Re: [SWMP] TCP, UDP, and multicast: are they really equivalent?

Roland Weber <ossfwot@dubioso.net> Sun, 09 September 2007 07:04 UTC

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Date: Sun, 09 Sep 2007 09:05:05 +0200
From: Roland Weber <ossfwot@dubioso.net>
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Subject: Re: [SWMP] TCP, UDP, and multicast: are they really equivalent?
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Jay C. Weber wrote:
> John:  I agree with your assessment that (UDP) datagrams are only appropriate 
> for intense streams of field updates, where reliability of individual datagrams 
> is not essential.  But as I'm sure you are aware, just as with intense streams 
> of audio or video data, datagrams can be significantly more efficient in terms 
> of both latency and bandwidth.

I'm missing practical experience here, but this is very intuitive.
Maybe it is oversimplified to just distinguish between TCP and UDP?
UDP in a local network should be much more reliable than UDP over
an internet connection. On the other hand, plain TCP could be
augmented by TLS for client authentication on the initial channel.
And then there's unidirectional multicast (probably reliable?).

How about defining a few channel classes, and leaving it up to
the implementations to choose the transport mechanism based on
configurations and available runtime data? For example:

RSD: reliable and slow, duplex. (TCP, TLS)
RFD: reliable and reasonably fast, duplex. (TCP, UDP/local)
UFD: unreliable and fast, duplex. (UDP)
RFS: reliable and fast, simplex. (multicast)
UFS: unreliable and fast, simplex. (UDP/firewall)

Gateways or proxies would be allowed to change the transport
where appropriate, for example from TCP/internet to UDP/local.

cheers,
  Roland


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