Anypoint

Extensible Transport Switching

Anypoint is a new model for one-to-many communication with ensemble sites---aggregations of end nodes that appear to the external Internet as a unified site. Anypoint routers reside at the network edge, redirecting individual client requests among the ensemble members. The extensible architecture allows routing policies to be defined by application-layer plugins in the switch.

Anypoint is the first general indirection approach that operates at the transport layer at the granularity of frames. The transport-layer solution enables reliable, ordered, rate-controlled Anypoint communication, complementing IP-layer approaches(e.g., Anycast and i3), which support wide-area ensembles but provide only best-effort packet delivery. By leveraging transports with framing, our approach is amenable to implementation on high-speed switches and routers.

Anypoint contributions:

• Service Extension and Virtualization with Anypoint- Anypoint enables transparent extension and virtualization of network services based on application-layer (L7) protocols, by interposing L7 plug-in extensions in network switches. This communication model generalizes ``L4-L7'' server switches that support server load balancing or content-based request routing for the Web and related services. Commercial Web switches are limited to service protocols (e.g., HTTP) that issue each request in a separate transport connection, or process requests on each connection serially. Anypoint extends this idea to allow independent, concurrent handling of multiple requests arriving on the same persistent transport connection, enabling a new class of virtualization switches for network storage protocols and other Internet services. We have developed an NFS L7 storage router,based on Slice, to explore the impact on service architecture.
• Anypoint-Compatible Protocol (ACP)- Anypoint is designed for advanced IP transports with partial ordering, explicit rate control, and application-level framing, as proposed by Clark and Tennenhouse over a decade ago. Reliance on these capabilities---which TCP does not support---enables an approach that is both more powerful and more elegant than solutions based on TCP connection migration. Our ACP prototype is based on TCP with the addition of a light-weight framing shim between the protocol stack and socket layer. It also supports explicit rate control mechanisms in the form of XCP [Katabi, et. al.].
• Transport Equivalence- Anypoint is transport-equivalent: end nodes use the same transport code for point-to-point and Anypoint connections. Note that---in contrast to application-level proxies---an Anypoint intermediary does not terminate transport connections. Anypoint avoids both the CPU and transport-layer buffering overhead associated with termination. In contrast to a terminating proxy, an Anypoint switch maintains state about the current number of outstanding frames in the network.

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