Network Layer Routing & Transport Layer

Question 1

goal of the network layer

Answer 1

deliver a datagram from its source to its
destination

Question 2

the way a packet is delivered to the next station

Answer 2

Forwarding

Question 3

process of selecting a path for traffic in a network or across multiple
networks

Answer 3

Routing

Question 4

if a datagram is destined for only one destination

Answer 4

Unicast Routing

Question 5

if a datagram is destined for several destinations

Answer 5

Multicast Routing

Question 6

A packet is routed, hop by hop, from its source to its destination by the help of

Answer 6

forwarding tables

Question 7

The source router chooses a route to the destination router in such a way that the total cost for the route is the least cost among all possible routes

Answer 7

Least Cost Routing

Question 8

Routing Algorithms

Answer 8

Distance-Vector Routing
Link-State Routing
Path-Vector Routing

Question 9

Each node maintains a vector (table) of minimum distances to every node

Answer 9

Distance-Vector Routing

Question 10

This method uses the term link-state to define the characteristic of a link (edge) that
represents a network in the internet

Answer 10

Link-State Routing

Question 11

The collection of states for all links is called the

Answer 11

link-state database (LSDB)

Question 12

To create a least-cost tree, each node needs a complete map of the network (using

Answer 12

Dijkstra’s Algorithm)

Question 13

The best path is determined by the source using the policy it imposes on the route, i.e.
the source controls the path

Answer 13

Path-Vector Routing

Question 14

In Path-Vector Routing, the path is also determined by the

Answer 14

best spanning tree.

Question 15

responsible for the delivery of a message from one process
to another

Answer 15

transport layer

Question 16

An application program on the local host,

Answer 16

client,

Question 17

an application program on the remote host (provides services)

Answer 17

server

Question 18

16-bit integers between 0 and 65,535

Answer 18

Port Number

Question 19

Client program defines itself with a port number chosen randomly by the transport layer software running in the client host

Answer 19

(ephemeral port number),

Question 20

Servers use universal port numbers

Answer 20

(well-known port number)

Question 21

Well-known ports ranging from

Answer 21

0 to 1023

Question 22

Well-known ports are assigned and controlled
by the (ICANN)

Answer 22

Internet Corporation for Assigned Names and Numbers

Question 23

Registered ports – ports ranging from:
They can only be registered to prevent duplication. (not assigned by ICANN)

Answer 23

1024 to 49,151

Question 24

ports ranging from 49,152 to 65,535 and are neither controlled nor registered. They can be used by any process

Answer 24

Dynamic (or private) ports

Question 25

In UNIX, the well-known ports are stored in a file called

Answer 25

/etc/services

Question 26

IP address + port number

Answer 26

Socket address

Question 27

Connectionless, unreliable transport protocol

Answer 27

User Datagram Protocol (UDP)

Question 28

Does not add anything to IP except provide process-to-process communication

Answer 28

User Datagram Protocol (UDP)

Question 29

Simple protocol using minimum overhead

Answer 29

User Datagram Protocol (UDP)

Question 30

UDP Datagram (composed of?)

Answer 30

header - 8 bytes Source port number - 16 bits Dest port number - 16 bits Length - 16 bits (total length, header + data) Checksum -16 bits

Question 31

used to detect errors over the entire user datagram

Answer 31

Checksum

Question 32

In a UDP header, source port number is the

Answer 32

1st 4 hexadecimal digits

Question 33

In a UDP header, dest port number is the

Answer 33

2nd 4 hexadecimal digits

Question 34

In a UDP header, total length is the

Answer 34

3rd 4 hexadecimal digits

Question 34

In a UDP header, how to get the length of data?

Answer 34

Length of whole packet - length of header (8 bits)

Question 34

If destination port number is a well-known port, the packet is from the...

Answer 34

client to a server

Question 35

port 7

Answer 35

echo

Question 36

port 9

Answer 36

discard

Question 37

port 11

Answer 37

users

Question 38

port 13

Answer 38

daytime

Question 39

Suitable for a process that requires simple request-response communication

Answer 39

UDP

Question 40

Connection-oriented, reliable transport protocol

Answer 40

Transmission Control Protocol (TCP)

Question 41

allows the sending process to deliver data as a stream of bytes and allows the receiving process to obtain data as stream of bytes

Answer 41

Transmission Control Protocol (TCP)

Question 42

RFC 768

Answer 42

User Datagram Protocol (UDP)

Question 43

RFC 793

Answer 43

Transmission Control Protocol (TCP)

Question 44

TCP numbers all data bytes that are transmitted in a connection.

