Acee - From: Acee Lindem (acee) <[email protected]> Sent: Wednesday, August 05, 2020 12:31 PM To: Tony Li <[email protected]>; Bruno Decraene <[email protected]> Cc: Les Ginsberg (ginsberg) <[email protected]>; [email protected] Subject: Re: [Lsr] draft-ietf-lsr-isis-area-proxy-02
Hi Tony, Bruno, Les, From: Lsr <[email protected]<mailto:[email protected]>> on behalf of Tony Li <[email protected]<mailto:[email protected]>> Date: Tuesday, August 4, 2020 at 11:26 AM To: Bruno Decraene <[email protected]<mailto:[email protected]>> Cc: "Les Ginsberg (ginsberg)" <[email protected]<mailto:[email protected]>>, "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: Re: [Lsr] draft-ietf-lsr-isis-area-proxy-02 Hi Bruno, [Bruno] Agreed so far. Do we agree that draft-ietf-lsr-isis-area-proxy uses the SID/Label sub-TLV? We both agree that this sub-TLV has no mention of the global flag nor the routing algoto be used. So far, we do NOT have agreement on that. Your argument yesterday (backed by Robert) is pretty compelling: go ahead and assign a prefix and now the Area SID may be advertised as a Node SID in the Proxy LSP. If we take that direction, this discussion is moot. Why wouldn’t we take this approach? Since the border routers are abstracting the area as a node, why wouldn’t we do the same for the Node-SID? [Les:] The original idea proposed by the draft authors was to have a SID which could be used to forward traffic to the inside area. Conceptually this does not require a prefix – and the encodings currently defined in the draft reflect this. Bruno has since commented that he prefers a prefix to be associated with the Area SID. I agree this is a viable approach, but if we go that way then I think what is needed is: a)Advertise the “Area Prefix” in the Area Proxy TLV – much as we do a router-id today in the Router-ID TLV. b)The remaining info (reachability and SID) can then be provided using existing Prefix Reachability advertisements – no need for new sub-TLV for “Area SID”. This eliminates any potential issues if the SID advertised by “Area SID sub-TLV” were to differ from the SID advertised in Prefix Reachability for the same prefix. There then remains the question as to whether the “Area Prefix” is anycast or unicast i.e., is it common to all IERs or is it unique to whomever gets elected Area Leader? Les Thanks, Acee Tony
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