Precisely Yours Irrespectively,
John > -----Original Message----- > From: BESS [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Thursday, March 26, 2015 10:51 PM > To: [email protected] > Subject: Re: [bess] Handshaking among PEs in an EVPN ES based on Paxos > algorithm > > Hi, > > Let me attempt at clarifying the exchange between the few of you. > > My understanding is that: > - RFC7432 already does a good job of avoiding forwarding loops thanks to the > split-horizon procedure that does not depend on DF election and has no > transient state > - RFC7432 may have transient periods where the DF election state is not yet > synchronized between the two peers: > * the transient period correspond to BGP route propagation times (not to > the DF election delay, although the wording in RFC 7432 could be made > clearer) > * during this period, if PEs do not block BUM traffic, some traffic may be > lost > * during this period, if PEs do not block BUM traffic, some traffic may be > duplicated, but this is not considered very harmful and hence preferred to > packet loss > > The opinion, as I understand, that has been expressed by some is that the > reduction of the transient period where duplicates may arise, is not worth > the cost of an handshaking approach. > > HTH, > > -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-rout > > e/ > > > > -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. 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
