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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: - If it's non DIS for that link, SHOULD not take any action. -- The document date (March 9, 2015) is 3335 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' ** Downref: Normative reference to an Informational RFC: RFC 3277 ** Obsolete normative reference: RFC 3784 (Obsoleted by RFC 5305) Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IS-IS IGP S. Hegde 3 Internet-Draft P. Sarkar 4 Intended status: Standards Track H. Gredler 5 Expires: September 10, 2015 Juniper Networks, Inc. 6 March 9, 2015 8 ISIS Link Overload 9 draft-hegde-isis-link-overload-00 11 Abstract 13 Many ISIS deployments run on overlay networks provisioned by means of 14 pseudo-wires or L2-circuits. when the devices in the underlying 15 network go for maintenance, it is useful to divert the traffic away 16 from the specific node(s), to some alternate paths, before the 17 maintenance is actually scheduled. Since the nodes in the underlying 18 network are not visible to ISIS, existing Avoidance of traffic 19 blackhole mechanism described in [RFC3277] cannot be used. It is 20 useful for routers in IS-IS routing domain to be able to advertise a 21 link being in overload state to indicate impending maintenance 22 activity in the underlying network devices. 24 This document describes the protocol extensions to disseminate link 25 overload information in IS-IS protocol. 27 Requirements Language 29 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 30 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 31 document are to be interpreted as described in RFC 2119 [RFC2119]. 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on September 10, 2015. 50 Copyright Notice 52 Copyright (c) 2015 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. ISIS Link overload bit . . . . . . . . . . . . . . . . . . . . 3 69 3. Elements of procedure . . . . . . . . . . . . . . . . . . . . . 3 70 3.1. Point-to-point links . . . . . . . . . . . . . . . . . . . 3 71 3.2. Broadcast links . . . . . . . . . . . . . . . . . . . . . . 4 72 4. Backward compatibility . . . . . . . . . . . . . . . . . . . . 4 73 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 74 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 75 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 76 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 77 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 78 8.2. Informative References . . . . . . . . . . . . . . . . . . 5 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 81 1. Introduction 83 It is useful for routers in IS-IS routing domain to be able to 84 advertise a link being in overload state to indicate impending 85 maintenance activity on the link. This document provides mechanisms 86 to advertise link overload state in the Link attributes TLV as 87 defined in [RFC5029] 89 2. ISIS Link overload bit 91 The link-attribute sub-TLV is carried within the TLV 22 and has a 92 format identical to the sub-TLV format used by the Traffic 93 Engineering Extensions for IS-IS ([RFC3784]): 1 octet of sub-type, 1 94 octet of length of the value field of the sub-TLV followed by the 95 value field -- in this case, a 16 bit flags field. 97 The following bit represents the Link in overload. 99 Link Overload: 0x04 When set, this indicates that the link is 100 overloaded. 102 3. Elements of procedure 104 The Link attributes sub TLV with link-overload bit set indicates that 105 the Link which carries the sub TLV is overloaded. The node that has 106 the link going for maintenance, sets metric of the link to MAX-METRIC 107 and re-originates the LSP. The metric in the reverse direction also 108 need to change to divert the traffic from reverse direction. The 109 node SHOULD originate Link attributes sub TLV and set the overload 110 bit and originate the LSP and flood it in the respective IS-IS level. 112 When the originator of the Link attributes sub TLV, purges the LSP or 113 re-originates it without the Link Overload bit set, the metric on the 114 remote node SHOULD be changed back to the original value. 116 Based on the link type of the overloaded link, actions listed below 117 MAY be taken by the receiver. 119 3.1. Point-to-point links 121 When a link attributes sub TLV with link overload bit set is received 122 for a point-to-point link the receiver SHOULD identify the local link 123 which corresponds to the overloaded link and set the metric to MAX- 124 METRIC. Receiver node MUST re-originate the LSP with the changed 125 metric and flood into the ISIS level. 127 3.2. Broadcast links 129 Broadcast networks in ISIS are represented by a star topology where 130 the Designated Intermediate System (DIS) is the central point to 131 which all other routers on the broadcast network connect. As a 132 result, routers on the broadcast network advertise only their 133 adjacency to the pseudo-node.As a result, routers on the broadcast 134 network advertise only their adjacency to the pseudo- node. Routers 135 that do not act as DIS do not advertise adjacencies with each other. 136 DIS originates pseudo-node which contains adjacenices with all the 137 neighbors. For the Broadcast links, the MAX-METRIC on the outgoing 138 link cannot be changed since all the adjacencies are on same link. 139 Setting the link cost to MAX- METRIC would impact paths going via all 140 neighbors. 142 When a link-attributes sub TLV with link-overload bit set is received 143 by the remote end for a broadcast link. 145 - If it's non DIS for that link, SHOULD not take any action. 147 - If receiving node is DIS for the link, it MUST set the metric from 148 the pseudo-node to the originator of the link overload bit to MAX- 149 METRIC and MUST re-originate the pseudo-node LSP and flood into the 150 ISIS Level. 152 4. Backward compatibility 154 The mechanism described in the document is fully backward 155 compatible.It is required that the originator and receiver of link- 156 overload bit understand the extensions defined in this document and 157 in case of broadcast links the originator and the DR need to 158 understand the extensions. Other nodes in the network compute based 159 on increased metric and hence the feature is backward compatible. 161 5. Security Considerations 163 This document does not introduce any further security issues other 164 than those discussed in [ISO10589] and [RFC1195]. 166 6. IANA Considerations 168 This specification updates one ISIS registry: ISIS Link attributes 169 Sub TLV 170 i) 0x04 - Link overload bit 172 7. Acknowledgements 174 8. References 176 8.1. Normative References 178 [ISO10589] 179 "Intermediate system to Intermediate system intra-domain 180 routeing information exchange protocol for use in 181 conjunction with the protocol for providing the 182 connectionless-mode Network Service (ISO 8473), ISO/IEC 183 10589:2002, Second Edition.", Nov 2002. 185 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 186 dual environments", RFC 1195, December 1990. 188 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 189 Requirement Levels", BCP 14, RFC 2119, March 1997. 191 [RFC3277] McPherson, D., "Intermediate System to Intermediate System 192 (IS-IS) Transient Blackhole Avoidance", RFC 3277, 193 April 2002. 195 [RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate 196 System (IS-IS) Extensions for Traffic Engineering (TE)", 197 RFC 3784, June 2004. 199 [RFC5029] Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link 200 Attribute Sub-TLV", RFC 5029, September 2007. 202 8.2. Informative References 204 Authors' Addresses 206 Shraddha Hegde 207 Juniper Networks, Inc. 208 Embassy Business Park 209 Bangalore, KA 560093 210 India 212 Email: shraddha@juniper.net 213 Pushpasis Sarkar 214 Juniper Networks, Inc. 215 Embassy Business Park 216 Bangalore, KA 560093 217 India 219 Email: psarkar@juniper.net 221 Hannes Gredler 222 Juniper Networks, Inc. 223 1194 N. Mathilda Ave. 224 Sunnyvale, CA 94089 225 US 227 Email: hannes@juniper.net