Linux Plumbers Conference

TCP Loss Probe (TLP): fast recovery for tail losses

Registered by LPC Submitter on 2012-05-16

This session is scheduled with "Linux Kernel implementation of Multipath TCP":
https://blueprints.launchpad.net/lpc/+spec/lpc2012-net-multipath-tcp

Fast recovery (FR) and retransmission timeouts (RTOs) are two mechanisms in TCP for detecting and recovering from packet losses. Fast recovery detects and repairs losses quicker than RTOs, however, it is only triggered when connections have a sufficiently large number of packets in transit. Short flows, such as the vast majority of Web transfers, are more likely to detect losses via RTOs which are expensive in terms of latency. While a single packet loss in a 1000 packet flow can be repaired within a round-trip time (RTT) by FR, the same loss in a one packet flow takes many RTTs to even detect. The problem is not just limited to short flows, but more generally losses near the end of transfers, aka tail losses, can only be recovered via RTOs.

In this talk, I will describe TCP Loss Probe (TLP) - a mechanism that allows flows to detect and recover from tail losses much faster than an RTO, thereby speeding up short transfers. TLP also unifies the loss recovery regardless of the "position" of a loss, e.g., a packet loss in the middle of a packet train as well as at the tail end will now trigger the same fast recovery mechanisms. I will also describe experimental results with TLP and its impact on Web transfer latency on live traffic.

Topic Lead: Nandita Dukkipati <email address hidden>
Nandita is a software engineer at Google working on making Networking faster for Web traffic and Datacenter applications. She is an active participant at the IETF and in networking research. Prior to Google she obtained a PhD in Electrical Engineering, Stanford University.

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