Dec 30, 2015

The maximum segment size (MSS) is a parameter of the options field of the TCP header that specifies the largest amount of data, specified in bytes, that a computer or communications device can receive in a single TCP segment. It does not count the TCP header or the IP header (unlike, for example, the MTU for IP datagrams). Destination unreachable (Fragmentation needed) [MTU of next hop: 1446] [TCP Dup ACK 967#1] 42484 -> 443 [ACK] [TCP Retransmission] 443 -> 42484 [ACK] This traffic shows that a packet of length 1514 bytes is not being allowed to pass through the gateway. So now the server knows to use an MTU of 1476 when talking to this client. With the MTU now being 1476 our math now sorts out like this… So using a new MTU of 1476 forces the TCP payload (MSS) down to a lower number to fit all of the headers in making the total frame size 1500 (excluding Ethernet framing)… client dev tun proto tcp remote 18.4.26.8 443 resolv-retry infinite nobind tun-mtu 64800 tun-mtu-extra 32 mssfix 1440 persist-key persist-tun auth-user-pass comp-lzo verb 3 I made some changes to MTU and MSSFIX from what I found on the web. Are there any kernel changes I could make? This is a CentOS 6.x box. Aug 18, 2008 · Ethernet interfaces, for example, have a default MTU of 1500 bytes, not including the Ethernet header or trailer. This means a host needing to send a TCP data stream would typically use the first 20 of these 1500 bytes for the IP header, the next 20 for the TCP header, and as much of the remaining 1460 bytes as necessary for the data payload. An IP MTU of 1500Bytes; A host TCP MSS of 1460Bytes; TCP & IP packet headers of 40Bytes (no TCP options) Use of a full duplex communications medium, i.e. the full bandwidth is available both upstream and downstream, at the same time

The TCP maximum segment size (MSS) specifies the maximum number of bytes in the TCP segment’s Data field, regardless of any other factors that influence segment size. The default MSS for TCP is 536, which results from taking the minimum IP MTU of 576 and subtracting 20 bytes each for the IP and TCP …

Determine the Correct MTU for Your Network: Launch the command prompt. From your desktop, …

MTU is Layer 1 and maximum amount of information that can be transferred at one time which is 1500. I have also seen it as 1518, where does the 18 come from ? this is in byte. MSS is your MTU minus layer 3 and 4 thus if we imagine 20 Byte for IP and 20 for TCP then MSS is 1460

HOW TO: Change the Default Maximum Transmission Unit (MTU