draft-ietf-ospf-mt-02.txt   draft-ietf-ospf-mt-03.txt 
Network Working Group Peter Psenak Network Working Group P. Psenak
Internet Draft Sina Mirtorabi Internet-Draft S. Mirtorabi
Expiration Date: September 2005 Abhay Roy Expires: September 27, 2005 A. Roy
File name: draft-ietf-ospf-mt-02.txt Liem Nguyen L. Nguyen
Padma Pillay-Esnault P. Pillay-Esnault
Cisco Systems Cisco Systems
March 29, 2005
March 2005
Multi-Topology (MT) Routing in OSPF Multi-Topology (MT) Routing in OSPF
draft-ietf-ospf-mt-03.txt
Status of This Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This draft describes an extension to OSPF in order to define This draft describes an extension to OSPF in order to define
independent IP topologies called Multi-Topologies (MTs). The MT independent IP topologies called Multi-Topologies (MTs). The MT
extension can be used for computing different paths for unicast extension can be used for computing different paths for unicast
traffic, multicast traffic, different classes of service, or traffic, multicast traffic, different classes of service, or in-band
in-band network management. [M-ISIS] describes a similar network management. [M-ISIS] describes a similar mechanism for ISIS.
mechanism for ISIS. An optional extension to exclude An optional extension to exclude selected links from the default
selected links from the default topology is also described. topology is also described.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Requirements notation . . . . . . . . . . . . . . . . . . 4
2.2 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Base MT Functional Specifications . . . . . . . . . . . . . . 5
3.1 MT Area Boundary . . . . . . . . . . . . . . . . . . . . . 5
3.2 Adjacency for MTs . . . . . . . . . . . . . . . . . . . . 5
3.3 Sending OSPF control packets . . . . . . . . . . . . . . . 5
3.4 Advertising MT Adjacencies and the Corresponding IP
Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4.1 Advertising MT Adjacencies and the Corresponding
IP Prefixes . . . . . . . . . . . . . . . . . . . . . 5
3.4.2 Inter-Area and External Routing . . . . . . . . . . . 6
3.5 Flushing MT Information . . . . . . . . . . . . . . . . . 6
3.6 MT SPF Computation . . . . . . . . . . . . . . . . . . . . 6
3.7 MT-ID Values . . . . . . . . . . . . . . . . . . . . . . . 7
3.8 Forwarding in MT . . . . . . . . . . . . . . . . . . . . . 7
4. Default Topology Link Exclusion Functional Specifications . . 8
4.1 Exclusion of Links in the Default Topology . . . . . . . . 8
4.2 New Area Data Structure Parameter . . . . . . . . . . . . 8
4.3 Adjacency Formation with Link Exclusion Capability . . . . 9
4.4 OSPF Control Packets Transmission Over Excluded Links . . 9
4.5 OSPF LSA Advertisement and SPF Computation for
Excluded Links . . . . . . . . . . . . . . . . . . . . . . 9
5. Interoperability between MT Capable and Non-MT Capable
Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Migration from non-MT-Area to MT-area . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1 Normative References . . . . . . . . . . . . . . . . . . . . 15
9.2 Informative References . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
B. OSPF data formats . . . . . . . . . . . . . . . . . . . . . . 18
B.1 Router-LSAs . . . . . . . . . . . . . . . . . . . . . . . 18
B.2 Network-LSAs . . . . . . . . . . . . . . . . . . . . . . . 19
B.3 Summary-LSAs . . . . . . . . . . . . . . . . . . . . . . . 19
B.4 AS-External-LSAs . . . . . . . . . . . . . . . . . . . . . 20
B.5 NSSA-LSAs . . . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . . 22
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 TOS metric in an earlier
specification [RFC1583] in order to announce a different link cost specification [RFC1583] in order to announce a different link cost
based on TOS. TOS based routing as described in [RFC1583] was never based on TOS. TOS based routing as described in [RFC1583] was never
deployed and was subsequently deprecated. deployed and was subsequently deprecated.
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 as MT-ID and MT-ID Metric and are used to advertise
different topologies by advertising separate metrics for each different topologies by advertising separate metrics for each of
of them. them.
