draft-ietf-lsr-isis-area-proxy-01.txt   draft-ietf-lsr-isis-area-proxy-02.txt 
Internet Engineering Task Force T. Li Internet Engineering Task Force T. Li
Internet-Draft S. Chen Internet-Draft S. Chen
Intended status: Experimental V. Ilangovan Intended status: Experimental V. Ilangovan
Expires: January 8, 2021 Arista Networks Expires: January 26, 2021 Arista Networks
G. Mishra G. Mishra
Verizon Inc. Verizon Inc.
July 7, 2020 July 25, 2020
Area Proxy for IS-IS Area Proxy for IS-IS
draft-ietf-lsr-isis-area-proxy-01 draft-ietf-lsr-isis-area-proxy-02
Abstract Abstract
Link state routing protocols have hierarchical abstraction already Link state routing protocols have hierarchical abstraction already
built into them. However, when lower levels are used for transit, built into them. However, when lower levels are used for transit,
they must expose their internal topologies to each other, leading to they must expose their internal topologies to each other, leading to
scale issues. scale issues.
To avoid this, this document discusses extensions to the IS-IS To avoid this, this document discusses extensions to the IS-IS
routing protocol that would allow level 1 areas to provide transit, routing protocol that would allow level 1 areas to provide transit,
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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."
This Internet-Draft will expire on January 8, 2021. This Internet-Draft will expire on January 26, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 29 skipping to change at page 2, line 29
2. Area Proxy . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Area Proxy . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Segment Routing . . . . . . . . . . . . . . . . . . . . . 6 2.1. Segment Routing . . . . . . . . . . . . . . . . . . . . . 6
3. Inside Router Functions . . . . . . . . . . . . . . . . . . . 6 3. Inside Router Functions . . . . . . . . . . . . . . . . . . . 6
3.1. The Area Proxy TLV . . . . . . . . . . . . . . . . . . . 6 3.1. The Area Proxy TLV . . . . . . . . . . . . . . . . . . . 6
3.2. Level 2 SPF Computation . . . . . . . . . . . . . . . . . 7 3.2. Level 2 SPF Computation . . . . . . . . . . . . . . . . . 7
4. Area Leader Functions . . . . . . . . . . . . . . . . . . . . 8 4. Area Leader Functions . . . . . . . . . . . . . . . . . . . . 8
4.1. Area Leader Election . . . . . . . . . . . . . . . . . . 8 4.1. Area Leader Election . . . . . . . . . . . . . . . . . . 8
4.2. Redundancy . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Redundancy . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Distributing Area Proxy Information . . . . . . . . . . . 8 4.3. Distributing Area Proxy Information . . . . . . . . . . . 8
4.3.1. The Area Proxy System Id Sub-TLV . . . . . . . . . . 8 4.3.1. The Area Proxy System Id Sub-TLV . . . . . . . . . . 8
4.3.2. The Area Segment SID Sub-TLV . . . . . . . . . . . . 9 4.3.2. The Area SID Sub-TLV . . . . . . . . . . . . . . . . 9
4.3.2.1. Flags . . . . . . . . . . . . . . . . . . . . . . 10 4.3.2.1. Flags . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Area Proxy LSP Generation . . . . . . . . . . . . . . . . 10 4.4. Proxy LSP Generation . . . . . . . . . . . . . . . . . . 10
4.4.1. The Protocols Supported TLV . . . . . . . . . . . . . 10 4.4.1. The Protocols Supported TLV . . . . . . . . . . . . . 10
4.4.2. The Area Address TLV . . . . . . . . . . . . . . . . 11 4.4.2. The Area Address TLV . . . . . . . . . . . . . . . . 11
4.4.3. The Dynamic Hostname TLV . . . . . . . . . . . . . . 11 4.4.3. The Dynamic Hostname TLV . . . . . . . . . . . . . . 11
4.4.4. The IS Neighbors TLV . . . . . . . . . . . . . . . . 11 4.4.4. The IS Neighbors TLV . . . . . . . . . . . . . . . . 11
4.4.5. The Extended IS Neighbors TLV . . . . . . . . . . . . 11 4.4.5. The Extended IS Neighbors TLV . . . . . . . . . . . . 11
4.4.6. The MT Intermediate Systems TLV . . . . . . . . . . . 12 4.4.6. The MT Intermediate Systems TLV . . . . . . . . . . . 12
4.4.7. Reachability TLVs . . . . . . . . . . . . . . . . . . 12 4.4.7. Reachability TLVs . . . . . . . . . . . . . . . . . . 12
4.4.8. The Router Capability TLV . . . . . . . . . . . . . . 13 4.4.8. The Router Capability TLV . . . . . . . . . . . . . . 13
