well a really bad 56k with a bad trace route. and lost packets will make you laggy /warpy , and it can pull your Frame rate down sometimes .. but you ussually end up discoed alot from the game .. I just came off a 56k connect and even though i had tons of disco's my frame rates ran decent in the main , even when i tested a amptron mb pc with onboard video , 256 ram, 1 ghz amd , my frames were in the 30's on that machine ..even on 1200kbps dsl connect the frames are staying in the 30's..
(I just tested this in the last 3 weeks )
learning to trouble shoot your machine is very important these days ... its not like 2 plus years ago when you could go online and have very few problems ... hell the OS (XP as example) can knock a great gaming machine right into the dirt , when it gets messed up.
Something to use as a reference is play the game offline , note the frame rates ... then play online in the main . you shouldnt see much difference , if there is a big difference then it can be your modem/ connection/ isp/phone line/ or trace route .
(note try to use the same map for this test )