CAPWAP latency limitations

[MICHAEL BURNS]

I have a new site I am bringing up in Japan, but I have my controllers based in a DC in Australia.  I am curious if there are any latency limitations to consider when installing the AP's.  I am using 3502i's.  I know with HREAP, there is a 300 ms limitaiton, but is there a latency limitation with CAPWAP?

[Scott Fella · Accepted solution]

That 300ms is for CAPWAP/LWAPP traffic.  There was a post not too ling ago, that someone had 500ms and no issues.  It might also depend on how many AP's you plan on putting at the remote end.

[Amjad Abdullah]

Mike:

From HREAP deployment and design guide you have to notice the following (about latency it is the third point  you should look at):

• An H REAP access point can be deployed with either a static IP address or a DHCP address. In the case of DHCP, a DHCP server must be available locally and must be able to provide the IP address for the access point at bootup.
• H REAP supports up to four fragmented packets or a minimum 500-byte maximum transmission unit (MTU) WAN link.
• Roundtrip latency must not exceed 300 milliseconds (ms) for data and 100 ms for voice and data between the access point and the controller, and CAPWAP control packets must be prioritized over all other traffic.
• The controller can send multicast packets in the form of unicast or multicast packets to the access point. In H REAP mode, the access point can receive multicast packets only in unicast form.
• In order to use CCKM fast roaming with H REAP access points, you need to configure H REAP groups.
• H REAP access points support multiple SSIDs.
• NAC out-of-band integration is supported only on WLANs configured for H REAP central switching. It is not supported for use on WLANs configured for H REAP local switching.

also, below that in the document it is mentioned that:

"In order to ensure that support for this stated latency limitation is in place, it is strongly recommended that between the access point and controller, priority be configured in the intermediary infrastructure to elevate CAPWAP (UDP port 5246) to the highest priority queue available. Without priority placed on CAPWAP control, spikes in other network traffic can very likely cause H REAP access points to frequently shift from connected to Standalone modes as WAN link congestion prevents access point/controller messages (and keep-alives) from being delivered. It is highly recommended to Network designers, who plan to deploy H REAP AP over WAN links, to test all their applications."

Reference: http://tiny.cc/hgn8bw

Hope this is useful.

Amjad