4.4.9. The Multi-Topology TLV . . . . . . . . . . . . . . . 13 4.4.9. The Multi-Topology TLV . . . . . . . . . . . . . . . 13
4.4.10. The SID/Label Binding and The Multi-Topology 4.4.10. The SID/Label Binding and The Multi-Topology
SID/Label Binding SID TLV . . . . . . . . . . . . . . 13 SID/Label Binding SID TLV . . . . . . . . . . . . . . 13
4.4.11. The SRv6 Locator TLV . . . . . . . . . . . . . . . . 13 4.4.11. The SRv6 Locator TLV . . . . . . . . . . . . . . . . 13
4.4.12. Traffic Engineering Information . . . . . . . . . . . 14 4.4.12. Traffic Engineering Information . . . . . . . . . . . 14
4.4.13. The Area Segment SID . . . . . . . . . . . . . . . . 14 4.4.13. The Area SID . . . . . . . . . . . . . . . . . . . . 14
5. Inside Edge Router Functions . . . . . . . . . . . . . . . . 14 5. Inside Edge Router Functions . . . . . . . . . . . . . . . . 15
5.1. Generating L2 IIHs to Outside Routers . . . . . . . . . . 14 5.1. Generating L2 IIHs to Outside Routers . . . . . . . . . . 15
5.2. Filtering LSP information . . . . . . . . . . . . . . . . 15 5.2. Filtering LSP information . . . . . . . . . . . . . . . . 15
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18 9.2. Informative References . . . . . . . . . . . . . . . . . 19
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18 9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
The IS-IS routing protocol IS-IS [ISO10589] currently supports a two- The IS-IS routing protocol IS-IS [ISO10589] currently supports a two-
level hierarchy of abstraction. The fundamental unit of abstraction level hierarchy of abstraction. The fundamental unit of abstraction
is the 'area', which is a (hopefully) connected set of systems is the 'area', which is a (hopefully) connected set of systems
running IS-IS at the same level. Level 1, the lowest level, is running IS-IS at the same level. Level 1, the lowest level, is
abstracted by routers that participate in both Level 1 and Level 2, abstracted by routers that participate in both Level 1 and Level 2,
and they inject area information into Level 2. Level 2 systems and they inject area information into Level 2. Level 2 systems
seeking to access Level 1, use this abstraction to compute the seeking to access Level 1, use this abstraction to compute the
skipping to change at page 4, line 40 skipping to change at page 4, line 40
topology, Level 2's requirement for connectivity can be satisfied topology, Level 2's requirement for connectivity can be satisfied
without the full overhead of the area's internal topology. It then without the full overhead of the area's internal topology. It then
becomes the responsibility of the Level 1 area to ensure the becomes the responsibility of the Level 1 area to ensure the
forwarding connectivity that's advertised. forwarding connectivity that's advertised.
For this discussion, we'll consider a single Level 1 IS-IS area to be For this discussion, we'll consider a single Level 1 IS-IS area to be
the Inside Area, and the remainder of the Level 2 area is the Outside the Inside Area, and the remainder of the Level 2 area is the Outside
Area. All routers within the Inside Area speak Level 1 and Level 2 Area. All routers within the Inside Area speak Level 1 and Level 2
IS-IS on all of the links within the topology. We propose to IS-IS on all of the links within the topology. We propose to
implement Area Proxy by having a Level 2 Proxy Link State Protocol implement Area Proxy by having a Level 2 Proxy Link State Protocol
Data Unit (PDU, LSP) that represents the entire Inside Area. This is Data Unit (PDU, LSP) that represents the entire Inside Area. We will
the only LSP from the area that will be flooded into the overall refer to this as the Proxy LSP. This is the only LSP from the area
Level 2 LSDB. that will be flooded into the overall Level 2 LSDB.
There are four classes of routers that we need to be concerned with There are four classes of routers that we need to be concerned with
in this discussion: in this discussion:
Inside Router A router within the Inside Area that runs Level 1 and Inside Router A router within the Inside Area that runs Level 1 and
Level 2 IS-IS. A router is recognized as an Inside Router by the Level 2 IS-IS. A router is recognized as an Inside Router by the
existence of its LSP in the Level 1 LSDB. existence of its LSP in the Level 1 LSDB.
