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New Member

QoS for UDP traffic

Hi all,

my problem refers to UDP traffic: in an ICT lab two servers (named A and B) are connected on the same VLAN.In particular:

-server A receives UDP traffic from cameras installed outside the lab

-server A then forward this traffic to server B which definitely stores it.

-A and B are respectively connected on fa0/10 and fa0/11 interfaces of a Cisco Catalyst 3560.

Aa a result, the traffic which directly comes out of server A is equal to the traffic entering into server A (that is, there is no packet loss between taking video streams from cameras and sending them to server B).

Conversely, packet loss occurs at the ingoing interface of server B. It seems that packets have a loss while flowing from A to B. I tried to change the IP addresses to the two servers, but the loss gets worse.

How could I solve this QoS problem? My scope is to maximize the number of packets coming from cameras to server B.

Thank you


Super Bronze

Re: QoS for UDP traffic

Is the packet loss on the switch, i.e. it's egress to server B, or on server B's NIC, ingress?

Are the interfaces running at 10 or 100?

Are the interface running in full duplex? (Are you sure about the server B connection?)

What's the average bandwidth utilization for this video stream? Is it very bursty?

Which model 3650? What's the installed IOS?

What else is the 3650 supporting? How much other traffic?

Is the 3560 only being used as a L2 switch?

Have you examined the 3560 port stats? What do they reveal?

What SDM template is being used?

What's the 3560's CPU history look like?

Is this UDP traffic unicast?

Answers to the above might provide more clues, but without them, some things to consider might be.

Insure links are running 100/full.

Port selection on the 3560 might be imporant.

Software levels for the 3650 and/or server's NIC.

New Member

Re: QoS for UDP traffic

Hi Joseph,

thanks for your reply. Here are some answers that I can give oyu so far:

First of all, the two servers are connected (they ping each other).

The packet loss is on server B's NIC, ingress.

The interfaces are running at 100 Mbps and in full duplex.

3560 is a L3 switch; IOS version: 12.2

Super Bronze

Re: QoS for UDP traffic

Unfortunately, doesn't help much. Most software for the 3560 is 12.2 something. The full version information would be more helpful. (Can be seen if you use "show version" on the switch.)

If the packet loss is on the server B NIC, then the problem is there and might not find much help on these forums.

Some things that might help, updating software on server's NIC, using a different NIC on the server, or "Shaping" traffic from the switch to the server (this to avoid quick bursts that might be overrunning the capacity of server's NIC.)