Hi Weiguo, I read your draft.
Your proposal introduces quite a bit of overhead as John has pointed out. It is indeed bringing the role of AD routes into the DF election which has been intentionally kept separate so far. As John points out, the AD routes will now be advertised ever so often, even to remote PEs that do not host the same Ethernet Segment. The per ES AD route also carries all the Route-Targets of all the EVIs, so anytime you want to advertise it again, it will need to be advertised with all these Route-Targets. It imposes quite a processing overhead as far as the extended communities are concerned. By this proposed feedback mechanism, it is going to delay the DF election. In section 3 of https://tools.ietf.org/html/draft-hao-bess-evpn-df-handshaking-00 you mention a sequence number but it is not clear how you use it. How does the scheme work when the PE reboots ? How will it remember the sequence number? Its a bit uncooked in the draft. Best, --Satya From: Haoweiguo <[email protected]<mailto:[email protected]>> Date: Wednesday, March 25, 2015 8:38 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>>, "Ali Sajassi (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
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