Cisco WS-X4604-GWY - VoIP Gateway Spezifikationen PDF herunterladen (Seite 180)

Chapter 8 Quality of Service

WAN QoS Model

8-6

Cisco IP Telephony Network Design Guide

78-11103-03

Figure 8-3 shows this prioritization scheme as follows:

• Voice is placed into a queue with priority queuing capabilities and is allocated

a bandwidth of 48 kbps. The entrance criterion to this queue should be the

differentiated services code point (DSCP) value of EF, or IP precedence value

of 5. Traffic in excess of 48 kbps would be dropped if the interface becomes

congested. Therefore, an admission control mechanism must be used to

ensure that this value is not exceeded.

• Video conferencing traffic is placed into a queue with priority queuing

capabilities and is allocated a bandwidth of 384 kbps. The entrance criterion

to this queue should be a DSCP value of AF41, or IP precedence value of 4.

Traffic in excess of 384 kbps would be dropped if the interface becomes

congested. It is therefore imperative, as in the case of voice, to use an

admission control mechanism to ensure that this value is not exceeded.

Note One-way video traffic, such as IP/TV, should use a

class-based weighted fair queuing scheme because the

delay tolerances are much higher.

• As the WAN links become congested, it is possible to completely starve the

voice control signaling protocols, thereby eliminating the ability of the IP

phones to complete calls across the IP WAN. Voice control protocol traffic,

such as H.323 and the Skinny Client Control Protocol, requires its own

class-based weighted fair queue with a minimum configurable bandwidth

equal to a DSCP value of AF31, which correlates to an IP precedence value

of 3.

• SNA traffic is placed into a queue that has a specified bandwidth of 56 kbps.

Queueing operation within this class is first-in-first-out (FIFO) with a

minimum allocated bandwidth of 56 kbps. Traffic in this class that exceeds

56 kbps is placed in the default queue. The entrance criterion to this queue

could be TCP port numbers, Layer 3 address, IP precedence, or a DSCP.

• All remaining traffic can be placed in a default queue. If a bandwidth is

specified, the queuing operation would be FIFO. Alternatively, by specifying

the keyword fair, the operation would be weighted fair queuing (WFQ).

1 2 ... 175 176 177 178 179 180 181 182 183 184 185 ... 261 262

Keine Kommentare

Cisco WS-X4604-GWY - VoIP Gateway Spezifikationen Seite 180