Method for effective pmtu discovery in vpn environment

Abstract

Methods are directed towards initializing a path maximum transmission unit value for two gateways in communication via a network tunnel (e.g., VPN environment). The initialized path maximum transmission unit value is used in establishing the network tunnel of the two gateways. Methods are also directed towards synchronizing path maximum transmission unit values for the two gateways after the network tunnel has been established. These methods minimize the occurrence of dropped data packets arising from mismatched path maximum transmission unit value between the gateways.

1 . A method for synchronizing path maximum transmission unit values, the method comprising:
 detecting a mismatch in maximum transmission unit values at a first gateway and at a second gateway, wherein a network tunnel is used to transmit data between the first gateway and the second gateway;   advertising a current maximum transmission unit value of the first gateway to the second gateway in response to the detected mismatch, wherein the second gateway advertises a current maximum transmission unit value of the second gateway to the first gateway;   acknowledging receipt of the current maximum transmission unit value of the second gateway;   establishing a maximum transmission unit value for synchronization between first gateway and the second gateway based on the current maximum transmission unit value at the first gateway and the current maximum transmission unit value advertised by the second gateway; and   transmitting a subsequent data packet using the established maximum transmission unit value as synchronized between the first gateway and the second gateway.   
     
     
         2 . The method of  claim 1 , further comprising detecting that the current maximum transmission unit value at the first gateway reflects a change from a previous maximum transmission unit at the first gateway, wherein synchronizing the maximum transmission unit value is triggered when the detected change exceeds a pre-determined threshold. 
     
     
         3 . The method of  claim 1 , wherein advertising the current maximum transmission unit comprises providing a notification message from the first gateway to the second gateway via the network tunnel. 
     
     
         4 . The method of  claim 3 , wherein the notification message is provided subsequent to transmission of a current data packet between the first gateway and the second gateway but before transmission of a next data packet via the network tunnel. 
     
     
         5 . The method of  claim 3 , wherein the notification message includes information regarding a change reflected in the current maximum transmission unit value at the first gateway. 
     
     
         6 . The method of  claim 1 , further comprising receiving a command that causes a change in the current maximum transmission unit at the first gateway. 
     
     
         7 . The method of  claim 1 , further comprising receiving a message indicating that one or more packets were dropped. 
     
     
         8 . The method of  claim 7 , wherein detecting the mismatch is based on the indication regarding the dropped packets. 
     
     
         9 . A non-transitory computer-readable storage medium having embodied thereon a program executable by a processor for implementing a method for synchronizing path maximum transmission unit values, the method comprising:
 detecting a mismatch in maximum transmission unit values at a first gateway—and at a second gateway, wherein a network tunnel is used to transmit data between the first gateway and the second gateway;   advertising a current maximum transmission unit value of the first gateway to the second gateway in response to the detected mismatch, wherein the second gateway advertises a current maximum transmission unit value of the second gateway to the first gateway;   acknowledging receipt of the current maximum transmission unit value of the second gateway;   establishing a maximum transmission unit value for synchronization between first gateway and the second gateway based on the current maximum transmission unit value at the first gateway and the current maximum transmission unit value advertised by the second gateway; and   transmitting a subsequent data packet using the established maximum transmission unit value as synchronized between the first gateway and the second gateway.   
     
     
         10 . The non-transitory computer-readable storage medium of  claim 9 , further comprising instructions executable to detect that the current maximum transmission unit value at the first gateway reflects a change from a previous maximum transmission unit at the first gateway, wherein synchronizing the maximum transmission unit value is triggered when the detected change exceeds a pre-determined threshold. 
     
     
         11 . The non-transitory computer-readable storage medium of  claim 9 , wherein advertising the current maximum transmission unit comprises providing a notification message from the first gateway to the second gateway via the network tunnel. 
     
     
         12 . The non-transitory computer-readable storage medium of  claim 11 , wherein the notification message is provided subsequent to transmission of a current data packet between the first gateway and the second gateway but before transmission of a next data packet via the network tunnel. 
     
     
         13 . The non-transitory computer-readable storage medium of  claim 11 , wherein the notification message includes information regarding a change reflected in the current maximum transmission unit value at the first gateway. 
     
     
         14 . The non-transitory computer-readable storage medium of  claim 9 , further comprising instructions executable to receive a command that causes a change in the current maximum transmission unit at the first gateway. 
     
     
         15 . The non-transitory computer-readable storage medium of  claim 9 , further comprising instructions executable to receive a message indicating that one or more packets were dropped. 
     
     
         16 . The non-transitory computer-readable storage medium of  claim 15 , wherein detecting the mismatch is based on the indication regarding the dropped packets. 
     
     
         17 . A apparatus for synchronizing path maximum transmission unit values, the apparatus comprising:
 a memory; and   a processor that executes instructions stored in memory to:
 detect a mismatch in maximum transmission unit values at a first gateway—and at a second gateway, wherein a network tunnel is used to transmit data between the first gateway and the second gateway, 
 advertise a current maximum transmission unit value of the first gateway to the second gateway in response to the detected mismatch, wherein the second gateway advertises a current maximum transmission unit value of the second gateway to the first gateway, 
 acknowledge receipt of the current maximum transmission unit value of the second gateway, and 
 establish a maximum transmission unit value for synchronization between first gateway and the second gateway based on the current maximum transmission unit value at the first gateway and the current maximum transmission unit value advertised by the second gateway, wherein a subsequent data packet is transmitted using the established maximum transmission unit value as synchronized between the first gateway and the second gateway. 
   
     
     
         18 . The apparatus of  claim 17 , wherein the processor executes further instructions to detect that the current maximum transmission unit value at the first gateway reflects a change from a previous maximum transmission unit at the first gateway, wherein synchronizing the maximum transmission unit value is triggered when the detected change exceeds a pre-determined threshold. 
     
     
         19 . The apparatus of  claim 17 , wherein advertising the current maximum transmission unit comprises providing a notification message from the first gateway to the second gateway via the network tunnel. 
     
     
         20 . The apparatus of  claim 19 , wherein the notification message is provided subsequent to transmission of a current data packet between the first gateway and the second gateway but before transmission of a next data packet via the network tunnel.