MBP doesn't play well with 3com access point

Dr_Maybe

macrumors 6502
Original poster
Sep 17, 2003
277
0
South America
When I download large files from the internet through my 3com AP, they tend to be corrupt. It tends to be files of more than 3MB or so. When using ethernet instead of wifi, there's no problem.

I never had that kind of problem with my previous g3 and g4 mac laptops, nor with my old PC laptop w/ a wifi pcmcia card.

I updated the firmware on the 3com AP, but the problem persists.

Any suggestions to find out what's wrong? Should I run some app to analyze the connection or something?

UPDATE: I just tried downloading something through a Linksys router, and it also failed verification!
 

ormandj

macrumors member
Aug 29, 2006
73
0
Dr_Maybe said:
When I download large files from the internet through my 3com AP, they tend to be corrupt. It tends to be files of more than 3MB or so. When using ethernet instead of wifi, there's no problem.

I never had that kind of problem with my previous g3 and g4 mac laptops, nor with my old PC laptop w/ a wifi pcmcia card.

I updated the firmware on the 3com AP, but the problem persists.

Any suggestions to find out what's wrong? Should I run some app to analyze the connection or something?
That's odd, because I'm assuming you're downloading over http/ftp which is TCP based, and should ACK for all packets, hence no problems. Something is bad wrong in that interaction, and it has to do with how that AP and your MB are playing together. I've used MB/MBPs before on wireless with no issues, but never with a 3com AP. Hopefully somebody else can chime in here.
 

Dr_Maybe

macrumors 6502
Original poster
Sep 17, 2003
277
0
South America
ormandj said:
That's odd, because I'm assuming you're downloading over http/ftp which is TCP based, and should ACK for all packets, hence no problems. Something is bad wrong in that interaction, and it has to do with how that AP and your MB are playing together. I've used MB/MBPs before on wireless with no issues, but never with a 3com AP. Hopefully somebody else can chime in here.
Yeah it's odd.

But according to wikipedia, the TCP checksum is weak:

The TCP checksum is a quite weak check by modern standards. Data Link Layers with a high probability of bit error rates may require additional link error correction/detection capabilities. If TCP were to be redesigned today, it would most probably have a 32-bit cyclic redundancy check specified as an error check instead of the current checksum. The weak checksum is partially compensated for by the common use of a CRC or better integrity check at layer 2, below both TCP and IP, such as is used in PPP or the Ethernet frame. However, this does not mean that the 16-bit TCP checksum is redundant: remarkably, surveys of Internet traffic have shown that software and hardware errors that introduce errors in packets between CRC-protected hops are common, and that the end-to-end 16-bit TCP checksum catches most of these simple errors. This is the end-to-end principle at work.
I hope I won't have to get a new AP. The 3com is small and blends nicely into the livingroom, unlike the black/blue/green monster looking linksys'es.
 
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