QoS in Cisco 1841 and Juniper WX-20

By bhavitparikh2001 ·
Quality of Service (QoS) is taking place on the Juniper WX-20 appliance and the Cisco 1841 router. QoS is based on Juniper???s strict prioritisation and Cisco???s Hierarchical queuing methods. Both the Cisco and Juniper devices use layer 3 ToS (Type of Service) based on both DSCP (differentiated services code point) and TCP/UDP port ranges of certain applications.

The Juniper WX-20 creates a reduction tunnel in which it selected applications are reduced in size thus saving bandwidth over the WAN link. It also has manipulates the applications to provide additional performance. In the case of QSC4, the traffic that traverses the WX-20 is printer, CITRIX and VoIP. The NEC VoIP is already compresses using CODEC G729, so there is no benefit reducing this further. This leaves the CITRIX and Printing. These applications are piped into the WX-20 and reduced. The WX-20 tunnel uses ports UDP/TCP 3577/3578. The Cisco 1841 router sees this tunnel as the mentioned ports and so is able to apply QoS on the router.

The QoS on the Cisco 1841 router was based on bandwidth allocation of all applications traversing the WX-20 and router. This allows dedicated bandwidth for each application under congestion. The order of the QoS prioritisation on the Cisco 1841 router is as follows:

1. VoIP (call setup and RTP stream), BW allocation 64Kb
2. SCADA, BW allocation 35Kb
3. WX-20 tunnel (all CITRIX and Printing traffic), BW allocation 100Kb
4. Defaut, all other traffic

The above traffic is then shaped to match the 256Kb WAN pipe (Satellite). This is known as Hierarchical Shaping. The QoS is applied to the router only under traffic congestion.

The NEC IP PABX and NEC IP Phones mark the voice and call setup packets with DSCP values. These are shown below.

Application DSCP Value HEX Value
Call setup 26 af31
RTP voice stream 46 ef

Anyway, Can I utilitise full 256kb WAN Pipe?? alternate solution willl also be considered.

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Can't help with the Juniper but

by NetMan1958 In reply to QoS in Cisco 1841 and Jun ...

as for the Cisco,
The default maximum bandwidth is 75 percent of the total available bandwidth on the interface. The remaining 25 percent of bandwidth is used for overhead, including Layer 2 overhead, routing traffic, and best-effort traffic.

If you find that it is necessary to change the maximum reserved bandwidth, you can change the maximum bandwidth by using the max-reserved-bandwidth command.

For more info see this article:

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