Networking Working Group L. Ginsberg, Ed. Internet-Draft Cisco Systems Intended status: Standards Track B. Decraene Expires: June 19, 2016 Orange S. Previdi Cisco Systems X. Xu Huawei U. Chunduri Ericsson December 17, 2015 IS-IS Prefix Attributes for Extended IP and IPv6 Reachability draft-ietf-isis-prefix-attributes-03.txt Abstract This document introduces new sub-TLVs to support advertisement of prefix attribute flags and the source router ID of the router which originated a prefix advertisement. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 19, 2016. Ginsberg, et al. Expires June 19, 2016 [Page 1] Internet-Draft isis-prefix-attributes December 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. New sub-TLVs for Extended Reachability TLVs . . . . . . . . . 3 2.1. IPv4/IPv6 Extended Reachability Attribute Flags . . . . . 3 2.2. IPv4/IPv6 Source Router ID . . . . . . . . . . . . . . . 5 2.3. Advertising Router IDs . . . . . . . . . . . . . . . . . 5 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. Normative References . . . . . . . . . . . . . . . . . . 7 6.2. Informational References . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction There are existing use cases in which knowing additional attributes of a prefix is useful. It is useful to know whether an advertised prefix is directly connected to the advertising router or not. In the case of [SR] knowing whether a prefix is directly connected or not determines what action should be taken as regards processing of labels associated with an incoming packet. It is useful to know what addresses can be used as addresses of the node in support of services (e.g., Remote Loop Free Alternate (RLFA) endpoint). Current formats of the Extended Reachability TLVs for both IP and IPv6 are fixed and do not allow the introduction of additional flags without backwards compatibility issues. Therefore a new sub-TLV is Ginsberg, et al. Expires June 19, 2016 [Page 2] Internet-Draft isis-prefix-attributes December 2015 introduced which allows for the advertisement of attribute flags associated with prefix advertisements. In cases where multiple node addresses are advertised by a given router it is also useful to be able to associate all of these addresses with a single Router-ID even when prefixes are advertised outside of the area in which they are originated. Therefore a new sub-TLV is introduced to advertise the router-id of the originator of a prefix advertisement. 2. New sub-TLVs for Extended Reachability TLVs The following new sub-TLVs are introduced: o IPv4/IPv6 Extended Reachability Attributes o IPv4 Source Router ID o IPv6 Source Router ID All sub-TLVs are applicable to TLVs 135, 235, 236, and/or 237. 2.1. IPv4/IPv6 Extended Reachability Attribute Flags This sub-TLV supports the advertisement of additional flags associated with a given prefix advertisement. The behavior of each flag when a prefix advertisement is leaked from one level to another (upwards or downwards) is explicitly defined below. All flags are applicable to TLVs 135, 235, 236, 237 unless otherwise stated. Ginsberg, et al. Expires June 19, 2016 [Page 3] Internet-Draft isis-prefix-attributes December 2015 Prefix Attribute Flags Type: 4 (suggested - to be assigned by IANA) Length: Number of octets to follow Value (Length * 8) bits. 0 1 2 3 4 5 6 7... +-+-+-+-+-+-+-+-+... |X|R|N| ... +-+-+-+-+-+-+-+-+... Bits are defined/sent starting with Bit #0 defined below. Additional bit definitions which may be defined in the future SHOULD be assigned in ascending bit order so as to minimize the number of bits which will need to be transmitted. Undefined bits MUST be transmitted as 0 and MUST be ignored on receipt. Bits which are NOT transmitted MUST be treated as if they are set to 0 on receipt. X-Flag: External Prefix Flag (Bit 0) Set if the prefix has been redistributed from another protocol. This includes the case where multiple virtual routers are supported and the source of the redistributed prefix is another IS-IS instance. The flag MUST be preserved when leaked between levels. In TLVs 236 and 237 this flag SHOULD always be sent as 0 and MUST be ignored on receipt. This is because there is an existing X flag defined in the fixed format of these TLVs as specified in [RFC5308] and [RFC5120]. R-Flag: Re-advertisement Flag (Bit 1) Set when the prefix has been leaked from one level to another (upwards or downwards). N-flag: Node Flag (Bit 2) Set when the prefix identifies the advertising router i.e., the prefix is a host prefix advertising a globally reachable address typically associated with a loopback address. The advertising router MAY choose to NOT set this flag even when the above conditions are met. If the flag is set and the prefix length is NOT a host prefix (/32 for IPV4, /128 for IPv6) then the flag MUST be