I have a private MPLS backbone built on the 7600 series platforms. Both the P and PE routers are 7606 routers with Sup720-3BXL's. A more detailed linecard breakout is below:
PE routers = 6748 10/100/1000 linecard for CE connections and connectivity to the P routers
P routers = 6748 for PE connections, SIP-200 for DS3 connections, and SIP-400 with SPA-2x1GE cards for GigE connections.
All IOS levels are 12.2-33SRA1 and FPD images are 12.2-33SRB.
The IGP is OSPF and all interfaces are MPLS enabled. Traffic into and out of the PE routers (on the 6748 linecard) gets really good throughput, and even traffic between the PE and P routers can experience excellent throughput; however, once traffic tries to leave the P router over one of the SIP cards - it is getting choked to ~1 or 2 Mbytes/s. These connections can be anywhere from a DS3 to Gig Speeds, yet the throughput rates on those cards are really limited.
If I remove the connections from the SIP linecards and run them into a 7206 or even flexwan cards with DS3 or Gig ports, throughput is back to normal ranges.
I'm curious if anyone has ever experienced similar issues with SIP cards and performance. I've got several angles already at work on this problem, including several Cisco TAC engineers, TME's and DE's, but figured it doesn't hurt to ask around!