Slow performance accessing web sites through Edge SWG without any changes to configuration

Products

• SSP-S210 PLATFORM

Issue/Introduction

Users accessing internet services through an Edge SWG.

All worked fine until a few days ago when users started to complain about slow performance accessing web sites.

No configuration changes were made on the proxy at around the time the problem appeared.

Slowness applied to standard browsing as well as downloading of file.

Bypassing the proxy shows normal performance.

Environment

Edge SWG.

Cause

Connectivity issues with upstream ISP.

Resolution

Contacted ISP to address network issues.

Additional Information

HAR files from the impacted users showed slow rendering of data, but connection establishment appeared to be fine.

To get a bigger pool of data, we had users download files from Gradle so that we could get a bigger pool of data to look at when taking a PCAP on the Proxy of the upstream and downstream traffic. 

Although the download was slow, we let it run for about 30 seconds to capture enough data to analyse. Analysing the data showed conclusively that the throughput was being throttled. In the following Wireshark throughput graph the throughput starts off quickly, ramps up to a peak of maximum 7mbps and just sits there until the connection was closed. There are no TCP drops/retransmissions at the time, and the network is behaving well. 

Armed with this information, customer approached the ISP who confirmed and addressed the issue on their side.