).
As with Summary LSAs, inter-area ARAs are originated by area border
routers into a target area based on a set of conditions in the source
area. For both intra and inter-are ARAs, there may be more than one
ARA which collectively make up the complete set of link-layer associa-
tions (recall that an implementation must not include identical asso-
ciations in more than one ARA). Inter-area ARAs must include, in one
or more ARA, all of the link-layer associations contained in their
'trigger' ARAs (see below for a description of the conditions for ABRs
to trigger inter-area ARAs).
The link-layer associations that comprise the 'trigger' ARAs (in the
source area) may include logical network IDs that are not in the ABR's
configured list of logical network IDs (i.e., the ABR itself may not
be able to set up a shortcut because it may be connected to a disjoint
set of logical networks). Despite the ABR's logical network
Coltun, Heinanen [Page 15]
affiliation, all trigger ARAs' link-layer associations are included in
the newly originated inter-area ARAs.
The origination process for type-3 and type-4 Summary LSAs (as dis-
cussed in section 12.4.3 of [OSPF]) consists of an ABR evaluating each
entry in the routing table. If an entry satisfies a set of condi-
tions, the ABR originates a Summary LSA into the target area.
This process is extended for inter-area ARA origination so that when a
Summary LSA is originated into an area by an ABR, the conditions for
the origination of inter-area ARAs are also evaluated. When these con-
ditions are satisfied, an inter-area ARA is originated into the target
area. Conversely, when a Summary route is withdrawn from an area by
an ABR and a corresponding ARA was previously originated into the
area, the ARA must be withdrawn from the target area. The following
sections describe the conditions for inter-area ARA origination.
The conditions for inter-area N-ARA origination are as follows.
o The ABR is originating a type-3 LSA for a network into the tar-
get area. The network and mask that triggered the origination of
the type-3 LSA must be identical to the network and mask of the
type-3 LSA. (i.e., the 'trigger network' is not included in the
area border router's configured area ranges).
o There are one or more reachable N-ARAs for the network in the
source area. These N-ARAs 1) must be valid (e.g., their ages
must not be MaxAge), 2) must have the same advertising router as
the LSA that triggered the origination of the type-3 LSA and 3)
the Vertex Type must correspond to the 'trigger' network's LSA
type (recall that only the contents of intra-area ARAs are adver-
tised into the backbone, whereas the contents of intra-area or
inter-area ARAs may be advertised into the other areas). These
conditions are verified by looking up an entry in source area's
ARA Association Table. The Vertex Type is 2 if the 'trigger'
network is an intra-area LSA and is Vertex Type 3 if the
'trigger' network is an inter-area LSA. The Vertex Identifier is
the 'trigger' network's IP network number and mask. The Vertex
Originator is the router ID of the trigger network's originator.
o The set of link-layer associations that are to be included in
the advertisement are contained in the ARA Association Table
entry. However, if the network that triggered the origination of
the type-3 LSA is an intra-area route, only the link-layer asso-
ciations whose ARA's P-bit were set may be advertised. (if no
associations have their P-bit set the inter-area N-ARA must not
be originated). The setting of the P-bit in the N-ARA by its
Coltun, Heinanen [Page 16]
originator gives the ABRs permission to propagate the resolution
information into other areas.
Inter-area R-ARAs redistribute link-layer associations for ASBRs to
other areas. Inter-area R-ARAs have a Vertex Type of 4. The Vertex
Identifiers for an inter-area R-ARA are 1) the advertising router
field of the ARA header and 2) the ASBR's Router ID which is found in
the body of the ARA. Vertex Type-4 R-ARAs are originated by an area
border router (ABR) into an area if the following conditions are met.
o The ABR originates a type-4 LSA for the ASBR into the target
area.
o Only the contents of intra-area ARAs are advertised into the
backbone, whereas the contents of intra-area or inter-area ARAs
may be advertised into the other areas. If the router advertise-
ment that triggered the origination of a type-4 LSA is an intra-
area advertisement (i.e., a type-1 LSA) then there must be a
corresponding intra-area R-ARA in the source area.
o If the router advertisement that triggered the origination of
the type-4 LSA is also a type-4 LSA (the source area is the OSPF
backbone), there must be a corresponding inter-area R-ARA in the
source area.
o The set of link-layer associations that are to be included in
the advertisement are contained in the ARA Association Table
entry. However, if the router advertisement that triggered the
origination of the type-3 LSA is an intra-area route, only the
link-layer associations whose ARA's P-bit are set may be adver-
tised in the newly originated inter-area R-ARA (if no associa-
tions have their P-bit set the inter-area N-ARA must not be ori-
ginated). The setting of the P-bit in the R-ARA by its origina-
tor gives the ABRs permission to propagate the resolution infor-
mation into other areas.
8.0 ARA Routing Table Extensions 8.0 ARA Routing Table Extensions
OSPF determines reachability and topology changes by performing the OSPF determines reachability and topology changes by performing the
algorithms described in the section entitled "Calculation of the rout- algorithms described in the section 16 of [OSPF] entitled "Calculation
ing table" (see section 16 of [OSPF]). ARAs are included in this cal- of the routing table". ARAs are included in this calculation for the
culation for the purpose of binding link-layer associations to IP purpose of binding link-layer associations to IP routing table
routing table entries. entries.
A link-layer association consists of the list of link-layer addresses, A link-layer association consists of the list of link-layer addresses,
link-layer service types and other link-layer objects such as Point- link-layer service types and other link-layer objects such as Point-
to-MultiPoint call identifiers and QoS service specific information.
