CCIE Voice Training, Setting the DSCP or TOS Discipline
January 13th,2012 by NicholasThe solution to this concern is determined by the sort of potential customers distinctions you would like to help make, likewise the version of IOS you're operating in your routers. CCIE Voice Training
There needs to be a thing that defines the different different kinds of targeted visitors that you simply want to prioritize. In general, the easier the distinctions are in making, the better. This is because every one of the exams get router resources and introduce processing delays. The most prevalent policies for distinguishing around targeted visitors styles use the packet's input interface and simple and easy IP header particulars like as TCP port quantities. The subsequent examples show the right way to set an IP Precedence price of instantaneous (2) for all FTP manage targeted traffic that arrives through the serial0/0 interface, and an IP Precedence of priority (one) for all FTP information page views. This distinction is possible due to the fact FTP control targeted traffic makes use of TCP port 21, and FTP knowledge utilizes port twenty.
The newest process for configuring this utilizes class maps. Cisco initially launched this aspect in IOS Edition 12.0(five)T. This process foremost defines a class-map that specifies how the router will recognize this sort of page views. It then defines a policy-map that really makes the changes to your packet's TOS discipline:
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#access-list 101 permit any eq ftp any
Router(config)#access-list 101 permit any any eq ftp
Router(config)#access-list 102 permit any eq ftp-data any
Router(config)#access-list 102 permit any any eq ftp-data
Router(config)#class-map match-all ser00-ftpcontrol
Router(config-cmap)#description branch ftp control traffic
Router(config-cmap)#match input-interface serial0/0
Router(config-cmap)#match access-group 101
Router(config-cmap)#exit
Router(config)#class-map match-all ser00-ftpdata
Router(config-cmap)#description branch ftp data traffic
Router(config-cmap)#match input-interface serial0/0
Router(config-cmap)#match access-group 102
Router(config-cmap)#exit
Router(config)#policy-map serialftppolicy
Router(config-pmap)#description branch ftp traffic policy
Router(config-pmap)#class ser00-ftpcontrol
Router(config-pmap-c)#set ip precedence immediate
Router(config-pmap-c)#exit
Router(config-pmap)#class ser00-ftpdata
Router(config-pmap-c)#set ip precedence priority
Router(config-pmap-c)#exit
Router(config-pmap)#exit
Router(config)#interface serial0/0
Router(config-if)#ip route-cache policy
Router(config-if)#service-policy input serialftppolicy
Router(config-if)#exit
Router(config)#end
Router#
For before IOS variations, just where class-maps ended up not on hand, you will have to implement policy-based routing to change the TOS subject inside of a packet. Applying this coverage to your interface tells the router to utilize this coverage to check all incoming packets on this interface and rewrite the ones that match the route map:Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#access-list 101 permit any eq ftp any
Router(config)#access-list 101 permit any any eq ftp
Router(config)#access-list 102 permit any eq ftp-data any
Router(config)#access-list 102 permit any any eq ftp-data
Router(config)#route-map serialftp-rtmap permit 10
Router(config-route-map)#match ip address 101
Router(config-route-map)#set ip precedence immediate
Router(config-route-map)#exit
Router(config)#route-map serialftp-rtmap permit 20
Router(config-route-map)#match ip address 102
Router(config-route-map)#set ip precedence priority
Router(config-route-map)#exit
Router(config)#interface serial0/0
Router(config-if)#ip policy route-map serialftp-rtmap
Router(config-if)#ip route-cache policy
Router(config-if)#exit
Router(config)#end
Router#
Earlier than you're able to tag a packet for exceptional therapy, you may have to possess a particularly apparent thought of what different types of site visitors ought amazing procedure, combined with specifically what kind of amazing procedure they're going to might need. Within the example, we've made a decision to give a extraordinary concern to FTP site visitors received on the targeted serial interface. We show the right way to do that implementing the two the previous and new configuration ways.
This may seem to get a considerably synthetic example. When all, why would you care about tagging inbound site traffic that you just have presently obtained from a low-speed interface? Actually, one of the many most important concepts for employing QoS in a network is always that you need to generally tag the packet as early as you possibly can, ideally in the edges within the network. Then, since it passes in the network, every router only has to look into the tag, and doesn't have to do any added classification. In this case, we'd be certain that the FTP customers returning while in the other route is tagged with the to start with router that receives it. So the outbound traffic has presently been tagged, and it is a waste of router resources to reclassify the outbound packets.
Some organizations truly just take this concept of marking at the edges a particular phase further more, and remark all received packet. This helps to ensure that end users aren't requesting special QoS privileges which they are not permitted to get. Having said that, you should be cautious of this as a result of it could actually quite often disrupt genuine markings. One example is, a real-time application might possibly use RSVP to order bandwidth from the network. It is usually valuable which the packets for this application have the best suited Expedited Forwarding (EF) DSCP marking or perhaps the network might not tackle them thoroughly. Nevertheless, additionally you do not prefer to permit other non-real-time purposes from this exact resource hold the very same EF concern level. So, for anyone who is heading to configure your routers to remark all incoming packets at the edges, confirm you know what incoming markings are respectable.
In that circumstance, the routers are managing DLSw to bridge SNA potential customers through an IP network. So the routers their selves essentially design the IP packets. This results in an additional challenge given that there is no incoming interface. In order that recipe takes advantage of nearby policy-based routing. The fact which the router results in the packets also gives it a very important advantage due to the fact it does not have to take into account any DLSw packets which may just come about to pass through.
The benefits belonging to the newer class-map method aren't clear in such a instance, but on the list of primary tremendous rewards seems if you want to utilize the more current DSCP tagging scheme. Since the mature policy-based routing method will not immediately support DSCP, you could have to fake it by environment both equally the IP Precedence and also TOS independently as follows.
Router(config)#route-map serialftp-rtmap permit 10
Router(config-route-map)#match ip address 115
Router(config-route-map)#set ip precedence immediate
Router(config-route-map)#set ip tos max-throughput
In this case, the packet will wind up with an IP Precedence value of immediate, or 2 (010 in binary), and TOS of max-throughput, or 4 (0100 in binary).
Doing the same thing with the class-map method is much more direct:
Router(config)#policy-map serialftppolicy
Router(config-pmap)#class serialftpclass
Router(config-pmap-c)#set ip dscp af21
Class-maps may even be valuable later on in this particular chapter after we talk about class-based weighted fair queuing and class-based page views shaping.
It is vital to notice that throughout this complete example, we've got only put a unique value into the packet's TOS or DSCP subject. This, by by itself, isn't going to have an impact on how the packet is forwarded by using the network. To do that, it's essential to be certain that as each router inside network forwards these marked packets, the interface queues will react appropriately to this information and facts.
Lastly, we should observe that even when this recipe shows two beneficial ideas of marking packets, utilising Committed Entry Fee (Car or truck) features. Autobus tends for being a great deal more productive on bigger speed interfaces.