2. Terminology 2. Terminology
We define the following terminology in this document: 2.1 Requirements notation
Non-MT router : Routers that do not have the MT capability
MT router : Routers that have MT capability as described in
this document
MT-ID : Renamed TOS field in LSAs to represent multi
topology ID.
Default topology : Topology that is built using the TOS 0 metric
(default metric)
MT topology : Topology that is built using the corresponding The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
MT-ID metric "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
MT : Shorthand notation for MT topology 2.2 Terms
MT#0 topology : Representation of TOS 0 metric in MT-ID format We define the following terminology in this document:
Non-MT-Area : An area that contains only non-MT routers Non-MT router
Routers that do not have the MT capability
MT router
Routers that have MT capability as described in this document
MT-ID
Renamed TOS field in LSAs to represent multitopology ID.
Default topology
Topology that is built using the TOS 0 metric (default metric)
MT topology
Topology that is built using the corresponding MT-ID metric
MT
Shorthand notation for MT topology
MT#0 topology
Representation of TOS 0 metric in MT-ID format
Non-MT-Area
An area that contains only non-MT routers
MT-Area
An area that contains both non-MT routers and MT routers or only
MT routers
MT-Area : An area that contains both non-MT routers and MT 3. Base MT Functional Specifications
routers or only MT routers
3. 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.
4. 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 single adjacency will be formed with neighbors on the interface even
even if the interface is configured to participate in multiple if the interface is configured to participate in multiple topologies.
topologies. Furthermore, adjacency formation will be independent Furthermore, adjacency formation will be independent of the
of the topologies configured for the interface or neighbors on that topologies configured for the interface or neighbors on that
interface. interface.
5. Sending OSPF control packets 3.3 Sending OSPF control packets
OSPF control packets MUST be sent over the default topology. OSPF control packets MUST be sent over the default topology.
OSPF control packets sent to the remote end-point of a virtual OSPF control packets sent to the remote end-point of a virtual link
link may need to traverse multiple hops. These control packets may need to traverse multiple hops. These control packets MUST be
MUST be correctly classified by the virtual link end-point correctly classified by the virtual link end-point routers as packets
routers as packets belonging to the default topology. Even though belonging to the default topology. Even though the VL may belong to
the VL may belong to one or more non-default topologies, OSPF control one or more non-default topologies, OSPF control packets sent to the
packets sent to the remote end of a virtual link MUST be forwarded remote end of a virtual link MUST be forwarded using the default
using the default topology. topology.
6. Advertising MT adjacencies and 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 We will reuse the TOS metric field in order to advertise a topology
and prefixes belonging to that topology. The TOS field is redefined and prefixes belonging to that topology. The TOS field is redefined
as MT-ID in the payload of Router-LSAs, Summary-LSAs, NSSA-LSAs, as MT-ID in the payload of Router-LSAs, Summary-LSAs, NSSA-LSAs, and
and AS-External-LSAs (see Appendix A). AS-External-LSAs (see Appendix A).
MT-ID metrics in LSAs SHOULD be in ascending order of MT-ID. If MT-ID metrics in LSAs SHOULD be in ascending order of MT-ID. If an
an MT-ID exists in an LSA or router link multiple times, the metric MT-ID exists in an LSA or router link multiple times, the metric in
in the first MT-ID instance MUST be used. the first MT-ID instance MUST be used.
6.1 Intra-area routing 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 will advertise 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 default topology and all
advertised prefixes belonging to the default topology will use advertised prefixes belonging to the default topology will use the
the TOS0 metric the same as in standard OSPF [OSPF]. TOS0 metric the same as in standard OSPF [OSPF].
Each MT has its own MT-ID metric field. When a link is not Each MT has its own MT-ID metric field. When a link is not part of a
part of a given MT, the corresponding MT-ID metric is excluded from given MT, the corresponding MT-ID metric is excluded from the LSA.
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 DR is
shared by all MTs. Hence, there is no change to the Network-LSA. shared by all MTs. Hence, there is no change to the Network-LSA.
