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

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

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id AAC58130EBA for <>; Wed, 30 Jan 2019 18:24:30 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -19.053
X-Spam-Status: No, score=-19.053 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-4.553, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id YR9PH7OYFbdE for <>; Wed, 30 Jan 2019 18:24:27 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 0F3231271FF for <>; Wed, 30 Jan 2019 18:24:26 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=10356; q=dns/txt; s=iport; t=1548901467; x=1550111067; h=from:to:subject:date:message-id:mime-version; bh=0MqXeg460tCfknOZF8o3a9KqtwIDpK//JrbLM8qa/fw=; b=kcWJsv7lPU5ttgu6/T7f8BcbdlAH8RW2tthRbAfxmGTjrEBPr0kvWwU2 ESAdzUWfmrl3RJGFlD3YVc0FoKPJQ+dU34c0MAR1DA8+e1nn8rb+QBjPt c0jF8EIPNLcwmB263/qHSPoPpRmHTtZLkxoJv/SRCkEgMg5wktsuIHQaA c=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.56,542,1539648000"; d="scan'208,217";a="511057891"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Jan 2019 02:24:25 +0000
Received: from ( []) by (8.15.2/8.15.2) with ESMTPS id x0V2OPtl027362 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=FAIL); Thu, 31 Jan 2019 02:24:25 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 30 Jan 2019 21:24:24 -0500
Received: from ([]) by ([]) with mapi id 15.00.1395.000; Wed, 30 Jan 2019 21:24:24 -0500
From: "Ali Sajassi (sajassi)" <>
To: Linda Dunbar <>, "" <>
Thread-Topic: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05
Thread-Index: AQHUuQwVi9GuU3fs0U21VBdde+DzFQ==
Date: Thu, 31 Jan 2019 02:24:24 +0000
Message-ID: <>
Accept-Language: en-US
Content-Language: en-US
user-agent: Microsoft-MacOutlook/
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: multipart/alternative; boundary="_000_F1F389CC99F845048F442E21A0F8BDD0ciscocom_"
MIME-Version: 1.0
Archived-At: <>
Subject: Re: [bess] Last call comment to draft-ietf-bess-evpn-inter-subnet-forwarding-05
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: BGP-Enabled ServiceS working group discussion list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 31 Jan 2019 02:24:31 -0000

Hi Linda,

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

From: BESS <> on behalf of Linda Dunbar <>
Date: Thursday, October 4, 2018 at 9:30 AM
To: "" <>, "" <>
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.


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

Thank you.

Linda Dunbar