Reza’s Blog

Few days ago, I faced problem at remote desktop connection. I could could connect to the remote pc through RDC but it was getting hanged after logging in. Later we found that there was change at remote server at firewall. I had to change adjust the TCP MTU to 1300 to get the connection properly. To adjust the TCP MTU I had to do the following things.

To modify the PPPoE MTU size, create the following registry key:

Then add the following registry entries.

To do this:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Ndiswan\Parameters
3. On the Edit menu, point to New, and then click Key.
4. Type Protocols, and then press ENTER.
5. On the Edit menu, point to New, and then click Key.
6. Type 0, and then press ENTER.
7. On the Edit menu, point to New, and then click DWORD Value.
8. Type ProtocolType, and then press ENTER.
9. On the Edit menu, click Modify.
10. Type 800, and then click OK.
11. On the Edit menu, point to New, and then click DWORD Value.
12. Type PPPProtocolType, and then press ENTER.
13. On the Edit menu, click Modify.
14. Type 21, and then click OK.
15. On the Edit menu, point to New, and then click DWORD Value.
16. Type ProtocolMTU, and then press ENTER.
17. On the Edit menu, click Modify.
18. Type the appropriate MTU size (decimal value), and then click OK.
    

    Tuning TCP MTU image 1

19. 19.   Browse to the TCP/IP registry keys under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parametersby expanding successive folders on the left panel and scrolling down as needed.
20. Create a MTU value according to this.
    

    MTU

    Key: Tcpip\Parameters\Interfaces\interfaceGUID

    Value Type: REG_DWORD—number

    ValidRange: 88–the MTU of the underlying network

    Default: 0xFFFFFFFF

    

    Adjusting TCP MTU at client pc image 2

    Description: This parameter overrides the default Maximum Transmission Unit (MTU) for a network interface. The MTU is the maximum IP packet size, in bytes, that can be transmitted over the underlying network. For values larger than the default for the underlying network, the network default MTU is used. For values smaller than 88, the MTU of 88 is used. I insert the MTU value 1300.

And Finally I could log in at the remote server through RDC successfully.

Actually I do not know much about this. Any comment or suggestion regarding this topic will be highly appriciated. Waiting to hear from you.