...
- Cisco: "collection of standards-based extensions to classical Ethernet that allows data center architects to create a data center transport layer that is:"
- stable
- lossless
- efficient
- Purpose is apparently to buck the trend of building multiple application-specific networks (IP, SAN, Infiniband, etc)
- how? better multi-tenacy (traffic class isolation/prioritisation), guaranteed delivery (lossless transmission), layer-2 multipath (higher bisectional bandwidth)
- A series of additional standards:
- "Class-based flow control" (CBFC)
- for multi-tenancy
- Enhanced transmission selection (ETS)
- for multi-tenancy
- Data center bridging exchange protocol (DCBCXP)
- Lossless Ethernet
- for guaranteed delivery
- Congestion notification
- end-to-end congestion management to avoid dropped frames (i.e. work around TCP congestion collapse, retrofit non-congestion-aware protocols to not cause trouble
)
- end-to-end congestion management to avoid dropped frames (i.e. work around TCP congestion collapse, retrofit non-congestion-aware protocols to not cause trouble
- "Class-based flow control" (CBFC)
In the field
- Google
- Use long-lived TCP connections
- pre-established and left open to avoid handshake overhead
- unclear how TCP has been tweaked for low-latency environment (retransmit timeouts, etc)
- Use long-lived TCP connections
Misc. Thoughts
- If networking costs only small part of total DC cost, why is there oversubscription currently?
- it's possible to pay more and reduce oversubscription - cost doesn't seem the major factor
- but people argue that oversubscription leads to significant bottlenecks in real DCs
- but, then, why aren't they reducing oversubscription from the get go?