This problem typically occurs during the publication of large Outlook Anywhere mail sends or SharePoint file uploads through a Forefront UAG 2010 server. However, this problem can affect any data transmissions between the client and the published server.
Depending on the network topologies and the pattern of data packets that are sent by the client, the Nagle algorithm may cause reduced data throughput. This is because the Nagle algorithm on the Forefront UAG server and the delayed acknowledgement timer (also known as the delayed ACK timer) on the published server may cause many 200ms delays. These delays occur for the following reasons:
- The Nagle algorithm lets only one small (non-full) TCP packet be outstanding on a network connection.
- The delayed ACK timer lets Windows acknowledge only every other TCP packet or acknowledge a single packet only after 200ms.
If a small TCP packet is outstanding on a TCP connection, the Nagle algorithm prevents Forefront UAG from sending additional data packets. This can cause a delay because the published web server waits 200ms to acknowledge the outstanding packet. The cumulative effect of many 200ms delays may cause decreased throughput.
For more information about the TcpAckFrequency value, go to the following Microsoft Developer Network (MSDN) website:
Article ID: 2811128 - Last Review: Feb 20, 2013 - Revision: 1