Re: [Taps] TCP components

[Erik Nygren <[e-mail]>]

Another major item to add to the list would be:

- MTU/MSS negotiation and management, including initial negotiation,
response to packet-too-big signals from middle-boxes, and optional probing.

To what degree is it worth talking about known design limitations and
issues associated with each?  For example, checksums in TCP not being large
enough to detect errors in many high-volume real-world scenarios?
Erik


On Jun 11, 2015 7:53 AM, "Mirja Kühlewind" <[e-mail]>
wrote:

> Hi all,
>
> we gave it a first try to rewrite the component section for TCP. The
> insight I took from the discussion on the list is that components probably
> are much more linked to the implementation (choices) a certain protocol
> made while features are probably more high-level having the question in
> mind what does an application potentially want/need to know.
>
> So for the components in TCP we now have the following list:
>
> - Connection-oriented bidirectional communication using three-way
> handshake connection setup with
>         feature negotiation and an explicit distinction between passive
> and active open:
>         This implies both unicast addressing and a guarantee of return
> routability.
> - Single stream-oriented transmission:
>         The stream abstraction atop the datagram service provided by IP is
> implemented by dividing
>         the stream into segments.
> - Limited control over segment transmission scheduling (Nagle's algorithm):
>         This allows for delay minimization in interactive applications.
> - Port multiplexing, with application-to-port mapping during connection
> setup:
>         Note that in the presence of network address and port translation
> (NAPT), TCP ports are
>         in effect part of the endpoint address for forwarding purposes.
> - Full reliability based on ack-based loss detection and retransmission:
>         Loss is sensed using duplicated acks ("fast retransmit"), which
> places a lower bound on
>         the delay inherent in this approach to reliability.
> - Error detection based on a checksum covering the network and transport
> headers as well as payload:
>         Packets that are detected as corrupted are dropped, relying on the
> reliability mechanism
>         to retransmit them.
> - Window-based flow control, with receiver-side window management and
> signaling of available window:
>         Scaling the flow control window beyond 64kB requires the use of an
> optional feature,
>         which has performance implications in environments where this
> option is not supported.
> - Window-based congestion control reacting to loss, delay, retransmission
> timeout, or
>         an explicit congestion signal (ECN):
>         Most commonly used is a loss signal from the reliability
> component's retransmission mechanism.
>         TCP reacts to a congestion signal by reducing the size of the
> congestion window;
>         retransmission timeout is generally handled with a larger reaction
> than other signals.
>
> We are currently still working on the list of features that results from
> thiese components but we are not there yet. Probably we not only need the
> features itself but also properties/aspects (or however you want to call
> this) of the feature. We already had this discussion a bit but wanted to
> postpone the decision if we really need to define an own term for this
> until we are sure that we need it.
>
> We are posting this list of (TCP) components now because we would like to
> get some feedback if this goes into the right direction/is on the right
> level of detail before we go on and apply this also to other protocols.
>
> Brian and Mirja
>
>
>
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