6.2 Inter-area and External Routing 3.4.2 Inter-Area and External Routing
In Summary-LSAs, NSSA-LSAs, and AS-External-LSAs, the TOS metric In Summary-LSAs, NSSA-LSAs, and AS-External-LSAs, the TOS metric
fields are defined as MT-ID metric fields and are used in order to fields are defined as MT-ID metric fields and are used in order to
advertise prefix and router reachability in the corresponding advertise 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, NSSA-LSA, or AS-External-LSA
that belongs to a set of MTs, it will include the corresponding cost that belongs to a set of MTs, it will include the corresponding cost
for each MT-ID. By default, the router participates in the default for each MT-ID. By default, the router 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 the same
as in standard OSPF [OSPF]. as in standard OSPF [OSPF].
Setting the P-bit in NSSA-LSAs is topology independent and pertains Setting the P-bit in NSSA-LSAs is topology independent and pertains
to all MT-ID advertised in the body of the LSA. to all MT-ID advertised in the body of the LSA.
7. 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].
8. 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 will be able to
compute multiple topologies and find paths to IP prefixes for each MT compute multiple topologies and find paths to IP prefixes for each MT
independently. A separate SPF will be computed for each MT-ID to find independently. A separate SPF will be computed for each MT-ID to
independent paths to IP prefixes. Each nexthop computed during the MT find independent paths to IP prefixes. Each nexthop computed during
SPF MUST belong to the same MT. 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 will be considered. Entries in the Router Routing table will
be MT-ID specific. be MT-ID specific.
During the SPF computation for the default topology only the TOS0 During the SPF computation for the default topology only the TOS0
metric is considered during the SPF computation. metric is considered during the SPF computation.
9. MT ID Values 3.7 MT-ID Values
Since AS-External-LSAs use the high order bit in the MT-ID field Since AS-External-LSAs use the high order bit in the MT-ID field (E
(E bit) for the external metric-type, only MT-IDs in the range bit) for the external metric-type, only MT-IDs in the range [0-127]
[0-127] are valid. The following MT-ID values are reserved: are valid. The following MT-ID values are reserved:
0 - Reserved for routers in MTRoutingExclusionCapability mode 0 - Reserved for advertising the metric associated with the
to advertise the metric associated with the default default topology (see Section 4.2)
topology (see section 11.2).
1 - Reserved for the default multicast topology. 1 - Reserved for advertising the metric associated with the
default multicast topology
Unknown MT-IDs SHOULD be ignored. MT-IDs [128-255] SHOULD be ignored.
10. Forwarding in MT 3.8 Forwarding in MT
Forwarding assures that only routes belonging to a single Forwarding assures that only routes belonging to a single topology
topology are used to forward a packet along its way from source to are used to forward a packet along its way from source to
destination. Therefore, user configuration MUST be consistently destination. Therefore, user configuration MUST be consistently
applied throughout the network so that an incoming packet is applied throughout the network so that an incoming packet is
associated with the same topology through each hop end to end. associated with the same topology through each hop end to end. It is
It is outside of the scope of this document to consider outside of the scope of this document to consider different methods
different methods of associating an incoming packet to a of associating an incoming packet to a corresponding topology.
corresponding topology.
11. Exclusion of links in the default topology 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 from the default topology and reserve them for some specific classes
classes of traffic. of traffic.
The multi-topologies extension for default topology link or prefix The multi-topologies extension for default topology link or prefix
exclusion is described in the following subsections. exclusion is described in the following subsections.
11.1 MT-bit in Hello packet 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 Router-LSAs in the default topology and to alternately use the
MT-ID#0 metric to advertise the metric associated with the default MT-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 default topology will be advertised.
The unused T-bit is defined as the MT-bit in the option field The unused T-bit is defined as the MT-bit in the option field in
in order to assure that a multi-topology link-excluding capable order to assure that a multi-topology link-excluding capable router
router will only form an adjacency with another similarly configured will only form an adjacency with another similarly configured router.
router.
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
|DN |O |DC |EA |NP |MC |E |MT | |DN |O |DC |EA |NP |MC |E |MT |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
MT-bit: This bit MUST be set in the Hello packet only if MT-bit: This bit MUST be set in the Hello packet only if
MTRoutingExclusionCapability is enabled (see section 11.2). MTRoutingExclusionCapability is enabled (see Section 4.2)
11.2 New parameter in the Area Data Structure 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:
MTRoutingExclusionCapability MTRoutingExclusionCapability
This is a configurable parameter that will be used to facilitate This is a configurable parameter that will be used to facilitate
the introduction of MT routers in an area and ensure backward the introduction of MT routers in an area and ensure backward
compatibility. compatibility.