Area Leader The Area Leader is an Inside Router that is elected to Area Leader The Area Leader is an Inside Router that is elected to
represent the Level 1 area by injecting the Proxy LSP into the represent the Level 1 area by injecting the Proxy LSP into the
skipping to change at page 6, line 25 skipping to change at page 6, line 25
value of the SRGB advertised by all Inside Nodes MUST start at the value of the SRGB advertised by all Inside Nodes MUST start at the
same value. The range advertised for the area will be the minimum of same value. The range advertised for the area will be the minimum of
all Inside Nodes. all Inside Nodes.
To support Segment Routing, the Area Leader will take the global SID To support Segment Routing, the Area Leader will take the global SID
information found in the L1 LSDB and convey that to L2 through the information found in the L1 LSDB and convey that to L2 through the
Proxy LSP. Prefixes with SID assignments will be copied to the Proxy Proxy LSP. Prefixes with SID assignments will be copied to the Proxy
LSP. Adjacency SIDs for Outside Edge Nodes will be copied to the LSP. Adjacency SIDs for Outside Edge Nodes will be copied to the
Proxy LSP. Proxy LSP.
To further extend Segment Routing, it would be helpful to have a SID To further extend Segment Routing, it would be helpful to have a
that refers to the entire Inside Area. This allows a path to refer segment that refers to the entire Inside Area. This allows a path to
to an area and have any node within that area accept and forward the refer to an area and have any node within that area accept and
packet. In effect, this becomes an anycast SID that is accepted by forward the packet. In effect, this becomes an anycast SID that is
all Inside Edge Nodes. The information about this SID is distributed accepted by all Inside Edge Nodes. The information about this SID is
in the Area Segment SID Sub-TLV, as part of the Area Leader's Area distributed in the Area SID Sub-TLV, as part of the Area Leader's
Proxy TLV (Section 4.3.2). The Inside Edge Nodes MUST establish Area Proxy TLV (Section 4.3.2). The Inside Edge Nodes MUST establish
forwarding based on this SID. The Area Leader SHALL also include the forwarding based on this SID. The Area Leader SHALL also include the
Area Segment SID in the Area Proxy LSP so that the remainder of L2 Area SID in the Proxy LSP so that the remainder of L2 can use it for
can use it for path construction. (Section 4.4.13). path construction. (Section 4.4.13).
3. Inside Router Functions 3. Inside Router Functions
All Inside Routers run Level 1-2 IS-IS and must be explicitly All Inside Routers run Level 1-2 IS-IS and must be explicitly
instructed to enable the Area Proxy functionality. To signal their instructed to enable the Area Proxy functionality. To signal their
readiness to participate in Area Proxy functionality, they will readiness to participate in Area Proxy functionality, they will
advertise the Area Proxy TLV. advertise the Area Proxy TLV.
3.1. The Area Proxy TLV 3.1. The Area Proxy TLV
skipping to change at page 7, line 11 skipping to change at page 7, line 11
The presence of the Area Proxy TLV in a node's LSP indicates that The presence of the Area Proxy TLV in a node's LSP indicates that
the node is enabled for Area Proxy. the node is enabled for Area Proxy.
An LSP containing the Area Proxy TLV is also an Inside Node. All An LSP containing the Area Proxy TLV is also an Inside Node. All
Inside Nodes, including pseudonodes, MUST advertise the Area Proxy Inside Nodes, including pseudonodes, MUST advertise the Area Proxy
TLV. TLV.
It is a container for sub-TLVs with Area Proxy information. It is a container for sub-TLVs with Area Proxy information.
A node advertises the Area Proxy TLV in its L2 LSP. The format of A node advertises the Area Proxy TLV in its L2 LSP. The Area Proxy
the Area Proxy TLV is: TLV is not used in the Proxy LSP. The format of the Area Proxy TLV
is:
0 1 2 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | TLV Length | Sub-TLVs ... | TLV Type | TLV Length | Sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type: YYY TLV Type: YYY
TLV Length: length of the sub-TLVs TLV Length: length of the sub-TLVs
3.2. Level 2 SPF Computation 3.2. Level 2 SPF Computation
When Outside Routers perform a Level 2 SPF computation, they will use When Outside Routers perform a Level 2 SPF computation, they will use
the Area Proxy LSP for computing a path transiting the Inside Area. the Proxy LSP for computing a path transiting the Inside Area.
Because the topology has been abstracted away, the cost for Because the topology has been abstracted away, the cost for
transiting the Inside Area will be zero. transiting the Inside Area will be zero.
