[Standards-JIG] Reliable message delivery (the tcp problem)
trejkaz at trypticon.org
Wed Apr 26 11:13:04 UTC 2006
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On 26/04/2006, at 03:23 AM, Jean-Louis Seguineau wrote:
> I agree with Peter on this one. Networks are not that bad nowadays
> that we
> must have a hop by hop acknowledgement.
Clearly there is a hop somewhere, even one hop, which isn't as
reliable as you claim. Otherwise we wouldn't be here talking about
reliable message delivery.
On 26/04/2006, at 02:38 AM, Peter Saint-Andre wrote:
> What is the definition of "unnecessary"? Personally I think that
> every XML stanza at each step in the routing process is
> unnecessary. In
> a typical architecture that would be:
> 1. My client sends a message intended for you.
> 2. ACK #1: my server acks back to my client.
> 3. My server routes the message to your server.
> 4. ACK #2: your server acks back to my server.
> 5. Your server routes the message to your client.
> 6. ACK #3: your client acks back to your server.
> That's 3 acks compared to 1 ack in the end-to-end case.
You seem to be forgetting that your "1 ack" actually turns into three
stanzas anyway. Look:
1. My client sends a message intended for you.
2. My server routes the message to your server.
3. Your server routes the message to your client.
4. ACK #1: your client acks back to my client, but then...
5. ACK #1: your server routes the ack back to my server, and then...
6. ACK #1: my server routes the ack back to my client.
However, the per-hop approach does have one major advantage -- if a
client doesn't think they need acking (see above) they can actually
choose to opt out of it. Also, if a person is paying for their
bandwidth, they may choose to opt out of it.
In other words, in your numbered points, ACK#1 or ACK#3 may not have
to happen. (I suppose ACK#2 could be left out as well, but I bet
that is where the majority of our messages are being eaten.)
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