Re: [nvo3] 回复： Application of a time slot in this ietf meeting//Re: New draft: Path Detection in VXLAN Overlay Network

[Tom Herbert <[e-mail]>]

On Sun, Jul 5, 2015 at 11:35 PM, Dapeng Liu <[e-mail]> wrote:
> Hi Tom,
>
> Thanks for the comments.
> The scenario discussed in the draft is: all the host traffic is encapsulated
> in VXLAN tunnel. So there will be no problem if the host traffic uses VXLAN
> port number.
>
I don't understand. You're assuming that *all* traffic generated by
hosts in a network is in VXLAN?

Tom

> --
> Dapeng Liu
>
> 在 2015年7月4日 星期六，上午8:06，Tom Herbert 写道：
>
> "The Extendable TLV field contains two TLVs. Both of them are set by
> the network devices along the transport path."-- this might be
> problematic. From draft-ietf-tsvwg-port-use-11.txt: "Ultimately, port
> numbers numbers indicate services only to the endpoints, and any
> intermediate device that assigns meaning to a value can be
> incorrect.". A host may legitimately send UDP packets to the VXLAN
> port number that aren't actually VXLAN, so if intermediate devices are
> modifying these packets based just on destination couldn't this result
> in data corruption? Magic numbers like those defined in SPUD or
> https://tools.ietf.org/html/draft-herbert-udp-magic-numbers-00 could
> mitigate such an issue.
>
> Tom
>
>
>
>
>
> On Fri, Jul 3, 2015 at 10:23 AM, Dapeng Liu <[e-mail]> wrote:
>
>
>
> 在 2015年7月2日 星期四，上午12:04，Dacheng Zhang 写道：
>
> HI, Shahram:
>
> Thanks for the comments.
>
> See my reply inline please..
>
> Cheers
>
> Dacheng
>
> 发件人: Shahram Davari <[e-mail]>
> 日期: 2015年6月30日 星期二 上午2:12
> 至: dacheng de <[e-mail]>
> 抄送: "[e-mail]" <[e-mail]>, "[e-mail]"
> <[e-mail]>, "[e-mail]"
> <[e-mail]>, Dapeng Liu <[e-mail]>
> 主题: RE: [nvo3] Application of a time slot in this ietf meeting//Re: New
> draft: Path Detection in VXLAN Overlay Network
>
>
>
>
>
> I read your draft and I don't think it can get the information that you
> claim it does.
>
>
>
> For example you have ingress interface TLV to record the ingress port of the
> ingress PE. First of all this interface is already communicated by the
> controller to the Ingress PE.
>
>
>
> Ingress/egress interface are refer to the interfaces on the data path. The
> controller will use another interface to communicate with the PE
>
>
>
> SD> What I mean is that the controller is asking the PE to inject this test
> packet to a tunnel via a specific PE interface. So the controller already
> knows which PE interfaces the packet is going to use.
>
>
> Dacheng\ That is why For the ingress PE, only EIID is mandatory.
>
>
>
> Secondly if you want to test the Correct IP forwarding you can just use BFD
> for the outer IP. If you like to use UDP, you could do BFD over UDP over IP.
>
> BFD works at layer 2. It’s mainly used to test whether the layer 2 data path
> is connected. In contrast, our method is focusing on the tracing function.
> (Our solution can help find out which switch on the path is broken.)
>
>
>
> SD> The way you have defined it does not test anything in L2, since your
> packet is not exercising any L2 forwarding. Your packet is L3 forwarded all
> the way.
>
>
> Dacheng\ I am trying to understand your point and please correct me if I am
> wrong. The purpose of this work is to check the error of paths over a l3
> network. (Pleas see figure 1.)
>
>
>
> Thirdly, your draft can't get the egress interface information of the egress
> PE, since there is nothing (No MAC or IP address) in your VXLAN payload that
> can be forwarded by the egress PE to the egress interface.
>
> Two TLV (IIID/EIID) could be used to record the ingress/egress interfaces ID
> of current router the OAM packet is flowing through. For the ingress PE,
> EIID is mandatory while for the egress PE IIID is mandatory. For the
> intermediate router, both IIID and EIID are mandatory. So, for the egress,
> EIID does not have to be transported to the controller.
>
>
>
> SD> I know you have TLV. But what I mean is that there is nothing in your
> draft that makes your packets to be L2 forwarded. For example you are not
> doing any (VXLAN/VNI forwarding) of your packet. As an example assume you
> packet arrives at the Final Egress PE. The Egress PE can’t forward this
> packet based on the IP destination address since it is 127/8.
>
>
> Dacheng\ Ok, our objective is to check the paths between vteps. So, the
> egress PE does not have to forward this packet to the tenant. Note we
> mentioned that for the egress PE only IIID is mandatory.
>
>
>
> Fourthly the path trace that you describe does not work. How does an
> intermediate router know it has to send a copy of this packet to CPU? The
> only method is to use TTL expiry, which already exists in IP trace route.
>
>
>
> In our method, o bit in VxLAN is used to indicate it’s a OAM packet, which
> should be copy to CPU. One OAM packet is able to trace n devices on the
> path, while TTL expire method needs n OAM packets to trace. Of course if you
> assume that the intermediate devices do not support our solution, our
> mechanism will not work properly then.
>
>
>
> SD> Are you suggesting that the intermediate routers need to do deep packet
> inspection and after finding this magical bit copy it to CPU? This is a
> layer violation and should NOT be done. You should not make decision on any
> layer when layers above it are not terminated.
>
>
>
> Basically you are expecting intermediate routers to look in to the packet,
> skip outer Ethernet, Skip IP, check IP payload is UDP, check UDP-Dest port
> is VXLAN, then check a specific bit in VXLAN header in order to decide to
> copy to CPU or not. This is architecturally wrong by any means.
>
>
> Dacheng\ Yes, we expect the intermediate routers can look into the packet.
> Our experiments have shown that this solution works very well and
> significantly reduce the complexity of detecting errors in complex networks.
> Hope other people can give us some comments on this argument.
>
>
> [Dapeng Liu] Yes. The deployment assumption in the draft is all the
> forwarding equipment should support VXLAN and this draft proposes a VXLAN
> function extension to support the OAM mechanism described in the draft.
>
> ----
> Dapeng Liu
>
>
>
>
>
>
> Regards,
>
> Shahram
>
>
>
>
> On Jun 26, 2015, at 10:15 PM, Dacheng Zhang <[e-mail]>
> wrote:
>
> Dear chairs:
>
>
>
> Can we get a time slot during the nvo3 session in Prague to discuss this
> draft? Dapeng Liu from Alibaba will be the presenter. 15 minutes would be
> good enough.
>
>
>
> Cheers
>
>
>
> Dacheng
>
>
>
> 发件人: Dapeng Liu <[e-mail]>
> 日期: 2015年6月21日星期日上午1:04
> 至: <[e-mail]>
> 主题: [nvo3] New draft: Path Detection in VXLAN Overlay Network
>
>
>
> Hello all,
>
>
>
> We have submitted a draft for path detection in VXLAN overlay network.
>
> http://datatracker.ietf.org/doc/draft-pang-nvo3-vxlan-path-detection/
>
>
>
> The draft proposes a method for path detection in VXLAN network and it
> defines the path detection packet format by using one reserve bit in the
> VXLAN header.
>
>
>
> Comments & suggestions are welcomed.
>
>
>
>
>
> --
>
> Dapeng Liu
>
>
>
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