what is the difference between classification and markings ?

[dolanduck.]

i was reading CCNA book and as much as i read the chapter it would not stick.

so from what i know classification put things in order like which goes first and marking

marks things so a ip phone tells the switch to mark it as important. ?

[Martin L]

Definition says Classification involves differentiating one packet from another so that we and any QoS tool can treat packets in one class differently than others. So, you can basically classify traffic as Voice traffic and gave it higher preference over non-voice traffic (all other traffic).  

Marking means we must somehow "mark" particular traffic we just classify as important (i.e. voice). This is usually done in the header of IP packet. 

usually we do not separate those two items when talking about QoS. i mean to mark traffic you must classify it first;  QoS tools like CB and NBAR perform both functions of classification and markings.  there is no separate tool to do markings.  

Regards, ML
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[dolanduck.]

i still don't get it i cant wrap my head around it

so what you are saying is that for classification

we have different types of traffic voice, video,and data

and we can set voice traffic to be first ?

[TONY SMITH]

Classification is simply distinguishing one type of traffic from another, which might be more or less complex depending on the network. For example you may want to classify an ERP system so it's traffic can get priority treatment, this classification may combine protocol and hosts, for example CItrix ICA to/from only certain servers.
Marking is making a change to the packet to reflect that classification, for example setting DSCP to CS2. Downstream devices can use that mark to decide what to treat as priority and don't have to be aware of the earlier decision making process. In my example you don't need to add the matching rules to distinguish ERP server from other Citrix into each and every router.

[Roger Kallberg]

Classification is what identify the traffic and marking is what sets the information used for priority of the traffic.

”Classification and marking is an essential component to establishing end-to-end quality of service (QoS), which ensures a reliable voice over IP (VoIP) infrastructure. Classification and marking is a system of identifying packets or traffic flows and assigning certain parameters within the packet headers in order to group them. Once the traffic is "identified," it can be marked or "colored" into groups so that QoS policies can be applied to them.”

[dolanduck.]

when you mean identify that the router or switch identifies the traffic as ether voice or video or data and puts it in to Que   ?

[Roger Kallberg]

You use classification to identify what traffic to later on mark with markings. These markings is then used to determine how to treat the traffic, aka what queue to put it in and so on.