Nortel Networks NN43001-563 User Manual
Page 145
Measure intranet QoS
145
68 bytes from (10.3.2.7):
icmp_seq=0 ttl=225
time=112ms
68 bytes from (10.3.2.7):
icmp_seq=0 ttl=225
time=97ms
^?
--- Richardson3 PING Statistics ---
8 packets transmitted, 8 packets received, 0% packet loss
round-trip (ms) min/avg/max = 94/96/112
The time field displays the round trip time (rtt).
So that the delay sample results match what the IP Trunk 3.01 (and later)
node can experience, the PING host must be on a working LAN segment
attached to the router supporting the IP Trunk 3.01 (and later) node. The
selection of destination host is just as important, following these same
guidelines for the source host.
Set the size of the PING probe packets to 60 bytes, to approximate the
size of probe packets sent by IP Trunk 3.01 (and later) used in determining
when new calls need to fall back.
Some implementations of PING support the -v option for setting the TOS.
IP Trunk 3.01 (and later) allows the 8-bit DiffServ/TOS field to be set to
any value specified by the IP network administrator for QoS management
purposes. For example, if a decimal value of 36 is entered in TM 3.1,
this is interpreted as TOS Precedence = Priority and Reliability = High. If
PING measurements are made on an intranet that uses prioritization based
on the TOS field, the rtt measured will be higher than the actual delay of
voice packets when the -v option is not used. See
Make note of the variation of rtt from the PING output. It is from repeated
sampling of rtt that a delay characteristic of the intranet can be obtained.
In order to obtain a delay distribution, the PING tool can be embedded
in a script which controls the frequency of the PING probes, timestamps
them, and stores the samples in a raw data file. The file can then be to be
analyzed later using spreadsheet and other statistics packages. Determine
if the intranet’s network management software has any delay measurement
modules which can obtain a delay distribution for specific site pairs.
Delay characteristics vary depending on the site pair and the time-of-day.
The assessment of the intranet should include taking delay measurements
for each IP Trunk 3.01 (and later) site pair. If there are significant fluctuations
of traffic in the intranet, it is best to include PING samples during the
intranet’s peak hour. For a more complete assessment of the intranet’s delay
characteristics, obtain PING measurements over a period of at least a week.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563
01.01
Standard
Release 5.0
30 May 2007
Copyright © 2007, Nortel Networks
.