(See section Appendix A for a more complete description of the Coltun, Heinanen [Page 17]
specific link-layer information distributed in ARAs). The associa- to-MultiPoint call identifiers and QoS service specific information
tions that are bound to a routing table entry are the associations (see Appendix A for a more complete description of the specific link-
that are closest to the originator of the routing table's network layer information distributed in ARAs). The associations that are
entry. The closest associations are determined during to the construc- bound to a routing table entry are the associations that are 1)
tion of the OSPF topology map. The associations that are bound to the closest to the destination and 2) are on the same logical network as
routing table entries are subsequently used by the ARA user applica- the calculating router (as identified by the logical network ID). The
tion to setup shortcut paths. Because a link-layer association may be closest associations are determined during to the construction of the
bound to more than one entry in the routing table, an ARA implementa- OSPF topology map. The associations that are bound to the routing
tion keeps a table of ARA derived link-layer associations which is table entries are subsequently used by the ARA user application to
referenced by the routing table entry. An entry in the ARA Associa- setup shortcut paths.
tion Table consists of a list of all association for a specific vertex
and vertex type. The lookup keys to an entry in the table include the Because a link-layer association may be bound to more than one entry
vertex type, vertex ID and, if the scope is area-local, the area ID. in the routing table, an ARA implementation keeps a table of ARA
derived link-layer associations which is referenced by the routing
table entry. Each area has its own ARA Association table. An entry
in the ARA Association Table consists of a list of all association for
a specific vertex and vertex type by a specific originator; the lookup
keys for an entry in the table include the Vertex Type, Vertex ID and
the Vertex Originator.
8.1 Adding ARA Routing Table Extensions 8.1 Adding ARA Routing Table Extensions
Section 16 of the OSPF specification is modified for the purpose of Section 16 of the OSPF specification is modified for the purpose of
adding the ARA routing table extensions. Transit vertex data struc- adding the ARA routing table extensions. Transit vertex data struc-
tures and the internal representation of Type-3, Type-4 and Type-5 tures and the internal representation of Type-3, Type-4 and Type-5
LSAs are extended to be able to reference a list of link-layer associ- LSAs are extended to be able to reference a list of link-layer associ-
ations (i.e., they have a reference to the ARA Association Table). ations (i.e., they have a reference to the ARA Association Table).
The vertex and LSA's list of link-layer associations are added to the The vertex and LSA's list of link-layer associations are added to the
routing table along with the entry. routing table along with the entry.
Prior to running the intra-area route calculation the ARA Association
Table is examined. Associations containing a logical network ID that
matches an entry in the router's list of logical network IDs are
marked 'active'.
8.1.1 Modifications To The Intra-Area Route Calculation 8.1.1 Modifications To The Intra-Area Route Calculation
The intra-area route calculation is enhanced (specifically section The intra-area route calculation is enhanced (specifically section
16.1 step 3) as follows. 16.1 step 3) as follows.
o Call the vertex that is about to be added to the SPF tree ver- o Call the vertex that is about to be added to the SPF tree ver-
tex M. If vertex M was originated by the calculating router skip tex M. If vertex M was originated by the calculating router skip
this procedure. this procedure.
o If vertex M is a transit network vertex lookup the link-layer o If vertex M is a transit network vertex lookup the link-layer
association entry in the ARA Association Table. This entry's association entry in the ARA Association Table. This entry's
vertex type will be type-2, the vertex identifier will consist of
a network and mask which are equivalent to those found in vertex Coltun, Heinanen [Page 18]
M and its area ID will be the one that is associated with the Vertex Type will be 2, the Vertex Identifier will be vertex M's
network and mask, the Vertex Originator will be vertex M's Router
ID and its area ID will be the one that is associated with the
shortest-path calculation. shortest-path calculation.
o If an entry is found reference this entry in vertex M's link- o If an active entry is found, reference this entry in vertex M's
layer association field. link-layer association field.
o If vertex M is a router vertex lookup the an entry in the ARA o If vertex M is a router vertex lookup the an entry in the ARA
Association Table. This entry's vertex type will be type-1, the Association Table. This entry's Vertex Type will be 1, the Ver-
vertex identifier will be vertex M's advertising router and its tex Identifier will be vertex M's advertising router, the Vertex
area ID will be the one that is associated with the shortest-path Originator will be vertex M's advertising router and its area ID
calculation. will be the one that is associated with the shortest-path calcu-
lation.
o If an entry is found reference this entry in vertex M's link- o If an an active entry is found, reference this entry in vertex
layer association field. M's link-layer association field.
o If no link-layer association entries are found, and vertex M's o If no active link-layer association entries are found, and ver-
parent vertex has link-layer association information, vertex M tex M's parent vertex has link-layer association information,
inherits it's parent vertex's information (else the information vertex M inherits it's parent vertex's information (else the
field is left blank). information field is left blank).
o When vertex M is added to the routing table, copy vertex M's o When vertex M is added to the routing table, copy the active
link-layer association list into the routing table entry's link- associations from vertex M's link-layer association list into the
layer association field. routing table entry's link-layer association field.
The following describes the enhancements to section 16.1 step 2 of The following describes the enhancements to section 16.1 step 2 of
[OSPF] which adds intra-area stub networks to the routing table. [OSPF] which adds intra-area stub networks to the routing table.
o Before adding the stub network to the routing table lookup the o Before adding the stub network to the routing table lookup the
entry in the ARA Association Table. This entry's vertex type entry in the ARA Association Table. This entry's Vertex Type
will be type-2, the vertex identifier will consist of a network will be 2, the Vertex Identifier will consist of the network and
and mask which are equivalent to those found in the stub network mask of the stub network, the Vertex Originator will be the
and its area ID will be the one that is associated with the advertising router's Router ID and its area ID will be the one
shortest-path calculation. that is associated with the shortest-path calculation.
o If an entry is found copy the entry's association information o If an active entry is found copy the entry's active association
into the routing table entry's link-layer association field. information into the routing table entry's link-layer association
field.
o If an entry is not found and the stub network's advertising o If an entry is not found and the stub network's advertising
router vertex has link-layer association information, the routing router vertex has link-layer association information, the routing
table entry will use the advertising router's information (else table entry will inherit the advertising router's information
the information field is left blank). (else the information field is left blank).
