Hi, Eric: Sorry for my missing your reply for quite a long time. I believe you understand my concern. However when I revisit the section3.7 of PS draft, I feel even confusing, it said: “ The optimal forwarding problem applies to both outbound and inbound traffic. For outbound traffic, the choice of outbound router determines the path of outgoing traffic from the VM, which may be sub-optimal after a VM move. For inbound traffic, the location of the VM within the IP subnet for the VM is not visible to the routers beyond the virtual network. Thus, the routing infrastructure will have no information as to which of the two externally visible gateways leading into the virtual network would be the better choice for reaching a particular VM. ” My point is multi-homing issue or one network endpoint is connecting to one VN through multiple first hop network devices may complicate optimal forwarding problem but seems not the basic problem for optimal forwarding. The basic problem for optima forwarding is the case each VN has one first hop network device or egress router.
For inbound traffic, even you only have one first hop network device that connect source network endpoint to one source VN, The location of the source VM within the source IP subnet(i.e.,VN) is also not visible to the destination routers in the destination VN beyond the source VN. Also it seems you don’t consider the outbound traffic for the case when VM is moved from VN1 to VN2 and each VN have only one first hop network device (could be a router) In such case, the traffic can be forwarded/tunnelled by first hop network device in VN1 to first hop network device in VN2, doesn’t it? Why this case is excluded? Also in this case, how the destination VM location within destination VN is visible to the source first hop network device in VN1 is still a problem, Doesn’t it? For other minors issues, like 1.terminology network endpoint, end system, endpoint, it is better to use consistent terminology. 2. I don’t understand the sentence “ A virtual network may have two routers for traffic to/from other VNs or external to all VNs ” What do you mean by virtual network have routers for traffic to external to all VNs. 3. Is router a right term? It seems in other place you use first hop network device, it doesn’t exclude switch to be used. I can come up a specific text proposal if you allow for couples of days. Thanks for taking my comment into account. Regards! -Qin 发件人: [email protected] [mailto:[email protected]] 代表 Eric Gray 发送时间: 2013年3月14日 23:21 收件人: [email protected] 主题: [nvo3] Comments on draft-ietf-nvo3-overlay-problem-statement Had to forward this as the commenter used an invalid email address. 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([2001:df8:0:16:7d23:71af:5434:aa14]) by mx.google.com<http://mx.google.com> with ESMTPS id qd8sm31117738pbc.29.2013.03.13.14.10.58 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 13 Mar 2013 14:10:59 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Subject: Your comment on draft-ietf-nvo3-overlay-problem-statement-02 From: Eric Gray <[email protected]<mailto:[email protected]>> Message-Id: <[email protected]<mailto:[email protected]>> Date: Wed, 13 Mar 2013 17:10:59 -0400 To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Mime-Version: 1.0 (1.0) X-Mailer: iPad Mail (10B146) Qin, In reading your comment, it seems that you're both asking what we mean by the text and answering the question with your next question. The text you ask about is identifying the case where more than one router connects a virtual network to an otherwise separate virtual network. The optimal forwarding concern is that it is difficult for a virtual host or server located within the first virtual network to know which of the multiple routers connecting the two virtual networks is the optimal choice for connecting to a host or server in the second virtual network. This is a concern when there are possibly multiple local forwarding devices between the first host/server and any of the potential routers that connect the two virtual networks and/or a similar situation exists in the second virtual network between any of these candidate routers and the second host/server. How is the host supposed to determine which of the multiple routers in this case provides the optimal path. This is pretty much the case you identify when you ask how we are "going to deal with the optimal forwarding between two VMs [that] belong to different subnet[s]." It seems that we're at least talking about the same thing. Can you make a specific text proposal that would make our text clearer? -- Eric You wrote: I reviewed the change in section 3.7 "optimal forwarding"of NVO3 problem statement. It said: " IP implementations in network endpoints typically do not distinguish between multiple routers on the same subnet - there may only be a single default gateway in use, and any use of multiple routers usually considers all of them to be one-hop away. " It seems you talk about one tenant system is multihomed to multiple NVEs in the same subnet. I am not sure how much of this is related to optimal forwarding? Are you assuming only one NVE is active? or all the NVEs placed in the same subnet are active? or some of NVE placed in the same subnet are active to a set of VMs while the other
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