When Inside Routers perform a Level 2 SPF computation, they MUST When Inside Routers perform a Level 2 SPF computation, they MUST
ignore the Area Proxy LSP. Further, because these systems do see the ignore the Proxy LSP. Further, because these systems do see the
Inside Area topology, the link metrics internal to the area are Inside Area topology, the link metrics internal to the area are
visible. This could lead to different and possibly inconsistent SPF visible. This could lead to different and possibly inconsistent SPF
results, potentially leading to forwarding loops. results, potentially leading to forwarding loops.
To prevent this, the Inside Routers MUST consider the metrics of To prevent this, the Inside Routers MUST consider the metrics of
links outside of the Inside Area (inter-area metrics) separately from links outside of the Inside Area (inter-area metrics) separately from
the metrics of the Inside Area links (intra-area metrics). Intra- the metrics of the Inside Area links (intra-area metrics). Intra-
area metrics MUST be treated as less than any inter-area metric. area metrics MUST be treated as less than any inter-area metric.
Thus, if two paths have different total inter-area metrics, the path Thus, if two paths have different total inter-area metrics, the path
with the lower inter-area metric would be preferred, regardless of with the lower inter-area metric would be preferred, regardless of
skipping to change at page 8, line 20 skipping to change at page 8, line 20
4.1. Area Leader Election 4.1. Area Leader Election
The Area Leader is selected using the election mechanisms and TLVs The Area Leader is selected using the election mechanisms and TLVs
described in Dynamic Flooding for IS-IS described in Dynamic Flooding for IS-IS
[I-D.ietf-lsr-dynamic-flooding]. [I-D.ietf-lsr-dynamic-flooding].
4.2. Redundancy 4.2. Redundancy
If the Area Leader fails, another candidate may become Area Leader If the Area Leader fails, another candidate may become Area Leader
and MUST regenerate the Area Proxy LSP. The failure of the Area and MUST regenerate the Proxy LSP. The failure of the Area Leader is
Leader is not visible outside of the area and appears to simply be an not visible outside of the area and appears to simply be an update of
update of the Area Proxy LSP. the Proxy LSP.
For consistency, all Area Leader candidates SHOULD be configured with For consistency, all Area Leader candidates SHOULD be configured with
the same Proxy System Id, Proxy Hostname, and any other information the same Proxy System Id, Proxy Hostname, and any other information
that may be inserted into the Proxy LSP. that may be inserted into the Proxy LSP.
4.3. Distributing Area Proxy Information 4.3. Distributing Area Proxy Information
The Area Leader is responsible for distributing information about the The Area Leader is responsible for distributing information about the
area to all Inside Nodes. In particular, the Area Leader distributes area to all Inside Nodes. In particular, the Area Leader distributes
the Proxy System Id and the Area Segment SID. This is done using two the Proxy System Id and the Area SID. This is done using two sub-
sub-TLVs of the Area Proxy TLV. TLVs of the Area Proxy TLV.
4.3.1. The Area Proxy System Id Sub-TLV 4.3.1. The Area Proxy System Id Sub-TLV
The Area Proxy System Id Sub-TLV MUST be used by the Area Leader to The Area Proxy System Id Sub-TLV MUST be used by the Area Leader to
distribute the Area Proxy System Id. This is an additional system distribute the Area Proxy System Id. This is an additional system
identifier that is used by Inside Nodes and an indication that Area identifier that is used by Inside Nodes and an indication that Area
Proxy is active. The format of this sub-TLV is: Proxy is active. The format of this sub-TLV is:
0 1 2 0 1 2
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
skipping to change at page 9, line 29 skipping to change at page 9, line 29
be logged. be logged.
The Area Leader and other candidates for Area Leader MAY withdraw the The Area Leader and other candidates for Area Leader MAY withdraw the
Area Proxy System Identifier when one or more Inside Routers are not Area Proxy System Identifier when one or more Inside Routers are not
advertising the Area Proxy Router Capability. This will disable Area advertising the Area Proxy Router Capability. This will disable Area
Proxy functionality. However, before withdrawing the Area Proxy Proxy functionality. However, before withdrawing the Area Proxy
System Identifier, an implementation SHOULD protect against System Identifier, an implementation SHOULD protect against
unnecessary churn from transients by delaying the withdrawal. The unnecessary churn from transients by delaying the withdrawal. The
amount of delay is implementation-dependent. amount of delay is implementation-dependent.
