Let's add:

0 - The two endpoints of a network connection may be (and usually are)
under independent control from one another.
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On Sun, Jul 3, 2022 at 4:32 PM Marc Donner <marc.donner@gmail.com> wrote:

> On June 28 Rob Pike wrote:
>
> "One of the reasons I'm not a networking expert may be relevant here. With
> networks, I never found an abstraction to hang my hat on. Unlike with file
> systems and files, or even Unix character devices, which provide a level of
> remove from the underlying blocks and sectors and so on, the Unix
> networking interface always seemed too low-level and fiddly, analogous to
> making users write files by managing the blocks and sectors themselves."
>
> I've been ruminating on the question of whether networks are different
> from disks (and other devices).  Here are a couple of observations:
>
> 1 - Two different packets may take two different paths from the sender to
> the receiver.
>
> 1a - The transit time for one packet may vary widely from that of the
> other.
>
> 1b - The two packets may arrive in an order different from the order in
> which they were transmitted.
>
> (Note - recently I have been reading Bob Gezelter's monograph [and PhD
> dissertation] and I've learned that modern high-performance disk systems
> behave more like networks in 1a and 1b.)
>
> 2 - A packet may never arrive.
>
> 3 - Behavior 2 not a sign of hard failure for networks, whereas it is
> generally considered so for other I/O devices.
>
> There is probably more to why networks are weird, but these are some of
> the big dissonances that seem to me to make Rob's comment resonate so
> loudly to me.
>
> Best,
>
> Marc
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>