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4-17
Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
956467
Chapter 4 QoS in an AVVID-Enabled Wide-Area Network
QoS Recommendations for WAN Aggregation Routers
The following commands can be used to verify that a voice, video and data QoS policies have been
applied correctly to a Frame Relay link.
·
show policy
·
show frame-relay pvc
For more information, see the
"Verifying QoS" section on page 4-34
.
Distributed-Platform Slow-Speed Frame Relay Links
Slow-speed Frame Relay policies on a distributed platform require the following:
·
CEF must be enabled in distributed mode
·
dTS policy (with nested queueing policies)
·
Bc set to CIR/125
·
Be set to 0
·
Queue-limit can be increased to (CIR*10) / (MTU*8)
·
FRF.12 must be enabled
·
CIR values need to reflect fragmentation headers and CRCs
·
CIR must be a multiple of 8000
Note
cRTP can be enabled.
For more information on cRTP, see
"Provisioning Tools" section on page 1-22
and
"When to Enable
cRTP" section on page A-5
.
One constraint of class-based shaping (which includes dTS) is that the CIR must be a multiple of 8000.
Therefore, the calculated FRTS CIR values from
Table 4-2
must be rounded down to the nearest multiple
of 8000 for dTS.
Because the Cisco 7500 requires that an interval (Tc) be defined in 4 ms increments, the FRTS optimal
recommendation of Bc=CIR/100 (which sets the interval to equal 10 ms) cannot be used. The nearest
(rounded-down) 4 ms interval is 8 ms. To set an 8 ms interval, the Bc value must be defined as CIR/125.
Be is held at 0.
Table 4-3
shows the recommended fragmentation, CIR, Bc and queue-limit values for
distributed-platform, slow-speed Frame Relay links.
Table 4-3
Distributed-Platform Fragmentation and (dTS) Shaping Values
PVC Speed
Fragment Sizes CIR
Bc
dTS Queue-Limits
56 kbps
70 Bytes
48000 bps
384 bits per Tc
Default (126 packets)
64 kbps
80 Bytes
56000 bps
448 bits per Tc
Default (126 packets)
128 kbps
160 Bytes
120000 bps
960 bits per Tc
Default (126 packets)
256 kbps
320 Bytes
248000 bps
1984 bits per Tc
213 packets
512 kbps
640 Bytes
504000 bps
4032 bits per Tc
427 packets
768 kbps
960 Bytes
760000 bps
6080 bits per Tc
640 packets