Answer 44

Byte number

Question 45

TCP assigns a ________ to each segment that is being sent.

Answer 45

sequence number

Question 46

When a connection is established, both parties can send and receive data at the same time. Each party uses an __________ to confirm the bytes it has received

Answer 46

acknowledgment number

Question 47

receiver of data controls the amount of data that are to be sent by the sender

Answer 47

Flow control

Question 48

to provide reliable service, TCP implements an error control mechanism

Answer 48

Error control

Question 49

amount of data sent by the sender is not only controlled by the receiver, but is also determined by the level of congestion in the network

Answer 49

Congestion control

Question 50

32-bit field that defines the number assigned to the first byte of data contained in the segment.

Answer 50

Sequence number

Question 51

During connection establishment, each party uses a random number generator to create an...

Answer 51

initial sequence number (ISN)

Question 52

32-bit field that defines the byte number that the receiver of the segment is expecting to receive from the other party

Answer 52

Acknowledgment number

Question 53

4-bit field indicates the number of the 4-byte word in the TCP header

Answer 53

Header length

Question 54

6-bit field for future use

Answer 54

Reserved

Question 55

6 different control bits or flags

Answer 55

Control

Question 56

16-bit field that defines the size of the window, in bytes, that the other party must maintain. Normally referred to as the receiving window

Answer 56

Window size

Question 57

Inclusion of the checksum in TCP is mandatory while it is optional in UDP

Answer 57

Checksum

Question 58

16-bit field that defines the number that must be added to the sequence number to obtain the number of the last urgent byte in the data section of the segment

Answer 58

Urgent pointer

Question 59

establishes a virtual path between the source and destination

Answer 59

TCP

Question 60

TCP requires 3 phases:

Answer 60

Connection establishment Data transfer Connection termination

Question 61

Process starts with the server where it tells its TCP that it is ready to start a connection

Answer 61

passive open

Question 62

A client that wishes to connect to an open server tells it TCP that it needs to be connected to that particular server

Answer 62

(active open)

Question 63

both process issue an active open. Both TCP transmit a SYN + ACK segment to each other, and one single connection is established between them

Answer 63

(simultaneous open)

Question 64

The sending TCP must not wait for the window to be filled, it must create a segment and send it immediately

Answer 64

Pushing Data

Question 65

Malicious attacker sends a large number of SYN segments to a server, pretending that each of them is coming from different clients by faking the source IP address in the datagrams

Answer 65

SYN flooding attack

Question 66

the sending application program wants a piece of data to be read out of order by the receiving application program

Answer 66

Urgent Data

Question 67

segment cannot carry data, but it does consume one sequence number

Answer 67

SYN+ACK

Question 68

segment, if carrying no data, consumes no sequence number

Answer 68

ACK

Question 69

segment consumes one sequence number if it does not carry data

Answer 69

FIN

Question 70

New reliable, message-oriented transport layer protocol It has also congestion control and flow control mechanisms

Answer 70

Stream Control Transmission Protocol

Question 71

Preserves the message boundaries and at the same time detects lost data, duplicate data and out-of-order data

Answer 71

Stream Control Transmission Protocol

Question 72

RFC 4960

Answer 72

Stream Control Transmission Protocol

Question 73

SCTP Services: (2)

Answer 73

Multiple Streams Multihoming

Question 74

In TCP, each connection between client and server involves a single stream, a loss at any point in the stream blocks the delivery of the rest of the data

Answer 74

Multiple Streams

Question 75

A TCP connection involves 1 source and 1 destination IP address, even if the sender or receiver is multihomed (connected to more than 1 physical address with multiple IP address), only one of these IP addresses per end can be used

Answer 75

Multihoming

Question 76

unit of data in SCTP is a data chunk. Data transfer is controlled by numbering the data chunk using TSN

Answer 76

Transmission Sequence Number (TSN):

Question 77

each stream in SCTP needs to be identified

Answer 77

Stream Identifier (SI)

Question 78

SCTP defines each data chunk in each stream. When a data chunk arrives at the destination, it is delivered to the appropriate stream and in the proper order

Answer 78

Stream Sequence Number (SSN)

Question 79

data are carried as data chunks, control information is carried as control chunks. Several control chunks and data chunks can be packed together in a packet

Answer 79

Packets

Question 80

number that matches a packet to an association. It serves as an identifier for the association and is repeated in every packet during the association

Answer 80

Verification tag

Question 81

32-bit field contains a CRC-32 checksum

Answer 81

Checksum