draft-ietf-ospf-mt-06.txt   draft-ietf-ospf-mt-07.txt 
Network Working Group P. Psenak Network Working Group P. Psenak
Internet-Draft S. Mirtorabi Internet-Draft Cisco Systems
Expires: August 5, 2006 A. Roy Intended status: Standards Track S. Mirtorabi
Expires: May 31, 2007 Force10 Networks
A. Roy
L. Nguyen L. Nguyen
P. Pillay-Esnault P. Pillay-Esnault
Cisco Systems Cisco Systems
February 1, 2006 November 27, 2006
Multi-Topology (MT) Routing in OSPF Multi-Topology (MT) Routing in OSPF
draft-ietf-ospf-mt-06.txt draft-ietf-ospf-mt-07.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 37 skipping to change at page 1, line 39
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 5, 2006. This Internet-Draft will expire on May 31, 2007.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
This draft describes an extension to OSPF in order to define This draft describes an extension to Open Shortest Path First (OSPF)
independent IP topologies called Multi-Topologies (MTs). The MT in order to define independent IP topologies called Multi-Topologies
extension can be used for computing different paths for unicast (MTs). The Multi-Topologies extension can be used for computing
traffic, multicast traffic, different classes of service based on different paths for unicast traffic, multicast traffic, different
flexible criteria, or an in-band network management topology. classes of service based on flexible criteria, or an in-band network
management topology.
[M-ISIS] describes a similar mechanism for ISIS.
An optional extension to exclude selected links from the default An optional extension to exclude selected links from the default
topology is also described. topology is also described.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Differences with RFC 1583 TOS Based Routing . . . . . . . 4 1.1. Differences between Multi-Topology and TOS Based
Routing . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Requirements notation . . . . . . . . . . . . . . . . . . 5 2.1. Requirements notation . . . . . . . . . . . . . . . . . . 5
2.2 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Base MT Functional Specifications . . . . . . . . . . . . . . 6 3. Base MT Functional Specifications . . . . . . . . . . . . . . 6
3.1 MT Area Boundary . . . . . . . . . . . . . . . . . . . . . 6 3.1. MT Area Boundary . . . . . . . . . . . . . . . . . . . . . 6
3.2 Adjacency for MTs . . . . . . . . . . . . . . . . . . . . 6 3.2. Adjacency for MTs . . . . . . . . . . . . . . . . . . . . 6
3.3 Sending OSPF control packets . . . . . . . . . . . . . . . 6 3.3. Sending OSPF control packets . . . . . . . . . . . . . . . 6
3.4 Advertising MT Adjacencies and the Corresponding IP 3.4. Advertising MT Adjacencies and the Corresponding IP
Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . 6 Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4.1 Advertising MT Adjacencies and the Corresponding 3.4.1. Inter-Area and External Routing . . . . . . . . . . . 7
IP Prefixes . . . . . . . . . . . . . . . . . . . . . 6 3.5. Flushing MT Information . . . . . . . . . . . . . . . . . 7
3.4.2 Inter-Area and External Routing . . . . . . . . . . . 7 3.6. MT SPF Computation . . . . . . . . . . . . . . . . . . . . 7
3.5 Flushing MT Information . . . . . . . . . . . . . . . . . 7 3.7. MT-ID Values . . . . . . . . . . . . . . . . . . . . . . . 7
3.6 MT SPF Computation . . . . . . . . . . . . . . . . . . . . 7 3.8. Forwarding in MT . . . . . . . . . . . . . . . . . . . . . 8
3.7 MT-ID Values . . . . . . . . . . . . . . . . . . . . . . . 8
3.8 Forwarding in MT . . . . . . . . . . . . . . . . . . . . . 8
4. Default Topology Link Exclusion Functional Specifications . . 9 4. Default Topology Link Exclusion Functional Specifications . . 9
4.1 Exclusion of Links in the Default Topology . . . . . . . . 9 4.1. Exclusion of Links in the Default Topology . . . . . . . . 9
4.2 New Area Data Structure Parameter . . . . . . . . . . . . 9 4.2. New Area Data Structure Parameter . . . . . . . . . . . . 9
4.3 Adjacency Formation with Link Exclusion Capability . . . . 10 4.3. Adjacency Formation with Link Exclusion Capability . . . . 10
4.4 OSPF Control Packets Transmission Over Excluded Links . . 11 4.4. OSPF Control Packets Transmission Over Excluded Links . . 11
4.5 OSPF LSA Advertisement and SPF Computation for 4.5. OSPF LSA Advertisement and SPF Computation for
Excluded Links . . . . . . . . . . . . . . . . . . . . . . 11 Excluded Links . . . . . . . . . . . . . . . . . . . . . . 11
5. Interoperability between MT Capable and Non-MT Capable 5. Interoperability between MT Capable and Non-MT Capable
Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 Demand Circuit Compatibility Considerations . . . . . . . 12 5.1. Demand Circuit Compatibility Considerations . . . . . . . 12
6. Migration from non-MT-Area to MT-area . . . . . . . . . . . . 13 6. Migration from non-MT-Area to MT-area . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1 Normative References . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16
9.2 Informative References . . . . . . . . . . . . . . . . . . 16 9.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 16 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 17
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 Appendix B. OSPF data formats . . . . . . . . . . . . . . . . . . 18
B. OSPF data formats . . . . . . . . . . . . . . . . . . . . . . 19 B.1. Router-LSAs . . . . . . . . . . . . . . . . . . . . . . . 18
B.1 Router-LSAs . . . . . . . . . . . . . . . . . . . . . . . 19 B.2. Network-LSAs . . . . . . . . . . . . . . . . . . . . . . . 19
B.2 Network-LSAs . . . . . . . . . . . . . . . . . . . . . . . 20 B.3. Summary-LSAs . . . . . . . . . . . . . . . . . . . . . . . 19
