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Zhenqiang Li @ China Mobile 77 th IETF @ Anaheim March 2010

Recommendations for LSP Checksum Calculation and Related Processing in M ulti-vendor Networks using IS-IS. Zhenqiang Li @ China Mobile 77 th IETF @ Anaheim March 2010. Content. Purpose Recommendations Checksum Calculation Zero Checksum LSP Processing

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Zhenqiang Li @ China Mobile 77 th IETF @ Anaheim March 2010

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  1. Recommendations for LSP Checksum Calculation and Related Processing in Multi-vendor Networks using IS-IS Zhenqiang Li @ China Mobile 77th IETF @ Anaheim March 2010

  2. Content Purpose Recommendations Checksum Calculation Zero Checksum LSP Processing Zero Remaining Lifetime LSP Processing Corrupt LSP Processing Next steps

  3. Purpose • To show the observations found in China Mobile’s network, consisting of hundreds of routers from several vendors. • To make the IS-IS enabled routers work more robustly and interoperably. • To make the IS-IS protocol itself more fault-tolerative, especially in a multi-vendor network environment.

  4. Checksum Calculation • To calculate the checksum of all LSPs correctly, including zero Remaining Lifetime LSP, although examining the checksum of a zero Remaining Lifetime LSP should always be successful. • Based on the specification, the checksum of a zero Remaining Lifetime LSP can be any value. In practice, some implementations fill the checksum with zero. • If router A does not generate correct checksum for zero Remaining Lifetime LSP and sends the LSP to router B, router B checks the LSP and discards it due to incorrect checksum. Router B should upgrade its implementation according to the IS-IS specification. • However, if router A correctly calculates checksums of all LSPs, it can work with router B. And there will be no problem in a network consisting of such routers.

  5. Zero Checksum LSP Processing In practice, some implementations check the checksum first, then the remaining lifetime.

  6. Zero Remaining Lifetime LSP Processing • Do not check the checksum of Zero Remaining Lifetime LSP. Zero Remaining Lifetime LSPs SHOULD always pass the check. • Although this was specified in ISO 10589 in 2002, we still found wrong implementations of routers in China Mobile’s network in 2007. • This point was not emphasized in RFC3719. It is useful to point it out in this draft both for the vendors and for the operators.

  7. Corrupt LSP Processing • Router receiving corrupt LSP shall • generate a corruptedLSPReceived circuit event • discard the PDU • If switch to control the the processing mechanism is provided, the default state of such switch SHOULD be in accordance with the correct behavior specified in the standards.

  8. Next steps • Any comments are welcome. • Move this draft forward to be a working group draft?

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