8.1.2 Modifications To The Inter-Area Route Calculations Coltun, Heinanen [Page 19]
8.1.2 Modifications To The Inter-Area Route Calculation
The following describes the enhancements to OSPF sections 16.2, 16.3, The following describes the enhancements to OSPF sections 16.2, 16.3,
16.5 which calculate inter-area routes. Before the destination associ- 16.5 which calculate inter-area routes. Before the destination associ-
ated with the LSA is added to the routing table the following is per- ated with the LSA is added to the routing table the following is per-
formed. formed.
o If the LSA is a Type-3 summary LSA, locate the area border o If the LSA is a Type-3 Summary LSA, lookup the entry in the ARA
router (ABR) that originated the advertisement. If link-layer Association Table. This entry's Vertex Type will be 3, the Vertex
association information is available for the ABR entry, copy the Identifier will be the Summary LSA's network and mask, the Vertex
contents of the ABR's link-layer association information field Originator will be the advertising router's Router ID and its
into the routing table entry's link-layer association field. area ID will be the one that is associated with the shortest-path
calculation. If an active entry is found copy the entry's active
o If the LSA is a Type-4 summary LSA, lookup the entry in the ARA association information into the routing table entry's link-layer
Association Table. This entry's vertex type will be type-1, the association field.
vertex identifier will the Type-4's Link-State ID (the link-state
ID identifies the ASBR) the area ID will not be used (the ARAs
have domain-wide scope).
o If an entry is found copy the entry's association information o If the LSA is a Type-4 Summary LSA, lookup a type-4 ARA in the
into the routing table entry's link-layer association field. ARA Association Table. This entry's Vertex Type will be 4, the
Vertex Identifier will be the Summary LSA's ASBR ID, the Vertex
Originator will be the advertising router's Router ID and its
area ID will be the one that is associated with the shortest-path
calculation. If an active entry is found copy the entry's active
association information into the routing table entry's link-layer
association field.
o If an entry is not found locate the area border router (ABR) o If an active entry was not found for the type-3 or type-4 LSA,
that originated the Type-4 advertisement. Copy the contents of locate the area border router (ABR) that originated the adver-
the ABR's link-layer association information field into the rout- tisement. If link-layer association information is available for
ing table entry's link-layer association field. the ABR entry, copy the contents of the ABR's link-layer associa-
tion information field into the routing table entry's link-layer
association field. If no active entry was found for the ABR the
routing table entry's information field will be left blank.
8.1.3 Modifications To The AS External Route Calculations 8.1.3 Modifications To The AS External Route Calculation
The following describes the enhancements to OSPF sections 16.4 and The following describes the enhancements to OSPF sections 16.4 and
16.6 which calculate AS external routes. Before the destination asso- 16.6 which calculate AS external routes. Before the destination asso-
ciated with the LSA is added to the routing table the following is ciated with the LSA is added to the routing table the following is
performed. performed.
o If the LSA has a forwarding address, look up the forward o If the LSA has a forwarding address, look up the forward
address in the routing table (this will be an internal OSPF address in the routing table (this will be an internal OSPF
route). Copy the contents of the route's link-layer association route). Copy the contents of the route's link-layer association
information field into the external route's routing table entry's information field into the external route's routing table entry's
link-layer association field. link-layer association field. The forwarding address' link-layer
Coltun, Heinanen [Page 20]
association information may have been added as a result of pro-
cessing intra-area or inter-area N-ARAs.
o If the LSA does not have a forwarding address, copy the con- o If the LSA does not have a forwarding address, copy the con-
tents of the advertising ASBR's link-layer association informa- tents of the advertising ASBR's link-layer association informa-
tion field into the routing table entry's link-layer association tion field into the routing table entry's link-layer association
field. Note that the ASBR's association information may have been field. The ASBR's link-layer association information may have
added from an intra-area or domain-wide R-ARAs. been added as a result of processing intra-area or inter-area R-
ARAs.
9.0 Receiving ARAs 9.0 Receiving ARAs
After the ARA has been processed according to section 13 of [OSPF] the After the ARA has been processed according to section 13 of [OSPF] the
ARA has been determined to be 1) a newer invocation of with the same ARA has been determined to be 1) a new ARA, 2) a newer instance of an
contents, 2) a newer invocation with different contents, 3) a new ARA existing ARA with the same contents, 3) a newer instance with dif-
or 4) a newer invocation that is being flushed by the ARA's origina- ferent contents, or 4) an ARA that is being withdrawn by it's origina-
tor. Actions need to be taken if the ARA is new, the ARA is being tor. Actions need to be taken if the ARA is new, the contents of the
purged or the contents of the ARA has changed. ARA have changed or the ARA is being withdrawn.
o Lookup the ARA's vertex in the ARA Association Table. If the
ARA is a LS Type-10, the table entry will reference the ARA's
associated area. If the ARA is Type-11 the table entry will not
be associated with an area.
o If the ARA is new and there is an existing entry, add the asso- o Lookup the entry for the ARA in the ARA Association Table. If
ciations found in the newly received ARA to the entry. The ARA there is no existing entry, create one which contains the associ-
application must be informed that new associations have been ations found in the ARA. The newly added associations should
added. reflect the state of the ARA's P-bit.
o If there is no existing entry, create one which contains the o If the there is an existing entry and the newly received ARA
associations found in the ARA. Reschedule the SPF calculation. contents have changed modify the entry to reflect the associa-
tions found in the newly received ARA. The changed associations
should reflect the state of the ARA's P-bit.
