PC Port on the Phone Issue

[Allan Choo]

Hi,

I am see a big difference in throughput when connecting a PC through the PC port on a Cisco 7942 phone, compared to when the PC is directly connected to a switch. My setup is a 2960G POE switch, CM 8.6 and 7962 phones.

For example if my PC is connected directly into the switch, I can transfer a file in Windows at about 50~60 MB/s

(Server)-----------(2960G)------------(PC)

But if I connect to the pass through port on the phone, my transfer speeds slows down to about 5~10 MB/s

(Server)--------(2960G)-----------(7942VoIP)------------(PC)

Now even though the phone is only at 10/100 speed, my throughput should be a lot better.  Could this be a configuration issue with QOS? if so, QOS is configured on the switch so wouldn't that affect the PC if the PC is connected directly to the switch?

I have 2 other locations with CMs that are not seeing this issue.

Regards,

Allan

[Jameson Gagnepain · Accepted solution]

Allan,

10/100 ethernet speed is in Megabits per second (Mbps), and it sounds like your transfer speeds are in MegaBytes per second (MB/s). Little b=bits, Big B=Bytes, 1 B = 8 b. 100 Megabits is equal to 12.5 Megabytes. A good portion of that will be lost to overhead. 5 -10 Megabytes per second is about what I would expect from a 10/100 ethernet connection, and the 50-60 MB/s you mention is indicative of a 10/100/1000 ethernet connection. I'm not seeing anything unusual here.

-Jameson

[Allan Choo]

Hi Jameson,

Yes, I am only looking at the transfer speed shown in Windows file transfer which shows in XX MB/s.

Let me do some testing with 10/100 switches which is what I have over here in this office. So if my switch is 10/100 and the PC port on the phone is 10/100, I wouldn't see too much of a difference whether I am connected to the phone or the switch directly. but there will be a difference if the switch ins 10/100/1000.

Regards,

Allan

[John Huthmaker · Accepted solution]

Just want to make sure I understand.  You said its a 2960G switch right?  That would be a gig switch.  Then you are plugging a 7942 phone in, and then plugging a pc in to the phone.  Is that all correct?  Cause the phone will only give you 100mg out, thus cutting you down to a 1/10th the speed of being plugged directly in to the switch.

[tahequivoice]

I have a customer with this problem, however, we do know its 100 Mbps, but throughput is only 160Kbps.