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Quality of Service for Packetized Voice 615
These features can be categorized as follows:
·
Best effort--Best effort is essentially no QoS. It provides only basic connectivity on a
best-effort basis, with no guarantees.
·
Differentiated service--Some traffic can be treated better than other traffic.
Differentiated service supports intelligent queuing schemes that can prioritize and classify
traffic types based on network and application requirements. IP precedence is often used
to implement this level of service.
·
Guaranteed network--This feature guarantees the reservation of network resources.
This QoS feature is recommended for voice. The goal of the guaranteed network is to
provide a virtual certainty that certain types of traffic will pass if the network is functional.
Figure 16-8 shows Cisco end-to-end QoS services.
Figure 16-8
Cisco End-to-End QoS Services
The following components are necessary to deliver QoS across a multiservice network:
·
QoS within a single network element, which includes queuing, scheduling, and traffic-
shaping features
·
QoS signaling techniques for coordinating QoS from end to end between network
elements
·
QoS policing and management functions to control and administer end-to-end traffic
across a network
IP
Wiring closet
Backbone
WAN edge
Router
WAN
QoS ingress
Admission control
classification
Catalyst 4000
Catalyst 5500
Catalyst 2900 XL
QoS core
Prioritization
Catalyst 6500
Catalyst 8500
QoS WAN edge
Prioritization
traffic shaping
fragmentation
Cisco routers
25/26/36/7X
Catalyst 8500 WAN
Catalyst 5500 WAN
87200333.book Page 615 Wednesday, August 22, 2001 1:41 PM