Cisco Cisco Flex 7510 Wireless Controller White Paper
Copyright © 2011 Miercom Wireless LAN Controllers Page 3
able to operate autonomously in the absence
of both the controller and the Radius server.
As expected, there was no visibility between
the APs and the controller, as the
management and control planes were down.
The Motorola system requires a controller in
order for the access points to remain
functional. Once that link was broken, it was
impossible to perform a test using only the
Radius server to authenticate with
communication down in the entire branch. The
Aruba VBN successfully maintained FTP
downloads to existing clients when the ACS
was unavailable. However, new clients were
unable to associate with an AP as the Aruba
access points are unable to authenticate
without a controller. In addition, existing clients
whose authentication timers happened to
expire were unable to re-authenticate as long
as the controller was unavailable.
of both the controller and the Radius server.
As expected, there was no visibility between
the APs and the controller, as the
management and control planes were down.
The Motorola system requires a controller in
order for the access points to remain
functional. Once that link was broken, it was
impossible to perform a test using only the
Radius server to authenticate with
communication down in the entire branch. The
Aruba VBN successfully maintained FTP
downloads to existing clients when the ACS
was unavailable. However, new clients were
unable to associate with an AP as the Aruba
access points are unable to authenticate
without a controller. In addition, existing clients
whose authentication timers happened to
expire were unable to re-authenticate as long
as the controller was unavailable.
Voice Fast Roam and Wireless
Resiliency
Resiliency
A key factor in wireless resiliency is the ability
of wireless clients to roam within the branch
during a WAN link failure. A client was
associated with the first branch access point,
AP-1. A voice call was initiated from the
wireless phone to a wired handset. The WAN
link was then brought down. Next, we forced a
roam by walking from the Branch AP-1 to
Branch AP-2. The voice call was monitored for
any drops.
of wireless clients to roam within the branch
during a WAN link failure. A client was
associated with the first branch access point,
AP-1. A voice call was initiated from the
wireless phone to a wired handset. The WAN
link was then brought down. Next, we forced a
roam by walking from the Branch AP-1 to
Branch AP-2. The voice call was monitored for
any drops.
Cisco FlexConnect uses both 802.1x and
distributed keys which are cached at the
access point. With distributed keys in the event
that the controller is unavailable, the keys are
still valid and wireless clients can still
authenticate. Fast Roam does not require the
clients to re-authenticate. A wireless voice
client successfully roamed between the branch
access points without any interruption to the
call. There is essentially no resiliency of
branch communications with the competing
solutions. The Motorola WiNG v5.0 requires
the controller to be available for the access
points to function. Once the WAN link is
brought down, wireless clients cannot roam
within the branch. Aruba VBN 2.0 maintained
the voice call as long as the client remained
associated with the initial access point. If the
client roams to another access point, the call is
lost and the client is unable to associate with
distributed keys which are cached at the
access point. With distributed keys in the event
that the controller is unavailable, the keys are
still valid and wireless clients can still
authenticate. Fast Roam does not require the
clients to re-authenticate. A wireless voice
client successfully roamed between the branch
access points without any interruption to the
call. There is essentially no resiliency of
branch communications with the competing
solutions. The Motorola WiNG v5.0 requires
the controller to be available for the access
points to function. Once the WAN link is
brought down, wireless clients cannot roam
within the branch. Aruba VBN 2.0 maintained
the voice call as long as the client remained
associated with the initial access point. If the
client roams to another access point, the call is
lost and the client is unable to associate with
the new access point. The client is also unable
to re-associate with the original access point, so
communication within the branch is effectively
lost. Aruba requires re-authentication of the client
with the access point when roaming occurs, and
is unable to authenticate clients locally to the
access point without a controller available.
to re-associate with the original access point, so
communication within the branch is effectively
lost. Aruba requires re-authentication of the client
with the access point when roaming occurs, and
is unable to authenticate clients locally to the
access point without a controller available.
Voice CAC
We verified how each solution supported call
admission control, and the options available for
load-based and static CAC. Call Admission
Control at the branch is crucial to preserving the
call quality of existing calls with limited WAN
bandwidth or latency issues exist by limiting the
addition of new client voice calls.
admission control, and the options available for
load-based and static CAC. Call Admission
Control at the branch is crucial to preserving the
call quality of existing calls with limited WAN
bandwidth or latency issues exist by limiting the
addition of new client voice calls.
On the Cisco Flex 7500 controller, CAC was set
to a static value of 5% bandwidth. A voice call
was placed between a pair of wireless handsets.
When we attempted to initiate another voice call,
the client received a “Network Busy” message,
indicating that CAC was limiting the number of
clients on the network. We observed that out of a
bandwidth available of 6 250 kbps, 1,072 kbps
were being used. Next, we changed the CAC to
20% of bandwidth. This time, the additional
wireless client was able to make a call
successfully. The bandwidth being used was
reported as 3,184 kbps out of 6,250 kbps
available. CAC functionality is only supported
when the access points are connected to the
wireless controller. See
to a static value of 5% bandwidth. A voice call
was placed between a pair of wireless handsets.
When we attempted to initiate another voice call,
the client received a “Network Busy” message,
indicating that CAC was limiting the number of
clients on the network. We observed that out of a
bandwidth available of 6 250 kbps, 1,072 kbps
were being used. Next, we changed the CAC to
20% of bandwidth. This time, the additional
wireless client was able to make a call
successfully. The bandwidth being used was
reported as 3,184 kbps out of 6,250 kbps
available. CAC functionality is only supported
when the access points are connected to the
wireless controller. See
Figure 1
on page 1.
Motorola WiNG v5.0 also supports CAC, and can
limit based on amount of airtime and by number
of wireless clients. The settings are somewhat
confusing, for example the setting for Maximum
Airtime specifies a range of 0-150, but it is
unclear what the unit of measurement is. We
began with Maximum Airtime set to 5. A call was
successfully established between a wireless
phone to a wired phone. Next we associated a
second wireless phone with the AP and
attempted a call. This phone received a “Network
Busy” message, and no call could be made. We
then increased the Maximum Airtime to 20. This
settings change requires a radio reboot at the
access point to take effect. A call was then
established between the wireless client and a
wired phone. A second call was successfully
established between two more wireless clients.
This demonstrated that Motorola was effectively
limiting the number of clients based on amount of
limit based on amount of airtime and by number
of wireless clients. The settings are somewhat
confusing, for example the setting for Maximum
Airtime specifies a range of 0-150, but it is
unclear what the unit of measurement is. We
began with Maximum Airtime set to 5. A call was
successfully established between a wireless
phone to a wired phone. Next we associated a
second wireless phone with the AP and
attempted a call. This phone received a “Network
Busy” message, and no call could be made. We
then increased the Maximum Airtime to 20. This
settings change requires a radio reboot at the
access point to take effect. A call was then
established between the wireless client and a
wired phone. A second call was successfully
established between two more wireless clients.
This demonstrated that Motorola was effectively
limiting the number of clients based on amount of