MTU size
I wanted to know what the MTU size is and why it's important? I presently have a client whose firewall (Sonicwall) is boucing. When I called Sonicwall they were able to verify that their equipment is working properly; however, they suggested we contact the ISP so that we could verify the negotiating on their side as well as the MTU size. They suggested that it should match up with the Sonicwall and vice versa.
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
MTU stands for Maximum Transmission Unit and determines the largest size a packet will be given in your network. If a large packet is sent over the WAN and encounters a network with a smaller MTU, the packet will have to be broken down into smaller packets in order to be forwarded. That overhead will slow down your overall transit speed. Most of the time, if your MTU is equal to or slightly lower than your upstream connection (your ISP), you will be fine. Occasionally, someone messes with the MTU, thinking that larger is better, and actually ends up slowing everything down. digitap's article is a good one. Additionally, you can do ping and traceroute tests, specifying the packet size, to see what is actually happening during your transmission.
Ideally, you should match the upstream MTU, or be slightly smaller in some cases (such as DSL which has overhead).