The MPLS WG Archive

[John Sparr <johnll44@yahoo.com>]

Hi Eric,

You are right. I made a mistake. In the example, A is
not the abstract node and B should set the L bit. 

My question is how node A handle the ERO. Does the ERO
created by A contains only B's addr or both A's addr
and B's addr, when A sent out path msg with ERO?
Assuming A want to send ERO to B and regardless the
intermediate nodes.

Thanks.

Regards,

John

--- Eric Gray <ewgray@mindspring.com> wrote:
> 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
> >
> > __________________________________________________
> > Do You Yahoo!?
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> 


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