[c-nsp] RSVP and TE bandwidth management

Pshem Kowalczyk pshem.k at gmail.com
Sun Nov 14 15:56:06 EST 2010


Hi,

On 15 November 2010 03:53, Ibrahim Abo Zaid <ibrahim.abozaid at gmail.com> wrote:
> Hi all
>
> I need to know if RSVP supports over-provisioning of TE tunnels on links or
> there is CAC mechanism ?
> can the current reservation on a single link exceed maximum-bandwidth

No, you can not overbook the link over the maximum-bandwidth.

> also if auto-bw adjustment isn't enabled , is the signaled BW is reserved
> for good even if no traffic load uses the tunnel ?

That is correct, the reservations are static.

> and if RSVP isn't used as QoS to guarantee BW in TE-links , how BW can be
> reserved for different LSP on TE-link ?

RSVP-TE is not really a QoS tool. It allows you to route tunnels
through the network according to some arbitrary constrains (bandwidth
being one of them) but it does not have ability to enforce the
bandwidth limits. You can easily send more bandwidth then the
reservation down the tunnel.

> i can think only about assigning each tunnel with EXP value and apply
> policy-map matches different EXP and assign BW , any other thoughts ?

The only way to enforce the tunnel bandwidth requirements is to make
sure, that the ingress traffic from the CEs is policed/shaped so it
does not exceed the reservation.
You can also use auto-bandwidth, but that only adjusts the tunnel
requirements every now and then (and you don't wan't it any more often
anyway), so you can still exceed the initial requirements.
Using EXP bits will work only if you have a up to 8 tunnels going
through any individual node (head, transit or tail), otherwise you're
going to run out of possible EXP values to distinguish the tunnels.

kind regards
pshem


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