4.3.2. The Area Segment SID Sub-TLV 4.3.2. The Area SID Sub-TLV
The Area Segment SID Sub-TLV allows the Area Leader to advertise a The Area SID Sub-TLV allows the Area Leader to advertise a SID that
SID that represents the entirety of the Inside Area to the Outside represents the entirety of the Inside Area to the Outside Area. This
Area. This sub-TLV is learned by all of the Inside Edge Nodes who sub-TLV is learned by all of the Inside Edge Nodes who should consume
should consume this SID at forwarding time. The Area Segment SID this SID at forwarding time. The Area SID Sub-TLV has the format:
Sub-TLV has the format:
0 1 2 0 1 2
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Flags | | Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Index/Label (variable) | | SID/Index/Label (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
skipping to change at page 10, line 30 skipping to change at page 10, line 30
proxy SID is used when forwarding IPv6-encapsulated traffic. proxy SID is used when forwarding IPv6-encapsulated traffic.
V: Value Flag. If set, then the proxy SID carries a value. V: Value Flag. If set, then the proxy SID carries a value.
L: Local Flag. If set, then the value/index carried by the proxy L: Local Flag. If set, then the value/index carried by the proxy
SID has local significance. SID has local significance.
Other bits: MUST be zero when originated and ignored when Other bits: MUST be zero when originated and ignored when
received. received.
4.4. Area Proxy LSP Generation 4.4. Proxy LSP Generation
Each Inside Router generates a Level 2 LSP, and the Level 2 LSPs for Each Inside Router generates a Level 2 LSP, and the Level 2 LSPs for
the Inside Edge Routers will include adjacencies to Outside Edge the Inside Edge Routers will include adjacencies to Outside Edge
Routers. Unlike normal Level 2 operations, these LSPs are not Routers. Unlike normal Level 2 operations, these LSPs are not
advertised outside of the Inside Area and MUST be filtered by all advertised outside of the Inside Area and MUST be filtered by all
Inside Edge Routers to not be flooded to Outside Routers. Only the Inside Edge Routers to not be flooded to Outside Routers. Only the
Area Proxy LSP is injected into the overall Level 2 LSDB. Proxy LSP is injected into the overall Level 2 LSDB.
The Area Leader uses the Level 2 LSPs generated by the Inside Edge The Area Leader uses the Level 2 LSPs generated by the Inside Edge
Routers to generate the Area Proxy LSP. This LSP is originated using Routers to generate the Proxy LSP. This LSP is originated using the
the Area Proxy System Identifier. The Area Leader MAY also insert Area Proxy System Identifier. The Area Leader MAY also insert the
the following additional TLVs into the Area Proxy LSP for additional following additional TLVs into the Proxy LSP for additional
information for the Outside Area. LSPs generated by unreachable information for the Outside Area. LSPs generated by unreachable
nodes MUST NOT be considered. nodes MUST NOT be considered.
4.4.1. The Protocols Supported TLV 4.4.1. The Protocols Supported TLV
The Area Leader SHOULD insert a Protocols Supported TLV (129) The Area Leader SHOULD insert a Protocols Supported TLV (129)
[RFC1195] into the Area Proxy LSP. The values included in the TLV [RFC1195] into the Proxy LSP. The values included in the TLV SHOULD
SHOULD be the protocols supported by the Inside Area. be the protocols supported by the Inside Area.
4.4.2. The Area Address TLV 4.4.2. The Area Address TLV
The Area Leader SHOULD insert an Area Addresses TLV (1) [ISO10589] The Area Leader SHOULD insert an Area Addresses TLV (1) [ISO10589]
into the Area Proxy LSP. into the Proxy LSP.
4.4.3. The Dynamic Hostname TLV 4.4.3. The Dynamic Hostname TLV
It is RECOMMENDED that the Area Leader insert the Dynamic Hostname It is RECOMMENDED that the Area Leader insert the Dynamic Hostname
TLV (137) [RFC5301] into the Area Proxy LSP. The contents of the TLV (137) [RFC5301] into the Proxy LSP. The contents of the hostname
hostname may be specified by configuration. The presence of the may be specified by configuration. The presence of the hostname
hostname helps to simplify debugging the network. helps to simplify debugging the network.
4.4.4. The IS Neighbors TLV 4.4.4. The IS Neighbors TLV
The Area Leader MAY insert the IS Neighbors TLV (2) [ISO10589] into The Area Leader MAY insert the IS Neighbors TLV (2) [ISO10589] into
the Area Proxy LSP for Outside Edge Routers. The Area Leader learns the Proxy LSP for Outside Edge Routers. The Area Leader learns of
of the Outside Edge Routers by examining the LSPs generated by the the Outside Edge Routers by examining the LSPs generated by the
Inside Edge Routers copying any IS Neighbors TLVs referring to Inside Edge Routers copying any IS Neighbors TLVs referring to
Outside Edge Routers into the Proxy LSP. Since the Outside Edge Outside Edge Routers into the Proxy LSP. Since the Outside Edge
Routers advertise an adjacency to the Area Proxy System Identifier, Routers advertise an adjacency to the Area Proxy System Identifier,
this will result in a bi-directional adjacency. this will result in a bi-directional adjacency.
