Hi Bruno, Please refer to my comments inline identified by '[Robin]'.
Regards, Robin ________________________________ 发件人: [email protected] [[email protected]] 发送时间: 2015年1月16日 15:55 收件人: DECRAENE Bruno IMT/OLN; Lizhenbin; [email protected] 主题: RE: New Comments on Segment Routing(1): Challenge of Ordered mode for SR-BE Path and Incremental Deployment 1 correction inlined. [Bruno2] From: spring [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, January 15, 2015 4:57 PM […] This is the first issue. (Non-SR) S11-----------S12----------S13---------S14 | | | | | | | | | | | | S21-----------S22----------S23---------S24 As above topoloby, there are 8 nodes and assume all the metics of the links are 1 and VPNs are deployed on S11/S21/S14/S24. If LDP is used as the tunnel for VPN on S11/S14, since LDP can support the ordered mode. The LSP for the S14 will be setup as the order S14->S13->S12->S11 for distribution of label mapping. And the shortest path for routes to S14 is also S11->S12->S13->S14. So the end-to-end LSP to S14 is setup. If one node (e.g. S13) does not support LDP, according to LDP ordered mode, the end-to-end LSP cannot setup since S12 does not receive the label mapping from the exact nexthop of the route, S13 and it will not distribute the label mapping to S11. And the result is that the VPN on S11 cannot take the LSP since the LSP cannot setup on S11. [Bruno] My understanding of your case is the following, please correct me if I’m wrong: There is no SPRING/SR. All nodes support LDP. S11, S12, S14 use ordered mode. S13 use independent mode. [Robin] I don't mean S13 use independent mode. I mean S13 doesn't support LDP. That is S13 is a non-LDP node. First, such cases happen today in multiple vendor networks since different implementation used different options. Then, I believe that your understanding of LDP independant mode is incorrect. In independent mode, S13 always advertises the S14 FEC to its neighbor, even if it don’t gets a label mapping from its downstream S14. This FEC is then propagated to S11 in ordered mode. As a result, S11 gets a label for S14 and will use S14 for the VPN. However in the forwarding plane the traffic will be dropped on S13. [Robin] Please rethink the use case taking into account that S13 cannot supported in LDP. Since S13 cannot send the label mapping to S12, this means S12 cannot receive the label mapping from its exact nexthop for the prefix S14, S12 will not send the label mapping for S14 to S11. [Bruno2] I withdraw my last sentence. In this fist cast, traffic is not dropped. It works fine. We only lose the propagation of LDP FEC status in the control plane. [Robin] I could not understand your point. In fact, this case is simple. It just explain that if the ordered LDP is incrementally deployed, the traffic can be dropped at the ingress node without leaking the traffic into the network. _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration, Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci. This message and its attachments may contain confidential or privileged information that may be protected by law; they should not be distributed, used or copied without authorisation. If you have received this email in error, please notify the sender and delete this message and its attachments. As emails may be altered, Orange is not liable for messages that have been modified, changed or falsified. Thank you.
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