The MPLS WG Archive

[John Sparr <johnll44@yahoo.com>]

Antonela,

I think it doesn't matter for the strict or loose
attribute set for the sender's first subobject in the
ERO.

The sender node just use it (itself addr) as an
evaluating for the first subobj and then delet it.

The L bit is meaningful fot the next hop. If the L bit
is set, phop can reach nhop freely, the very adjcance
is not nessary.

For example:  A--B--C--D

A is a sender and D is a receiver. For the ERO A
created should be in order: A,B,C,D.

When A send out path msg with ERO, the first subobj
(A's addr) is deleted. When B received path msg with
the ERO, it see itself addr first.

Is that clear?

If wrong, please correct me.


Regards,

John

--- Antonela Paraschiv <antonela@nortelnetworks.com>
wrote:
> Hi John,
> 
> According to the
> draft-ietf-mpls-rsvp-lsp-tunnel-07.txt, when the
> path
> message leaves node A (in your example with A, A1,
> A2, B nodes), the ERO
> should have
> 
>    ERO = {A1, B}.
> 
> The following paragraphs from the spec (from
> 4.3.4.1. Selection of the
> Next Hop) state that if a node receives a path
> message in which the
> first ERO subobject does not belong to it, it has to
> reply with Bad
> initial object.
> 
>    "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."
> and
>    "6) Finally, the node replaces the first
> subobject with any subobject
> 
>    that denotes an abstract node containing the next
> hop.  This is
>    necessary so that when the explicit route is
> received by the next
>    hop, it will be accepted."
> 
> Note please that step 1) above does not mention
> ANYTHING about first ERO
> subobject being strict or loose.
> 
> Can any of the authors please confirm/infirm the
> above?
> 
> Best regards,
> Antonela
> 
> 
> 
> 
> John Sparr wrote:
> 
> > 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
> 
=== message truncated ===


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