B.3 Summary-LSAs . . . . . . . . . . . . . . . . . . . . . . . 20 B.4. AS-external-LSAs . . . . . . . . . . . . . . . . . . . . . 20
B.4 AS-External-LSAs . . . . . . . . . . . . . . . . . . . . . 21 B.5. Type-7 AS-external-LSAs . . . . . . . . . . . . . . . . . 22
B.5 NSSA-LSAs . . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . 23 Intellectual Property and Copyright Statements . . . . . . . . . . 24
1. Introduction 1. Introduction
OSPF uses a fixed packet format, therefore it is not easy to OSPF uses a fixed packet format, therefore it is not easy to
introduce any backward compatible extensions. However, the OSPF introduce any backward compatible extensions. However, the OSPF
specification [OSPF] introduced TOS metric in an earlier specification [OSPF] introduced Type of Service (TOS) metric in an
specification [RFC1583] in order to announce a different link cost earlier specification [TOS-OSPF] in order to announce a different
based on TOS. TOS based routing as described in [RFC1583] was never link cost based on TOS. TOS based routing as described in [TOS-OSPF]
deployed and was subsequently deprecated. was never deployed and was subsequently deprecated. [M-ISIS]
describes a similar mechanism for ISIS.
We propose to reuse the TOS based metric fields. They have been We propose to reuse the TOS based metric fields. They have been
redefined as MT-ID and MT-ID Metric and are used to advertise redefined and are used to advertise different topologies by
different topologies by advertising separate metrics for each of advertising separate metrics for each of them.
them.
1.1 Differences with RFC 1583 TOS Based Routing 1.1. Differences between Multi-Topology and TOS Based Routing
Multi-topology routing differs from RFC 1583 TOS based routing in the Multi-Topology routing differs from [TOS-OSPF] TOS based routing in
following ways: the following ways:
1. With RFC 1583 TOS routing, the TOS or DSCP in the IP header is 1. With TOS routing [TOS-OSPF], the TOS or DSCP in the IP header is
mapped directly to the the corresponding OSPF SPF calculation and mapped directly to the corresponding OSPF SPF calculation and
routing table. This limits the number and definition of the routing table. This limits the number and definition of the
topologies to the 16 TOS values specified is section 12.3 of RFC topologies to the 16 TOS values specified in section 12.3 of
1583 [RFC1583]. With multi-topology routing, the classification [TOS-OSPF]. With Multi-Topology routing, the classification of
of what type of traffic maps to which topology is not within the what type of traffic maps to which topology is not within the
scope of the document. scope of the document.
2. With RFC 1583 TOS routing, traffic which is unreachable in the 2. With TOS routing [TOS-OSPF], traffic which is unreachable in the
routing table associated with the corresponding TOS will revert routing table associated with the corresponding TOS will revert
to the TOS 0 routing table. With multi-topology routing, this is to the TOS 0 routing table. With Multi-Topology routing, this is
optional. optional.
3. With RFC 1583 TOS routing, individual links or prefixes could not 3. With TOS routing [TOS-OSPF], individual links or prefixes could
be excluded from a topology. If the LSA options T-bit was set, not be excluded from a topology. If the LSA options T-bit was
all links or prefixes were either advertised explicitly or set, all links or prefixes were either advertised explicitly or
defaulted to the TOS 0 metric. With multi-topology routing, defaulted to the TOS 0 metric. With Multi-Topology routing,
links or prefixes that are not advertised for a specific topology links or prefixes that are not advertised for a specific topology
do not exist in that topology. do not exist in that topology.
2. Terminology 2. Terminology
2.1 Requirements notation 2.1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119]. document are to be interpreted as described in RFC 2119
[RFC-KEYWORDS].
2.2 Terms 2.2. Terms
We define the following terminology in this document: We define the following terminology in this document:
Non-MT router Non-MT router
Routers that do not have the MT capability Routers that do not have the MT capability
MT router MT router
Routers that have MT capability as described in this document Routers that have MT capability as described in this document
MT-ID MT-ID
Renamed TOS field in LSAs to represent multitopology ID. Renamed TOS field in LSAs to represent Multi-Topology ID.
Default topology Default topology
Topology that is built using the TOS 0 metric (default metric) Topology that is built using the TOS 0 metric (default metric)
MT topology MT topology
Topology that is built using the corresponding MT-ID metric Topology that is built using the corresponding MT-ID metric
MT MT
Shorthand notation for MT topology Shorthand notation for MT topology
skipping to change at page 6, line 7 skipping to change at page 6, line 7
Non-MT-Area Non-MT-Area
An area that contains only non-MT routers An area that contains only non-MT routers
MT-Area MT-Area
An area that contains both non-MT routers and MT routers or only An area that contains both non-MT routers and MT routers or only
MT routers MT routers
3. Base MT Functional Specifications 3. Base MT Functional Specifications
3.1 MT Area Boundary 3.1. MT Area Boundary
Each OSPF interface belongs to a single area and all MTs sharing that Each OSPF interface belongs to a single area and all MTs sharing that
link need to belong to the same area. Therefore the area boundaries link need to belong to the same area. Therefore the area boundaries
for all MTs are the same but each MT's attachment to the area is for all MTs are the same but each MT's attachment to the area is
independent. independent.
