Enterprise QoS Solution Reference Network Design Guide

Chapter 3 WAN Aggregator QoS Design
Version 3.3
rate 41000 bps
Class-map: Call Signaling (match-any)
251 packets, 142056 bytes
30 second offered rate 3000 bps, drop rate 0 bps
Match: ip dscp cs3
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af31
251 packets, 142056 bytes
30 second rate 3000 bps
Queueing
Output Queue: Conversation 265
Bandwidth 5 (%)
Bandwidth 38 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 255/144280
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
51674 packets, 28787480 bytes
30 second offered rate 669000 bps, drop rate 16000 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 256
(total queued/total drops/no-buffer drops) 36/458/0
WAG-7206-Left#
WAN Edge Link-Specific QoS Design
In Example 3-12, the Voice class map and Call-Signaling class map are receiving matches on their
classification criteria (DSCP EF and DSCP CS3/AF31, respectively). However, because Cisco IP
Telephony products currently mark Call-Signaling traffic to DSCP AF31, Call-Signaling traffic is
matching only on DSCP AF31 in this example.
The last line of every class map output is important because this line indicates whether any drops are
occurring on this traffic class. In this example, there are no drops in the Voice or Call-Signaling classes,
which is the desired behavior. A few drops are occurring in class-default, but this is expected when the
interface is congested (which is the trigger to engage queuing).
Also of note, and specific to this particular configuration, are the cRTP statistics included under the
Voice class map. These cRTP statistics are displayed because class-based cRTP was enabled in this
example (instead of enabling cRTP on the interface). Remember, cRTP must be enabled on both ends of
the links for compression to occur; otherwise, these counters will never increment.
Medium-Speed (£ T1/E1) Leased Lines
Recommendation: MLP LFI is not required; cRTP is optional.
Medium-speed leased lines (as shown in Figure 3-8) can use HDLC, PPP, or MLP encapsulation. An
advantage of using MLP encapsulation is that future growth (to multiple T1/E1 links) will be easier to
manage. Also, MLP includes all the security options of PPP (such as CHAP).
Figure 3-8 Medium-Speed Leased Lines
WAN Aggregator
MLP T1/E1 Link
Branch Router
Enterprise QoS Solution Reference Network Design Guide
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