Computer Networks

1.For real time multimedia, file transfer, DNS and email, the transport layer protocols used are respectively
TCP, UDP, TCP and UDP UDP, UDP, TCP and TCP UDP, TCP, UDP and TCP TCP, TCP, UDP and UDP

2.A device that can look at all protocol headers up to the transport layer is called l ayer-4 firewall. Which one of the following statement is true layer-4 firewall?
It cannot block all ICMP traffic It cannot block entire HTTP traffic during 9:00pm and 5:00am It cannot block TCP traffic from a specific user on a multi-user system during 9:00pm and 5:00am It cannot stop incoming traffic from a specific IP address but allow outgoing traffic to the same address

3.The source and destination are connected through two intermediate routers. During the data transmission from source to destination how many times each packet has to visit the network layer and the data link layer?
Network layer – 6 times and data link layer – 4 times Network layer – 4 times and data link layer – 2 times Network layer – 4 times and data link layer – 6 times Network layer – 2 times and data link layer – 3 times

4.For the application layer in the Internet stack, the protocol data unit (PDU) is
Datagram Message Frame Segment

5.The transport layer protocols that is used to support electronic mail is
TCP SMTP UDP IP