3.2 Adjacency for MTs 3.2. Adjacency for MTs
Each interface can be configured to belong to a set of topologies. A Each interface can be configured to belong to a set of topologies. A
single adjacency will be formed with neighbors on the interface even single adjacency is formed with neighbors on the interface even if
if the interface is configured to participate in multiple topologies. the interface is configured to participate in multiple topologies.
Furthermore, adjacency formation will be independent of the Furthermore, adjacency formation is independent of the topologies
topologies configured for the interface or neighbors on that configured on the local interface and the neighboring router.
interface.
3.3 Sending OSPF control packets 3.3. Sending OSPF control packets
Sending OSPF control packets is unchanged from RFC2328. For OSPF Sending OSPF control packets is unchanged from [OSPF]. For OSPF
control packets sent to the remote end of a virtual link, the transit control packets sent to the remote end of a virtual link, the transit
area path MUST be composed solely of links in the default topology area path MUST be composed of links participating in the default
and the OSPF control packets MUST be forwarded using the default topology and the OSPF control packets MUST be forwarded using the
topology. default topology.
3.4 Advertising MT Adjacencies and the Corresponding IP Prefixes 3.4. Advertising MT Adjacencies and the Corresponding IP Prefixes
We will reuse the TOS metric field in order to advertise a topology The TOS metric field is reused to advertise topology specific metric
and prefixes belonging to that topology. The TOS field is redefined for links and prefixes belonging to that topology. The TOS field is
as MT-ID in the payload of Router-LSAs, Summary-LSAs, NSSA-LSAs, and redefined as MT-ID in the payload of Router, Summary, Type-5 and
AS-External-LSAs (see Appendix A). Type-7 AS-external LSAs (see Appendix A).
MT-ID metrics in LSAs SHOULD be in ascending order of MT-ID. If an MT-ID metrics in LSAs SHOULD be in ascending order of MT-ID. If an
MT-ID exists in an LSA or router link multiple times, the metric in MT-ID exists in an LSA or router link multiple times, the metric in
the first MT-ID instance MUST be used. the first MT-ID instance MUST be used.
3.4.1 Advertising MT Adjacencies and the Corresponding IP Prefixes
When a router establishes a FULL adjacency over a link that belongs When a router establishes a FULL adjacency over a link that belongs
to a set of MTs, it will advertise the corresponding cost for each to a set of MTs, it advertises the corresponding cost for each MT-ID.
MT-ID.
By default, all links are included in default topology and all By default, all links are included in the default topology and all
advertised prefixes belonging to the default topology will use the advertised prefixes belonging to the default topology will use the
TOS0 metric the same as in standard OSPF [OSPF]. TOS0 metric as in [OSPF].
Each MT has its own MT-ID metric field. When a link is not part of a Each MT has its own MT-ID metric field. When a link is not part of a
given MT, the corresponding MT-ID metric is excluded from the LSA. given MT, the corresponding MT-ID metric is excluded from the LSA.
The Network-LSA does not contain any MT information since the DR is The Network-LSA does not contain any MT information since the
shared by all MTs. Hence, there is no change to the Network-LSA. Designated Router (DR) is shared by all MTs. Hence, there is no
change to the Network-LSA.
3.4.2 Inter-Area and External Routing 3.4.1. Inter-Area and External Routing
In Summary-LSAs, NSSA-LSAs, and AS-External-LSAs, the TOS metric In Summary-LSAs, Type-5 and Type-7 AS-external-LSAs the TOS metric
fields are defined as MT-ID metric fields and are used in order to fields are redefined as MT-ID metric fields and are used to advertise
advertise prefix and router reachability in the corresponding prefix and router reachability in the corresponding topology.
topology.
When a router originates a Summary-LSA, NSSA-LSA, or AS-External-LSA When a router originates a Summary-LSA, Type-5 or Type-7 AS-external-
that belongs to a set of MTs, it will include the corresponding cost LSA that belongs to a set of MTs, it includes the corresponding cost
for each MT-ID. By default, the router participates in the default for each MT-ID. By default, the prefix participates in the default
topology and uses the TOS0 metric for the default topology the same topology and uses the TOS0 metric for the default topology, similar
as in standard OSPF [OSPF]. to standard OSPF [OSPF].
Setting the P-bit in NSSA-LSAs is topology independent and pertains Setting the P-bit in Type-7 AS-external-LSA is topology independent
to all MT-ID advertised in the body of the LSA. and pertains to all MT-ID advertised in the body of the LSA.
3.5 Flushing MT Information 3.5. Flushing MT Information
When a certain link or prefix that existed or was reachable in a When a certain link or prefix that existed or was reachable in a
certain topology is no longer part of that topology or is unreachable certain topology is no longer part of that topology or is unreachable
in that topology, a new version of the LSA must be originated in that topology, a new version of the LSA MUST be originated
excluding metric information representing the link or prefix in that excluding metric information representing the link or prefix in that
topology. topology.
The MT metric in the Router-LSA can also be set to the maximum The MT metric in the Router-LSA can also be set to the maximum
possible metric to enable the router to become a stub in a certain possible metric to enable the router to become a stub in a certain
topology [STUB]. topology [STUB].
