Hi Thomas and Weiguo, Agree with the below statement. I don’t see any loops in EVPN with the ESI label, that is recommended to be used for single-active/all-active and also not only from NDF to DF but also from DF to NDF. Hence even in transient states with more than one DF - if at all possible - split-horizon takes care of the loops. The only thing you might get in that case is a few duplicate packets.
Weiguo, please let me know if I am missing something. Thank you. Jorge -----Original Message----- From: "[email protected]" <[email protected]> Organization: Orange Date: Thursday, March 26, 2015 at 8:59 PM To: Haoweiguo <[email protected]>, "[email protected]" <[email protected]> Subject: Re: [bess] Handshaking among PEs in an EVPN ES based on Paxos algorithm >Hi Weiguo, > >2015-03-26, Haoweiguo: > > Thomas: >> > - RFC7432 may have transient periods where the DF election state is >> > not yet synchronized between the two peers: > > >> [weiguo]: Yes, i think RFC 7432 has transient periods of traffic loop > >Note well that I didn't write that there can be transient _loops_ . >I tried to capture the exchange you had all, and what I gather is that >the split-horizon procedure _prevents_loops_, independently of any >transient period where DF state is not synchronized and which may lead >to transient _duplicates_. > >-Thomas > >> >> 26/03/2015 20:05, John E Drake : >>> >>> Weiguo, >>> >>> I guess I wasn’t clear. I think you draft, for the reasons I have >>> detailed, is a non-solution to a non-problem with tremendous control >>> plane cost. >>> >>> Yours Irrespectively, >>> >>> John >>> >>> *From:*Haoweiguo [mailto:[email protected]] >>> *Sent:* Thursday, March 26, 2015 6:17 PM >>> *To:* John E Drake; Patrice Brissette (pbrisset) >>> *Cc:* Ali Sajassi (sajassi); [email protected] >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> Pls see below. >>> >>> Thanks, >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*John E Drake [[email protected]] >>> *Sent:* Friday, March 27, 2015 6:00 >>> *To:* Haoweiguo; Patrice Brissette (pbrisset) >>> *Cc:* Ali Sajassi (sajassi); [email protected] <mailto:[email protected]> >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> To recap, >>> >>> We have established that your proposal is untenable because of its >>> control plane load. >>> >>> We have established that your proposal is based upon a flawed >>> understanding of the DF election in RFC 7432. >>> >>> [weiguo]: In ethernet world, traffic loop is serious than short timer >>> traffic disruption. If you want to implement transiet traffic loop >>> process, i will modify my draft to solve your issue. >>> >>> If i am the developer, i will prefer short timer traffic disruption >>> based on current EVPN protocol. >>> >>> What you are now arguing is that your draft prevents two or more PEs >>> from being DF simultaneously. This is clearly nonsense. >>> >>> [weiguo]: I will modify the draft problem statements, and use the same >>> handshaking solution to solve it. >>> >>> Furthermore, we have established that having two or more DFs for what >>> even you admit is a brief transient leads to duplicate traffic, which >>> is acceptable, but not loops, your assertion to the contrary. >>> >>> [weiguo]: It is transient loop and traffic duplication issue. >>> >>> Yours Irrespectively, >>> >>> John >>> >>> *From:*Haoweiguo [mailto:[email protected]] >>> *Sent:* Thursday, March 26, 2015 5:37 PM >>> *To:* John E Drake; Patrice Brissette (pbrisset) >>> *Cc:* Ali Sajassi (sajassi); [email protected] <mailto:[email protected]> >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> John, >>> >>> As your understanding of the EVPN draft, the DF election mechanism has >>> more serious side effect, it will have short time traffic loop,i.e., >>> dual DF PEs will exist for a short time. I think dual DF PEs is >>> absolutely not tolerated, because native ethernet header has no TTL, >>> up to several hundred ms traffic loop normally not tolerated in >>> commertial networks. >>> >>> As your understanding, the PEs