alpha2zee

Thanks for this exchange - the info on MTU helped me too to solve the router problem. I also did some search to know more about MTU. This is a brief with the new-found information; please pardon and correct any mistake: TCP/ IP, for internet browsing, etc., is a four- layer protocol. The Ethernet standard of local area networking is at the lowest or primary level. Ethernet protocol is for transmission of blocks of data called frames. Frames have to be 64-1492 bytes in size. 1492 bytes is the maximum size of a frame and this defines the maximum transmission unit or MTU for Ethernet. Larger blocks of data must be fragmented to fit within the MTU and then reassembled on arrival at their destination. Suppose the server computer sends informations with certain MTU. If a downstream router uses a smaller MTU, then the data sent by the server is fragmented to the lower MTU. This fragmentations slows down the data transfer. Thus, when two computers interact (like a website server and the browsing client computer), the smallest MTU of the two, also called the path MTU, is critical. In case of internet, a website server and a browsing client computer actually interact through many other computers, like ISP computers, routers, etc. So, the path MTUs will vary from day to day depending on all the intermediaries that the interactions happen through. Identification of path MTU is crucial for proper data transmission. A protocol called ICMP is used to identify the path MTU. However, ICMP may be blocked by firewalls, etc., leading to randomly occurring problems in browsing websites.