Hi Mach, Thanks for the fast answer. I still have some comments:
>Mach>> Yes, for inter-AS TE link, the AS number attribute is essential, as > I pointed out in my previous message, the AS number is needed in the PCE- > based path computation senario. To be more precise, my question is not to know if the AS number sub TLV is useful cause I agree that it is. But rather is it madatory to encode such sub TLV in each inter domain TE link. There are some scenario where it is useful (e.g. PCE based path computation), maybe it is not in some other scenarios. For instance RFC3630 states that " The Link Type and Link ID sub-TLVs are mandatory, i.e., must appear exactly once", and I think the same kind statement should be done to explicitly indicate if the AS number sub TLV is mandatory or optional in case of inter domain TE link. Note that if it is optional it is even more important to have a different link type. >Mach>> Since there is no OSPF adjancy runing on the inter-AS TE links, to >advertise both directions of the TE link can make sure that the inter-AS TE >link is valid for path computation. As Vishwas Manral said, CSPF >implementations will do a two way check before using the TE link for path >computation. Ok. But then if the only purpose of having 2 links LSA is to be able to do 2 way connectivity check, why not rather stating that the inter domain TE link is bidirectional (unlike intra domain link). That is, this TE link would be advertised only if the advertising routers has checked the 2-way connectivity. Thanks Fabien -----Message d'origine----- De : Mach Chen [mailto:[EMAIL PROTECTED] Envoyé : jeudi 26 juillet 2007 17:32 À : [EMAIL PROTECTED]; 'Acee Lindem'; 'Adrian Farrel' Cc : 'OSPF List' Objet : Re: [OSPF] Inter-AS TE Hi Fabien, pls see inline. Hi, I have some comment/questions on this topic. First about the link type I would be concerned if we use the same link type for intra and inter domain link because I think it may lead to some confusion on legacy system. RFC3630 states that unrecognised sub TLV must be ignored. So a legacy system will actually see inter domain link as intra domain link. Generally this would probably have no consequence but the link Id of intra and inter AS link, if I understand correctly, are allocated from 2 different address spaces. So an inter AS link Id may actually match an OSPF router Id of the local domain. In this case I think it may lead to some wrong intra AS path computation from legacy system. Besides I don't really see the advantage of having a single link type. Mach>> Agree, a deferent link type will bring us many benifits. i.e. giving a easy way to identify a inter-AS link, OAM ... A question: is the AS sub TLV mandatory? I guess yes but I'm not sure the draft states it. Mach>> Yes, for inter-AS TE link, the AS number attribute is essential, as I pointed out in my previous message, the AS number is needed in the PCE-based path computation senario. Another question for my understanding about the need to advertise both directions of the TE link. I'm not sure to understand what is the goal of this. Is it to be able to advertise asymmetric TE information for each direction of the link? Mach>> Since there is no OSPF adjancy runing on the inter-AS TE links, to advertise both directions of the TE link can make sure that the inter-AS TE link is valid for path computation. As Vishwas Manral said, CSPF implementations will do a two way check before using the TE link for path computation. Best regards, Mach _______________________________________________ OSPF mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ospf