ignored. The flag MUST be preserved when leaked between levels. Ginsberg, et al. Expires June 19, 2016 [Page 4] Internet-Draft isis-prefix-attributes December 2015 2.2. IPv4/IPv6 Source Router ID When a reachability advertisement is leaked from one level to another, the source of the original advertisement is unknown. In cases where the advertisement is an identifier for the advertising router (e.g., N-flag set in the Extended Reachability Attribute sub- TLV as described in the previous section) it may be useful for other routers to know the source of the advertisement. The sub-TLVs defined below provide this information. Note that the Router ID advertised is always the Router ID of the IS- IS instance which originated the advertisement. This would be true even if the prefix has been learned from another protocol (X-flag set as defined in Section 2.1). IPv4 Source Router ID Type: 11 (suggested - to be assigned by IANA) Length: 4 Value: IPv4 Router ID of the source of the advertisement Inclusion of this TLV is optional and MAY occur in TLVs 135, 235, 236, or 237. When included the value MUST be identical to the value advertised in Traffic Engineering router ID (TLV 134) defined in [RFC5305]. If present the sub-TLV MUST be included when the prefix advertisement is leaked to another level. IPv6 Source Router ID Type: 12 (suggested - to be assigned by IANA) Length: 16 Value: IPv6 Router ID of the source of the advertisement Inclusion of this TLV is optional and MAY occur in TLVs 135, 235, 236, or 237. When included the value MUST be identical to the value advertised in IPv6 TE Router ID (TLV 140) defined in [RFC6119]. If present the sub-TLV MUST be included when the prefix advertisement is leaked to another level. 2.3. Advertising Router IDs [RFC5305] and [RFC6119] define the advertisement of router IDs for IPv4 and IPv6 respectively. Although both drafts discuss the use of router ID in the context of Traffic Engineering (TE), the advertisement of router IDs is explicitly allowed for purposes other Ginsberg, et al. Expires June 19, 2016 [Page 5] Internet-Draft isis-prefix-attributes December 2015 than TE. The use of router IDs to identify the source of a prefix advertisement as defined in the previous section is one such use case. Therefore, whenever the source router ID sub-TLVs defined in the previous section are used, the originating router SHOULD also advertise the corresponding address-family specific router ID TLV(s). 3. IANA Considerations This document adds the following new sub-TLVs to the registry of sub- TLVs for TLVs 135, 235, 236, 237. Value: 4 (suggested - to be assigned by IANA) Name: Prefix Attribute Flags Value: 11 (suggested - to be assigned by IANA) Name: IPv4 Source Router ID Value: 12 (suggested - to be assigned by IANA) Name: IPv6 Source Router ID This document also introduces a new registry for bit values in the Prefix Attribute Flags sub-TLV. Registration policy is Expert Review as defined in [RFC5226]. This registry is to be part of the IS-IS TLV Codepoints registery. Defined values are: Bit # Name ----- ------------------------ 0 External Prefix Flag 1 Re-advertisement Flag 2 Node Flag 4. Security Considerations Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310]. Advertisement of the additional information defined in this document introduces no new security concerns. 5. Contributors The following people gave a substantial contribution to the content of this document and should be considered as co-authors: Ginsberg, et al. Expires June 19, 2016 [Page 6] Internet-Draft isis-prefix-attributes December 2015 Clarence Filsfils Cisco Systems Email: cf@cisco.com Stephane Litkowski Orange Business Service Email: stephane.litkowski@orange.com 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, . [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, October 2008, . [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009, . Ginsberg, et al. Expires June 19, 2016 [Page 7] Internet-Draft isis-prefix-attributes December 2015 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, February 2011, . 6.2. Informational References [SR] "IS-IS Extensions for Segment Routing, draft-ietf-isis- segment-routing-extensions-06(work in progress)", December 2015. Authors' Addresses Les Ginsberg (editor) Cisco Systems 510 McCarthy Blvd. Milpitas, CA 95035 USA Email: ginsberg@cisco.com Bruno Decraene Orange 38 rue du General Leclerc Issy Moulineaux cedex 9 92794 France Email: bruno.decraene@orange.com Stefano Previdi Cisco Systems Via Del Serafico 200 Rome 0144 Italy Email: sprevidi@cisco.com Xiaohu Xu Huawei Email: xuxiaohu@huawei.com Ginsberg, et al. Expires June 19, 2016 [Page 8] Internet-Draft isis-prefix-attributes December 2015 Uma Chunduri Ericsson Email: uma.chunduri@ericsson.com Ginsberg, et al. Expires June 19, 2016 [Page 9]