3.6 MT SPF Computation 3.6. MT SPF Computation
By considering MT-ID metrics in the LSAs, OSPF will be able to By considering MT-ID metrics in the LSAs, OSPF computes multiple
compute multiple topologies and find paths to IP prefixes for each MT topologies and finds paths to IP prefixes for each MT independently.
independently. A separate SPF will be computed for each MT-ID to A separate SPF will be computed for each MT-ID to find independent
find independent paths to IP prefixes. Each nexthop computed during paths to IP prefixes.
the MT SPF MUST belong to the same MT.
Network-LSAs are used by all topologies during the SPF computation. Network-LSAs are used by all topologies during the SPF computation.
During the SPF for a given MT-ID, only the links and metrics for that During the SPF for a given MT-ID, only the links and metrics for that
MT-ID will be considered. Entries in the Router Routing table will MT-ID are considered. Entries in the Router Routing table are also
be MT-ID specific. MT-ID specific.
During the SPF computation for the default topology only the TOS0
metric is considered during the SPF computation.
3.7 MT-ID Values 3.7. MT-ID Values
Since AS-External-LSAs use the high order bit in the MT-ID field (E Since AS-External-LSAs use the high order bit in the MT-ID field (E
bit) for the external metric-type, only MT-IDs in the range [0-127] bit) for the external metric-type, only MT-IDs in the 0 to 127 range
are valid. The following MT-ID values are reserved: are valid. The following MT-ID values are reserved:
0 - Reserved for advertising the metric associated with the 0 - Reserved for advertising the metric associated
default topology (see Section 4.2) with the default topology (see Section 4.2)
1 - Reserved for advertising the metric associated
1 - Reserved for advertising the metric associated with the with the default multicast topology
default multicast topology 2-127 - Reserved for definition as per local policy and
configuration
MT-IDs [128-255] SHOULD be ignored. 128-255 - Invalid and SHOULD be ignored.
3.8 Forwarding in MT 3.8. Forwarding in MT
It's outside of the scope of this document to specify how the It is outside of the scope of this document to specify how the
information in various topology specific forwarding structures are information in various topology specific forwarding structures are
used during packet forwarding or how incoming packets are associated used during packet forwarding or how incoming packets are associated
with the corresponding topology. For correct operation, both with the corresponding topology. For correct operation, both
forwarding behavior and methods of associating incoming packets to a forwarding behavior and methods of associating incoming packets to a
corresponding topology must be consistently applied in the network. corresponding topology must be consistently applied in the network.
4. Default Topology Link Exclusion Functional Specifications 4. Default Topology Link Exclusion Functional Specifications
The multi-topologies imply that all the routers participate in the The Multi-Topologies imply that all the routers participate in the
default topology. However, it can be useful to exclude some links default topology. However, it can be useful to exclude some links
from the default topology and reserve them for some specific classes from the default topology and reserve them for some specific classes
of traffic. of traffic.
The multi-topologies extension for default topology link or prefix The Multi-Topologies extension for the default topology link or
exclusion is described in the following subsections. prefix exclusion is described in the following subsections.
4.1 Exclusion of Links in the Default Topology 4.1. Exclusion of Links in the Default Topology
OSPF does not have the notion of an unreachable link. All links can OSPF does not have the notion of an unreachable link. All links can
have a maximum metric of 0xFFFF advertised in the Router-LSA. The have a maximum metric of 0xFFFF advertised in the Router-LSA. The
link exclusion capability requires routers to ignore TOS0 metrics in link exclusion capability requires routers to ignore TOS0 metrics in
Router-LSAs in the default topology and to alternately use the MT- Router-LSAs in the default topology and to alternately use the MT-
ID#0 metric to advertise the metric associated with the default ID#0 metric to advertise the metric associated with the default
topology. Hence, all routers within an area MUST agree on how the topology. Hence, all routers within an area MUST agree on how the
metric for default topology will be advertised. metric for the default topology will be advertised.
The unused T-bit is defined as the MT-bit in the option field in The unused T-bit is defined as the MT-bit in the option field in
order to assure that a multi-topology link-excluding capable router order to assure that a Multi-Topology link-excluding capable router
will only form an adjacency with another similarly configured router. will only form an adjacency with another similarly configured router.
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
|DN |O |DC |EA |NP |MC |E |MT | |DN |O |DC |EA |NP |MC |E |MT |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
MT-bit: If DefaultExclusionCapability is enable, this bit MUST Figure 1: OSPF Option Bits
MT-bit: If DefaultExclusionCapability is enabled, the bit MUST
be set in Hello packets and SHOULD be set in Database be set in Hello packets and SHOULD be set in Database
Description packet (see Section 4.2). Description packet (see Section 4.2).
4.2 New Area Data Structure Parameter 4.2. New Area Data Structure Parameter
We define a new parameter in the Area Data Structure: We define a new parameter in the Area Data Structure:
DefaultExclusionCapability DefaultExclusionCapability
This configurable parameter ensures that all routers in an area This configurable parameter ensures that all routers in an area
have this capability enabled before the default topology can be have this capability enabled before the default topology can be
disabled on a router link in the area without causing backward disabled on a router link in the area without causing backward
compatibility problems. compatibility problems.
