TCP packet size?

[Mike Fletcher]

Hmm, I'm very surprised you're needing to get down to this level when you're
using something as "high level" as XML as your encoding.  XML is so
inefficient as a network protocol that most people would just use standard
TCP streams (i.e. open a stream socket and let TCP take care of the
ordering/guaranteeing/decomposition/reassembly), instead of trying to send
TCP packets as raw packets (heck of a lot of work for no real benefit I can
see).  Or do you mean that you're doing a network sniff and are upset that
the packets are getting broken up and reassembled?
 
I do lots of work with UDP-based protocols where these issues come up, but
since UDP is non-guaranteeing, you wind up explicitly dealing with the
issues regardless (they're not easy, incidentally, lots of soft tradeoffs
dependent on current network conditions, required QOS, priority among
messages, etceteras).  I tend to favour breaking messages up more (I target
256 bytes, include 26 byte UDP header), rather than less, as small UDP
packets may get through a crowded network, while larger UDP messages will
get dropped when load is high (or at least, that's what certain articles
have me believe :) ).  To do it right, of course, you need a dynamically
adapting system that increases message size when load is low (and does a
thousand other optimisations, as well).
 
If I've missed the point, bear with me and explain again.  Since I've not
actually grokked what the "problem" being tackled is, it's quite likely I
have missed the point one way or another.  Enjoy yourself,
Mike
 
-----Original Message-----
From: chris [mailto:chris at rpgarchive.com]
Sent: Thursday, June 15, 2000 2:53 AM
To: Python List
Subject: TCP packet size?


Is there a way to ensure or predict packet size when using TCP?  I'm
developing a Multi-user application that functions much like a muli-player
game.  The applications are sharing xml data.  The xml data can get very big
3000-6000 bytes.  Unfortunately, when the size of the network message gets
over about 2000, its to get broken up into smaller packets.  So, when I send
a 3000 byte message it gets cut up into 2-3 packets.  Anther problem I get
is when I send two small messages back to back, they are sometimes received
together.  Is there something I'm missing here? 

I tried using headers and breaking up messages into smaller chunks, but the
size of the receiving packets doesn't always match what I sent.  I'd
appreciate any help or suggestions on how I can tackle this problem.  I'd be
happy to send someone my network code. 


Thanks 

-- 

chris davis

chris at rpgarchive.com

 

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