Day Of Exam

Question 1

TCP/IP

Answer 1

Transmission Control Protocol. Internet Protocol.

Question 2

Four layers of TCP/IP

Answer 2

Link Layer (host / network interface layer), Internet Layer, Transport Layer, Application Layer.

Question 3

Describe Link Layer:

Answer 3

Corresponds to OSI physical and data link layers.

Question 4

Internet Layer, describe:

Answer 4

Defines IP. Two main functions: 1)host addressing & identification. 2) Packet Routing, forwarding packet to next router.

Question 5

Transport Layer describe:

Answer 5

Same as OSI model. Creates distinct network connection. error control. application addressing (port numbers). Two end to end message transmission protocols: TCP & UDP

Question 6

Application Layer describe:

Answer 6

Contains higher level protocols like FTP, DNS, SMTP

Question 7

TCP?

Answer 7

Transmission Control Protocol (reliable connection oriented protocol).

Question 8

UDP?

Answer 8

User Datagram Protocol (unreliable connectionless protocol).

Question 9

MAC?

Answer 9

Medium Access Control. A component of the Link Layer.

Question 10

What does MAC do?

Answer 10

This protocol deals with issues like addressing, assigning multiplex channels to different users, avoiding collisions. Resolves contention.

Question 11

Channel Allocation Problem?

Answer 11

The problem of allocating a single broadcast channel amongst many users.

Question 12

Channel Allocation Problem solutions?

Answer 12

Static: FDM, TDM. Dynamic: (Collision)Pure Aloha, Persistent CSMA, non-persistent CSMA, CSMA/CD. (non-collission) bit map protocl, binary countdown, adaptive tree walk.

Question 13

When are collision based protocols good?

Answer 13

when network load is low.

Question 14

When are collision free protocols good?

Answer 14

when network load is high

Question 15

Pure Aloha:

Answer 15

Nodes send regardless of other nodes. Collision detected, wait then send again.

Question 16

Slotted aloha:

Answer 16

Divide into intervals corresponding to frame. Efficiency doubled on pure aloha.

Question 17

Carrier Sense?

Answer 17

Where a station can check if channel is in use.

Question 18

CSMA / CD

Answer 18

Carrier Sense Multiple Access / Collision Detection.

Question 19

Ethernet: 4 parts to it

Answer 19

Medium (lead), Segment (a single shared medium), Node (devices attached to the segment), Frame (nodes communicate in frames).

Question 20

TCP header as list:6

Answer 20

Source destination port, sequence number, acknowledge number, checksum, window size, flags

Question 21

TCP 4 characteristics:

Answer 21

Provides reliable delivery. User acknowledged delivery.

Question 22

TCP header:

Answer 22

Source and destination port, sequence number, acknowledged number, checksum, window size, flags.

Question 23

ARP?

Answer 23

Address resolution protocol. Solves problem of mapping MAC to IP.

Question 24

ICMP?

Answer 24

Internet control message protocol. Internet monitored by routers, something wrong is reported by ICMP.

Question 25

Subnet mask?

Answer 25

Separated IP into network and host addresses. Find subnet address by performing but wise AND operation on IP and subnet mask.

Question 26

NAT?

Answer 26

Network address translation. Way to add more addresses. Translates packets going to Internet.

Question 27

IP header?

Answer 27

Version, IHL, type of service, total length, ID, fragment offset, time to live, protocol, checksum, source address, destination address, options. 32 bits.

Question 28

Conmectionless service?

Answer 28

Data sent between nodes without knowing if destination busy. UDP is connection less.

Question 29

Connection less algorithms, static and dynamic?

Answer 29

Static: shortest path-examine each node in turn, dynamic: vector distance routing - router tables used.

Question 30

Three way handshake?

Answer 30

H1 to h2: connection request (CR) TPDU with seq=x.
H2 to h1: replies with ACK TPDU ack=x and seq=y.
H1 to h2: sends data TPDU with ack=y, seq=x

Question 31

Two types of releasing connection:

Answer 31

Asymmetric(1 can break), symmetric(communication after break).

Question 32

TPDU? And layout?

Answer 32

Transport Protocol Data Unit. Frame header, packet header, TPDU header. Segment for TCP, Datagram for UDP.