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Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 4 QoS in an AVVID-Enabled Wide-Area Network
QoS Recommendations for WAN Aggregation Routers
Example 4-6
Slow-Speed MLP Links
interface Multilink40
description MLP Link to BRANCH#40
bandwidth 768
ip address 10.200.40.1 255.255.255.252
ip tcp header-compression iphc-format
This command is automatically added when cRTP is enabled.
service-policy output WAN-EDGE
This command applies the MQC policy to the interface
.
ppp multilink
ppp multilink fragment-delay 10
This command sets the maximum delay to 10 milliseconds.
ppp multilink interleave
This command enables LFI for MLP.
multilink-group 40
ip rtp header-compression iphc-format
This command enables cRTP.
!
!
interface Serial0/0
description MEMBER MLP GROUP 40
bandwidth 768
no ip address
encapsulation ppp
no fair-queue
ppp multilink
multilink-group 40
High-Speed Frame Relay Links
Frame Relay networks are the most popular WANs in use today because of the low costs associated with
them. Frame Relay is an NBMA technology that uses oversubscription to achieve costs savings. To
manage oversubscription, a traffic shaping mechanism must be used. FRTS is the shaping mechanism
for Frame Relay WAN media. FRTS requires the following parameters to be defined:
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Tip
For more information, see Configuring Frame Relay Traffic Shaping.
Committed Information Rate
Recommendation:
CIR set to PVC speed.
In most Frame Relay networks, a central site uses a T1 link, or something faster, to terminate WAN
connections from many remote offices. The central site sends data out at 1.536 Mbps, while a remote
site may have only a 56 kbps circuit. In addition, there is typically a many-to-one ratio of remote offices
to central hubs. It is possible for all the remote sites to send traffic at a rate that can overwhelm the T1
at the hub. Both of these scenarios can cause frame buffering in the provider network that introduces
loss, delay, and delay variation.
The only solution is to use traffic shaping at both the central and remote routers and to define a consistent
Committed Information Rate (CIR) at both ends of the Frame Relay DLCI. For high-speed (greater than
768 kbps) Frame Relay links, the CIR should be set to the Permanent Virtual Circuit (PVC) speed.