should do as following: >>> >>> 1. Accurate timer sync. NTP accuracy is bad, 1588v2 is good but have >>> rarely deployment. >>> >>> Assuming PE1,PE2 and PE3 have consistent timer clock, when PE3 joins >>> ESI and trigger DF re-election. When reception timer expires: >>> >>> PE1 upgrades to DF PE. >>> >>> After reception timer+ ES route transmission timer: >>> >>> PE2 downloads to non-DF PE. >>> >>> So in timer clock sync case, dual DF PEs will exist at least >>> transmission timer. >>> >>> If NTP is used for timer sync, because it has bad accuracy, dual DF >>> PEs will exist more longer timer. >>> >>> So as your understanding for DF election, the drawback is more clear. >>> >>> Thanks, >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*John E Drake [[email protected]] >>> *Sent:* Friday, March 27, 2015 4:41 >>> *To:* Haoweiguo; Patrice Brissette (pbrisset) >>> *Cc:* Ali Sajassi (sajassi); [email protected] <mailto:[email protected]> >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> Weiguo, >>> >>> We have already established that your proposal is untenable because of >>> its control plane load. >>> >>> What we are now discussing is that your proposal is based upon a >>> misunderstanding of the algorithm in RFC 7432. You are assuming that >>> PE1 will advertise an ES route and then wait for the configured >>> interval before performing the DF election while PE2 and PE3 will >>> perform the DF election as soon as they receive the ES route from PE1. >>> This is not what RFC 7432 says. >>> >>> Rather, what is says is that the advertisement of the ES route by PE1 >>> and its receipt by PE2 and PE3 causes all three PEs to start the >>> configured interval timer - “3. When the timer expires, each PE >>> builds an ordered list of the IP addresses of all the PE nodes >>> connected to the Ethernet segment (including itself), in increasing >>> numeric value.” >>> >>> Yours Irrespectively, >>> >>> John >>> >>> *From:*Haoweiguo [mailto:[email protected]] >>> *Sent:* Thursday, March 26, 2015 3:26 PM >>> *To:* John E Drake; Patrice Brissette (pbrisset) >>> *Cc:* Ali Sajassi (sajassi); [email protected] <mailto:[email protected]> >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> Pls read my detail replies to Satya. If you still can't catch it, pls >>> read my draft and EVPN base protocol, thanks >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*John E Drake [[email protected]] >>> *Sent:* Friday, March 27, 2015 1:28 >>> *To:* Patrice Brissette (pbrisset) >>> *Cc:* Haoweiguo; Ali Sajassi (sajassi); [email protected] >>> <mailto:[email protected]> >>> *Subject:* Re: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> I think Patrice is correct. Your proposal doesn't solve the problem >>> and it does so at huge cost. >>> >>> Sent from my iPhone >>> >>> >>> On Mar 26, 2015, at 10:34 AM, Patrice Brissette (pbrisset) >>> <[email protected] <mailto:[email protected]>> wrote: >>> >>> Weiguo, >>> >>> I’m not sure I’m following here. >>> >>> Don’t you have the same issue with your handshaking mechanism? >>> >>> If you don’t know your peer, how can you handshake? >>> >>> Regards, >>> >>> Patrice >>> >>> Image removed by sender. >>> >>> *Patrice Brissette* >>> TECHNICAL LEADER.ENGINEERING >>> >>> [email protected] <mailto:[email protected]> >>> Phone: *+1 613 254 3336* >>> >>> >>> >>> *Cisco Systems Canada Co. / Les Systemes Cisco Canada CIE* >>> Canada >>> Cisco.com <http://www.cisco.com/global/CA/> >>> >>> >>> >>> Image removed by sender.Think before you print. >>> >>> This email may contain confidential and privileged material for >>> the sole use of the intended recipient. Any review, use, >>> distribution or disclosure by others is strictly prohibited. If >>> you are not the intended recipient (or authorized to receive for >>> the recipient), please contact the sender by reply email and >>> delete all copies of this message. >>> >>> Please click here >>> >>><http://www.cisco.com/web/about/doing_business/legal/cri/index.html> >>> for Company Registration Information. >>> >>> >>> *From: *Haoweiguo <[email protected] >>><mailto:[email protected]>> >>> *Date: *Thursday, March 26, 2015 at 10:24 AM >>> *To: *Patrice Brissette <[email protected] >>> <mailto:[email protected]>>, John E Drake <[email protected] >>> <mailto:[email protected]>>, Ali Sajassi <[email protected] >>> <mailto:[email protected]>>, "[email protected] >>> <mailto:[email protected]>" <[email protected] <mailto:[email protected]>> >>> *Subject: *RE: [bess] Handshaking among PEs in an EVPN ES based on >>> Paxos algorithm >>> >>> Hi Patrice, >>> >>> Up to reception timer traffic disruption in transient phase is >>> one of the issues. >>> >>> Thanks, >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*Patrice Brissette (pbrisset) [[email protected] >>> <mailto:[email protected]>] >>> *Sent:* Thursday, March 26, 2015 20:54 >>> *To:* Haoweiguo; John E Drake; Ali Sajassi (sajassi); >>> [email protected] <mailto:[email protected]> >>> *Subject:* Re: [bess] Handshaking among PEs in an EVPN ES >>> based on Paxos algorithm >>> >>> Weiguo, >>> >>> You mention "But if your draft have not solved all issues”, >>> >>> Can you explain what Satya’s draft is not solving? >>> >>> Regards, >>> >>> Patrice >>> >>> Image removed by sender. >>> >>> *Patrice Brissette* >>> TECHNICAL LEADER.ENGINEERING >>> >>> [email protected] <mailto:[email protected]> >>> Phone: *+1 613 254 3336* >>> >>> >>> >>> *Cisco Systems Canada Co. / Les Systemes Cisco Canada CIE* >>> Canada >>> Cisco.com <http://www.cisco.com/global/CA/> >>> >>> >>> >>> Image removed by sender.Think before you print. >>> >>> This email may contain confidential and privileged material >>> for the sole use of the intended recipient. Any review, use, >>> distribution or disclosure by others is strictly prohibited. >>> If you are not the intended recipient (or authorized to >>> receive for the recipient), please contact the sender by reply >>> email and delete all copies of this message. >>> >>> Please click here >>> >>><http://www.cisco.com/web/about/doing_business/legal/cri/index.html> >>> for Company Registration Information. >>> >>> >>> *From: *Haoweiguo <[email protected] >>> <mailto:[email protected]>> >>> *Date: *Wednesday, March 25, 2015 at 10:38 PM >>> *To: *John E Drake <[email protected] >>> <mailto:[email protected]>>, Ali Sajassi <[email protected] >>> <mailto:[email protected]>>, "[email protected] >>> <mailto:[email protected]>" <[email protected] <mailto:[email protected]>> >>> *Subject: *Re: [bess] Handshaking among PEs in an EVPN ES >>> based on Paxos algorithm >>> >>> Hi John, >>> >>> Firstly i think EVPN community should reach consensus on >>> the issues of current DF election mechanism. All these >>> issues should be resolved in a single new DF election >>> draft,rather than in multiple separate drafts. If your >>> draft can solve all these issues and stable, i have no >>> question for its progressing. But if your draft have not >>> solved all issues, i think it had better combine with >>> other drafts to provide a comprehensive solution. I think >>> the issues listed in draft-rabadan-bess-evpn-ac-df-01 and >>> draft-hao-bess-evpn-df-handshaking-00 is valid, it should >>> be resolved. So i think although your new Hash algorithm >>> for DF election is good, it only includes partial >>> enhancements, maybe it still needs some time for >>>consensus. >>> >>> Thanks, >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*John E Drake [[email protected] >>> <mailto:[email protected]>] >>> *Sent:* Thursday, March 26, 2015 7:16 >>> *To:* Haoweiguo; Ali Sajassi (sajassi); [email protected] >>> <mailto:[email protected]> >>> *Subject:* RE: [bess] Handshaking among PEs in an EVPN ES >>> based on Paxos algorithm >>> >>> Weiguo, >>> >>> Your proposal introduces a control plane processing load >>> that is O(#EVIs * PEs) per DF election and given that >>> there can be 4K EVIs per ES, this looks like a >>> **substantial** load. Furthermore, >>> >>> you can’t use the ES route to co-ordinate DF election >>> because you would need to carry your