Network Working Group Peter Psenak
Internet Draft Sina Mirtorabi
Expiration Date: April 2005 Abhay Roy
File name: draft-ietf-ospf-mt-00.txt Liem Nguyen
Cisco Systems
Padma Pillay-Esnault
Juniper Networks
October 2004
MT-OSPF: Multi Topology (MT) Routing in OSPF
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet Drafts are working documents of the Internet Engineering
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Abstract
This draft describes the extension to OSPF in order to define
independent IP topologies called Multi-Topologies (MTs). The MT
extension can be used for computing different paths for different
classes of service, in-band management network or incongruent
topologies for unicast and multicast. M-ISIS describes a similar
mechanism for ISIS.
This draft also describes an optional extension of
Multi-topologies whereby some links might be excluded from the
default topology.
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1. Introduction
OSPF uses a fixed packet format, therefore it is not easy to
introduce any backward compatible extensions. However the OSPF
specification [2] introduced TOS metric in an earlier specification
[3] in order to announce a different link's cost based on TOS. The
TOS based routing as described in [3] was never deployed in the field
and later was removed from the spec.
We propose to reuse the TOS based metric fields. They have been
redefined as MT-ID and MT-ID Metric, to announce different topologies
by advertising separate metrics for each of them.
2. Terminology
We define the following terminology in this document:
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
MT-ID metric
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
3. MT area boundary
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
for all MTs are the same but each MT's attachment to the area is
independent.
4. Adjacency for MTs
Each interface can be configured to belong to a set of topologies. A
single adjacency will be formed with the remote neighbor even if the
interface is configured to participate in multiple topologies and
independently of the MT-IDs.
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5. Sending OSPF control packets
OSPF control packets should be sent over the default topology.
OSPF control packets sent to the remote end-point of the virtual
link may need to traverse multiple hops. These control packets
should be correctly classified by the routers as packets belonging
to the default topology. Event though the VL may belong to other than
default topology (or multiple of them), OSPF control packets sent to
the remote end of the virtual link should be forwarded using the
default topology.
6. Advertising MT adjacencies and corresponding IP prefixes
We will reuse the TOS metric field in order to announce a topology or
prefixes that belongs to a given MT. The TOS field is renamed to
MT-ID in the LSAs payload (see Appendix A).
6.1 Intra-area routing
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
MT-ID.
All links are by default included in default topology, all
advertised adjacency belonging to the default topology will use
the TOS0 metric as in standard OSPF.
Each MT has its own MT-ID metric field and when a link is not part of
a given MT, the corresponding MT-ID metric will not appear in the LSA.
The Network LSA does not contain any MT information as the DR is
shared by all MTs and thus there is no change to the Network LSA.
6.2 Inter-area and external routing
In Summary and External LSAs, the TOS metric fields are renamed to
MT-ID metric fields and are used in order to announce prefix/router
reachability in the corresponding topology.
When a router originates a type 3/4/5/7 LSA that belongs to a set of MTs,
it will include the corresponding cost for each MT-ID. The router
by default participate in default topology and use the TOS0 metric
for default topology as in standard OSPF.
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7. Flushing MT information
When a certain link/prefix that existed or was reachable in a certain
topology is no longer part of this topology or the reachability of
the link/prefix in this topology was lost, a new version of the LSA
that advertised the link/prefix must be originated. This new version
of the LSA must not include any metric information representing the
link/prefix in this topology.
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
topology [4].
8. MT SPF Computation
By considering MT-ID metrics in the LSAs, OSPF will be able to
compute multiple topologies, one for each MT the router is part of
and find paths to IP prefixes for each MT independently. A separate
SPF will be computed for each MT-ID to find independent paths to IP
prefixes. Each nexthop computed during the MT SPF MUST belong to the
same MT.
Network LSAs are used by all topologies during the SPF computation.
During SPF for a given MT-ID, only the link/metric for the given
MT-ID will be considered. Entries in the Router Routing table will
be MT-ID specific.
During the SPF computation for default topology the TOS0 metric is
considered during the SPF computation.
9. MT ID Values
Only MT-IDs in the range [0-127] are valid, because external LSAs use
one bit in the MT-ID field (E bit) for the external metric-type.
Following MT-ID values are reserved:
0 - reserved for routers in MTRoutingExclusionCapability mode
to advertise the metric associated with default topology
(see section 11.2).
1 - reserved for default multicast topology.
Any unknown MT-ID should be ignored.
