Aggregate Bandwidth Rate Limiting with CiR/CAR Rate Limiting
Posted on 2007-08-08
I am looking for a solution to do traffic-shaping and rate limiting on an aggregate port-based / traffic path basis...
Here is the problem; my ISP has allocated us a block of 16 static IPs on a 2 Mb up/down connection. However, they control the routing, and we do not have access to the router to do any kind of QoS, etc.
Let's say that I have 6 devices attached to this network using the static IPs. Naturally, since I only have one wire coming down from the router, they must be connected to a switch. Unfortunately this allows me zero percent control over the QoS and badnwidth that the various devices use.
The trouble comes in that one of those devices is a video conference endpoint that I want to dedicate 1 Mb of bandwidth to. Of course, using an inexpensive switch with rate-limiting capbilities, I can throttle the bandwidth; I could rate-limit each of the 5 other devices to 200k each; this would ensure that I always have 1Mb available to the conference unit.
The obvious solution here is to develop some kind of aggregate policy, say, the sum of ports 1 through 6 must not exceed 2Mb, and port 6 (The VC device) must have a commited information rate of 1Mb (But if the unit is not in use, then the whole 2Mb should be available to the other ports) This becomes slightly more complex when you realize that the traffic from the other 5 devices may potentially be flowing between each other; thus you cannot simply police the sum of the ingress and egress traffic on the ports.
The ultimate solution would allow for policing of the traffic flowing from ports 1-6 to port 8 where the router is connected, but not any of the traffic flowing between any of ports 1-6 to each other.
The more I think about this, the more complex it appears, yet it seems to me a situation that would be rather common. (3 of the 4 network locations I manage have this issue, and I can see many other network managers having similar issues)
Does anyone know of an elegant solution? I can't seem to find a layer 2 switch that can do what I'm looking for, and although it appears there are a few layer 3 switches that could, they all have far more than the 8 to 16 ports necessary and are quite costly. Thoughts?