When an area data structure is created the DefaultExclusionCapability When an area data structure is created, the
is disabled by default. DefaultExclusionCapability is disabled by default.
If DefaultExclusionCapability is disabled: If DefaultExclusionCapability is disabled:
o The MT-bit MUST be cleared in Hello packet and SHOULD be cleared o The MT-bit MUST be cleared in Hello packet and SHOULD be cleared
in Database Description packets. in Database Description packets.
o If a link participates in a non-default topology, it is o If a link participates in a non-default topology, it is
automatically included in the default topology to support backward automatically included in the default topology to support backward
compatibility between MT and non-MT routers. This is accomplished compatibility between MT and non-MT routers. This is accomplished
through advertisement via the TOS0 metric field the same as in using the TOS0 metric field as in [OSPF].
standard OSPF [OSPF].
If DefaultExclusionCapability is enabled: If DefaultExclusionCapability is enabled:
o The MT-bit MUST be set in Hello and SHOULD be set in Database o The MT-bit MUST be set in Hello packets and SHOULD be set in
Description packets Database Description packets.
o The router will only accept a Hello packet if the MT-bit is set o The router will only accept a Hello packet if the MT-bit is set
(see Section 4.3) (see Section 4.3).
When DefaultExclusionCapability is set to enabled a router is said to When DefaultExclusionCapability is set to enabled a router is said to
be operating in DefaultExclusionCapability mode. be operating in DefaultExclusionCapability mode.
4.3 Adjacency Formation with Link Exclusion Capability 4.3. Adjacency Formation with Link Exclusion Capability
In order to have a smooth transition from a non-MT area to an MT- In order to have a smooth transition from a non-MT area to an MT-
area, an MT router with DefaultExclusionCapability disabled will form area, an MT router with DefaultExclusionCapability disabled will form
adjacencies with non-MT routers and will include all links as part of adjacencies with non-MT routers and will include all links as part of
default topology. the default topology.
A link may cease participating in default topology if A link may cease participating in the default topology if
DefaultExclusionCapability is set to enabled. In this state, a DefaultExclusionCapability is set to enabled. In this state, a
router will only form adjacency with routers that set the MT-bit in router will only form adjacency with routers that set the MT-bit in
their Hello packets. This will ensure that all routers have their Hello packets. This will ensure that all routers have
DefaultExclusionCapability enabled before the default topology can be DefaultExclusionCapability enabled before the default topology can be
disabled on a link. disabled on a link.
Receiving OSPF Hello packets as defined in section 10.5 of [OSPF] is Receiving OSPF Hello packets as defined in section 10.5 of [OSPF] is
modified as follows: modified as follows:
o If the DefaultExclusionCapability in the Area Data structure is o If the DefaultExclusionCapability in the Area Data structure is
set to enabled, Hello packets are discarded if the the received set to enabled, Hello packets are discarded if the received packet
packet does not have the MT-bit set in the header options. does not have the MT-bit set in the Header Options.
Receiving OSPF Database Description packets as defined in section Receiving OSPF Database Description packets as defined in section
10.6 of [OSPF] is unchanged. While packet options are validated in 10.6 of [OSPF] is unchanged. While packet options are validated in
hello packets, the only option checking performed for Database Hello packets, the only option checking performed for Database
Description packets is assuring that the options do not change during Description packets is assuring that the options do not change during
the database exchange process. the database exchange process.
4.4 OSPF Control Packets Transmission Over Excluded Links 4.4. OSPF Control Packets Transmission Over Excluded Links
If DefaultExclusionCapability is enabled, the default topology can be If DefaultExclusionCapability is enabled, the default topology can be
disabled on an interface. Disabling the default topology on an disabled on an interface. Disabling the default topology on an
interface does not impact the installation of connected routes for interface does not impact the installation of connected routes for
the interface in the default topology. It only affects what a router the interface in the default topology. It only affects what a router
advertises in its Router-LSA. advertises in its Router-LSA.
This allows OSPF control packets to be sent and received over an This allows OSPF control packets to be sent and received over an
interface even if the default topology is disabled on the interface. interface even if the default topology is disabled on the interface.
4.5 OSPF LSA Advertisement and SPF Computation for Excluded Links 4.5. OSPF LSA Advertisement and SPF Computation for Excluded Links
When DefaultExclusionCapability is enabled and the link does not When DefaultExclusionCapability is enabled and the link does not
participate in the default topology, the MT-ID#0 metric is not participate in the default topology, MT-ID#0 metric is not
advertised. The link's TOS0 metric is ignored during the default advertised. The link's TOS0 metric is ignored during the default
topology SPF computation. topology SPF computation.
When DefaultExclusionCapability is enabled and a link participates in When DefaultExclusionCapability is enabled and a link participates in
the default topology, MT-ID#0 metric is used to advertise the metric the default topology, MT-ID#0 metric is used to advertise the metric
associated with the default topology. The link's TOS0 metric is associated with the default topology. The link's TOS0 metric is
ignored during the default topology SPF computation. ignored during the default topology SPF computation.
Independent of the DefaultExclusionCapability setting, the TOS0 Independent of the DefaultExclusionCapability, the TOS0 metric is
metric is used for Summary-LSAs, NSSA-LSAs, and AS-External-LSAs. used for Summary-LSAs, Type-5 and Type-7 AS-external-LSAs.
o If the prefix or router does not exist in the default topology, o If the prefix or router does not exist in the default topology,
the TOS0 metric is set to infinity (0xFFFFFF). the TOS0 metric is set to infinity (0xFFFFFF).
o If the prefix or router exists in default the topology, the TOS0 o If the prefix or router exists in the default topology, the TOS0
metric is used to advertise the metric in the default topology. metric is used to advertise the metric in the default topology.
