RE: doubts

[James Kistruck <James.Kistruck@dataconnection.com>]

Rams,

Inline below - look for [JWK]

Regards,

James.

> -----Original Message-----
> From: ramasamy ramanathan [mailto:ramsrm@tdd.sj.nec.com]
> Sent: 28 September 2003 01:55
> To: ccamp@ops.ietf.org
> Subject: doubts
> 
> 
> Hi all,
> 
> I have few doubts, could u please explain me?
> 
> For Contrl Channel Separation in GMPLS, IF_ID_RSVP_HOP object 
> is used to
> control the particlar data channel.
> 
> In case of unnumbered data links, we have unnumbered interface id
> object[RFC3477] to specify the explicit path.  so when we form the
> IF_ID_RSVP_HOP object we can take the router id and interface id from
> unnumbered interface id subobject  of explcit route obect.

[JWK]  The links specified in the IF_ID RSVP_HOP object are specified "from
the viewpoint of the sender of the Path message" - see section 8.1.2 in
rfc3473.

The links specified in the Unnumbered Interface ID subobject may be
specified in terms of either end of the link, provided that for a strict
ERO, each node is mentioned at least once in the ERO - see section 4.2 of
rfc 3477.

+-----+            +-----+               +-----+
|  A  |            |  B  |               |  C  |
|     1------------4     1---------------4     |
|     2------------5     2---------------5     |
|     3------------6     3---------------6     |
|     |            |     |               |     |
+-----+            +-----+               +-----+

In the diagram above, the following are all valid strict EROs

 [A, B, C]
 [A.1, B.1, C]
 [A, B.4, C.4]
 [A.1, B.4, B.1, C.4]


Therefore a node may need to do some translation between remote and local
numbering when building the IF_ID RSVP_HOP object.  LMP provides one way to
discover this mapping between local and remote numbering.
[/JWK]

> 
> In case of numbered data links,  In explicit route object we 
> don't have any
> subobject to mention the data channel's interface address. 

[JWK]  Actually, numbered data links can be put in the ERO, and the
corresponding IPv4 or IPv6 TLVs are placed in the IF_ID RSVP_HOP object (see
9.1.1 in rfc3471).

> Whatever present
> in ERO object gives the control channel's interface address 
> right? 

[JWK]  No.  The ERO specifies the TE links and nodes to be used by the data
path.  There is no requirement for addresses in the ERO to be for signaling
capable links.

> so when
> we form the IF_ID_RSVP_HOP object, from where do we get the 
> actual data
> channel address along which the label has to be allocated? 
> how to carry the
> explcit route( RouterID and Data channel's address) computed 
> by CSPF along
> the PATH.
> 

[JWK]  As above, the ERO can carry all the data link addresses calculated by
CSPF.  How the corresponding signaling addresses are determined is a local
matter.  LMP's control channel support provides one method for doing this,
although it is common for data links to be unnumbered, and for the router ID
to be a routeable, signaling-capable IPv4 address.  In this case the
conversion from remote data link identifier to remote signaling address is
trivial.

> If my assumptions are wrong please correct me.
> 
> thanks
> rams.
> 
> 
>