Re: [Isis-wg] CCAMP LC: draft-ietf-ccamp-isis-interas-te-extension-02.txt

Hi Hannes,

> | >
> | > i am asking specifically about the inter-AS reachability TLV.
> | > what should get inserted in the first seven octects ?
> | > what should get inserted if the neighboring AS runs OSPF ?
> |
> | No matter what the neighboring AS runs ISIS or OSPF, we consider that 
> local
> | System-ID+0 or local Router ID+0 could get inserted into the first seven
> | octects, and there will not be any extra configuration required. The
> | System-ID or Router-ID can be used for indicating the source of the 
> inter-AS
> | reach TLV.
>
> well that does not feel right. just consider the intra-level case.
> a node with system-ID XXX is advertising some reachability to node XXX.
>
> all the existing IS-Reach TLVs are carrying edges to
> *neighboring* routers, i.e. not to yourself.

I guess you misunderstand what I mean.

There is a little bit different between inter-AS reach TLV and IS-Reach TLV, 
the inter-AS Reach TLV does not need to advertise the reachability by 
carrying System-ID. The System-ID field( may be called Originator ID or 
something else, just like the Router ID of "IS-IS Router CAPABILITY TLV" 
which defined in RFC 4971) in the inter-AS Reach TLV is just used as the 
identifier of the source who generates the inter-AS Reach TLV.

So:
 The Inter-AS Reachability TLV has type 141 (which needs to be
 confirmed by IANA see Section 6.1), it contains a data structure
 consisting of:

      6 octets of System ID( indicate the source of the inter-AS reach TLVs)
      3 octets of default metric
      1 octet of control information, consisting of:
         1 bit of flooding-scope information
         1 bit of up/down information
         6 bits reserved
      1 octet of length of sub-TLVs
      0-244 octets of sub-TLVs
         where each sub-TLV consists of a sequence of:
           1 octet of sub-type
           1 octet of length of the value field of the sub-TLV
           0-242 octets of value

Best regards,
Mach

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