During the summary and external prefix calculation for the default During the summary and external prefix calculation for the default
topology the TOS0 metric is used for Summary-LSAs, NSSA-LSAs, and AS- topology the TOS0 metric is used for Summary-LSAs, Type-5 and Type-7
External-LSAs. AS-external-LSAs.
5. Interoperability between MT Capable and Non-MT Capable Routers 5. Interoperability between MT Capable and Non-MT Capable Routers
The default metric field is mandatory in all LSAs (even when metric The default metric field is mandatory in all LSAs (even when metric
value is 0). Even when a link or prefix does not exist in the value is 0). Even when a link or prefix does not exist in the
default topology, a non-MT router will consider the zero value in the default topology, a non-MT router will consider the zero value in the
metric field as a valid metric and consider the link or prefix as metric field as a valid metric and consider the link or prefix as
part of the default topology. part of the default topology.
In order to prevent the above problem, an MT capable router will In order to prevent the above problem, an MT capable router will
include all links as part of the default topology. If links need to include all links as part of the default topology. If links need to
be removed from the default topology, an MT capable router MUST be be removed from the default topology, an MT capable router must be
configured in DefaultExclusionCapability mode. In this mode, configured in DefaultExclusionCapability mode. In this mode, routers
routers will assure that all other routers in the area are in the will assure that all other routers in the area are in the
DefaultExclusionCapability mode before considering the MT-ID#0 metric DefaultExclusionCapability mode before considering the MT-ID#0 metric
in the SPF calculation. Only then can the TOS0 metric field in in the SPF calculation. Only then the TOS0 metric field in Router
Router LSAs be safely ignored during the default topology SPF LSAs can be safely ignored during the default topology SPF
computation. computation.
Note that for any prefix or router to become reachable in a certain Note that for any prefix or router to become reachable in a certain
topology, a contiguous path inside that topology must exist between topology, a contiguous path inside that topology must exist between
the calculating router and the destination prefix or router. the calculating router and the destination prefix or router.
5.1 Demand Circuit Compatibility Considerations 5.1. Demand Circuit Compatibility Considerations
A change to an area's DefaultExclusionCapability requires additional A change to an area's DefaultExclusionCapability requires additional
processing for area neighbors that are suppressing hellos as processing for area neighbors that are suppressing Hello packets as
specified in "Extending OSPF to Support Demand Circuits" [DEMAND]. specified in "Extending OSPF to Support Demand Circuits" [DEMAND].
When the DefaultExclusionCapability for an area is changed, hello When the DefaultExclusionCapability for an area is changed, Hello
suppression must be disabled for these neighbors for a period of suppression must be disabled for these neighbors for a period of
RouterDeadInterval seconds. This implies that hello packets are sent RouterDeadInterval seconds. This implies that Hello packets are sent
with the DC bit clear as specified in section 3.2.1 of [DEMAND] with the DC bit clear as specified in section 3.2.1 of [DEMAND]
during this period. After RouterDeadInterval seconds, either the during this period. After RouterDeadInterval seconds, either the
adjacency will be taken down due to rejection of hellos with a adjacency will be taken down due to rejection of Hello packets with a
conflicting MT-bit or hello suppression will be renegotiated. conflicting MT-bit or Hello suppression will be renegotiated.
6. Migration from non-MT-Area to MT-area 6. Migration from non-MT-Area to MT-area
Introducing MT-OSPF into a network can be done gradually to allow MT Introducing MT-OSPF into a network can be done gradually to allow MT
routers and non-MT routers to participate in the default topology routers and non-MT routers to participate in the default topology
while MT routers participate in other topologies. while MT routers participate in other topologies.
If there is a requirement to exclude some links from the default If there is a requirement to exclude some links from the default
topology in an area, all routers in the area MUST be in topology in an area, all routers in the area MUST be in
DefaultExclusionCapability mode. In this section we describe the DefaultExclusionCapability mode. In this section we describe the
skipping to change at page 13, line 30 skipping to change at page 13, line 30
1. As required, part of an area is upgrade to be MT capable. The MT 1. As required, part of an area is upgrade to be MT capable. The MT
routers will interact with non-MT routers in the default topology routers will interact with non-MT routers in the default topology
and participate in other topologies as required. and participate in other topologies as required.
2. If a new non-backbone area is created for MT routers, it may be 2. If a new non-backbone area is created for MT routers, it may be
configured in DefaultExclusionCapability mode since there is no configured in DefaultExclusionCapability mode since there is no
interaction required with non-MT routers. In this mode, the interaction required with non-MT routers. In this mode, the
default topology can be excluded on links as required. default topology can be excluded on links as required.
3. If there is more than one non-backbone areas where MT is being 3. If there are several non-backbone areas where MT is being used,
used, it is desirable that the backbone area first be upgraded to it is desirable that the backbone area first be upgraded to be MT
be MT capable so that inter-area routing is assured for MT capable so that inter-area routing is assured for MT destinations
destinations in different areas. in different areas.
