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MTU Ping

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MTU (Maximum Transmission Unit) 

MTU is the size (in bytes) of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface (NIC, serial port, etc.). Standards (Ethernet, for example) can fix the size of an MTU; or systems (such as point-to-point serial links) may decide MTU at connect time.
A larger MTU brings greater efficiency because each packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means a slight improvement in bulk protocol throughput. A larger MTU also means processing of fewer packets for the same amount of data. In some systems, per-packet-processing can be a critical performance limitation.
To test your MTU connection, we can use ping test with command : ping xxx -f -l yyy while yyy is packet size. 

example :
C:\Users\admin>ping yahoo.com -f -l 1472 
Pinging yahoo.com [209.191.122.70] with 1472 bytes of
Reply from 209.191.122.70: bytes=1472 time=248ms TTL=4
Reply from 209.191.122.70: bytes=1472 time=248ms TTL=4
Reply from 209.191.122.70: bytes=1472 time=245ms TTL=4
Reply from 209.191.122.70: bytes=1472 time=248ms TTL=4

Ping statistics for 209.191.122.70:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)
Approximate round trip times in milli-seconds:
    Minimum = 245ms, Maximum = 248ms, Average = 247ms

C:\Users\admin>ping yahoo.com -f -l 1473 
Pinging yahoo.com [209.191.122.70] with 1473 bytes of
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 209.191.122.70:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss)

In that example, the largest packet size not fragmented from ping test is 1472, add 28 to 1472 to get a total of 1500, which is your MTU setting right now.

You can change the MTU setting by modify the registry or using DrTCP.
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