[c-nsp] 10G options for 7600s

[Justin Shore]

Greetings,

I'm in search or recommendations for 10G linecard options for our 7600s 
(current chassis have Sup720-3BXL but all new chassis have 3CXLs and old 
one will be eventually replaced).  These ports will be used for backbone 
links between other 7600 chassis in a MPLS cloud supporting a 
triple-play offering that will ultimately include HD video, VoD, VoIP, 
and high-speed data over FTTx.  These ports would not be 
customer-facing.  I'm looking at the new S chassis to complement our 
existing 7613s.

I'm aware of the 10G SPA option but my understanding is that I can only 
get wire speed out of 2 10G SPA ports on a SIP-600 because it only has a 
single 20G backplane connection.  The ES20 would be nice if only it was 
more dense.  $80k for 2 ports before optics is not terribly feasible. 
The $40k Advanced IP license for the ES20 is also both surprising and 
painful.  The ES40 would be an option if it comes in at the price of the 
ES20 (or less) but my understanding is that it is more than a year out. 
  The only option I see is the 6704 (6708 would be alright until we 
actually near the 40G backplane limit).  The Dynamic Config Tool also 
claims that none of the 6708 models are compatible with SRB but the 6704 
is supported.  Is this another side-effect of the BU split?

I'm looking at a PPT of the differences between the ES20, SIP-600, and 
67xx linecards.  It points to differences in queues (1/2RX, 4/8 TX); 
shaping, HQoS, LLQ (use strict priority), VPLS uplink, VPLS with MPLS 
edge, and local VLAN significance are all not supported.  It also points 
out a difference in the scheduler for the ports.  Nothing in this list 
jumps out at me as something I'll need for this particular deployment of 
P routers.  The price difference is very significant as well.

So, that said, can anyone think of any reasons why we shouldn't go with 
the 6704/8 over the ES20, at least until the ES40 comes out?  What else 
am I missing?

Thanks
  Justin