Jun,
>I am just trying to think aloud here:
>
>If there is an LSP passing through the router, it
>comes into interface A, goes out of interface B,
>the RSVP reservation is only on interface B, is this
>right? If so, how could we guarantee interface A will
>have enough bandwidth for the tunnel, since its
>bandwidth could be less than the outbound interface B.
Normally that would not happen because the upstream node
that's connected to interface A should fail the reservation
(or actually the preceeding PATH) since it *should* have an
accurate idea of the links's remaining reservable bandwidth.
However, that holds true mainly for P2P links, not multiple
nodes on a shared media. Even worse, consider the following:
Ingress(GigE)-Switch-(FastE)NodeA(GigE)--(GigE)Egress
Here NodeA has only one upstream neighbor, which could swamp
NodeA's FastEthernet interface. I don't think any CSPF
implementations will check the "back-link" to prevent this
(although I could be wrong). I suppose this is one situation
that an offline path calculation server could address.
This is more of an issue with the RSVP/RSVP-TE and not cisco's
implementation per se. You should read the RFCs for a bit and
perhaps post to mpls-ops@mplsrc.com if you still have concerns.
Sean
>
>Thanks
>JUN
>
>
>--- Shankar Vemulapalli <svemulap@cisco.com> wrote:
>> There is no need to reserve on inbound ...
>>
>> The path message goes out asking for reservation
>> followed by resv message coming back either
>> confirming or not.
>> Once we receive the confirmation, we guarantee the
>> reservation on the outgoing interface...
>>
>> So, the ingress traffic could be IP and doesn't
>> have any reservation associated with it ... It
>> now can get label switched on the outgoing interface
>> because we have an LSP which is set up with some
>> bandwidth guarantees...
>>
>> So, why do we need to make reservation on inbound
>> interface ??
>>
>> Am I missing something ??
>>
>> Thanks,
>>
>> /Shankar
>>
>> At 2:13pm 05/01/02 -0700, JUN wrote:
>> > Shankar,
>> >
>> > I understand that it is for simplex traffic, but
>> it
>> > takes two interfaces to handle a reservation, an
>> > inbound and an outbound, why it is only necessary
>> to
>> > make reservation at outbound?
>> >
>> > Thanks
>> > JUN
>> >
>> > --- Shankar Vemulapalli <svemulap@cisco.com>
>> wrote:
>> > > Well, as per the RFC2205 -
>> > >
>> > > " RSVP requests resources for simplex flows,
>> i.e.,
>> > > it requests
>> > > resources in only one direction.
>> > > "
>> > >
>> > > You may want to look into this RFC for more
>> > > information
>> > > as to how RSVP works...
>> > >
>> > > Also, look into RFC 3209 - (if you need further
>> > > info.)
>> > >
>> > > Thanks,
>> > >
>> > >
>> > > /Shankar
>> > >
>> > > At 1:06pm 05/01/02 -0700, JUN wrote:
>> > > > I noticed that when an LSP passing through a
>> > > router,
>> > > > RSVP only reserves bandwidth of the outbound
>> > > > interface, why it doesn't make reservation at
>> > > inbound?
>> > > >
>> > > > Thanks
>> > > > JUN
>>
>
>
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This archive was generated by hypermail 2b29 : Sun Aug 04 2002 - 04:13:43 EDT