By default, when an area data structure is created the When an area data structure is created the
MTRoutingExclusionCapability is disabled. MTRoutingExclusionCapability is disabled by default.
If MTRoutingExclusionCapability is disabled: If MTRoutingExclusionCapability is disabled:
o The MT-bit MUST be cleared in Hello packets. o The MT-bit MUST be cleared in Hello packets.
o If a link participates in a non-default topology, o If a link participates in a non-default topology, it is
it is automatically included in the default topology automatically included in the default topology to support backward
to support backward compatibility between MT and compatibility between MT and non-MT routers. This is accomplished
non-MT routers. This is accomplished through advertisement through advertisement via the TOS0 metric field the same as in
via the TOS0 metric field the same as in standard OSPF [OSPF]. standard OSPF [OSPF].
If MTRoutingExclusionCapability is enabled: If MTRoutingExclusionCapability is enabled:
o The MT-bit MUST be set in Hello packets o The MT-bit MUST be set in Hello packets
o The router will only accept a Hello if the MT-bit is set (see o The router will only accept a Hello if the MT-bit is set (see
section 11.3) Section 4.3)
When MTRoutingExclusionCapability is set to enabled a router is When MTRoutingExclusionCapability is set to enabled a router is said
said to be operating in MTRoutingExclusionCapability mode. to be operating in MTRoutingExclusionCapability mode.
11.3 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 In order to have a smooth transition from a non-MT area to an
MT-area, an MT router with MTRoutingExclusionCapability disabled will MT-area, an MT router with MTRoutingExclusionCapability disabled will
form adjacencies with non-MT routers and will include all links form adjacencies with non-MT routers and will include all links as
as part of default topology. part of default topology.
A link may cease participating in default topology if A link may cease participating in default topology if
MTRoutingExclusionCapability is set to enabled. In this state, a MTRoutingExclusionCapability is set to enabled. In this state, a
router will only form adjacency with routers that set the MT-bit router will only form adjacency with routers that set the MT-bit in
in their Hello packets. This will ensure that all routers have their Hello packets. This will ensure that all routers have
MTRoutingExclusionCapability enabled before the default topology MTRoutingExclusionCapability enabled before the default topology can
can be disabled on a link. be 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 MTRoutingExclusionCapability of the Area Data structure o If the MTRoutingExclusionCapability of the Area Data structure is
is set to enabled, the Hello packets are discarded if the set to enabled, the Hello packets are discarded if the the
the received Hello packet does not have the MT-bit in the hello received Hello packet does not have the MT-bit in the hello
options set. options set.
11.4 OSPF Control Packets Transmission Over Excluded Links 4.4 OSPF Control Packets Transmission Over Excluded Links
If MTRoutingExclusionCapability is enabled and the default If MTRoutingExclusionCapability is enabled and the default topology
topology is not configured on an interface, connected routes MUST is not configured on an interface, connected routes MUST exist for
still exist for the default topology and should enable OSPF control the default topology so that OSPF control packets can be sent and
packets to be sent and received over that interface. received on that interface.
11.5 OSPF LSA Advertisement and SPF Computation for Excluded Links 4.5 OSPF LSA Advertisement and SPF Computation for Excluded Links
When MTRoutingExclusionCapability is enabled and the link does When MTRoutingExclusionCapability is enabled and the link does not
not participate in the default topology, the MT-ID#0 metric is not participate in the default topology, the MT-ID#0 metric is not
advertised. The TOS0 metric is set to infinity (0xFFFF) but is advertised. The link's TOS0 metric is ignored during the default
ignored during the default topology SPF computation. topology SPF computation.
When MTRoutingExclusionCapability is enabled and a link participates When MTRoutingExclusionCapability is enabled and a link participates
in the default topology, MT-ID#0 metric is used to advertise the in the default topology, MT-ID#0 metric is used to advertise the
metric associated with the default topology. The TOS0 metric is set metric associated with the default topology. The link's TOS0 metric
to the same value as the MT-ID#0 metric but is ignored during the is ignored during the default topology SPF computation.
default topology SPF computation.
