Hot answers tagged

6

I have no practical experience in running CoS/DSCP in ISP networks, but a logical explanation would be that it doesn't make sense to just change fields in a header. Even if I as an intermediate ISP wouldn't be interested in these fields, the receiver or some other intermediate party could be. Resetting DSCP fields just because I'm not using them sounds like ...


6

Fair Queuing share the link in equal capacity among the different flow. Weighted Fair Queuing give allows schedulers to specify, for each flow, which fraction of the capacity will be given. This prevent a single flow from using all the link bandwidth, effectively denying other flows. But those mechanisms don't provide a priority system (I.E. which flow ...


5

14 egress queues seems a bit excessive - most devices I dealt with use 3, 4 (most common), or up to 8 queues. I'd just use four which simplifies things: critical traffic (very low-bandwidth, critical control traffic like OSPF, RIP) real-time applications (low bandwidth traffic like VoIP) normal applications (everything not in 1,2 or 4) low-priority (backup, ...


5

There's an excellent post by a Cisco employee on Cisco support forums covering this: The QoS value is not part of BPDU frame, but an internal value assigned on the RBUS (assuming 6500 platform) for BPDU frames. BPDUs are marked with BPDU bit in the code and treated differently -- it always gets to the high priority queue (ingress & egress) on ...


3

Something has to set the DSCP values. In a traditional network, that comes from either the end user / application, or intervening network hardware. Unless you have significant control of the device/application -- eg. VoIP phone -- the former can be a very dangerous road. The later is a very complicated, and tedious process. It is this area that machine ...


3

No protocols will break due to a changed DSCP - how they are treated by upstream devices may change however (traffic may be more likely to be dropped, or aggressively shaped), so this will need to be taken into consideration if you don't have control/visibility end-to-end. In your VPN example, traffic encapsulated in a tunnel header will have it's DSCP ...


3

Does WRED only make sense if there is more than 1 dscp marking in a queue ? Not really. The point of Weighted RED is to assign different weights to different traffic classes. Doesn't make much sense if you only have one class. What is the difference between 1 big queue, with higher drop rate for lower priority traffic vs. 2 different queues, with 1 ...


2

i find a success method to policy a traffic of Specify ip's or else on CISCO ASR 903 IOS XE 3.18S for example i have ip's 74.0.0.0/8 for some serivce (Like google) 1-subnet a full range from 1.0.0.0/8 to 255.0.0.0/8 and Cust your ip('s) you want enter link description here 2-now you have two range 1.0.0.0/8 2.0.0.0/7 4.0.0.0/6 8.0.0.0/5 16.0....


2

I understand packets are given a Class, 1-4. The higher the Class number, the higher priority that packet gets. I must assume that higher priority means lower chance of being dropped. Is this assumption correct: Higher Class = Higher Priority = Lower chance of being dropped? During congestion, does higher Class traffic have precedence over ...


1

There is no way to compare two DSCP values without the specific network QoS configurations. By default, a network device ignores DSCP values, and you must configure QoS on the device. Also remember that QoS is meaningless unless there is congestion at a point where a device has been configured to use QoS. There is an RFC that recommends some things, but ...


1

More than likely, packets from the phone have the correct DSCP values: EF for the data, and something like AF31 for the control traffic (you really do not want the control traffic marked as EF). Your switch will change the traffic to BE unless you use the mls qos trust dscp interface command. Yes, you can set DSCP values on the packets with that switch. It ...


1

You want to configure up policy based routing. In the gui this is found: Router > Static > Policy Routes. You can do this by using TOS rather than DSCP. WAN1: Incoming interface: LAN Source Address: Opsview Machine IP Destination Address: Remote Site WAN IP TOS: Assigned Value Outgoing Interface: WAN1 Gateway Address: Next-hop for that WAN. Do the same for ...


1

An application may set the priorities, a switch may set the priorities, a router may set the priorities, or really any device through which your packets travel may set the priorities. Switches may even set layer-2 priorities. When designing your QoS policies, you need to determine the trust points. These would be the demarcation places where packets on one ...


Only top voted, non community-wiki answers of a minimum length are eligible