What is the difference between
data.len filters? I thought that both mean data size traveling in the segment (not including
TCP header). I have a problem related to
MTU issue and I'm trying to figure if data size from application layer is greater than the
MSS announced by the server.
The capture shows some TCP packets encapsulating 1434 Bytes:
But the TCP layer analysis displays the same TCP packets with
len = 1448
I think that this TCP segment is encapsulating 1448 Bytes. 1448B plus 32B of TCP header (some TCP options are enabled) plus 20B of IP Header = 1500 Bytes as it is displayed in the analysis of the IP layer.
So I have a question related to this one about
MSS clamping. LAN clients are connected to the router using
Ethernet with MTU = 1500 Bytes and router is connected to the Internet using
PPPoE with MTU = 1492 Bytes. The router is manipulating
MSS field in every TCP packet with
SYN flag enabled in both directions, this is known as
MSS clamping. This way LAN clients receive MSS = 1452 from servers on the Internet and the servers receive MSS = 1452 from the LAN clients.
But what happens if server announces MSS < 1452? LAN clients will receive MSS = 1452 from the server so only
PMTUD can work here?