Independent of the MTRoutingExclusionCapability setting, the TOS0 Independent of the MTRoutingExclusionCapability setting, the TOS0
metric is used for Summary-LSAs, NSSA-LSAs, and AS-External-LSAs. metric is used for Summary-LSAs, NSSA-LSAs, and 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 default the topology, the metric is used to advertise the metric in the default topology.
TOS0 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 topology the TOS0 metric is used for Summary-LSAs, NSSA-LSAs, and
AS-External-LSAs. AS-External-LSAs.
12. 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 can consider the zero value default topology, a non-MT router can consider the zero value in the
in the metric field as a valid metric and consider the link or metric field as a valid metric and consider the link or prefix as
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 include all links as part of the default topology. If links need to
to be removed from the default topology, an MT capable router be removed from the default topology, an MT capable router MUST be
MUST be configured in MTRoutingExclusionCapability mode. In this configured in MTRoutingExclusionCapability mode. In this mode,
mode, routers will assure that all other routers in the area are routers will assure that all other routers in the area are in the
in the MTRoutingExclusionCapability mode before considering the MTRoutingExclusionCapability mode before considering the MT-ID#0
MT-ID#0 metric in the SPF calculation. Only then can the TOS0 metric metric in the SPF calculation. Only then can the TOS0 metric field
field in Router LSAs be safely ignored during the default topology in Router LSAs be safely ignored during the default topology SPF
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.
13. 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 Introducing MT-OSPF into a network can be done gradually to allow MT
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
MTRoutingExclusionCapability mode. In this section we describe the MTRoutingExclusionCapability mode. In this section we describe the
migration steps to consider while transitioning from a non-MT network migration steps to consider while transitioning from a non-MT network
to an MT network. to an MT network.
Consider a network with a backbone area and a set of non-backbone Consider a network with a backbone area and a set of non-backbone
areas functioning in standard OSPF mode. We would like to migrate to areas functioning in standard OSPF mode. We would like to migrate to
an MT network either partially or completely. an MT network either partially or completely.
1) As required, part of an area is upgrade to be MT capable. The 1. As required, part of an area is upgrade to be MT capable. The MT
MT routers will interact with non-MT routers in the default routers will interact with non-MT routers in the default topology
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 MTRoutingExclusionCapability mode since there is no configured in MTRoutingExclusionCapability 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 is more than one non-backbone areas where MT is being
used, it is desirable that the backbone area first be upgraded to used, it is desirable that the backbone area first be upgraded to
be MT capable so that inter-area routing is assured for MT be MT capable so that inter-area routing is assured for MT
destinations in different areas. destinations 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.
14. Acknowledgments 7. Security Considerations
The authors would like to thank Scott Sturgess and Alvaro Retana for
their comments on the document. Thanks to Acee Lindem for review and
extensive editing.
15. Security Consideration
The described protocol extension does not introduce any new security This document does not raise any security issues that are not already
issues into the OSPF protocol. covered in [OSPF].
16. 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 [RFC1583] 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. Similarly, the TOS field
for Router-LSAs, Summary-LSAs, NSSA-LSAs, and AS-External LSAs as for Router-LSAs, Summary-LSAs, NSSA-LSAs, and AS-External LSAs as
defined in [OSPF] is redefined as MT-ID in this document. defined in [OSPF] is redefined as MT-ID in this document.
17. Normative References 9. References
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. 9.1 Normative References
[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.
[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994.
[RFC2119] 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.
18. Informative References 9.2 Informative References
[M-ISIS] Przygienda, T., Shen, N., Sheth, N., [M-ISIS] Przygienda, T., Shen, N. and N. Sheth, "M-ISIS: Multi
"M-ISIS: Multi Topology (MT) Routing in IS-IS", Topology (MT) Routing in IS-IS",
draft-ietf-isis-wg-multi-topology-07.txt, draft-ietf-isis-wg-multi-topology-07.txt (work in
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, June McPherson, "OSPF Stub Router Advertisement", RFC 3137, June
2001. 2001.
