Packets 1456 bytes in size (MTU setting) are being fragmented by routers causing slow WinPE downloads

Products

• Deployment Solution
• Ghost Solution Suite

Issue/Introduction

By default the MTU size is set to 1456.  In most environments, this allows the WinPE preboot to download at the optimum speed.  However, in some environments, the 1456 size is too large for routers to properly handle and the router fragments the files to transfer them them.  This fragmentation takes time and resources and hence the download of the files slows down significantly.

No error is displayed other than the speed of the transfer slows significantly.

Environment

All build of GSS and Deployment solution

Cause

Routers, switches etc in customer networks break up the 1456 byte files and reassemble them to transfer the files

Resolution

The solution is to change the MTU setting to a lower setting.  E.g 1000.  This value will vary as each network will have a different byte size where the routers begin to fragment the file.  

For example, if it is determined that the router starts to fragment the packets at the size of '1400', change the MTU size to '1300'.    Set the MTU size as close to the byte size where the fragmentation occurs for the greatest download speed.