draft-ietf-lsr-isis-area-proxy-02.txt   draft-ietf-lsr-isis-area-proxy-03.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 26, 2021 Arista Networks Expires: February 6, 2021 Arista Networks
G. Mishra G. Mishra
Verizon Inc. Verizon Inc.
July 25, 2020 August 5, 2020
Area Proxy for IS-IS Area Proxy for IS-IS
draft-ietf-lsr-isis-area-proxy-02 draft-ietf-lsr-isis-area-proxy-03
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,
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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 26, 2021. This Internet-Draft will expire on February 6, 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
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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 SID Sub-TLV . . . . . . . . . . . . . . . . 9 4.3.2. The Area SID Sub-TLV . . . . . . . . . . . . . . . . 9
4.3.2.1. Flags . . . . . . . . . . . . . . . . . . . . . . 10
4.4. 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 . . . . . . . . . . . . . 11
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 SID . . . . . . . . . . . . . . . . . . . . 14 4.4.13. The Area SID . . . . . . . . . . . . . . . . . . . . 14
5. Inside Edge Router Functions . . . . . . . . . . . . . . . . 15 5. Inside Edge Router Functions . . . . . . . . . . . . . . . . 14
5.1. Generating L2 IIHs to Outside Routers . . . . . . . . . . 15 5.1. Generating L2 IIHs to Outside Routers . . . . . . . . . . 14
5.2. Filtering LSP information . . . . . . . . . . . . . . . . 15 5.2. Filtering LSP information . . . . . . . . . . . . . . . . 15
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Normative References . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . 16
9.2. Informative References . . . . . . . . . . . . . . . . . 19 9.2. Informative References . . . . . . . . . . . . . . . . . 18
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
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
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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 SID Sub-TLV 4.3.2. The Area SID Sub-TLV
The Area SID Sub-TLV allows the Area Leader to advertise a SID that The Area SID Sub-TLV allows the Area Leader to advertise a prefix and
represents the entirety of the Inside Area to the Outside Area. This SID that represents the entirety of the Inside Area to the Outside
sub-TLV is learned by all of the Inside Edge Nodes who should consume Area. This sub-TLV is learned by all of the Inside Edge Nodes who
this SID at forwarding time. The Area SID Sub-TLV has the format: should consume this SID at forwarding time. The Area SID 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: BBB in the Area Proxy TLV, ZZZ in TLV 149 or 150. Type: BBB
Length: variable (1 + SID length) Length: variable (1 + SID length)
Flags: 1 octet. Flags: 1 octet.
SID/Index/Label: as defined in [RFC8667] Section 2.1.1.1 SID/Index/Label: as defined in [RFC8667] Section 2.1.1.1
4.3.2.1. Flags Prefix Length: 1 octet
Prefix: 0-16 octets
The Flags octet is defined as follows: The Flags octet is defined as follows:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|F|V|L| | |F|V|L| |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where: where:
F: Address-Family Flag. If unset, then this proxy SID is used F: Address-Family Flag. If unset, then this proxy SID is used
when forwarding IPv4-encapsulated traffic. If set, then this when forwarding IPv4-encapsulated traffic. If set, then this
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
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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 SID 4.4.13. The Area SID
When SR is enabled, it may be useful to advertise an Area SID which When SR is enabled, it may be useful to advertise an Area SID which
will direct traffic to any of the Inside Edge Routers. The Binding/ will direct traffic to any of the Inside Edge Routers. The
MT Binding TLVs described in RFC 8667 Section 2.4 are used to information for the Area SID is distributed to all Inside Edge
advertise such a SID. Routers using the Area SID sub-TLV (Section 4.3.2) by the Area
Leader.
The following extensions to the Binding TLV are defined in order to
support Area 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 The Area Leader SHOULD advertise the Area SID information in the
identical to the Area SID (Section 4.3.2). Other uses of the Area Proxy LSP as a Node SID as defined in [RFC8667] Section 2.1. The
SID are outside the scope of this document. Documents which define advertisement in the Proxy LSP informs the remainder of the network
other use cases for the Area SID MUST specify whether the SID value that packets directed to the SID will be forwarded by one of the
should be the same or different from that used in support of Area Inside Edge Nodes and the Area SID will be consumed.
Proxy.
If the Area Leader is advertising an Area SID in the Area SID sub-TLV Other uses of the Area SID are outside the scope of this document.
of the Area Proxy TLV, then the Area Leader SHOULD advertise the Area Documents which define other use cases for the Area SID MUST specify
SID in the Proxy LSP. The advertisement in the Proxy LSP informs the whether the SID value should be the same or different from that used
remainder of the network that packets directed to the SID will be in support of Area Proxy.
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
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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 SID | This document | | BBB | Area SID | This document |
+-------+------------------------------+---------------+ +-------+------------------------------+---------------+
This memo also requests that IANA allocate a code point (ZZZ) for the
Area SID subTLV in the registry for Sub-TLVs for TLVs 149 and 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
9.1. Normative References 9.1. Normative References
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