Subject: Loose ERO subobject

From: Rita Hui <[email-masked]>
Date: Mon, 13 Nov 2000 18:21:02 -0800 (PST)

Hi,

In RSVP-TE, when a LSR receives a PATH message with
the first ERO subobject being a LOOSE one, which of
the following behaviour is correct?

1) It generates error "Bad Initial subobject" if the
node does not belong to the address described by the
subobject.
2)  It does not generate the "bad initial subobject"
error, but directly send the message off towards that
address.  If it does not have a path, generate "Bad
loose node".

If it does evaluate the first ERO subobject even if it
is loose, this is different than what CR-LDP, which
only evalutes when the first ERO subobject is strict. 
What is the rationale for this distinct behaviour?

Thanks in advance,

Rita

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---

From: "Sanford, Bill" <[email-masked]>
Date: Tue, 14 Nov 2000 11:31:59 -0500

-----Original Message-----
From: Rita Hui [mailto:[email-masked]]
Sent: Monday, November 13, 2000 9:21 PM
To: [email-masked]
Subject: Loose ERO subobject

Hi,

*****
Rita, if the LSR gets the PATH message and strips off its own hop address,
and the next hop it has is loose, the packet should send it out to the next
hop (if it is in its table) or send it out an interface or interfaces to
establish a connection to the next hop.  The LSR *should* add ERO hops if it
can find the next ERO at more than the next hop away.  If it can't find it,
the LSR should return with an error of "No Route Found" with say a "bad
loose node" error code.

*****
I would think that this would keep dynamic rerouting working at a particular
point in the network, if there were known problems at some of the next hops
of the LSR.

Thanks in advance,

Rita

---

From: Adrian Farrel <[email-masked]>
Date: Wed, 15 Nov 2000 19:55:03 -0000

Hi,

Just to clarify what Bill has said...

>From: Sanford, Bill [mailto:[email-masked]]
>Sent: Tuesday, November 14, 2000 4:32 PM
>To: 'Rita Hui'; [email-masked]
>Subject: RE: Loose ERO subobject
>
>
>
>

This is the key point in Rita's question.  The LSR, when it 
receives a Path with ERO, expects to be a member of the abstract
node described by the top subobject.  This is not a loose/strict
issue, but rather one of specific address versus prefix/AS number.

If, at the previous LSR, the top subobject was loose and the 
current LSR is not part of the abstract node defined by that
subobject, the previous LSR MUST insert a new subobject to
define an abstract node that includes the current LSR (this 
would normally be an explicit address).

>and the next hop it has is loose, the packet 
>should send it out to the next hop (if it is in its table) or
>send it out an interface or interfaces to establish a 
>connection to the next hop.  The LSR *should* add ERO hops if 
>it can find the next ERO at more than the next hop away.  If it
>can't find it, the LSR should return with an error of "No Route
>Found" with say a "bad loose node" error code.
>****
>
>I would think that this would keep dynamic rerouting working 
>at a particular point in the network, if there were known 
>problems at some of the next hops of the LSR.
>*****
>
>Rita

--
Adrian Farrel  mailto:[email-masked]
Network Convergence Group
Data Connection Ltd., Chester, UK
http://www.dataconnection.com/
Tel: +44 (0) 1244 313440  Fax: +44 (0) 1244 312422