Appendix A. 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
The authors would like to thank Scott Sturgess, Alvaro Retana, and
David Kushi for their comments on the document. Thanks to Acee
Lindem for review and editing.
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.
A.1 Router-LSAs B.1 Router-LSAs
Router-LSAs are the Type 1 LSAs. Each router in an area originates Router-LSAs are the Type 1 LSAs. Each router in an area originates a
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 concerning the construction of router-LSAs, see Section 12.4.1
12.4.1 [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 11, line 42 skipping to change at page 18, line 42
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID | | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data | | Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | # MT-ID | metric | | Type | # MT-ID | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | 0 | MT-ID metric | | MT-ID | 0 | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | 0 | MT-ID metric | | MT-ID | 0 | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID | | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data | | Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
A.2 Network-LSAs 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
skipping to change at page 12, line 40 skipping to change at page 19, line 40
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length | | LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask | | Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attached Router | | Attached Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
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 of the network to the attached routers is 0 and DR is shared by all
all topologies. topologies.
A.3 Summary-LSAs B.3 Summary-LSAs
Summary-LSAs are the Type 3 and 4 LSAs. These LSAs are originated Summary-LSAs are the Type 3 and 4 LSAs. These LSAs are originated by
by area border routers. Summary-LSAs describe inter-area area border routers. Summary-LSAs describe inter-area destinations.
destinations. For details concerning the construction of summary- For details concerning the construction of summary- LSAs, see Section
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
the destination is an AS boundary router, a Type 4 summary-LSA is the destination is an AS boundary router, a Type 4 summary-LSA is
used, and the Link State ID field is the AS boundary router's OSPF used, and the Link State ID field is the AS boundary router's OSPF
Router ID. (To see why it is necessary to advertise the location of Router ID. (To see why it is necessary to advertise the location of
each ASBR, consult Section 16.4 of [OSPF]). Other than the difference each ASBR, consult Section 16.4 of [OSPF]). Other than the
in the Link State ID field, the format of Type 3 and 4 summary-LSAs difference in the Link State ID field, the format of Type 3 and 4
is identical. summary-LSAs is identical.
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 | 3 or 4 | | LS age | Options | 3 or 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID | | Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 14, line 5 skipping to change at page 20, line 37
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | metric | | 0 | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric | | MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric | | MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A.4.5 AS-external-LSAs 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 [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). network's "host" bits set; see Appendix E [OSPF] for details).
skipping to change at page 15, line 5 skipping to change at page 21, line 44
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| MT-ID | MT-ID metric | |E| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address | | Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag | | External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A.4.6 NSSA-LSAs B.5 NSSA-LSAs
NSSA-LSAs are the Type 7 LSAs. These LSAs are originated by NSSA-LSAs are the Type 7 LSAs. These LSAs are originated by AS
AS boundary routers local to an NSSA, and describe destinations boundary routers local to an NSSA, and describe destinations external
external to the AS. The changes to NSSA-LSAs are identical to those to the AS. The changes to NSSA-LSAs are identical to those for
for External-LSAs (Appendix A.4.5). For details concerning the External-LSAs (Appendix A.4.5). For details concerning the
construction of NSSA-LSAs see Section 2.4 [NSSA]. construction of NSSA-LSAs see Section 2.4 [NSSA].
Authors' address Intellectual Property Statement
Peter Psenak Abhay Roy
Cisco Systems Cisco systems
Parc Pegasus, 170 W. Tasman Dr.
De Kleetlaan 6A San Jose, CA 95134
1831 Diegem, Belgium USA
E-mail: ppsenak@cisco.com E-mail: akr@cisco.com
Sina Mirtorabi Liem Nguyen
Cisco Systems Cisco Systems
225 West Tasman drive 7025 Kit Creek Rd.
San Jose, CA 95134 Research Triangle Park, NC 27709
USA USA
E-mail: sina@cisco.com E-mail: lhnguyen@cisco.com
Padma Pillay-Esnault
Cisco Systems
3750 Cisco Way
San Jose, CA 95134
USA
E-mail: ppe@cisco.com
Full Copyright Statement
Copyright (C) The Internet Society (2004). 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
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Acknowledgement 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 (2005). 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
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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