10. Forwarding in MT
Forwarding must make sure that only routes belonging to the single
topology are used to forward the packet along its way from source to
destination, therefore user configuration MUST be consistently
applied throughout the network so that an incoming packet is
associated with the same topology on each hop as it is being
forwarded. It is outside of the scope of this document to consider
different methods of associating an incoming packet to the
corresponding MT.
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11. Exclusion of links in the default topology
The multi-topologies imply that all the routers participate in the
default topology. However, it is useful in some circumstances
to exclude some links from the default topology and reserve them
for some specific classes of traffic.
The multi-topologies extension for default topology link exclusion
is described in the following sections.
11.1 MT-bit in Hello packet
OSPF does not have the notion of unreachable link. All links can
have a maximum metric of 0xFFFF carried in the Router LSA. The link
exclusion capability requires routers to ignore TOS 0 metric in
router-LSA in default topology and use MT-ID#0 metric instead to
advertise the metric associated with the default topology. Hence,
all routers within an area MUST agree on how the metric for default
topology will be advertised.
The unused T-bit is renamed (MT) in the option field in order to
enforce that a multi-topology link-excluding capable router will
only interact with another similarly configured router.
+---+---+---+---+---+---+---+---+
|DN |O |DC |EA |NP |MC |E |MT |
+---+---+---+---+---+---+---+---+
MT-bit: This bit MUST be set in the Hello packet only if
MTRoutingExclusionCapability is Enabled (see section 11.2).
11.2 New parameter in the Area Data Structure
We define a new parameters in the Area Data Structure:
MTRoutingExclusionCapability
This is a configurable parameter that will be used to facilitate
the introduction of MT routers in an area and ensure the backward
compatibility.
By default, when an area data structure is created the
MTRoutingExclusionCapabilty is disabled.
If MTRoutingExclusionCapability is disabled:
o MT-bit MUST be cleared in the Hello packet
o If a link participates in a non-default topology,
it is automatically included in default topology (by using
the default metric field as it is done in standard OSPF [2])
so that MT routers interact correctly with non-MT routers.
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If MTRoutingExclusionCapability is set to Enabled:
o MT-bit MUST be set in the Hello packet
o The router will only accept a Hello if the MT-bit is set (see
section 11.3)
We call MTRoutingExclusionCapability "mode", when
MTRoutingExclusionCapability is set to Enabled.
11.3. Forming adjacency with link exclusion capability.
In order to have a smooth transition from a non-MT area to MT-area, a
MT router with MTRoutingExclusionCapability set to disable will form
adjacency with non-MT routers and it will include all links as part
of default topology.
A link can cease participating in default topology if
MTRoutingExclusionCapability is set to Enabled. In this state, a
router will only form adjacency with routers that set the MT-bit
in their Hello packets. This will ensure that all routers are in
Enabled mode before default topology can be disabled on a link.
Receiving OSPF Hello packets defined in section 8.2 of [2] are
modified as follows:
If the MTRoutingExclusionCapability of the Area Data structure
is set to Enabled, the Hello packets are discarded if:
o the received Hello packet does not have the MT-bit set
11.4. Sending OSPF control packets over an excluded link.
If MTRoutingExclusionCapability is set to Enabled and default
topology is not configured on the interface, connected route should
still exist for a default topology that would enable the OSPF
control packets to be sent and received.
11.5. Modified MT SPF Computation with link exclusion capability.
When MTRoutingExclusionCapability is set to Enabled, MT#0 can be
removed if a link does not participate in default topology. In that
case the TOS0 metric is set to infinity (0xFFFF) and ignored during
the MT#0 SPF computation.
When MTRoutingExclusionCapability is set to Enabled and a link
participates in default topology, MT-ID#0 metric is used to advertise
metric associated with the default topology. Further TOS0 metric is
set to the same value as MT-ID#0 metric. However TOS 0 metric is
ignored during SPF for default topology and only MT-ID#0 metric
is used for SPF in default topology.
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When originating Summary and External LSAs, if
MTRoutingExclusionCapability is set to Enabled:
o if the prefix / router does not exist in default topology, TOS0
metric is set to infinity (0xFFFFFF).
o if the prefix / router exist in default topology, TOS0 metric
is used to announce a prefix / router in default topology.
During the Summary and External prefix calculation for default topology
TOS0 metric is used in LSA Type-3/4/5/7.
12. Interoperability between MT capable and non-MT capable routers
The default metric field is mandatory in all LSAs (even when metric
value is 0). Even when the link or a prefix does not exist in the
default topology, a non MT capable router can consider the zero value
in the metric field as a valid metric and consider the link/prefix as
part of the default topology.
