loss event but not use or obay the recommendations i.e. values set by it in some
cases.
Here is an attempt to solve that confusion by following relevant RFCs/drafts.
Stack only sets congestion window/slow start threshold values when there is no
CC module availalbe to take that action. All CC modules are inspected and
updated when needed to take appropriate action on loss.
tcp_stacks/fastpath module has been updated to adapt these changes.
Note: Probably, the most significant change would be to not bring congestion
window down to 1MSS on a loss signaled by 3-duplicate acks and letting
respective CC decide that value.
In collaboration with: Matt Macy <mmacy at nextbsd dot org>
Discussed on: transport@ mailing list
Reviewed by: jtl
MFC after: 1 month
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D8225
- Wrong integer type was specified.
- Wrong or missing "access" specifier. The "access" specifier
sometimes included the SYSCTL type, which it should not, except for
procedural SYSCTL nodes.
- Logical OR where binary OR was expected.
- Properly assert the "access" argument passed to all SYSCTL macros,
using the CTASSERT macro. This applies to both static- and dynamically
created SYSCTLs.
- Properly assert the the data type for both static and dynamic
SYSCTLs. In the case of static SYSCTLs we only assert that the data
pointed to by the SYSCTL data pointer has the correct size, hence
there is no easy way to assert types in the C language outside a
C-function.
- Rewrote some code which doesn't pass a constant "access" specifier
when creating dynamic SYSCTL nodes, which is now a requirement.
- Updated "EXAMPLES" section in SYSCTL manual page.
MFC after: 3 days
Sponsored by: Mellanox Technologies
algorithm described in the paper "Improved coexistence and loss tolerance for
delay based TCP congestion control" by Hayes and Armitage. It is implemented as
a kernel module compatible with the recently committed modular congestion
control framework.
CHD enhances the approach taken by the Hamilton-Delay (HD) algorithm to provide
tolerance to non-congestion related packet loss and improvements to coexistence
with loss-based congestion control algorithms. A key idea in improving
coexistence with loss-based congestion control algorithms is the use of a shadow
window, which attempts to track how NewReno's congestion window (cwnd) would
evolve. At the next packet loss congestion event, CHD uses the shadow window to
correct cwnd in a way that reduces the amount of unfairness CHD experiences when
competing with loss-based algorithms.
In collaboration with: David Hayes <dahayes at swin edu au> and
Grenville Armitage <garmitage at swin edu au>
Sponsored by: FreeBSD Foundation
Reviewed by: bz and others along the way
MFC after: 3 months
