Re: Half-duplex Ethernet Video over IP

benadams · ‎01-08-2002

Okay, need a little help.

At one location I have a 2620 on a T1 Internet circuit with a Polycom Viewstation FX. The FX has a 10/10 autonegotiating port and by checking the router I see that it has sync'd up at Full-Duplex 100Mbps. At another location I have another 2620 with a T1 Internet port, this time with a Polycom Viewstation 128. The Viewstation 128 has a 10Mbps Half-duplex only port. When I do a video over IP call, I check the stats on the site with the FX and there is no problem. When I check the stats for the location with the 128 I am showing massive amounts of collisions on the ethernet port of the router. I have the calling speed on both video units at 512kbps. Can anyone confirm that the half-duplex on one side and the full-duplex on the other is causing the collision errors on the site with the Viewstation 128?

jamess · ‎01-09-2002

When auto-negotiation occurs with the VS model x Polycom's, not just do you see collision counters incrementing, but the video is lousy (when there is live full motion video on both end-hosts). The serial interfaces don't really care about the duplex on the ethernet interface. When connecting a Polycom VS X to any Cisco ethernet interface, I hard-set the ether int duplex to half. They do not auto-negotiate well together.

benadams · ‎01-11-2002

The Viewstation FX autonegotiated just fine. The Viewstation 128 did not however. I did try hard coding the router to half-duplex and 10Mbps but that didnt fix the collision problem. Ultimately I put a 10/100 switch between the two and the collisions went away on the router, but still got a collision light on the Polycom port of the switch. I think that pretty much tells me that they Polycom ethernet port is fubar. I am replacing it with a unit that has a 10/00 Full duplex port and that SHOULD fix the collision problem.

shankariyer · ‎01-10-2002

Yes. It will affect the video quality. Even you try to connect two ethenet ports, back to back, setting one in Full Duplex and other in Half Duplex will result in poor quality video.

Shankar