Now before traffic policies can be applied to packets, the packets need to be put into a class.
So as an example, before you're allowed to take a first class seat, someone checks your ticket to
ensure that you are a first class passenger.
So in other words, before quality of service is applied to your packet, the route or switch needs
to determine which class you belong to.
If you belong to the platinum class, you will get a platinum service.
But if you belong to the economy class, you'll only get an economy service.
But before the service is applied, the rider or switch needs to determine which class you belong to,
and it can do that as an example by looking at the marking.
A FedEx sorting depot will sort packets based on the marking on a package.
Packages with next day delivery or high importance will be processed differently to packages that have
standard delivery markings on them.
Best practices state that you should classify and mark as close to the edge of the network as possible.
So as an example, IP phones will mark their traffic as it leaves the IP phone for other traffic types.
You want to try and do your classification and marking on your edge switches.
So marking takes place on the edge, but every device along the path uses classification to determine
what quality of service that traffic gets.
It can do the classification based on three criteria, either by looking at the marking in a header
such as the costs or DHCP value.
It could also look at IP addressing such as the destination IP subnet that you're going to or source
IP address or layer two MAC address or some other addressing criteria.
So as an example, it could look at destination port number.
Are you going to a specific IP address and specific port number or are you going to something like Cisco
dot com versus Facebook.com?
So a domain address.
In addition, routers can support deeper payload inspections by using application signatures.
So by using network based application recognition or Inbar, a router can look deep into a packet to
determine how important the traffic is.
So Inbar uses Layers 47 for deep packet inspection.
It is more CPU intensive and therefore you generally only do it at the edge of your network.
Most applications can be identified using layer three or layer four criteria, such as IP addresses
or well-known port numbers.
But other applications require deeper packet inspection.
As an example, HTTP uses port 80.
You don't want your routers classifying traffic going to Cisco AECOM in the same way as Facebook.com.
Both of them could be using port 80 or port 43 https, so you may need to look deeper into the packet
to determine where it's going.
So as an example, look at the domain name and then do your quality of service based on the destination
domain name and bar supports two modes of operation.
We have passive mode and active mode.
Passive mode provides real time statistics on applications per protocol per interface and gives bi directional
statistics such as bitrate packet and byte counts.
Active mode classifies applications for traffic marking so that quality of service policies can be applied.
So are we actively looking at traffic types and then applying quality of service, or are we just viewing
statistics of traffic going through a network?
So passive mode provides statistics, but doesn't do marking.
Active mode allows you to do markings and apply quality of service policies.