4. Gradually the whole network can be made MT capable. 4. Gradually the whole network can be made MT capable.
Note that inter-area routing for the MT-area still depends on the Note that inter-area routing for the MT-area still depends on the
backbone area. Therefore, if different areas configured for a given backbone area. Therefore, if different areas configured for a given
topology need to communicate, the backbone area also needs to be topology need to communicate, the backbone area also needs to be
configured for this topology. configured for this topology.
7. Security Considerations 7. Security Considerations
This document does not raise any security issues that are not already This document does not raise any security issues that are not already
covered in [OSPF]. covered in [OSPF].
8. IANA Considerations 8. IANA Considerations
The T-bit as defined in [RFC1583] for a router's TOS capability is The T-bit as defined in [TOS-OSPF] for a router's TOS capability is
redefined as the MT-bit in this document. Similarly, the TOS field redefined as the MT-bit in this document. No IANA action is required
for Router-LSAs, Summary-LSAs, NSSA-LSAs, and AS-External LSAs as for the MT-bit.
defined in [OSPF] is redefined as MT-ID in this document.
Similarly, the TOS field for Router-LSAs, Summary-LSAs, Type-5 and
Type-7 AS-external LSAs as defined in [OSPF] is redefined as MT-ID in
Section 3.7.
MT-ID space is one byte and the entire range is defined by this
document. No IANA action is required to manage the MT-ID space.
9. References 9. References
9.1 Normative References 9.1. Normative References
[DEMAND] Moy, J., "Extending OSPF to Support Demand Circuits", [DEMAND] Moy, J., "Extending OSPF to Support Demand Circuits",
RFC 1793, April 1995. RFC 1793, April 1995.
[NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", [NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, January 2003. RFC 3101, January 2003.
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. [RFC-KEYWORDS]
Bradner, S., "Key words for use in RFC's to Indicate
[RFC2119] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2119, March 1997. Requirement Levels", RFC 2119, March 1997.
9.2 Informative References [TOS-OSPF]
Moy, J., "OSPF Version 2", RFC 1583, March 1994.
9.2. Informative References
[M-ISIS] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi [M-ISIS] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in IS-IS", Topology (MT) Routing in IS-IS",
draft-ietf-isis-wg-multi-topology-07.txt (work in draft-ietf-isis-wg-multi-topology-07.txt (work in
progress). progress).
[STUB] Retana, A., Nguyen, L., White, R., Zinin, A., and D. [STUB] Retana, A., Nguyen, L., White, R., Zinin, A., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 3137, McPherson, "OSPF Stub Router Advertisement", RFC 3137,
June 2001. June 2001.
Authors' Addresses
Peter Psenak
Cisco Systems
Parc Pegasus, De Kleetlaan 6A
1831 Diegem
Belgium
Email: ppsenak@cisco.com
Sina Mirtorabi
Cisco Systems
225 West Tasman Drive
San Jose, CA 95134
USA
Email: sina@cisco.com
Abhay Roy
Cisco Systems
225 West Tasman Drive
San Jose, CA 95134
USA
Email: akr@cisco.com
Liem Nguyen
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
USA
Email: lhnguyen@cisco.com
Padma Pillay-Esnault
Cisco Systems
225 West Tasman Drive
San Jose, CA 95134
USA
Email: ppe@cisco.com
Appendix A. Acknowledgments Appendix A. Acknowledgments
The authors would like to thank Scott Sturgess, Alvaro Retana, David The authors would like to thank Scott Sturgess, Alvaro Retana, David
Kushi, Yakov Rekhter, Tony Przygienda, and Naiming Shen for their Kushi, Yakov Rekhter, Tony Przygienda, and Naiming Shen for their
comments on the document. Special thanks to Acee Lindem for editing comments on the document. Special thanks to Acee Lindem for editing
and to Tom Henderson for an extensive review during the OSPF Working and to Tom Henderson for an extensive review during the OSPF Working
Group last call. Group last call.
Appendix B. OSPF data formats Appendix B. OSPF data formats
LSA content defined in [OSPF] is modified to introduce the MT-ID. LSA content defined in [OSPF] is modified to introduce the MT-ID.
B.1 Router-LSAs B.1. Router-LSAs
Router-LSAs are the Type 1 LSAs. Each router in an area originates a Router-LSAs are the Type 1 LSAs. Each router in an area originates a
router-LSA. The LSA describes the state and cost of the router's router-LSA. The LSA describes the state and cost of the router's
links (i.e., interfaces) to the area. All of the router's links to links (i.e., interfaces) to the area. All of the router's links to
the area must be described in a single router-LSA. For details the area must be described in a single router-LSA. For details
concerning the construction of router-LSAs, see Section 12.4.1 concerning the construction of router-LSAs, see Section 12.4.1 of
[OSPF]. [OSPF].
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 | 1 | | LS age | Options | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID | | Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
skipping to change at page 20, line 5 skipping to change at page 18, line 51
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | 0 | MT-ID metric | | MT-ID | 0 | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID | | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data | | Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
B.2 Network-LSAs Figure 2: Router-LSA Format
B.2. Network-LSAs
Network-LSAs are the Type 2 LSAs. A network-LSA is originated for Network-LSAs are the Type 2 LSAs. A network-LSA is originated for
each broadcast and NBMA network in the area which supports two or each broadcast and NBMA network in the area which supports two or
more routers. The network-LSA is originated by the network's more routers. The network-LSA is originated by the network's
Designated Router. The LSA describes all routers attached to the Designated Router. The LSA describes all routers attached to the
network, including the Designated Router itself. The LSA's Link network, including the Designated Router itself. The LSA's Link
State ID field lists the IP interface address of the Designated State ID field lists the IP interface address of the Designated
Router. Router.
