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Now before traffic policies can be applied to packets, the packets need to be put into a class.

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So as an example, before you're allowed to take a first class seat, someone checks your ticket to

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ensure that you are a first class passenger.

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So in other words, before quality of service is applied to your packet, the route or switch needs

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to determine which class you belong to.

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If you belong to the platinum class, you will get a platinum service.

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But if you belong to the economy class, you'll only get an economy service.

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But before the service is applied, the rider or switch needs to determine which class you belong to,

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and it can do that as an example by looking at the marking.

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A FedEx sorting depot will sort packets based on the marking on a package.

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Packages with next day delivery or high importance will be processed differently to packages that have

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standard delivery markings on them.

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Best practices state that you should classify and mark as close to the edge of the network as possible.

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So as an example, IP phones will mark their traffic as it leaves the IP phone for other traffic types.

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You want to try and do your classification and marking on your edge switches.

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So marking takes place on the edge, but every device along the path uses classification to determine

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what quality of service that traffic gets.

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It can do the classification based on three criteria, either by looking at the marking in a header

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such as the costs or DHCP value.

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It could also look at IP addressing such as the destination IP subnet that you're going to or source

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IP address or layer two MAC address or some other addressing criteria.

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So as an example, it could look at destination port number.

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Are you going to a specific IP address and specific port number or are you going to something like Cisco

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dot com versus Facebook.com?

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So a domain address.

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In addition, routers can support deeper payload inspections by using application signatures.

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So by using network based application recognition or Inbar, a router can look deep into a packet to

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determine how important the traffic is.

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So Inbar uses Layers 47 for deep packet inspection.

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It is more CPU intensive and therefore you generally only do it at the edge of your network.

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Most applications can be identified using layer three or layer four criteria, such as IP addresses

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or well-known port numbers.

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But other applications require deeper packet inspection.

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As an example, HTTP uses port 80.

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You don't want your routers classifying traffic going to Cisco AECOM in the same way as Facebook.com.

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Both of them could be using port 80 or port 43 https, so you may need to look deeper into the packet

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to determine where it's going.

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So as an example, look at the domain name and then do your quality of service based on the destination

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domain name and bar supports two modes of operation.

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We have passive mode and active mode.

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Passive mode provides real time statistics on applications per protocol per interface and gives bi directional

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statistics such as bitrate packet and byte counts.

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Active mode classifies applications for traffic marking so that quality of service policies can be applied.

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So are we actively looking at traffic types and then applying quality of service, or are we just viewing

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statistics of traffic going through a network?

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So passive mode provides statistics, but doesn't do marking.

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Active mode allows you to do markings and apply quality of service policies.