[e2e] common congestion controller for TCP connections

[Michael Savoric]

Joe Touch wrote:

> Question - from the title, I couldn't get a sense of what the primary
> focus of your contribution is. I can consider two aspects:
> 
>         1) the architecture for sharing
>                 seems like you're using TCBI, per se, right?
>                 there really isn't anything here that is outside
>                 what TCBI described - 2140 described true shared
>                 state, in addition to long-timescale caching and
>                 state resolution.
> 
>         2) the algorithms for how to share the variables
>                 which would be an implementation of "policy",
>                 as referred to in TCBI, right?
> 
> There really is a difference, BTW, between TCBI and CM, as I pointed out
> on the list. And E-TCP is an instance of TCBI. SPAND seems like it's a
> version of TCBI as well, at least as far as I can tell, shared over a
> LAN, which is also mentioned in RFC2140.
> 
> Joe

Hi,
basically, the EFCM controller is a TCBI-instantiation. The
main focus of the EFCM controller is on the algorithms how
available network information can be shared and how TCP
connections (later also other flows, e.g., UDP) can be jointly
controlled. This common congestion control is done by
manipulating some TCP control variables. No additional internal
structures like a packet scheduler are needed.
What is needed for a single ensemble are aggregated values for the
jointly controlled variables and a pointer to the TCP sender
instance whose CWND is increased after the receive of the next
ACK (ensemble ack clocking). The control algorithms have a low
additional complexity compared to standard TCP.

Under packet loss events, an ensemble of n EFCM-controlled TCP
connections has a comparable aggressiveness to the network than a
virtual ensemble of n standard TCP connections (assumption:
packet loss events are equally distributed over the TCP
connections).


Best regards,
Michael Savoric

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