An entry for a neighbor in both the IS Neighbors TLV and the Extended An entry for a neighbor in both the IS Neighbors TLV and the Extended
IS Neighbors would be functionally redundant, so the Area Leader IS Neighbors would be functionally redundant, so the Area Leader
SHOULD NOT do this. SHOULD NOT do this.
4.4.5. The Extended IS Neighbors TLV 4.4.5. The Extended IS Neighbors TLV
The Area Leader MAY insert the Extended IS Reachability TLV (22) The Area Leader MAY insert the Extended IS Reachability TLV (22)
[RFC5305] into the Area Proxy LSP. The Area Leader SHOULD copy each [RFC5305] into the Proxy LSP. The Area Leader SHOULD copy each
Extended IS Reachability TLV advertised by an Inside Edge Router Extended IS Reachability TLV advertised by an Inside Edge Router
about an Outside Edge Router into the Proxy LSP. about an Outside Edge Router into the Proxy LSP.
If the Inside Area supports Segment Routing and Segment Routing If the Inside Area supports Segment Routing and Segment Routing
selects a SID where the L-Flag is unset, then the Area Lead SHOULD selects a SID where the L-Flag is unset, then the Area Lead SHOULD
include an Adjacency Segment Identifier sub-TLV (31) [RFC8667] using include an Adjacency Segment Identifier sub-TLV (31) [RFC8667] using
the selected SID. the selected SID.
If the inside area supports SRv6, the Area Leader SHOULD copy the If the inside area supports SRv6, the Area Leader SHOULD copy the
"SRv6 End.X SID" and "SRv6 LAN End.X SID" sub-TLVs of the extended IS "SRv6 End.X SID" and "SRv6 LAN End.X SID" sub-TLVs of the extended IS
skipping to change at page 12, line 34 skipping to change at page 12, line 34
Extended IP Reachability TLV (135) [RFC5305] Extended IP Reachability TLV (135) [RFC5305]
IPv6 Reachability TLV (236) [RFC5308] IPv6 Reachability TLV (236) [RFC5308]
Multi-Topology Reachable IPv4 Prefixes TLV (235) [RFC5120] Multi-Topology Reachable IPv4 Prefixes TLV (235) [RFC5120]
Multi-Topology Reachable IPv6 Prefixes TLV (237) [RFC5120] Multi-Topology Reachable IPv6 Prefixes TLV (237) [RFC5120]
For TLVs in the Level 1 LSDB, for a given TLV type and prefix, the For TLVs in the Level 1 LSDB, for a given TLV type and prefix, the
Area Leader SHOULD select the TLV with the lowest metric and copy Area Leader SHOULD select the TLV with the lowest metric and copy
that TLV into the Area Proxy LSP. that TLV into the Proxy LSP.
When examining the Level 2 LSDB for this function, the Area Leader When examining the Level 2 LSDB for this function, the Area Leader
SHOULD only consider TLVs advertised by Inside Routers. Further, for SHOULD only consider TLVs advertised by Inside Routers. Further, for
prefixes that represent Boundary links, the Area Leader SHOULD copy prefixes that represent Boundary links, the Area Leader SHOULD copy
all TLVs that have unique sub-TLV contents. all TLVs that have unique sub-TLV contents.
If the Inside Area supports Segment Routing and the selected TLV If the Inside Area supports Segment Routing and the selected TLV
includes a Prefix Segment Identifier sub-TLV (3) [RFC8667], then the includes a Prefix Segment Identifier sub-TLV (3) [RFC8667], then the
sub-TLV SHOULD be copied as well. The P-Flag SHOULD be set in the sub-TLV SHOULD be copied as well. The P-Flag SHOULD be set in the
copy of the sub-TLV to indicate that penultimate hop popping SHOULD copy of the sub-TLV to indicate that penultimate hop popping SHOULD
NOT be performed for this prefix. The E-Flag SHOULD be reset in the NOT be performed for this prefix. The E-Flag SHOULD be reset in the
copy of the sub-TLV to indicate that an explicit NULL is not copy of the sub-TLV to indicate that an explicit NULL is not
required. The R-Flag SHOULD simply be copied. required. The R-Flag SHOULD simply be copied.
