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

[Mach Chen <[e-mail]>]

Hi Hannes,

> On Tue, Jul 22, 2008 at 04:39:07PM +0800, Mach Chen wrote:
> | 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
>
> i see, so you basically want to retain sort of originator-ID when leaking
> information across levels. - may i remind you that the same problem 
> already
> has been solved in the caps-code extension - see 
> http://www.ietf.org/rfc/rfc4971.txt
> here the originator-id is a 32-bit router-ID.

Thanks for your remind.

> IMO we should stick with router-IDs as originator-IDs for TE related 
> information, since
> they are universally applicable (e.g. even when leaking TE information 
> between
> a IS-IS and a non-IS-IS domain).

Deal:)

I will change the System-ID field to Router ID field with 4 octets.

Thanks again for your useful comments and suggestions!

>
> /hannes 


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