[MUD-Dev] Transport layer (UDP vs TCP)

[Niklas Elmqvist]

On Wed, 18 Mar 1998, Ben Greear wrote:

[snip]

> If your packets can be fragmented at the last step (I'm assuming most
> players will be using PPP over a modem) then it could become very nasty
> as far as reading a complete packet in no?  Does the UDP somehow keep
> you from reading half of a packet (the other half of which has been lost
> forever?)

Nope, luckily not.

> For instance, I send a 512 byte UDP packet.  Can the receiver ever just
> receive the first 256 bytes or so?  Surely not, as this would make it
> basically impossible to code anything without writing another layer on
> top of it...

I believe UDP is little more than plain IP with a few other features
thrown in. One is a checksum which used to check the integrity of the
data, the other is the ability to multiplex information across port
numbers. As such, UDP does not guarantee delivery, and neither does it
guarantee sequential delivery, but it does guarantee correct datagrams --
if the checksum is invalid, the datagram is discarded.

> Ben Greear (greear at cyberhighway.net)  http://www.primenet.com/~greear 

-- Niklas Elmqvist (d97elm at dtek.chalmers.se) ----------------------
"You can't trample infidels when you're a tortoise. I mean, all you 
 could do is give them a meaningful look."	 
	- Terry Pratchett, Small Gods