4.4.8. The Router Capability TLV 4.4.8. The Router Capability TLV
The Area Leader MAY insert the Router Capability TLV (242) [RFC7981] The Area Leader MAY insert the Router Capability TLV (242) [RFC7981]
into the Area Proxy LSP. If Segment Routing is supported by the into the Proxy LSP. If Segment Routing is supported by the inside
inside area, as indicated by the presence of an SRGB being advertised area, as indicated by the presence of an SRGB being advertised by all
by all Inside Nodes, then the Area Leader SHOULD advertise an SR- Inside Nodes, then the Area Leader SHOULD advertise an SR-
Capabilities sub-TLV (2) [RFC8667] with an SRGB. The first value of Capabilities sub-TLV (2) [RFC8667] with an SRGB. The first value of
the SRGB is the same value as the first value advertised by all the SRGB is the same value as the first value advertised by all
Inside Nodes. The range advertised for the area will be the minimum Inside Nodes. The range advertised for the area will be the minimum
of all ranges advertised by Inside Nodes. The Area Leader SHOULD use of all ranges advertised by Inside Nodes. The Area Leader SHOULD use
its own Router Id in the Router Capability TLV. its own Router Id in the Router Capability TLV.
If SRv6 Capability sub-TLV [RFC7981] is advertised by all Inside If SRv6 Capability sub-TLV [RFC7981] is advertised by all Inside
Routers, the Area Leader should insert an SRv6 Capability sub-TLV in Routers, the Area Leader should insert an SRv6 Capability sub-TLV in
the Router Capability TLV. Each flag in the SRv6 Capability sub-TLV the Router Capability TLV. Each flag in the SRv6 Capability sub-TLV
should be set if the flag is set by all Inside Routers. should be set if the flag is set by all Inside Routers.
skipping to change at page 13, line 43 skipping to change at page 13, line 43
topology, then the Area Leader MUST advertise the 'O' bit for that topology, then the Area Leader MUST advertise the 'O' bit for that
topology. If any Inside Node is advertising the 'A' (Attach) bit for topology. If any Inside Node is advertising the 'A' (Attach) bit for
a given topology, then the Area Leader MUST advertise the 'A' bit for a given topology, then the Area Leader MUST advertise the 'A' bit for
that topology. that topology.
4.4.10. The SID/Label Binding and The Multi-Topology SID/Label Binding 4.4.10. The SID/Label Binding and The Multi-Topology SID/Label Binding
SID TLV SID TLV
If an Inside Node advertises the SID/Label Binding or Multi-Topology If an Inside Node advertises the SID/Label Binding or Multi-Topology
SID/Label Binding SID TLV [RFC8667], then the Area Leader MAY copy SID/Label Binding SID TLV [RFC8667], then the Area Leader MAY copy
the TLV to the Area Proxy LSP. the TLV to the Proxy LSP.
4.4.11. The SRv6 Locator TLV 4.4.11. The SRv6 Locator TLV
If the inside area supports SRv6, the Area Leader SHOULD copy all If the inside area supports SRv6, the Area Leader SHOULD copy all
SRv6 locator TLVs [I-D.ietf-lsr-isis-srv6-extensions] advertised by SRv6 locator TLVs [I-D.ietf-lsr-isis-srv6-extensions] advertised by
Inside Routers to the Proxy LSP. Inside Routers to the Proxy LSP.
4.4.12. Traffic Engineering Information 4.4.12. Traffic Engineering Information
If the inside area supports TE, the Area Leader SHOULD advertise a TE If the inside area supports TE, the Area Leader SHOULD advertise a TE
Router ID TLV (134) [RFC5305] in the Proxy LSP. It SHOULD copy the Router ID TLV (134) [RFC5305] in the Proxy LSP. It SHOULD copy the
Shared Risk Link Group (SRLS) TLVs (138) [RFC5307] advertised by Shared Risk Link Group (SRLS) TLVs (138) [RFC5307] advertised by
Inside Edge Routers about links to Outside Edge Routers. Inside Edge Routers about links to Outside Edge Routers.
If the inside area supports IPv6 TE, the Area Leader SHOULD advertise If the inside area supports IPv6 TE, the Area Leader SHOULD advertise
an IPv6 TE Router ID TLV (140) [RFC6119] in the Proxy LSP. It SHOULD an IPv6 TE Router ID TLV (140) [RFC6119] in the Proxy LSP. It SHOULD
also copy the IPv6 SRLG TLVs (139) [RFC6119] advertised by Inside also copy the IPv6 SRLG TLVs (139) [RFC6119] advertised by Inside
Edge Routers about links to Outside Edge Routers. Edge Routers about links to Outside Edge Routers.