The distance from the network to all attached routers is zero. This The distance from the network to all attached routers is zero. This
is why metric fields need not be specified in the network-LSA. For is why metric fields need not be specified in the network-LSA. For
details concerning the construction of network-LSAs, see Section details concerning the construction of network-LSAs, see Section
12.4.2 [OSPF]. 12.4.2 of [OSPF].
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 | 2 | | LS age | Options | 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID | | Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number | | LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length | | LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask | | Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attached Router | | Attached Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
Figure 3: Network-LSA Format
Note that network LSA does not contain any MT-ID fields as the cost Note that network LSA does not contain any MT-ID fields as the cost
of the network to the attached routers is 0 and DR is shared by all of the network to the attached routers is 0 and DR is shared by all
topologies. topologies.
B.3 Summary-LSAs B.3. Summary-LSAs
Summary-LSAs are the Type 3 and 4 LSAs. These LSAs are originated by Summary-LSAs are the Type 3 and 4 LSAs. These LSAs are originated by
area border routers. Summary-LSAs describe inter-area destinations. area border routers. Summary-LSAs describe inter-area destinations.
For details concerning the construction of summary- LSAs, see Section For details concerning the construction of summary- LSAs, see Section
12.4.3 [OSPF]. 12.4.3 [OSPF].
Type 3 summary-LSAs are used when the destination is an IP network. Type 3 summary-LSAs are used when the destination is an IP network.
In this case the LSA's Link State ID field is an IP network number In this case the LSA's Link State ID field is an IP network number
(if necessary, the Link State ID can also have one or more of the (if necessary, the Link State ID can also have one or more of the
network's "host" bits set; see Appendix E [OSPF] for details). When network's "host" bits set; see Appendix E [OSPF] for details). When
skipping to change at page 21, line 37 skipping to change at page 20, line 40
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | metric | | 0 | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric | | MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric | | MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
B.4 AS-External-LSAs Figure 4: Summary-LSA Format
B.4. AS-external-LSAs
AS-external-LSAs are the Type 5 LSAs. These LSAs are originated by AS-external-LSAs are the Type 5 LSAs. These LSAs are originated by
AS boundary routers, and describe destinations external to the AS. AS boundary routers, and describe destinations external to the AS.
For details concerning the construction of AS-external-LSAs, see For details concerning the construction of AS-external-LSAs, see
Section 12.4.3 [OSPF]. Section 12.4.3 of [OSPF].
AS-external-LSAs usually describe a particular external destination. AS-external-LSAs usually describe a particular external destination.
For these LSAs the Link State ID field specifies an IP network number For these LSAs the Link State ID field specifies an IP network number
(if necessary, the Link State ID can also have one or more of the (if necessary, the Link State ID can also have one or more of the
network's "host" bits set; see Appendix E [OSPF] for details). AS- network's "host" bits set; see Appendix E [OSPF] for details). AS-
external-LSAs are also used to describe a default route. Default external-LSAs are also used to describe a default route. Default
routes are used when no specific route exists to the destination. routes are used when no specific route exists to the destination.
When describing a default route, the Link State ID is always set to When describing a default route, the Link State ID is always set to
DefaultDestination (0.0.0.0) and the Network Mask is set to 0.0.0.0. DefaultDestination (0.0.0.0) and the Network Mask is set to 0.0.0.0.
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 | 5 | | LS age | Options | 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID | | Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 22, line 44 skipping to change at page 21, line 46
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| MT-ID | MT-ID metric | |E| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address | | Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag | | External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
B.5 NSSA-LSAs Figure 5: AS-External-LSA Format
NSSA-LSAs are the Type 7 LSAs. These LSAs are originated by AS B.5. Type-7 AS-external-LSAs
boundary routers local to an NSSA, and describe destinations external
to the AS. The changes to NSSA-LSAs are identical to those for
External-LSAs (Appendix A.4.5). For details concerning the
construction of NSSA-LSAs see Section 2.4 [NSSA].
Intellectual Property Statement Type-7 AS-external-LSAs are originated by AS boundary routers local
to an NSSA, and describe destinations external to the AS. The
changes to Type-7 AS-external-LSAs are identical to those for AS-
external-LSAs (Appendix A.4.5). For details concerning the
construction of Type-7 AS-external-LSAs see Section 2.4 of [NSSA].
Authors' Addresses
Peter Psenak
Cisco Systems
Mlynske Nivy 43
821 09
Bratislava
Slovakia
Email: ppsenak@cisco.com
Sina Mirtorabi
Force10 Networks
1440 McCarthy Blvd
Milpitas, CA 95035
USA
Email: sina@force10networks.com
Abhay Roy
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: akr@cisco.com
Liem Nguyen
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: lhnguyen@cisco.com
Padma Pillay-Esnault
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: ppe@cisco.com
Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
skipping to change at page 23, line 29 skipping to change at page 24, line 45
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is provided by the IETF
Internet Society. Administrative Support Activity (IASA).
 End of changes. 101 change blocks. 
254 lines changed or deleted 265 lines changed or added

This html diff was produced by rfcdiff 1.33. The latest version is available from http://tools.ietf.org/tools/rfcdiff/