The MPLS WG Archive

[John Sparr <johnll44@yahoo.com>]

Hi Bill,

Thanks for the comments.

I was still a little bit confused about the first
subobject in the ERO. Lets say the following example.

    A--A1--A2--A3--B--C

Assuming A is the sender node and B is the receiver
node, A1-A3 are the intermediate nodes. A creates an
ERO with the first subobj A's addr (loose) and second
subobj B's addr. When A sends Path msg with the ERO
towards B, what should A do to the ERO, it should
delete the first subobj (itself addr)? or send both
subobjs to B? I think A should delet the first subobj,
but if it is, it's no use to add the first subobj(
itself addr) at the beginning of creating ERO.

Please correct me.

Thanks in advance

Regards,

John




--- "Sanford, Bill" <bills@netplane.com> wrote:
> John, see the comments below:
> 
> > -----Original Message-----
> > From: John Sparr [mailto:johnll44@yahoo.com]
> > Sent: Tuesday, January 02, 2001 3:43 PM
> > To: mpls@UU.NET
> > Subject: ERO and strict/loose subobject
> > 
> > 
> > Hi all,
> > 
> > One question about the ERO object in RSVP:
> > 
> > Assuming there is a sender node and it creates an
> ERO.
> > Should the ERO include the ip address of sender
> > itself? If yes, why?
> 
> Lets say the ERO is not set with the sender node and
> is started on the next
> hop.  How does the LSP you want to set up know that
> there are no other hops
> in between the sender and next hop?  If you don't
> have the senders ip
> address as the first subobject, there isn't any way
> to set the properties of
> the link to the next hop to loose or strict.
> 
> In the implementation in
> draft-ietf-mpls-rsvp-lsp-tunnel-07.txt, if you
> didn't have the sender address in the ERO, it would
> immediately error with
> "Bad EXPLICIT_ROUTE object" error.
> 
> In 4.3.4.1. Selection of the Next Hop, it explains:
> 
> 1) The node receiving the RSVP message MUST first
> evaluate the first
>    subobject.  If the node is not part of the
> abstract node described by
>    the first subobject, it has received the message
> in error and SHOULD
>    return a "Bad initial subobject" error.  If there
> is no first
>    subobject, the message is also in error and the
> system SHOULD return
>    a "Bad EXPLICIT_ROUTE object" error.
> 
> > 
> > Another question is about strict/loose object:
> > 
> > The draft of RSVP-TE says "The path between a
> strict
> > node and its preceding node MUST include only
> network
> > nodes from the strict node and its preceding
> abstract
> > node."
> > 
> > Does it mean if there is strict subobject in ERO,
> then
> > ther is no loose subobject and if there is loose
> > subobject, then there is no strict subobject?
> 
> Not at all.  You can have both strict hops and loose
> hops as part of the
> same ERO.  On a "strict" hop link, there isn't any
> other route it can take
> except for the next hop in the ERO list.  On a
> "loose" hop link, there can
> be additional hops between the nodes provided that
> it ends up on the next
> hop.
> 
> Bill


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