o If the ARA's contents have changed, modify the existing entry o If the ARA is being withdrawn and there is an existing entry,
and inform the ARA application that there has been a change to remove the associations from the link-layer entry that were pre-
the contents of the link-layer association entry for the speci- viously included in the ARA. If the contents of the table entry
fied vertex. is now empty remove the entry from the table.
o If the ARA is being flushed and there is an existing entry, If the above process has resulted in a modification to the ARA table,
remove the associations from the link-layer entry that were the SPF calculation must be rescheduled. (see section 8.1 entitled
included in the ARA. If the contents of the entry is now empty, "Adding ARA Routing Table Extensions"). If the receiving router is an
remove the entry from the table and reschedule the SPF calcula- ABR the inter-area origination process must be scheduled to be run
tion. If the entry still contains associations inform the ARA following the SPF calculation (see section 7.1 entitled "Originating
user application that there has been a change to the contents of Inter-area ARAs").
the entry.
10.0 Additional Data Structures And APIs 10.0 Additional Data Structures And APIs
Coltun, Heinanen [Page 21]
This section lists the additional data structures and APIs needed to This section lists the additional data structures and APIs needed to
support the OSPF ARA option. support the OSPF ARA option.
o The implementation must support the Opaque LSA option as o The implementation must support the Opaque LSA option as
defined in [OPAQ]. defined in [OPAQ].
o Configuration flag to enable the OSPF ARA option. o A configuration flag to enable the OSPF ARA option.
o A ARA Association Table is added. An entry in this table con- o A router implementing the ARA option maintains a table of
tains the list of link-layer associations for a specific vertex link-layer associations for each of its OSPF areas. The ARA
and vertex type. The lookup keys to an entry in the table include Association Table is used in calculating the ARA routing table
the vertex type, vertex ID and, if the scope is area-local, the extensions and in the inter-area ARA origination process. The
area ID. The table is referenced by the routing table and the indexes for an entry in this table entry are the Vertex Type,
data structures used in the SPF calculation. Vertex ID and the Vertex Originator. The Vertex Type identifies
the type of IP topology element that the link-layer information
is being associated with (i.e., a router or a network). The Ver-
tex ID identifies a piece of a specific OSPF network's topology
(i.e., a router ID or an IP network number). The Vertex Origina-
tor is the originator of the ARA's router ID. Entries in this
table may be either active or non-active. Active entries are
ones whose Logical Network IDs match one of the router's config-
ured (and currently active) Logical Network IDs.
o Transit vertex data structures and the internal representation o Transit vertex data structures and the internal representation
of Type-3, Type-4 and Type-5 LSAs are extended to contain a of Type-3, Type-4 and Type-5 LSAs are extended to contain a
reference to the an entry in the ARA Association Table. reference to the an entry in the ARA Association Table.
o The routing table is extended to contain a reference to the an o The routing table is extended to contain a reference to the an
entry in the ARA Association Table. entry in the ARA Association Table.
o To be able to flood ARA information to other ARA capable o To be able to flood ARA information to other ARA capable
routers an implementation must provide an API which allows the routers an implementation must provide an API which allows the
ARA user application to have its local OSPF entity distribute ARA user application to have its local OSPF entity distribute
resolution information in ARA format (if the scope is area-local, resolution information in ARA format (if the scope is area-local,
a reference to the area must also be supplied). Additionally the a reference to the area must also be supplied). Additionally,
API must be able to purge the associations that were previously the API must allow for associations to be withdrawn when they are
distributed when they are no longer valid and send out new ver- no longer valid and for new versions of associations to be ori-
sions when the associations information has changed. ginated when association information has changed.
A.1 ARA Formats o A router running the ARA option may be configured with a list
of logical network IDs. This list is used when the router calcu-
lates the link-layer associations for its routing table and when
receiving ARAs to determine the change in active status for its
ARA Association Table entries. Status information is kept for
each of the router's attached logical network so that a router
can determine which logical networks are active at a given point
in time. To insure that ARA reachability is up-to-date, a change
in status of one of the router's connected logical networks must
This document defines three different types of Address Resolution Coltun, Heinanen [Page 22]
result in the SPF calculation being rerun.
The absence of entries in the router's list of Logical Network
IDs means that the router will only activate ARA Association
Table entries with the default Logical Network ID which is Logi-
cal Network ID 0.
A router may originate ARAs with Logical Network IDs that are not
contained in its list of Logical Network IDs. This may be used,
for example, to enable shortcuts to be set up from any router to
any server but to disable shortcuts from being set up between
routers that are not associated with a server.
Appendix A: ARA Packet Formats
This document defines four different types of Address Resolution
Advertisements. Each type of ARA begins with a standard 20-byte Opaque Advertisements. Each type of ARA begins with a standard 20-byte Opaque
LSA header [OPAQ]. This header is described in section A.1.1. Subse- LSA header [OPAQ]. This header is described in section A.1. Subsequent
quent sections describe the specific advertisements and their content sections describe the specific advertisements and their content
(i.e., the formats of the resolution information). including the formats of the resolution information. An ARA capable
router may use the ARAs to build shortcut paths to other ARA capable
routers.
Each ARA describes a link-layer association for a piece of the OSPF Each ARA describes a link-layer association for a piece of the OSPF
routing domain. Any router may originate intra-area router ARAs and routing domain. Any router may originate intra-area router and network
network ARAs. These ARAs are distributed throughout the local area. ARAs. These ARAs advertise address resolution information for routers
ASBRs may originate domain-wide router ARAs. An ARA capable router and networks within the local area and are advertised locally (they
may use the ARAs to build shortcut paths to other ARA capable routers. have an area-local scope).
A.1.1 The ARA Header Area border routers may originate inter-area network and router ARAs.
