Ali,

It is very possible that One NVE can do inter-subnet forwarding for X, but 
can’t do inter-subnet forwarding for Y. Therefore, the NVE must have a policy 
on which Subnets it can forward.
Therefore a NVE cannot behave properly if it doesn’t a policy on which subnets 
it can forward.

Ø  The discussion of policy and mapping them to subnet configuration is outside 
of the scope of this document.
Linda

From: Ali Sajassi (sajassi) [mailto:saja...@cisco.com]
Sent: Wednesday, January 30, 2019 8:24 PM
To: Linda Dunbar <linda.dun...@huawei.com>; bess@ietf.org
Subject: Re: [bess] Last call comment to 
draft-ietf-bess-evpn-inter-subnet-forwarding-05

Hi Linda,

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

From: BESS <bess-boun...@ietf.org<mailto:bess-boun...@ietf.org>> on behalf of 
Linda Dunbar <linda.dun...@huawei.com<mailto:linda.dun...@huawei.com>>
Date: Thursday, October 4, 2018 at 9:30 AM
To: "bess@ietf.org<mailto:bess@ietf.org>" 
<bess@ietf.org<mailto:bess@ietf.org>>, "i...@ietf.org<mailto:i...@ietf.org>" 
<i...@ietf.org<mailto:i...@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



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