Quality of Service guidelines
314 Avaya Application Solutions IP Telephony Deployment Guide
serialization delay for a variety of packet sizes and line speeds. The formula for determining
serialization delay is:
Because of all these configuration variables, properly implementing QoS on a router is no trivial
task. However, QoS is needed most on the router where, because most WAN circuits terminate
on routers.
QoS guidelines
There is no all-inclusive rule regarding the implementation of QoS because all networks and
their traffic characteristics are unique. It is good practice to baseline the IP Telephony response
on a network without QoS, and then apply QoS as necessary. Avaya Network Consulting
Services can help with baselining services. Conversely, it is bad practice to enable multiple QoS
features simultaneously, not knowing what effects, if any, each feature is introducing.
Generally, for newer network equipment, best practices involve enabling Layer 3 (DiffServ) QoS
on WAN links traversed by voice. Tag voice and data with DiffServ Code Point 46 (Expedited
Forwarding), and set up a strict priority queue for voice. If voice quality is still not acceptable, or
if QoS is desired for contingencies such as unexpected traffic storms, QoS can then be
implemented on the LAN segments as necessary.
Table 72: Serialization delay matrix
WAN
line
speed
Packet size
64
bytes
128
bytes
256
bytes
512
bytes
1024
bytes
1500
bytes
56 kbps
9 ms
18 ms
36 ms
72 ms
144 ms
214 ms
64 kbps
8 ms
16 ms
32 ms
64 ms
128 ms
187 ms
128 kbps
4 ms
8 ms
16 ms
32 ms
64 ms
93 ms
256 kbps
2 ms
4 ms
8 ms
16 ms
32 ms
46 ms
512 kbps
1 ms
2 ms
4 ms
8 ms
16 ms
23 ms
768 kbps
640 µs
1.28 ms
2.56 ms
5.12 ms
10.24 ms
15 ms
Serialization delay
Packet size (bits)
Line speed
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Summary of Contents for Application Solutions
Page 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Page 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Page 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Page 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Page 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Page 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...