These ARAs advertise address resolution to areas that are beyond the
source local area. Inter-area network and router ARAs correspond to LS
Type-3 and LS Type-4 advertisements.
A.1 The ARA Header
All ARAs begin with a common 20-byte header. This header contains All ARAs begin with a common 20-byte header. This header contains
enough information to uniquely identify the ARA. The header, which is enough information to uniquely identify the ARA. The header, which is
a subset of the standard LSA header, includes the ARA Vertex Type and a subset of the standard LSA header, includes the ARA Vertex Type and
distribution scope. The Vertex Type is derived from the Opaque Type distribution scope. The Vertex Type is derived from the Opaque Type
field. field; the distribution scope is derived from the LS type field. ARAs
have an area-local scope (LS Type = 10).
The vertex identifier for a Router ARA (R-ARA) is the advertising The Vertex Identifier for an intra-area Router ARA is the advertising
router field of the ARA header. The vertex identifier for a Network router field of the ARA header; for inter-area Router ARAs the vertex
ARA (N-ARA) is contained in the body of the advertisement. A N-ARA may
only identify a single network (i.e., lists of networks are not per- Coltun, Heinanen [Page 23]
mitted). A router may originate multiple (N or R) ARAs each contain- is identified by the advertising router field and the ASBR Router ID
ing different associations or may originate a single (N or R) ARA con- field which is in the body of the advertisement.
taining a list of associations.
The Vertex Identifier for both intra and inter-area Network ARAs is
contained in the network and mask field (which is in the body of the
advertisement). A N-ARA may only identify a single network (i.e.,
lists of networks are not permitted).
ARAs make use of the P-bit in the same as the NSSA option [NSSA].
That is, ARAs may not be advertised beyond area borders unless the P-
bit is set in the original intra-area ARA. See the section entitled
"Originating Inter-Area ARAs" for a further discussion on this topic.
All of a router's associations for a specific vertex may be described
in a single ARA or they may distributed over several ARAs. That is, a
router may originate multiple (N or R) ARAs each containing different
associations or may originate a single (N or R) ARA containing a list
of associations.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type | | LS age | Options | LS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Type | Opaque ID | | Opaque Type | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number | | LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length | | LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LS age LS age
The time in seconds since the ARA was originated. The time in seconds since the ARA was originated.
Options Options
The optional capabilities supported by the described portion The optional capabilities supported by the described portion
of the routing domain. OSPF's optional capabilities are of the routing domain. The ARA uses two option bits.
documented in Section A.2 of [OSPF].
O-bit
This bit describes the router's willingness to
Coltun, Heinanen [Page 24]
receive and forward Opaque-LSAs as specified in
[OPAQ]. All routers supporting the ARA option as
described in this document support the Opaque
option.
P-Bit
ARAs make use of the P-Bit in a manner consistent
with [NSSA]. An ARA may not be advertised beyond
an area border unless the P-bit is set in the ori-
ginal intra-area ARA.
The remainder of OSPF's optional capabilities are documented
in Section A.2 of [OSPF].
LS Type LS Type
The type of the LSA. Each LSA type has a separate The type of the LSA. Each LSA type has a separate advertise-
advertisement format. The AR LSA as defined in this docu- ment format. The ARA LSA as defined in this document are LS
ment may be Type-10 (for N-ARAs and R-ARAs with intra-area Type-10 advertisements (they all have an intra-area scope).
scope) or Type-11 (for ASBR R-ARA with inter-domain scope).
Opaque Type Opaque Type
The link-state ID of the Opaque LSA is divided into an The link-state ID of the Opaque LSA is divided into an
Opaque Type field (the first 8 bits) and an Opaque ID (the Opaque Type field (the first 8 bits) and an Opaque ID (the
remaining 24 bits). The Address Resolution Advertisements remaining 24 bits). The Address Resolution Advertisements
are Opaque-types 1 and 2. Opaque-type 1 advertisements are are Opaque-types 1 - 4. The Opaque Type field identifies
Router Address Resolution Advertisements and contain associ- the Vertex Type.
ations for the advertising router. R-ARAs may be encapsu-
lated in type-10 (Opaque) LSAs when the associations are to
be distributed within the area or encapsulated in type-11
(Opaque) LSAs when the associations are to be coordinated
with inter-area ASBR (LS Type-4) advertisements (i.e., the
router is an ASBR).
Opaque-type 2 advertisements area Network Address Resolution Opaque Type-1 advertisements are intra-area Router Address
Advertisements and contain associations for one of the Resolution Advertisements and contain link-layer associa-
advertising router's directly connected IP networks (or tions for the advertising router. These ARAs are advertised
hosts). N-ARAs are encapsulated in LS Type-10 (Opaque) LSAs throughout the local area.
(i.e., their scope is area local).
Opaque Type-2 advertisements are intra-area Network Address
Resolution Advertisements and contain link-layer associa-
tions for a router's directly connected IP networks (or
hosts). These ARAs are advertised throughout the local
area.
Opaque Type-3 advertisements are inter-area Network Address
Resolution Advertisements and contain link-layer associa-
tions for IP networks that reside in other areas. Inter-
area N-ARAs are coordinated with inter-area network (LS
Type-3) advertisements.
Opaque-type 4 advertisement are inter-area Router Address
Resolution Advertisements and contain link-layer associa-
tions for ASBR that reside in other areas. Inter-area R-
ARAs are coordinated with inter-area ASBR (LS Type-4) adver-
tisements.
Coltun, Heinanen [Page 25]
Opaque ID Opaque ID
A 24-bit semantic-less LSA identifier which serves to dif- A 24-bit semantic-less LSA identifier which serves to dif-
ferentiate between multiple LSAs originated by the same ferentiate between multiple LSAs originated by the same
router. The Opaque ID must be unique for an advertising router. The Opaque ID must be unique for an advertising
router within the advertising scope of the LSA. router within the advertising scope of the LSA.
