addition to the determination of how much bandwidth is needed for an 802.11b VoIP call,
you must also consider overall radio contention for a particular RF channel. The general rule
is that you should not deploy any more than 20 to 25 802.11b endpoints per AP. The more
endpoints you add to an AP, the more you reduce the amount of overall bandwidth and
potentially increase transmission delays. The maximum number of phones per AP depends on
the calling patterns of individual users (based on Erlang ratios). Cisco recommends that no
more than seven concurrent calls use G.711 or eight concurrent calls use G.729. Beyond that
number of calls, when excessive background data is present, the voice quality of all calls
becomes unacceptable. Packetization rates for these recommendations are based on 20−ms
sample rates with VAD disabled. This rate generates 50 packets per second (pps) in each
direction. A larger sample size (such as 40 ms) can result in a larger number of simultaneous
calls, but it also increases the end−to−end delay of the VoIP calls.
The number of 802.11b phones you can deploy per Layer−2 subnet or VLAN depends on
these factors:
Use no more than seven G.711 or eight G.729 active calls per AP.♦
The calling ratio is used to determine the number of active and non−active calls. This
ratio is often determined with Erlang calculators. Based on these factors and normal
business−class Erlang ratios (between 3:1 and 5:1), Cisco recommends that you
deploy no more than 450 to 600 Cisco 7920 phones per Layer−2 subnet or VLAN.
♦
Refer to the Network Sizing section of Wireless Network Infrastructure, as well as Is Your
WLAN Ready for Voice? for more detailed information.
Q. How can I stop an AP 1200 from processing authentication requests
after a set number of tries?
A. You can use the maximum retries option on the AAA server to limit the number of times
the clients can try to access a network. The value of the maximum retries can be configured
manually on the AAA server, or you can use the default number of retries, which depends
upon the AAA server that is used.
Q. Where can I find information on the differences in the various
platforms of APs and LAPs?
A. Refer to the Cisco Wireless Hardware Frequently Asked Questions. This document
contains useful information that compares the different AP and LAP models.
Q. Is Point−to−Point−Protocol over Ethernet (PPPoE) supported in Cisco
Aironet Access Points?
A. No, PPPoE is not supported in Cisco Aironet Access Points.
Q. Is VLAN Trunking Protocol (VTP) supported in Cisco Aironet Access
Points?
A. No, VTP is not supported in Cisco Aironet Access Points.
Q. Does the Cisco Aironet AP support 802.11f standard Inter−Access
Point Protocol (IAPP)?
(100 stránky)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Komentáře k této Příručce