4 ms·

Can it be used for ,,pausing'' TCP connections? When I go into an elevator, the WIFI / 4G connection can drop for half minute for example, then it reconnects l

Can it be used for ,,pausing'' TCP connections? When I go into an elevator, the WIFI / 4G connection can drop for half minute for example, then it reconnects later. Or for example switching from one wifi network where the connection is slow to another one (my fast tethered mobile network).

vlan0 4y ago
This isn’t a gab at you. But this question doesn’t make sense. I think the things you don’t know you don’t know about TCP and distributed system design make this difficult to pick apart. Remember, your identity in a TCP connection is your IP address. If you connect from another IP and want your session to continue, identity must be handled higher in the stack. TCP connection technically live forever by default. It’s up to either party to complete the handshake. Without that mechanism, your box would run out of ports.
- topspin 4y ago
  > Remember, your identity in a TCP connection is your IP address The essential tuple of a stateful IP session, the "5-tuple," is the source IP address, source port number, destination IP address, destination port number and the IP protocol number, in this case TCP. None of those elements can change during the lifetime of the connection. Or rather, changing any element constitutes a different connection. Not that you needed to be told that; you probably know this already. It's just an interesting factoid that I imagine others might find interesting or useful when thinking about networking. In the guts of every device that handles TCP state (clients, servers, middle boxes, whatever) there is a table of all in-flight 5-tuples that marries every incoming packet with some state.
  - remram 4y ago
    Port numbers are not an IP concept. "IP session"?
    - mrkstu 4y ago
      Most protocols atop IP have the concept of ports- i.e. TCP or UDP.
  - vlan0 4y ago
    Indeed! I always appreciate help explaining. I've been deep in networking for so long that I struggle threading the needle between not enough and too much information.
pgorczak 4y ago
TCP can survive those interruptions on its own, unless the application sets short timeouts or the IP address changes. MPTCP keeps working when either side of the connection changes addresses.

vlan0 4y ago

This isn’t a gab at you. But this question doesn’t make sense. I think the things you don’t know you don’t know about TCP and distributed system design make this difficult to pick apart. Remember, your identity in a TCP connection is your IP address. If you connect from another IP and want your session to continue, identity must be handled higher in the stack. TCP connection technically live forever by default. It’s up to either party to complete the handshake. Without that mechanism, your box would run out of ports.

topspin 4y ago
> Remember, your identity in a TCP connection is your IP address The essential tuple of a stateful IP session, the "5-tuple," is the source IP address, source port number, destination IP address, destination port number and the IP protocol number, in this case TCP. None of those elements can change during the lifetime of the connection. Or rather, changing any element constitutes a different connection. Not that you needed to be told that; you probably know this already. It's just an interesting factoid that I imagine others might find interesting or useful when thinking about networking. In the guts of every device that handles TCP state (clients, servers, middle boxes, whatever) there is a table of all in-flight 5-tuples that marries every incoming packet with some state.
- remram 4y ago
  Port numbers are not an IP concept. "IP session"?
  - mrkstu 4y ago
    Most protocols atop IP have the concept of ports- i.e. TCP or UDP.
- vlan0 4y ago
  Indeed! I always appreciate help explaining. I've been deep in networking for so long that I struggle threading the needle between not enough and too much information.

pgorczak 4y ago

TCP can survive those interruptions on its own, unless the application sets short timeouts or the IP address changes. MPTCP keeps working when either side of the connection changes addresses.