Reply to post: TCP is a wire-centric protocol

TCP is a wire-centric protocol being forced to cut the cord, painfully

Warm Braw

TCP is a wire-centric protocol

It isn't, really. However, its retransmission mechanism is really there to deal with routers dropping packets owing to congestion, not to fix problems in the link layer. When early connectionless networks were designed, wired links (using modems) were as much prone to intermittent packet loss. What was different was that the "wires" had their own protocols (DDCMP/SDLC/etc) to manage the retransmission process and so transport implementations were typically less aggressive about doing it themselves.

There's nothing to stop a wireless network deploying its own link-level protocol, it's just that since the advent of Ethernet, the reasons for the existence of datalink protocols seem to have been forgotten.

Now, there may be cases where even with management at layer 2 you get significant and unpredictable latency and it's true that TCP can't cope with that, but nothing can. It might be that under those circumstances you might want to throw data away rather than retransmit it, but in that case, you want a different sort of Layer 4 protocol altogether.

You can't really build a network out of damp string and expect everything to be fixed at the transport layer. It's interesting to review Jon Postel's comments from 1977 on the initial attempts to specify TCP/IP. He said We are screwing up in our design of internet protocols by violating the principle of layering. Specifically we are trying to use TCP to do two things: serve as a host level end to end protocol, and to serve as an internet packaging and routing protocol.. Unfortunately, I think we're now seeing the ultimate expression of the tendency he detected then - functionality has gradually been squeezed out of the lower layers (and that applies as much to the typical over-extended LAN as to a mobile network) in the mistaken belief that the solution to the resulting problems can be punted up the stack.

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