new extended >>> community for each EVI and they would not all fit. You >>> also can’t use the Per EVI Ethernet AD route because that >>> is processed by all PEs in the EVI. >>> >>> I think that from a practical perspective the new DF >>> election proposed in Satya’s draft is sufficiently stable >>> that it renders your draft moot, even if it could be made >>> to work. >>> >>> Yours Irrespectively, >>> >>> John >>> >>> *From:*BESS [mailto:[email protected]] *On Behalf Of >>> *Haoweiguo >>> *Sent:* Wednesday, March 25, 2015 5:34 PM >>> *To:* Ali Sajassi (sajassi); [email protected] >>> <mailto:[email protected]> >>> *Subject:* Re: [bess] Handshaking among PEs in an EVPN ES >>> based on Paxos algorithm >>> >>> Hi Ali, >>> >>> Thanks for your information. I scanned through this draft, >>> it really introduces inter-chassis message for DF election >>> handshaking, the requirements in this draft is to >>> eliminate transiet Loop and traffic duplication. Current >>> EVPN DF election mechanism already eliminated loop and >>> traffic duplication by configuring long reception timer on >>> each multi-homed PE, but up to reception timer traffic >>> disruption issue still exist. EVPN for DCI is an important >>> use case for EVPN, up to reception timer traffic >>> disruption can't be tolerated for service providers, it >>> should be improved. >>> >>> Also for accuracy, i think handshaking state machine on >>> each multi-homed PE is also needed. From solution >>> perspective, in my draft, no inter-chassis message is >>> introduced, only one new extended community is introduced, >>> i think the process is comparatively simple than your >>> following draft. >>> >>> Current EVPN DF election has some drawbacks, so there are >>> three new drafts about DF election emerged. I think BESS >>> WG can consider these three drafts in global view, a >>> single,comprehensive new DF election draft is hoped. >>> >>> thanks. >>> >>> Thanks, >>> >>> weiguo >>> >>> >>>------------------------------------------------------------------------ >>> >>> *From:*BESS [[email protected] >>> <mailto:[email protected]>] on behalf of Ali Sajassi >>> (sajassi) [[email protected] <mailto:[email protected]>] >>> *Sent:* Thursday, March 26, 2015 0:21 >>> *To:* [email protected] <mailto:[email protected]> >>> *Subject:* [bess] Handshaking among PEs in an EVPN ES >>> based on Paxos algorithm >>> >>> FYI- First published July 4, 2011 >>> >>> >>>https://datatracker.ietf.org/doc/draft-sajassi-l2vpn-evpn-segment-route/ >>> >>> -Ali >>> >>> >>> >>> _______________________________________________ >>> BESS mailing list >>> [email protected] >>> https://www.ietf.org/mailman/listinfo/bess >> >> >> >> >> >> >> >> >> >> >> >> >> >> >>_________________________________________________________________________ >>________________________________________________ >> >> Ce message et ses pieces jointes peuvent contenir des informations >>confidentielles ou privilegiees et ne doivent donc >> pas etre diffuses, exploites ou copies sans autorisation. 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Si vous avez >recu ce message par erreur, veuillez le signaler >a l'expediteur et le detruire ainsi que les pieces jointes. Les messages >electroniques etant susceptibles d'alteration, >Orange decline toute responsabilite si ce message a ete altere, deforme >ou falsifie. Merci. > >This message and its attachments may contain confidential or privileged >information that may be protected by law; >they should not be distributed, used or copied without authorisation. >If you have received this email in error, please notify the sender and >delete this message and its attachments. >As emails may be altered, Orange is not liable for messages that have >been modified, changed or falsified. >Thank you. > >_______________________________________________ >BESS mailing list >[email protected] >https://www.ietf.org/mailman/listinfo/bess _______________________________________________ BESS mailing list [email protected] https://www.ietf.org/mailman/listinfo/bess
