1. How FTP works?
FTP uses two separate TCP connections and one is called as command channel (server uses port 21) and other is called as data channel (Server uses port 20) and client always uses port greater than 1023 for both command and data channel.
2. How TCP works?
TCP working principle is based on three way handshaking between Host-A and Host-B. Host-A transmits SYN (synchronizing bit of where Host-A will transmit) and in order to acknowledge this Host-B will transmit ACK with what type of SYN bit Host-B is going to transmit and in order ( No more data from the sender bit) will be transmitted to indicate that no data are going to be transmitted between the hosts.
3. Is TCP sends the data as continuous stream of bytes or packets?
TCP sends the data as continuous stream of bytes not as individual packets. With help of sequence number and acknowledgment number in TCP header, TCP takes care of maintaining the sequence in which the bytes send and received.
4. What are the two types of DNS n/w activities?
a. Lookups (when client request the information from the server such as IP-address of the host name or the host-name of the IP-address etc. UDP/TCP)
b. Zone transfer (occurs when secondary server trying to request the primary server that it knows about the zone information-TCP)
5. How SIP works ?
SIP is application layer protocol borrows most of the syntax from HTTP and SMTP. It is a signaling protocol used to transmit and control Video/Voice over IP protocol. SIP needs user agent to be more intelligent which can handle SIP signals from SIP client to SIP server and it can work on any one of the following underlying protocol
1. User datagram protocol (UDP)
2. Transmission Control Protocol (TCP)
3. Stream Control Transmit protocol (SCTP)