The MPLS WG Archive

[Eric Gray <ewgray@mindspring.com>]

John,

    I believe part of the issue is your use of terms.
In the example you give, I believe that either the
"address" A must be that of an abstract node that
includes addresses A1, A2 and A3 OR B needs
to have the L bit set to indicate that it does not
have to be the very next (adjacent) peer. I am
sure that A cannot forward the Path message
to A1, let alone to B, otherwise.

    I think if you recast your question in terms of
"loose hops" and "abstract nodes" and re-read
the applicable sections of the specification, your
answer will emerge.

--
Eric Gray

John Sparr wrote:

> 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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