This is a request for comments. Redundant Data Bundling (RDB) is a mechanism for TCP aimed at reducing the latency for applications sending time-dependent data. Latency-sensitive applications or services, such as online games and remote desktop, produce traffic with thin-stream characteristics, characterized by small packets and a relatively high ITT. By bundling already sent data in packets with new data, RDB alleviates head-of-line blocking by reducing the need to retransmit data segments when packets are lost. RDB is a continuation on the work on latency improvements for TCP in Linux, previously resulting in two thin-stream mechanisms in the Linux kernel (https://github.com/torvalds/linux/blob/master/Documentation/networking/tcp-thin.txt).
The RDB implementation has been thoroughly tested, and shows significant latency reductions when packet loss occurs[1]. The tests show that, by imposing restrictions on the bundling rate, it can be made not to negatively affect competing traffic in an unfair manner. Note: Current patch set depends on a recently submitted patch for tcp_skb_cb (tcp: refactor struct tcp_skb_cb: http://patchwork.ozlabs.org/patch/510674) These patches have been tested with as set of packetdrill scripts located at https://github.com/bendikro/packetdrill/tree/master/gtests/net/packetdrill/tests/linux/rdb (The tests require patching packetdrill with a new socket option: https://github.com/bendikro/packetdrill/commit/9916b6c53e33dd04329d29b7d8baf703b2c2ac1b) Detailed info about the RDB mechanism can be found at http://mlab.no/blog/2015/10/redundant-data-bundling-in-tcp, as well as in the paper "Latency and Fairness Trade-Off for Thin Streams using Redundant Data Bundling in TCP"[2]. [1] http://home.ifi.uio.no/paalh/students/BendikOpstad.pdf [2] http://home.ifi.uio.no/bendiko/rdb_fairness_tradeoff.pdf Bendik Rønning Opstad (2): tcp: Add DPIFL thin stream detection mechanism tcp: Add Redundant Data Bundling (RDB) Documentation/networking/ip-sysctl.txt | 23 +++ include/linux/skbuff.h | 1 + include/linux/tcp.h | 9 +- include/net/tcp.h | 34 ++++ include/uapi/linux/tcp.h | 1 + net/core/skbuff.c | 3 +- net/ipv4/Makefile | 3 +- net/ipv4/sysctl_net_ipv4.c | 35 ++++ net/ipv4/tcp.c | 19 ++- net/ipv4/tcp_input.c | 3 + net/ipv4/tcp_output.c | 11 +- net/ipv4/tcp_rdb.c | 281 +++++++++++++++++++++++++++++++++ 12 files changed, 415 insertions(+), 8 deletions(-) create mode 100644 net/ipv4/tcp_rdb.c -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
