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Branch Office setup - Access Point's Poor and Slow Performance

 

 

Introduction

Issue with branch office setup.

Core Issue

For some reason the performance of the clients is problematic. Webpages will frequently not load correctly, they experience some freezing, and with one application we use - it refuses to load completely.

If we bring these same computers to an AP connected to our central network, on the same SSID they work flawlessly.

Topology

asa5505.gif

Remote office setup using an ASA 5505 to establish an easy vpn connection to the central network. The connection at the branch office is a 20/5 cable modem, the central network has a 25/25 fiber connection.

Running WCS 7.0.230.0 and the WLCs are on 7.0.116.0. The ASA is running a pretty basic configuration with the easy vpn configuration entered.

Details

Wired clients work fine at this branch office, at least 95% of the time. A lightweight AP can come up and join the controllers at the central network without any problem. No changes with H-REAP so all traffic is tunneled back to the WLC.

Wireless clients can authenticate to the AP and getting 15-20ms ping response with latency close to the 600ms proposed limit with CAPWAP.

For some reason the performance of the clients is problematic. Webpages will frequently not load correctly, they experience some freezing and with one application we use - it refuses to load completely.

If we bring these same computers to an AP connected to our central network, on the same SSID, they work flawlessly.

Something about this particular location is causing a lot of issues.

Solution

On that remote AP adjust the TCP MSS, the default is 1363, keep trimming until it gets an better performance.

User changed the MSS to 1300 on that access point and things are greatly improved.

Configuring the TCP MSS

If the client's maximum segment size (MSS) in a Transmission Control Protocol (TCP) three-way handshake is greater than the maximum transmission unit can handle, the client might experience reduced throughput and the fragmentation of packets. To avoid this problem in controller software release 6.0, you can specify the MSS for all access points joined to the controller or for a specific access point.

When you enable this feature, the access point checks for TCP packets to and from wireless clients in its data path. If the MSS of these packets is greater than the value you configured or greater than the default value for the CAPWAP tunnel, the access point changes the MSS to the new configured value.

Using the controller CLI, follow these steps to configure the TCP MSS.

Step 1 To enable or disable the TCP MSS on a particular access point or on all access points, enter this command:

config ap tcp-adjust-mss {enable | disable} {Cisco_AP | all} size

where the size parameter is a value between 536 and 1363 bytes. The default value varies for different clients.

Step 2 To save your changes, enter this command:

save config

Step 3 To see the current TCP MSS setting for a particular access point or all access points, enter this command:

show ap tcp-mss-adjust {Cisco_AP | all}

Information similar to the following appears:AP Name

TCP State MSS Size------------------ --------

-------AP-1140

enabled 536

AP-1240 disabled -

AP-1130 disabled -

Reference

Configuring the TCP MSS

This document was generated from the following discussion: Branch Office setup

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