[PATCH RFC net-next 0/2] tcp: Redundant Data Bundling (RDB)

From: Bendik RÃnning Opstad
Date: Fri Oct 23 2015 - 16:55:43 EST



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 RÃnning 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

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