Traffic Classification

Question

How does the switch or router differentiate between voice and data traffic?

What are the parameters used in the different layers to classify this traffic?

Answer 1

How does the switch or router differentiate between voice and data traffic? It doesn't unless you tell them.

What are the parameters used in the different layers to classify this traffic? Applications Jitter and delay requirement is what generally prompts administrators to classify traffic. to classify traffic. Now, people usually classify voice/video(and few more) as priority traffic. Data traffic gets help from upper layer protocols as they have flow control and re-transmission capabilities, so they are classified as lesser priority.

Layer -2 you have COS bits in 802.1Q frames which will help you mark traffic. Layer-3 has TOS bits which can be marked. MPLS has exp bit and so on... depending on where you are in the network, use the marking tools your device provides and classify them.

Answer may seem vague but QOS is a vast topic :)

Answer 2

How does the switch or router differentiate between voice and data traffic?

First, there’s no practical difference between a voice and data packet.

Switch switches within the subnet, that is switching. In switching packets are transfered from source to destination using MAC address. Switching is done within the network.

Whereas Router routes between the network. Routing is a process which is done between two networks using IP addresses.

basically routing is a intelligent switching

Answer 3

You can classify packets by many different criteria. The classification is done on packets using the DSCP bits in the IPv4 header or Traffic Class field in the IPv6 header (the first six bits of the Traffic Class IPv6 header field are the same as the DSCP bits in the IPv4 header).

At layer-2, trunks can use CoS bits to classify frames.

You can classify traffic just about any way you want. You could do this by VLAN, network, IP address, layer-4 protocol, application protocol, etc.

The important thing is that you create a comprehensive and consistent classification plan and marking across your entire network.

To a switch or router, VoIP traffic is data traffic. Frames are frames, and packets are packets. Only your classification will distinguish between VoIP and data, and only if you have configured your network devices to distinguish between the markings, which doesn't happen by default.