John> One question about the
ERO object in RSVP:
John> Assuming there is a sender node and it
creates an ERO. Should the ERO include the
ip address of sender itself? If yes,
why?
Doesn't
the ERO list have to include the sender as the first hop so it can evaluate the
next hop it has to go to?
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
> > > 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!?
> > Yahoo! Photos - Share your holiday photos online!
> > http://photos.yahoo.com/
>
__________________________________________________
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--
Antonela Paraschiv
Passport MPLS, Carrier Data Networks, Nortel Networks
Tel: (978)288-6136 (Esn : 248-6136)
E-mail: antonela@nortelnetworks.com