[c-nsp] RSVP bandwidths > 10G

[Richard A Steenbergen]

On Wed, Aug 20, 2008 at 04:46:53PM +0200, Oliver Boehmer (oboehmer) wrote:
> Richard A Steenbergen <> wrote on Wednesday, August 20, 2008 4:30 PM:
> 
> > 7600router(config-if)#ip rsvp bandwidth ?
> >   <1-10000000>  Reservable Bandwidth (kbps)
> > 
> > How is one supposed to configure RSVP bandwidths greater than 10Gbps,
> > if say for example you're doing RSVP over a 8x10G port-channel. I see
> > the same hard-coded limitatin for RSVP bandwidth in all 7600 code,
> > including current SRC.
> 
> DDTS CSCsh56847 requests to bump up the limit. I guess for now you might
> be able to do "ip rsvp bandwidth" without an argument to have the router
> allocate 75% of the available BW dynamically. Haven't tried this on a
> 10GE channel though.

Yeah the docs on the subject seem to indicate that it can sometimes work 
by using percent (well I assume they meant percent, they seem to have 
neglected the actual keyword, but I don't think they mean 100Kbps :P):

http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/mp_bundle_interface.html

And if left to its own devices the port-channel interface DOES seem to 
find correct bandwidth values:

Port-channel1 is up, line protocol is up (connected)
  Hardware is EtherChannel, address is 001a.6c97.cab6 (bia 001a.6c97.cab6)
  MTU 9216 bytes, BW 40000000 Kbit, DLY 10 usec, 

However, it doesn't look like this handles layer 3 SVIs trunked over a 
port-channel switchport, which happens to be my configuration. The SVIs 
always come up with a bandwidth of 10Gbps, no matter what interfaces they 
are trunked to:

Vlan60 is up, line protocol is up 
  Hardware is EtherSVI, address is 0018.741f.85c0 (bia 0018.741f.85c0)
  MTU 9170 bytes, BW 1000000 Kbit, DLY 10 usec, 

And of course, you can't manually configure the bandwidth values higher 
than 10Gbps either, on either the port-channel or vlan:

router(config)#int port-ch1
router(config-if)#bandwidth ?
  <1-10000000>  Bandwidth in kilobits
  inherit       Specify how bandwidth is inherited

router(config-if)#int vlan60
router(config-if)#bandwidth ?
  <1-10000000>  Bandwidth in kilobits
  inherit       Specify how bandwidth is inherited

> TE over a channel is a challenge anyway as RSVP doesn't take the actual
> load-sharing into account.. I.e. RSVP might allow two 8G reservations
> which end up being hashed over the same physical port, resulting in
> packet loss..

Wouldn't this be a function of the port-channel hash algorithm, not RSVP? 
Why would RSVP know or care about the individual L2 channel members, other 
than maybe not having a configured flow size biger than the individual 
member capacity? I suppose you'd have a tough time achieving a good 
balance if you can only hash on the mpls label and not the payload when 
doing you hash calculation, but thats another story...

FWIW this is exactly how we do multi-10G parallel links on Juniper today, 
and it signals 80G RSVP across a single L3 interface on a 8x10G LACP 
bundle then looks inside the labels for l3/l4 payload when doing hash 
calculation damn near perfectly. :)

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)