as I look to the characteristics of these 2 products they are quite similar if using supervisor engine 720. They both share several modules, interfaces...
The main requirement for us is to have full MPLS functionalities. Do you (experts) have a preference according to your appreciated experience ?
Can you elaborate a little more - why 3bxl is required and 3b is not enough to do MPLS L3 VPNs? As I understand from cisco docs, 3b should be enough to do all MPLS stuff.
I dont believe the 3B actually assigns the labels. You would require OSM cards to do the actaul label assignment. The 3BXL was the first card on the 7600 that properly supported L3VPNS along with a whole load of other stuff. I would check with your Cisco SE.
The following doc outlines most of the differences:
i think contrast to pfc3b and pfc3bxl is volume of memory,pfc3bxl has 1G memory. if you need more vpn you need more memories.
i have once installed pfc3a for customer mpls vpn. i config 7609 with pfc3a for PE function, and config 3 7609 with pfc3a and 10720 to compose a dpt ring,. i found L3 mpls vpn work well. but found a problem , after we config more than 300 interface vlan and 100 physical interface, the cpu on 7609 reach 80% after we telnet into 7609 router.
really we can config mpls vpn PE on pfc3a , but someone told me there were some bugs which cisco can't resolve on pfc3a( i don't know). on cisco cco, pfc3a didn't support mpls vpn pe offically.
i think you may ask cisco se for help.
We used sup2/msfc2 cards in 6509 chassie and now we upgraded them with sup720Bs. In both cases we use this router in MPLS/VPN environment as a PE router. I will answer your questions if I can.