CONNECTIONS
6 CONNECTIONS
Connections- Control Connection o Created in the same ways as other applications O Server issues a passive open on port 2 1 and waits O Clients uses an ephemeral port and issues an active open o Remains open during the entire process o Needs minimize delay for service
7 Connections – Control Connection ⚫Created in the same ways as other applications Server issues a passive open on port 21 and waits Clients uses an ephemeral port and issues an active open ⚫Remains open during the entire process ⚫Needs minimize delay for service
Passive open Control 21 Control process ocess Data transfer Data transfer process process Client Server a Passive open by server Active open Control 62010 21 Control process process Data transfer Data transfer rocess p rocess Client Server b. active open by clien Figure 20-2
8 Figure 20 - 2
Connection -Data Connection o Uses the port 20 usually at the server side o Creation of a data connection includes O Client issues a passive open using an ephemeral port O Client sends this port number to the server using PORT cOmmand O Server receives the port number and issues an active open using the well-known port
9 Connection – Data Connection ⚫Uses the port 20 usually at the server side ⚫Creation of a data connection includes Client issues a passive open using an ephemeral port Client sends this port number to the server using PORT command Server receives the port number and issues an active open using the well-known port
Control Control 62010 process process Data transfer Data transfer 63000 Passive proces open process Client rvel a. Passive open by client PORT 6300Q Control 62010 Control proces process Data transfer 63000Passive Data transfer process process Client erver b. Sending ephemeral port number to server Control Control 62010 process process Data transfer 63000 Data transfer process process Client S A ctive open by serv Figure 20-5
Figure 20-3