TCP/IP Questions and Answers

Answer: C

IP addresses are assigned automatically by DHCP.

The Dynamic Host Configuration Protocol lets a device joining a network obtain an IP address, subnet mask, default gateway and DNS server from a DHCP server, through the discover, offer, request and acknowledge exchange, without manual configuration.

FTP transfers files, SMTP sends email, and DNS translates domain names into IP addresses but does not hand addresses out to hosts.

Answer: B

DNS translates domain names to IP addresses.

The Domain Name System is the internet's directory: when you type a name such as tpsc.tripura.gov.in, a DNS resolver looks up the IP address that the network actually uses to reach the server, so people can use names instead of numbers.

MAC addresses are burned into network hardware, not assigned by DNS. Encryption is done by protocols such as TLS, and routing packets is the job of routers at the network layer.

Answer: D

The Application layer of TCP/IP covers OSI's session and presentation layers.

The TCP/IP model has four layers: network access, internet, transport and application. Its application layer takes in the work of OSI layers 5, 6 and 7, so session handling, data formatting and encryption are done by the application protocols themselves (HTTP, SMTP, FTP and so on).

The internet layer corresponds to OSI's network layer, the transport layer to OSI's transport layer, and the network access layer to the data link and physical layers.

Answer: B

The protocol is UDP.

Real-time multimedia such as voice and video streams is usually carried over UDP, often with RTP on top. UDP has no connection set-up, no retransmission and no congestion back-off, so late or lost packets are simply skipped instead of holding up the stream, which suits audio and video better than delay.

TCP is a transport protocol but its retransmissions add delay. HTTP is an application-layer protocol, and ICMP is a network-layer protocol for error and control messages, so neither is a transport protocol.

Answer: B

The valid version is IPv6.

The Internet Protocol versions in use are IPv4, with 32-bit addresses, and IPv6, with 128-bit addresses, standardised by the IETF to replace it as IPv4 addresses ran out.

Version number 5 was assigned to the experimental Internet Stream Protocol (ST), which was never deployed as an IP version, so there is no IPv5. IPv7 and IPv8 were names used only in early proposals for a successor to IPv4; none became a standard Internet Protocol.

Answer: C

The Commission's key gives FLOW LABEL.

The IP datagram header usually meant in such questions is the IPv4 header, whose fields are version, header length, type of service, total length, identification, flags, fragment offset, time to live, protocol, header checksum and the two addresses. VERSION and CHECKSUM are both there. FLOW LABEL is a field of the IPv6 header, so it is not in the IPv4 header.

HOP LIMIT is the IPv6 name for what IPv4 calls time to live, and it too is absent from the IPv4 header by that name, so the option set is not clean: HOP LIMIT could also be defended. The key picks FLOW LABEL, the field that has no IPv4 counterpart at all, and that is the letter to give on this paper.

Answer: C

The email transfer protocol is SMTP.

SMTP (Simple Mail Transfer Protocol) moves email from a sender's client to a mail server and between mail servers, normally over TCP port 25 (or 587 for submission). Mail is then read from the server with POP3 or IMAP.

FTP transfers files, HTTP transfers web pages and other web resources, and ICMP carries network error and control messages such as ping. None of them is designed to transfer email between servers.

Answer: B

The Commission's key gives HTTP.

A URL begins with a scheme naming the protocol used to reach the resource, as in http://example.com. HTTP, with its secure form HTTPS, is the scheme in everyday use, and it is the one the key expects.

SMTP and ICMP are not URL schemes used to fetch resources: SMTP is for sending mail between servers and ICMP is a network-layer error and control protocol. FTP is the awkward option, because ftp:// is also a valid URL scheme, so the stem does not single HTTP out strictly. On this paper the keyed letter is HTTP.

Answer: C

It is the SNMP Get Command.

An SNMP manager reads the value of a specific managed object (a variable in an agent's MIB) by sending a GetRequest message; the agent answers with a response carrying that value. This retrieval operation is the Get command.

The Set command sends a SetRequest to change a value, and Get-Next sends a GetNextRequest to read the next object in the MIB tree, used for walking tables. Since Get matches, 'None of these' is wrong.

Answer: B

The protocol is UDP.

The 8-bit protocol field of the IPv4 header tells the receiving host which protocol the payload belongs to. The assigned numbers include 1 for ICMP, 6 for TCP and 17 for UDP.

So 17 identifies UDP alone. TCP would carry 6, which also rules out 'Either (A) or (B)'.