Re: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05

"Ali Sajassi (sajassi)" <sajassi@cisco.com> Thu, 31 January 2019 02:24 UTC

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From: "Ali Sajassi (sajassi)" <sajassi@cisco.com>
To: Linda Dunbar <linda.dunbar@huawei.com>, "bess@ietf.org" <bess@ietf.org>
Thread-Topic: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05
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Date: Thu, 31 Jan 2019 02:24:24 +0000
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Subject: Re: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05
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Hi Linda,

Please refer to my reply inline marked with “AS>”

From: BESS <bess-bounces@ietf.org> on behalf of Linda Dunbar <linda.dunbar@huawei.com>
Date: Thursday, October 4, 2018 at 9:30 AM
To: "bess@ietf.org" <bess@ietf.org>rg>, "ietf@ietf.org" <ietf@ietf.org>
Subject: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05

Ali, et al:

Sorry for the late comments. I remember reviewing/contributing to this draft many years ago. Happy to see it is finally moving to IESG Last Call.

The draft describes the mechanism to allow TSs belonging to different subnets attached to same PE to be communicated by the PE (instead hair pinned to the L3GW). Very good optimization.

However, not every PE has the needed policies for any two subnet communication (that is why the traffic was to be sent to L3GW).. Therefore, the draft needs a section to describe how the PEs determine if it has the needed policies for specific inter subnets communication.
In addition, when subnets are scatted among many different PEs, it requires the L3GW to maintain all the mappings. In Data center when there are many VMs or Containers, the number of mappings for L3GW to maintain is huge (it practically becomes host routing for tens of thousands of VMs or Containers). It doesn’t scale well. Therefore, the mechanism should allow some PEs to maintain some of the mappings, i.e. becoming a designated L3GW for some subnets..

AS> The discussion of policy and mapping them to subnet configuration is outside of the scope of this document. If the subnets are configured in a central GW, then that becomes the traditional DC use case of having a L2-domain terminated by centralized L3GW. This document deals with distributed GW where TS default GW functionality is pushed all the way to the edge of the overlay network  - i.e., to the NVEs.

Cheers,
Ali

If you are willing to accept this comment, I can provide the text on “Inter-subnet communication Policy on PE”.

Thank you.

Linda Dunbar