In order to prevent the above problem, a MT capable router will
by default include all links as part of the default topology. If links
need to be removed from the default topology, a MT capable router
MUST be configured in MTRoutingExclusionCapability mode. In this mode
the router will make sure that all routers in the area are in the
MTRoutingExclusionCapability mode before forming any adjacency so that
TOS0 metric field can be safely ignored during the MT#0 SPF computation.
Note that for any prefix or router to become reachable in a certain
topology, a contiguous path inside that topology must exist between the
calculating router and the destination prefix or router.
13. Migration from non-MT-Area to MT-area
Introducing MT-OSPF in a network can be gradually done since MT
routers will interact in default topology with non-MT routers,
yet exchanging information about other topologies with other MT
capable routers.
If there is a requirement to exclude some links from default topology
in an area, all routers MUST be in MTRoutingExclusionCapability mode.
In this section we describe migrations steps to consider while
transitioning from a non-MT network to a MT network.
Migration Steps
---------------
Consider a network with a backbone area and a sets of non-backbone
areas functioning in standard OSPF mode. We would like to migrate to
a MT network either partially or completely.
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1) Part of an area is upgraded as needed to have MT capability, the
MT routers will interact with non-MT routers in default topology,
further MT routers will participate in MT topology as needed.
2) If a new non-backbone area is created for MT routers, it may be
set in MTRoutingExclusionCapability mode as there is no interaction
required with non-MT routers, in this mode default topology
can be excluded if required.
3) If there is more than one non-backbone areas where MT is being
used, it is desirable that area 0 be first upgraded to MT capable
routers so that inter-area routing is assured for MT destinations
in different areas.
4) Gradually the whole network can be made MT aware
Note that Inter-area routing for the MT-area still depends on the
backbone area. Therefore if different areas in a given MT-ID need to
communicate, the backbone area also needs to be configured for this
MT-ID.
14. Acknowledgments
The authors would like to thank Scott Sturgess and Alvaro Retana for
their comments on the document.
15. Security Consideration
No specific security issues with the proposed solutions are known.
16. IANA Considerations
T-bit defined in [3] for router's TOS capability is reclaimed as
MT-bit in this document. Likewise, TOS field in type 1,3,4,5,7 LSAs
defined in [2] is reclaimed as MT-ID in this document.
17. References
[1] Przygienda, Shen, Sheth, "Multi Topology (MT) Routing in IS-IS",
draft-ietf-isis-wg-multi-topology-06.txt, Work in progress.
[2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[3] Moy, J., "OSPF Version 2", RFC 1583, Proteon, Inc., March 1994.
[4] Retana, Nguyen, White, "OSPF Stub Router Advertisement",
RFC 3137, June 2001.
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Appendix A.
LSAs content defined in [2] are modified to introduce MT-ID.
A.1 Router-LSAs
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
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
concerning the construction of router-LSAs, see Section 12.4.1. [2]
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|*|*|*|N|W|V|E|B| 0 | # links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | # MT-ID | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | 0 | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | 0 | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
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A.2 Network-LSAs
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
more routers. The network-LSA is originated by the network's
Designated Router. The LSA describes all routers attached to the
network, including the Designated Router itself. The LSA's Link
State ID field lists the IP interface address of the Designated
Router.
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
details concerning the construction of network-LSAs, see Section
12.4.2. [2]
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attached Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
Note that network LSA does not contain any MT-ID field as the cost of
the network to the attached routers is 0 and DR is shared by all MT.
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A.3 Summary-LSAs
Summary-LSAs are the Type 3 and 4 LSAs. These LSAs are originated
by area border routers. Summary-LSAs describe inter-area
destinations. For details concerning the construction of summary-
LSAs, see Section 12.4.3. [2]
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
(if necessary, the Link State ID can also have one or more of the
network's "host" bits set; see Appendix E [2] for details). When 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 Router
ID. (To see why it is necessary to advertise the location of each
ASBR, consult Section 16.4 of [2]). Other than the difference in the
Link State ID field, the format of Type 3 and 4 summary-LSAs is
identical.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 3 or 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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A.4.5 AS-external-LSAs
AS-external-LSAs are the Type 5 LSAs. These LSAs are originated by
AS boundary routers, and describe destinations external to the AS.
For details concerning the construction of AS-external-LSAs, see
Section 12.4.3. [2]
AS-external-LSAs usually describe a particular external destination.
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 network's "host" bits set; see Appendix E [2] for details). AS-
external-LSAs are also used to describe a default route. Default
routes are used when no specific route exists to the destination.
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.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| 0 | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| MT-ID | MT-ID metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Authors' address
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
Juniper Networks
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
USA
E-mail: padma@juniper.net
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