Advertising Router Advertising Router
The Router ID of the router that originated the ARA. For The Router ID of the router that originated the ARA. For
R-ARAs the Advertising Router also serves as the ARA vertex intra-area R-ARAs the Advertising Router also serves as the
identifier. ARA Vertex Identifier.
LS sequence number LS Sequence Number
Detects old or duplicate ARAs. Successive instances of an Detects old or duplicate ARAs. Successive instances of an
ARA is given successive LS sequence numbers. See Section ARA are given successive LS sequence numbers. See Section
12.1.6 of [OSPF] for more details. 12.1.6 of [OSPF] for more details.
LS checksum LS Checksum
The Fletcher checksum of the complete contents of the ARA, The Fletcher checksum of the complete contents of the ARA,
including the ARA header but excluding the LS age field. See including the ARA header but excluding the LS age field. See
Section 12.1.7 of [OSPF] for more details. Section 12.1.7 of [OSPF] for more details.
Length Length
The length in bytes of the LSA. This includes the 20 byte The length in bytes of the ARA. This includes the 20 byte
ARA header. ARA header.
A.1.2 Router ARAs A.2 Intra-Area Router ARAs
Opaque-type 1 advertisements are Router Address Resolution Advertise- Opaque Type-1 advertisements are intra-area Router Address Resolution
ments and contain associations for the advertising router. R-ARAs may Advertisements and contain associations for the advertising router.
be encapsulated in LS Type-10 (Opaque) LSAs when the associations are
to be distributed within the area or encapsulated in LS Type-11 If the originating router is an ASBR and wishes to have the contents
(Opaque) LSAs when the associations are to be coordinated with inter- of the R-ARA distributed beyond the local area (i.e., translated into
area ASBR (LS Type-4) advertisements (i.e., the router is an ASBR). an inter-area R-ARA), the R-ARA must have the P-bit set in its Options
All of the router's associations may be described in a single R-LSA or field.
they may distributed over several R-LSAs.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 or 11 | | LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Opaque ID | | 1 | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Coltun, Heinanen [Page 26]
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number | | LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length | | LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+ Vertex Association +-+ +-+ Vertex Association +-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+ Vertex Association +-+ +-+ Vertex Association +-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The body of the R-ARA consists of a list of associations for the The body of the R-ARA consists of a list of associations for the
advertising router. Each Vertex Association begins with a common 6- advertising router. Each Vertex Association begins with a common 6-
byte header (described in Section A.1.4) followed by association- byte header (described in Section A.6) followed by association-
specific resolution information (described in Section A.1.5). specific resolution information (described in Section A.7).
A.1.3 Network ARAs A.3 Intra-Area Network ARAs
Opaque-type 2 advertisements area Network Address Resolution Adver-
tisements and contain associations for one of the advertising router's Opaque Type-2 advertisements are intra-area Network Address Resolution
directly connected IP networks (or hosts). N-ARAs are encapsulated in Advertisements and contain associations for one of the advertising
LS Type-10 (Opaque) LSAs (i.e., their scope is area local). router's directly connected IP networks (or hosts).
If the originating router is wishes the contents of the N-ARA are to
be distributed beyond the local area (i.e., translated into an inter-
area N-ARA) the N-ARA must have the P-bit set in its Options field.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 | | LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | Opaque ID | | 2 | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number | | LS Sequence Number |
Coltun, Heinanen [Page 27]
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length | | LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Network Number | | IP Network Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Network Mask | | IP Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+ Vertex Association +-+ +-+ Vertex Association +-+
| | | |
skipping to change at page 22, line 5 skipping to change at page 36, line ?
IP Network Number IP Network Number
One of the router's directly connect network. This number One of the router's directly connect network. This number
represents an IP network/subnet/supernet. represents an IP network/subnet/supernet.
IP Network Mask IP Network Mask
A 32-bit number indicating the range of IP addresses resid- A 32-bit number indicating the range of IP addresses resid-
ing on a single IP network/subnet/supernet. ing on a single IP network/subnet/supernet.
The body of the N-ARA consists of a list of associations for this IP The body of the N-ARA consists of a list of associations for this IP
Network Number. Each Vertex Association begins with a common 6-byte Network Number. Each Vertex Association begins with a common 6-byte
header (described in Section A.1.4) followed by association-specific header (described in Section A.6) followed by association-specific
resolution information (described in Section A.1.5). resolution information (described in Section A.7).
A.1.4 Vertex Association A.4 Inter-Area Network ARAs
Opaque Type-3 advertisements are inter-area Network Address Resolution
Advertisements and contain associations for a remote area's IP net-
works (or hosts). Inter-area N-ARAs are coordinated with LS type-3
advertisements.
Inter-area network ARAs are originated by an area border router into a
target area if 1) the ABR originates a type-3 LSA for the network into
the target area, 2) the network is not included in any of the area
border router's configured area ranges, 3) there is an N-ARA for the
Coltun, Heinanen [Page 28]
network in the source area and 4) the source N-ARA is an intra-area
N-ARA with a P-bit set in the options field (which denotes that the
originator of the N-ARA will allow the N-ARA to be propagated into
other areas) or the source N-ARA is an inter-area N-ARA.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Network Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+ Vertex Association +-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+ Vertex Association +++
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IP Network Number
One of the router's directly connect network. This number
represents an IP network/subnet/supernet.
IP Network Mask
A 32-bit number indicating the range of IP addresses resid-
ing on a single IP network/subnet/supernet.
The body of the N-ARA consists of a list of associations for this IP
Coltun, Heinanen [Page 29]
Network Number. Each Vertex Association begins with a common 6-byte
header (described in Section A.6) followed by association-specific
resolution information (described in Section A.7).
