IS-IS Working Group Z. Li Internet Draft L. Li Intended status: BEST CURRENT PRACTICE X. Duan Expires: September 1, 2009 China Mobile March 2, 2009 Recommendations for Processing Mechanism for Checksum Error LSP in Interoperable Networks using Intermediate System to Intermediate System (IS-IS) draft-li-isis-error-lsp-processing-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on September 2,2009. Copyright Notice Copyright (c) 2009 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, Li Expires September 2,2009 [Page 1] Internet-Draft draft-li-isis-error-lsp-processing March 2009 as they describe your rights and restrictions with respect to this document. Abstract This document discusses the processing mechanism for the Link State Protocol Data Unit (LSP) with an incorrect LSP Checksum in the interoperable networks using IS-IS. It is suggested to add a configurable switch to control the processing mechanism of checksum error LSP. This document clarifies the processing mechanism for zero checksum LSP and zero remaining lifetime LSP, and gives advices to calculate the checksum of all kinds of LSPs as well. 1. Introduction Intermediate System to Intermediate System (IS-IS) Protocol [1] is one of the Interior Gateway Protocols. It is widely deployed in the carrier backbone networks. Section 7.3.14.2 e) of [1] states: An Intermediate system receiving a Link State PDU (LSP) with an incorrect LSP Checksum or with an invalid PDU syntax shall 1) generate a corruptedLSPReceived circuit event, 2) discard the PDU. However practically, operators usually request that equipments can provide control switch in order to control the processing mechanism of Checksum error LSP. Actually, some equipment manufacturers have provided such configuration switch, such as Cisco's IGNORE-LSP- ERRORS switch and Huawei's IGNORE-LSP-CHECKSUM-ERROR switch. But for the lack of unified standards, the default state of the switch is usually diverse, and the processing mechanism of checksum error LSP is not exactly the same. Many unexpected failures may occur in the multi-manufacture environment. Besides, the processing mechanism of zero Remaining Lifetime LSP for different manufacturers is not completely the same. This document aims at posing these issues, and gives uniform suggestion. 2. Terminology 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 [2]. Li Expires September 1,2009 [Page 2] Internet-Draft draft-li-isis-error-lsp-processing March 2009 3. On-off Switch All the devices implementing IS-IS SHOULD provide an on-off switch to control the processing mechanism when they receive a LSP with an incorrect LSP Checksum. The on-off switch SHOULD be configurable through the Command Line Interface (CLI). When the on-off switch is on, the processing mechanism for the checksum error LSP SHOULD be accordant with what is stated in Section 7.3.14.2 e) of [1]. When the on-off switch is off, the equipment SHOULD treat the received checksum error LSP in the same way as the LSP whose remaining lifetime equals 0. The processing mechanism is specified in Section 7.3.16.4 of [1]. It is RECOMMENDED that the default state of the on-off switch be on. In this way, the default processing mechanism is in accordance with Section 7.3.14.2 e) of [1]. 4. Zero checksum RFC 3719 [3], section 7, suggests an implementation SHOULD treat all LSPs with a zero checksum and a non-zero remaining lifetime as if they had as checksum error. Equipments with on-off switch SHOULD treat such LSPs in accordance with the processing mechanism mentioned in the previous section 3. ISO 10589, section 7.3.16.4, note 36, states: A check of the checksum of a zero Remaining Lifetime LSP succeeds even though the data portion is not present. Therefore, the LSP with a zero checksum and a zero remaining lifetime SHOULD be treated as the LSP with correct checksum, and the processing mechanism SHOULD NOT be affected by the switch state. To insure the interoperability and maintain network stability, it is RECOMMENDED that the checksum of all LSPs, including the LSP with a zero remaining lifetime, SHOULD be calculated correctly, just as described in section 6. 5. Zero remaining lifetime ISO 10589, section 7.3.16.4, note 36, states: A check of the checksum of a zero Remaining Lifetime LSP succeeds even though the data portion is not present. Therefore, a zero Remaining Lifetime LSP SHOULD be treated as correct LSP, no matter whether its checksum is correct or not. The processing mechanism SHOULD NOT be affected by the on-off switch and the details can be seen in section 7.3.16.4. Li Expires September 1,2009 [Page 3] Internet-Draft draft-li-isis-error-lsp-processing March 2009 However, in order to insure the interoperability and maintain network stability, the checksum of zero Remaining Lifetime LSP is RECOMMENDED to be calculated correctly as well, as described in section 6. 6. Checksum calculation Although note 36, section 7.3.16.4, ISO 10589 prescribes that examining the checksum of a zero Remaining Lifetime LSP is always successful, to insure the interoperability and maintain network stability, it is RECOMMENDED to calculate the checksum of all LSPs correctly, including zero Remaining Lifetime LSP. The calculation method is presented in Section 7.3.11, ISO 10589. 7. Security Considerations The suggestions and clarifications in this document will not cause extra new security concerns. 8. References [1] ISO 10589 V2 Telecommunications and information exchange between systems-Intermediate System to Intermediate System [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] J. Parker, Ed., "Recommendations for Interoperable Networks using Intermediate System to Intermediate System (IS- IS)", RFC 3719, February 2004. Author's Addresses Zhenqiang Li (editor) China Mobile Research Institute Gate 2 Dacheng Plaza No. 28 Xuanwumen West Street Xuanwu District, Beijing 100053 China Phone: +86 1391 163 5816 Email: lizhenqiang@chinamobile.com Li Expires September 1,2009 [Page 4] Internet-Draft draft-li-isis-error-lsp-processing March 2009 Lianyuan Li China Mobile Research Institute Gate 2 Dacheng Plaza No. 28 Xuanwumen West Street Xuanwu District, Beijing 100053 China Phone: +86 1391 178 9703 Email: lilianyuan@chinamobile.com Xiaodong Duan China Mobile Research Institute Gate 2 Dacheng Plaza No. 28 Xuanwumen West Street Xuanwu District, Beijing 100053 China Phone: +86 1391 019 1797 Email: duanxiaodong@chinamobile.com Li Expires September 1,2009 [Page 5]