ISIS Work Group Fangwei. Hu Internet-Draft Qiang. Wu Intended status: Standards Track ZTE Corporation Expires: June 21, 2015 Andrew. Qu MediaTec December 18, 2014 ISIS LSP Flooding Optimization draft-hu-isis-lsp-flooding-optimization-00.txt Abstract This proposal introduces a LSP flooding optimization mechanism for the Non-SPF Calculation-based LSP. The Non-SPF Calculation-based LSP is forwarded through the interfaces belonging to a distribution tree rather than all the adjacencies interfaces of the IS. There is no backward compatibility issue for this solution. 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/. 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Expires June 21, 2015 [Page 1] Internet-Draft ISIS LSP December 2014 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. O Bit Flag . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Distribution Tree for Non-SPF Calculation-based LSP Flooding 4 5. LSP Flooding . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Backward Compatibility Considerations . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction Once acquiring its directly connected neighbors and building up adjacencies through Hello PDU, the IS (Intermediate System) originates the LSP (Link States PDU) to describe its link state information and sends it to the network through all the interfaces established adjacencies with neighbors. The IS also receives and stores the LSP from all the other LSPs in the whole network and forms as LSDB (Link State Database). The IS calculates the best forwarding path for the destination based on the LSDB and SPF algorithm. When receiving LSPs from an interface, they will forwards these LSP to their neighbors through all the other interfaces except the received interface. As a result, all the ISs in the giving scope have the same LSDB. We call this procedure as LSP flooding[IS-IS]. Usually, LSP needs to be fragmented before sending, and the Fragment- ID indicates what fragment number the LSP is. The LSP fragment zero and some of the Non-zero fragments contain the mandatory information for SPF computation, we name them as SPF Calculation-based LSP, and the other Non-zero fragments are named as Non-SPF Calculation-based LSP, which is not used for the SPF computation. If all the IS have flooded the Calculation-based LSP in the entire network, we could establish a distribution tree based on the SPF algorithm and the information announced by the Calculation-based LSP. The distribution tree coves all the IS node in the network, and could be used to forward the Non-SPF Calculation-based LSP, which reduces the number of Non-SPF Calculation-based LSP, because the IS only forwards the Non-SPF Calculation-based LSP through the interfaces belonging to the distribution tree rather than all the interfaces of that IS node. Hu, et al. Expires June 21, 2015 [Page 2] Internet-Draft ISIS LSP December 2014 2. Terminology Distribution Tree: is used for Non-SPF calculation-based LSP flooding in this document. Non-SPF Calculation-based LSP: some of the non-zero fragment LSPs which don't contain the neighbor information. The information in Non-SPF calculation-based LSP usually is the IP reachabilities information, and is not used for SPF calculation. SPF Calculation-based LSP: the zero fragment LSPs and the LSPs containing the neighbor information. SPF calculation-based LSP carries the vital information for SPF calculation. 3. O Bit Flag The first reserved bit in the common LSP header(Figure 1) is redefined as O bit in this document. If O bit is set to 0, the LSP is SPF Calculation-based LSP, and if set to 1, the LSP is Non-SPF Calculation-based LSP. +--------------------------------------------+ |Intra-domain Touting Protocol Discriminator | +--------------------------------------------+ | Header Length Indicator | +--------------------------------------------+ | Version/Protocol ID Extension | +--------------------------------------------+ | ID Length | +--------------------------------------------+ | O | R | R | PDU Type | +--------------------------------------------+ | PDU Version | +--------------------------------------------+ | Reserved | +--------------------------------------------+ | Maximum Area Addresses | +--------------------------------------------+ | PDU Specific Fields | | | +--------------------------------------------+ | TLV Section | | | +--------------------------------------------+ IS-IS common header Hu, et al. Expires June 21, 2015 [Page 3] Internet-Draft ISIS LSP December 2014 4. Distribution Tree for Non-SPF Calculation-based LSP Flooding The IS uses distribution tree to flood the Non-SPF Calculation-based LSP. The IS with maximum system-ID elected as the root for that distribution tree, and the metric of neighbour announced by the non- pseudo node is 1. The OL (overload) flag is ignored when calculating the distribution tree, which ensure that the tree could cover all the IS node in the network. 5. LSP Flooding The IS floods LSP based on the distribution tree rather than all the other interfaces. The details flood procedure is as following: o When IS originates SPF Calculation-based LSP, it sets the O bit flag to zero in the common header of LSP, and sends the LSP through all the interfaces. We should pay attention that the SPF calculation LSPs are always forwarded through all the interfaces whether O bit flag is set or not for that LSPs. o The IS should forwards the self-originated Non-SPF Calculation- based LSPs (the O bit is set to 1 of the LSP) through the interfaces belonged to the distribution tree rather than all the interfaces. The IS forwards the received Non-SPF Calculation- based LSPs through the interfaces belonged to the distribution tree, but except the interfaces received that LSPs. o If the distribution tree is failed and could not forward LSPs, the IS should forward all the self-originated LSPs besides the Non-SPF Calculation-based LSP through all the interfaces of the IS, and forward the received LSPs through all the other interfaces except the interface received that LSPs. 6. Backward Compatibility Considerations There is no backward compatibility issue for this solution. The IS does not support O bit and distribution tree forwarding for Non-SPF Calculation-based LSP would ignore the O bit when received the LSP with O bit set, and forward that LSP through all the interfaces except the interfaces received that LSP. 7. Security Considerations 8. Acknowledgements Hu, et al. Expires June 21, 2015 [Page 4] Internet-Draft ISIS LSP December 2014 9. IANA Considerations 10. Normative References [IS-IS] ISO/IEC 10589:2002, Second Edition,, "Intermediate System to Intermediate System Intra-Domain Routing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", 2002. Authors' Addresses Fangwei Hu ZTE Corporation No.889 Bibo Rd Shanghai 201203 China Phone: +86 21 68897637 Email: hu.fangwei@zte.com.cn Qiang Wu ZTE Corporation No.86 Zijinhua Rd Nanjing, Jiang Su 210012 China Email: wu.qiang4@zte.com.cn Andrew Qu MediaTec Email: andrew.qu@mediatek.com Hu, et al. Expires June 21, 2015 [Page 5]