A.5 Inter-Area Router ARAs
Opaque Type-4 advertisements are inter-area Router Address Resolution
Advertisements and contain associations for the an autonomous system
boundary router. Inter-area R-ARAs are coordinated with LS type-4
advertisements.
Inter-area router ARAs are originated into a target area if 1) the ABR
originates a type-4 LSA for the ASBR into the target area, 2) there is
a R-ARA for the ASBR in the source area and 3) the source R-ARA is an
intra-area R-ARA with a P-bit set in the options field (which denotes
that the originator of the R-ARA will allow the R-ARA to be propagated
into other areas) or the source R-ARA is an inter-area R-ARA.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+ Vertex Association +-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+ Vertex Association +-+
| |
Coltun, Heinanen [Page 30]
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASBR Router ID
The router ID of the ASBR being advertised. This field
corresponds to the link-state ID of the LS type-4 advertise-
ment.
The body of the inter-area R-ARA consists of a list of associations
for the advertising router. Each Vertex Association begins with a
common 6-byte header (described in Section A.6) followed by
association-specific resolution information (described in Section
A.7).
A.6 Vertex Association
The Vertex Association field consists of the link service type, The Vertex Association field consists of the link service type,
IntServ service name, administrative weight, association length, logi- IntServ service name, administrative weight, association length, logi-
cal network ID followed by the association-specific resolution infor- cal network ID followed by the association-specific resolution infor-
mation. mation.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Svc Type | IS Svc Name | Admin Weight | Assoc Length + | Link Svc Type | IS Svc Name | Admin Weight | Assoc Length +
skipping to change at page 22, line 31 skipping to change at page 36, line ?
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Remaining Octets of Resolution Information padded to 32-bits + + Remaining Octets of Resolution Information padded to 32-bits +
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Link Svc Type Link Svc Type
Identifies the link-layer functionality for this associa- Identifies the link-layer functionality for this associa-
tion. Link Service Types 1, 2 and 3 are defined by this tion. Link Service Types 1, 2 and 3 are defined by this
specification. All other Link Service Types are reserved specification. All other Link Service Types are reserved
Coltun, Heinanen [Page 31]
for definition by the IANA (iana@isi.edu). The current list for definition by the IANA (iana@isi.edu). The current list
of Link Service Types is described below in Table 1. of Link Service Types is described below in Table 1.
Link Service Type Description Link Service Type Description
------------------------------------------------- -------------------------------------------------
1 ATM Point-To-Point 1 ATM Point-To-Point
2 ATM MultiPoint-To-Point 2 ATM MultiPoint-To-Point
3 ATM Point-To-MultiPoint 3 ATM Point-To-MultiPoint
Table 1 Table 1
IS Svc Name IS Svc Name
The IntServ Service Name. Refer to [IS] as a reference for The IntServ Service Name. Refer to [IS] as a reference for
the IETF defined service specifications. the IETF defined service specifications.
Admin Weight Admin Weight
When more than one equivalent association has been adver- When more than one equivalent association has been adver-
tised for a specific vertex, this field is used to denote tised for a specific vertex, this field is used to denote
the advertising router's preference for each association. the advertising router's preference for each association.
skipping to change at page 23, line 22 skipping to change at page 36, line ?
tised for a specific vertex, this field is used to denote tised for a specific vertex, this field is used to denote
the advertising router's preference for each association. the advertising router's preference for each association.
Equivalent associations are ones that have identical Link Equivalent associations are ones that have identical Link
Service Type, IS Svc Name and Logical Network Identifier Service Type, IS Svc Name and Logical Network Identifier
fields. fields.
Assoc Length Assoc Length
The length in bytes of this association. The length in bytes of this association.
Logical Network ID Logical Network ID
When more than one virtual overlay network is used to estab- When more than one overlay network is used to establish
lish shortcut paths within the OSPF domain, this number shortcut paths within the OSPF domain, this number identi-
identifies a specific virtual overlay network. The router fies a specific logical network. This function may also be
must have an active attachment to the specific logical net- used to support a variation of closed user groups so that
work to use the associated resolution information. An ARA shortcuts are limited to those routers that are configured
capable router is configured with a list of Logical Network to be in the same logical network. To use the association
IDs. The default value (i.e., only one virtual overlay net- information, a router must have an active attachment to the
work or too lazy to care) for the ID is 0. specific logical network identified in the resolution infor-
mation. An ARA capable router is configured with a list of
Logical Network IDs. The default value (i.e., only one
overlay network or too lazy to care) for the ID is 0.
Resolution Information Resolution Information
The resolution information field includes link-layer and The resolution information field includes link-layer and
service-type specific information. The contents of this service-type specific information. The contents of this
field is defined in section A.1.5 of this document. The field is defined in section A.7 of this document. The Ver-
Vertex Association may include several resolution informa- tex Association may include several resolution information
tion items.
A.1.5 Resolution Information Coltun, Heinanen [Page 32]
items.
A.7 Resolution Information
The resolution information field is an extensible field that includes The resolution information field is an extensible field that includes
link-layer and service-type specific information. link-layer and service-type specific information.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Res Type | Res Length | Resolution Value | | Res Type | Res Length | Resolution Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| remaining octets of Resolution Value padded to 32-bits | | remaining octets of Resolution Value padded to 32-bits |
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Res Type Res Type
Identifies the resolution being advertised. Resolution Identifies the resolution being advertised. Resolution
Types 1 and 2 are defined by this specification. Resolution Types 1 and 2 are defined by this specification. Resolution
Type 1 is defined in A.1.6, Type 2 is defined in A.1.7. All Type 1 is defined in A.7.1, Type 2 is defined in A.7.2. All
other resolution types are reserved for definition by the other resolution types are reserved for definition by the
IANA (iana@isi.edu). The current list of resolution types is IANA (iana@isi.edu). The current list of resolution types is
described below in Table 2. described below in Table 2.
