Re: [dcrg-interest] IP over IP solution for data center interconnect

Benson Schliesser <> Fri, 23 December 2011 17:44 UTC

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From: Benson Schliesser <>
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Date: Fri, 23 Dec 2011 11:44:48 -0600
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To: Xuxiaohu <>
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Subject: Re: [dcrg-interest] IP over IP solution for data center interconnect
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On Dec 23, 2011, at 12:38 AM, Xuxiaohu wrote:

> By the way, the ARP table scaling issue on DC gateways, which is deemed by the ARMD WG as the only worthy ARP problem in data center networks, could also be solved with the IP over IP solution.

Two comments:

First, if anybody is interested in exploring additional address resolution issues in the datacenter, please speak up now on the ARMD mailing list. We are attempting to finish our Problem Statement soon. The Problem Statement will only include those issues that are described by WG contributors. So if you think we should deem other issues to be worthy problems, please contribute to the discussion.

Second, at a high-level I think that a number of ARMD participants will agree with your comment about ARP scale issues being solved by "IP over IP" solutions. In fact, it's not just IP-over-IP that can help. Any map-and-encap scheme, including L2-over-IP, can help by shifting the burden to a mapping mechanism. Local ARP/ND proxy functions (e.g. in the VM v-switch, TOR, etc) could take advantage of the mapping mechanism to facilitate address resolution.

In my personal opinion: The real problem is figuring out how to do the mapping, what the right mapping approach is for a datacenter, etc.  This is the topic of the NVO3 effort that was discussed during L2VPN in Taipei.