What's the benefit of keeping the data plane on the cisco/junpier hardware?
To be clear, it's not literally Cisco/Juniper hardware, but it's similar (ASIC-based).
on the WAN links you could get away with 6 or so ports in a PC-like chassis running software routing
ASICs are line rate, denser, and cheaper per port than x86 servers. Roughly $15K buys you either an x86 server with 6 10G ports or an OpenFlow switch with 64 10G ports. Since Google has over 100 ports per switch (according to EE Times), they presumably need the ports and the savings is significant at that scale.
To be clear, it's not literally Cisco/Juniper hardware, but it's similar (ASIC-based).
on the WAN links you could get away with 6 or so ports in a PC-like chassis running software routing
ASICs are line rate, denser, and cheaper per port than x86 servers. Roughly $15K buys you either an x86 server with 6 10G ports or an OpenFlow switch with 64 10G ports. Since Google has over 100 ports per switch (according to EE Times), they presumably need the ports and the savings is significant at that scale.