Resolution Type Description Resolution Type Description
------------------------------------------------- -------------------------------------------------
1 ATM Address 1 ATM Address
2 ATM LIJ Call Identifier 2 ATM LIJ Call Identification
Table 2 Table 2
Res Length Res Length
The total length in octets of this resolution information The total length in octets of this resolution information
field This value includes the Res Type and Res Length field This value includes the Res Type and Res Length
fields. fields.
Resolution Value Resolution Value
Coltun, Heinanen [Page 33]
The resolution type-specific data. The resolution type-specific data.
A.1.6 ATM Address A.7.1 ATM Address
An ATM address is the Resolution Type 1. This includes the type and An ATM address is the Resolution Type 1. This includes the type and
length of ATM number (8 bits), the type and length of ATM subaddress length of ATM number (8 bits), the type and length of ATM subaddress
(8 bits), the ATM number (x octets) and possibly the ATM subaddress (y (8 bits), the ATM number (x octets) and possibly the ATM subaddress (y
octets). octets).
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| Type And Len Of ATM Number | | Type And Len Of ATM Number |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
skipping to change at page 25, line 32 skipping to change at page 36, line ?
Bit(s) Description Bit(s) Description
------------------------------------------------- -------------------------------------------------
8 Reserved = 0 (for future use) 8 Reserved = 0 (for future use)
7 Type = 0 ATM Forum NSAPA format 7 Type = 0 ATM Forum NSAPA format
= 1 E.164 format = 1 E.164 format
6-1 Length = 6 bit unsigned octet length of 6-1 Length = 6 bit unsigned octet length of
address (MSB = bit.6, LSB = bit.1). address (MSB = bit.6, LSB = bit.1).
Value range is from 0 to 20 (decimal). Value range is from 0 to 20 (decimal).
Coltun, Heinanen [Page 34]
A non-existing ATM subaddress is indicated by setting the subaddress A non-existing ATM subaddress is indicated by setting the subaddress
length to zero. If the subaddress length is zero, the corresponding length to zero. If the subaddress length is zero, the corresponding
type field MUST be ignored and the ATM subaddress field MUST NOT con- type field MUST be ignored and the ATM subaddress field MUST NOT con-
sume any octets in the packet. sume any octets in the packet.
The ATM number and ATM subaddress fields are encoded as defined by the The ATM number and ATM subaddress fields are encoded as defined by the
ATM Forum UNI 3.1 [AF] signalling specification. ATM Forum UNI 3.1 [AF1] signalling specification.
A.7.2 ATM LIJ Call Identification
An ATM LIJ Call Identification is the Resolution Type 2. This
includes an ATM address as defined in A.7.1 followed by a four octet
Leaf Initiated Join Call Identifier Value, which together uniquely
identify an ATM Point-To-Multipoint or Multipoint-To-Point call at a
root's interface.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Address as defined in A.7.1 +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Remaining Octets of ATM Address +
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf Initiated Join Call Identifier Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format Of LIJ Call Identification
The Leaf Initiated Join Call Identifier Value is encoded as defined in
Section 6.1.2.1 of the ATM Forum UNI 4.0 [AF2] signalling specifica-
tion.
References References
[AF] ATM Forum, "ATM User-Network Interface (UNI) Specification
[AF1] ATM Forum, "ATM User-Network Interface (UNI) Specification
Version 3.1.", ISBN 0-13-393828-X, Prentice-Hall, Inc., Upper Version 3.1.", ISBN 0-13-393828-X, Prentice-Hall, Inc., Upper
Coltun, Heinanen [Page 35]
Saddle River, NJ, 07458, September, 1994. Saddle River, NJ, 07458, September, 1994.
[AF2] ATM Forum, "ATM User-Network Interface (UNI) Signalling
Specification", July 1996.
[HEIN] Heinanen, J., "Intra-area IP unicast among routers over legacy ATM", [HEIN] Heinanen, J., "Intra-area IP unicast among routers over legacy ATM",
Internet Draft, July 1997, <draft-ietf-ion-intra-area-unicast-00.txt> Internet Draft, July 1997, <draft-ietf-ion-intra-area-unicast-00.txt>
[IS] S. Shenker and J. Wroclawski. "Network Element QoS Control [IS] S. Shenker and J. Wroclawski. "Network Element QoS Control
Service Specification Template". Internet Draft, July 1996, <draft- Service Specification Template". Internet Draft, July 1996, <draft-
ietf-intserv-svc-template-03.txt> ietf-intserv-svc-template-03.txt>
[OPAQ] Coltun, R., "The OSPF Opaque LSA Option", Internet Draft [OPAQ] Coltun, R., "The OSPF Opaque LSA Option", Internet Draft
May 1997, <draft-ietf-ospf-opaque-01.txt> May 1997, <draft-ietf-ospf-opaque-01.txt>
[OSPF] Moy, J., "OSPF Version 2", RFC 2178, July 1997 [OSPF] Moy, J., "OSPF Version 2", RFC 2178, July 1997
[NHRP] Luciani, J., Katz, D., Piscitello, D., Cole, B., "NBMA [NHRP] Luciani, J., Katz, D., Piscitello, D., Cole, B., "NBMA
Next-Hop Resolution Protocol", Internet Draft, March 1997, Next-Hop Resolution Protocol", Internet Draft, March 1997,
<draft-ietf-rolc-nhrp-11.txt> <draft-ietf-rolc-nhrp-11.txt>
[NSSA] Coltun, R. and V. Fuller, "The OSPF NSSA Option", RFC 1587,
RainbowBridge Communications, Stanford University, March 1994.
 End of changes. 

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