[PCN] Second thoughts on detail in draft-moncaster-pcn-baseline-encoding
Bob Briscoe <rbriscoe@jungle.bt.co.uk> Wed, 16 July 2008 18:20 UTC
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Date: Wed, 16 Jul 2008 19:20:15 +0100
To: "MONCASTER, Toby" <toby.moncaster@bt.com>
From: Bob Briscoe <rbriscoe@jungle.bt.co.uk>
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Subject: [PCN] Second thoughts on detail in draft-moncaster-pcn-baseline-encoding
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Toby, Commenting on my own draft to the list... Section 4: Encoding two PCN States in IP ---------------------------------------- >Any packet that belongs to a PCN capable flow MUST have the ECN >field set to one of the two ECT codepoints 10 or 01 at the PCN-ingress-node. Delete 'or 01' Reasoning: By saying either 10 or 01 it limits future flexibility. It would allow a future use of ECT(1) if we made up our minds and specified the PCN ingress must only set ECT(0). And a terminology nit: >The PCN encoding states are defined using the Type of Service field >of the IP header which is a combination of the DSCP field and ECN field. Change to: 'The PCN encoding states are defined using a combination of the Differentiated Services field and ECN field.' Reasoning: When RFC2780 split the TOS field into the DS field and the ECN field, I don't think it intended the pair of fields to still be called the TOS field. It would be safer to just use 'modern' terminology. Appendix A. Tunnelling Constraints ---------------------------------- I think we should refer to draft-briscoe-tsvwg-ecn-tunnel-01.txt from the last para of this appendix, saying we're trying to fix this problem so PCN doesn't have to be an exception. When I introduced the -00 version to tsvwg a year ago, it attracted general support (Sally Floyd, David Black etc), as it makes all IP in IP tunnelling consistent with what IPsec now does since RFC4301. I agreed with the Transport Area Directors' request to hold this ecn-tunnel draft back for a year - until it was clearer what the PCN wire encoding would be. So I've just posted -01, as I think PCN encodign is now converging. Pls comment on tsvwg about ecn-tunnel (support please!), cross-posting to PCN if relevant. Appendix B. ---------- I've lost touch with what the proper PCN terminology is, but this appendix seems to be inconsistent. Ignore me if I'm wrong. Bob ____________________________________________________________________________ Bob Briscoe, <bob.briscoe@bt.com> Networks Research Centre, BT Research B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK. +44 1473 645196 _______________________________________________ PCN mailing list PCN@ietf.org https://www.ietf.org/mailman/listinfo/pcn