4.4.13. The Area Segment SID 4.4.13. The Area SID
If the Area Leader is advertising an Area Segment SID in the Area When SR is enabled, it may be useful to advertise an Area SID which
Segment SID sub-TLV of the Area Proxy TLV, then the Area Leader will direct traffic to any of the Inside Edge Routers. The Binding/
SHOULD advertise the Area Segment SID in the Proxy LSP. The MT Binding TLVs described in RFC 8667 Section 2.4 are used to
advertisement in the Proxy LSP informs the remainder of the network advertise such a SID.
that packets directed to the SID will be forwarded by one of the
Inside Edge Nodes and the Area Segment SID will be consumed.
Area Segment SIDs are advertised using the SID/Label Binding TLV The following extensions to the Binding TLV are defined in order to
[RFC8667], Section 2.4 or the Multi-Topology SID/Label Binding TLV, support Area SID:
section 2.5. The Area Segment SID Sub-TLV (Section 4.3.2) is used in
either TLV to convey the SID. A new flag is defined:
T-flag: The SID directs traffic to an area. (Bit 5)
When T-flag is set:
M and A flag MUST be clear
Range and Prefix are ignored
Section 2.4.4 of RFC 8667 is altered to say:
"The Prefix-SID sub-TLV MUST be present in the SID/Label
Binding TLV when the M-Flag and T-flag are both clear. The
Prefix-SID sub-TLV MUST NOT be present when either the M-Flag
or T-flag are set."
Regarding the SID/Label sub-TLV Section 2.4.5 of RFC 8667 is
altered to say:
"It MUST be present in the SID/Label Binding TLV when either
the M-Flag or T-flag is set in the Flags field of the parent
TLV."
When used in support of Area Proxy, the SID advertised MUST be
identical to the Area SID (Section 4.3.2). Other uses of the Area
SID are outside the scope of this document. Documents which define
other use cases for the Area SID MUST specify whether the SID value
should be the same or different from that used in support of Area
Proxy.
If the Area Leader is advertising an Area SID in the Area SID sub-TLV
of the Area Proxy TLV, then the Area Leader SHOULD advertise the Area
SID in the Proxy LSP. The advertisement in the Proxy LSP informs the
remainder of the network that packets directed to the SID will be
forwarded by one of the Inside Edge Nodes and the Area SID will be
consumed.
5. Inside Edge Router Functions 5. Inside Edge Router Functions
The Inside Edge Router has two additional and important functions. The Inside Edge Router has two additional and important functions.
First, it MUST generate IIHs that appear to have come from the Area First, it MUST generate IIHs that appear to have come from the Area
Proxy System Identifier. Second, it MUST filter the L2 LSPs, Partial Proxy System Identifier. Second, it MUST filter the L2 LSPs, Partial
Sequence Number PDUs (PSNPs), and Complete Sequence Number PDUs Sequence Number PDUs (PSNPs), and Complete Sequence Number PDUs
(CSNPs) that are being advertised to Outside Routers. (CSNPs) that are being advertised to Outside Routers.
5.1. Generating L2 IIHs to Outside Routers 5.1. Generating L2 IIHs to Outside Routers
skipping to change at page 16, line 23 skipping to change at page 17, line 9
Size, format, and syntax of registry entries: Value (0-255), Name, Size, format, and syntax of registry entries: Value (0-255), Name,
and Reference and Reference
Initial assignments and reservations: IANA is requested to assign Initial assignments and reservations: IANA is requested to assign
the following code points: the following code points:
+-------+------------------------------+---------------+ +-------+------------------------------+---------------+
| Value | Name | Reference | | Value | Name | Reference |
+-------+------------------------------+---------------+ +-------+------------------------------+---------------+
| AAA | Area Proxy System Identifier | This document | | AAA | Area Proxy System Identifier | This document |
| BBB | Area Segment SID | This document | | BBB | Area SID | This document |
+-------+------------------------------+---------------+ +-------+------------------------------+---------------+
This memo also requests that IANA allocate a code point (ZZZ) for the This memo also requests that IANA allocate a code point (ZZZ) for the
Area Segment SID subTLV in the registry for Sub-TLVs for TLVs 149 and Area SID subTLV in the registry for Sub-TLVs for TLVs 149 and 150.
150.
8. Security Considerations 8. Security Considerations
This document introduces no new security issues. Security of routing This document introduces no new security issues. Security of routing
within a domain is already addressed as part of the routing protocols within a domain is already addressed as part of the routing protocols
themselves. This document proposes no changes to those security themselves. This document proposes no changes to those security
architectures. architectures.
9. References 9. References
 End of changes. 34 change blocks. 
77 lines changed or deleted 110 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/