Networking

Question 1

List at least two criteria for choosing a network physical media type

Answer 1

Transmission rate and shared or direct access among users

Question 2

Why layering is needed in networking?

Answer 2

The explicit structure allows identification, and relationship of complex system’s pieces. Modularization eases the maintenance and updating of the system. Structure developers can work in one layer or multiple layer without disturbing the whole networking

Question 3

List the sources of packet delay.

Answer 3

propagation delay, transmission delay, queuing delay, and processing delay.

Question 4

How does packet loss occur?

Answer 4

When one or more transmitted data packets fail to arrive at their destination due to network congestion, hardware issues, software bugs, and a number of other factors

Question 5

What do we mean by a network protocol?

Answer 5

Network protocols are rules that define the format, order of messages sent and received among network entities, and actions taken on msg transmission, receipt communication activity on the Internet governed by protocols

Question 6

Give some examples of end systems (hosts) and packet switches (networking devices).

Answer 6

end systems=servers, workstations, network-interface print devices, and routers. packet swithces= Ethernet and Frame Relay

Question 7

What are the key network-layer functions?

Answer 7

The first one is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network

Question 8

What Network-layer service model the Internet provides?

Answer 8

The Internet uses a datagram network layer. With a datagram network layer, each time an end system wants to send a packet, it stamps the packet with the address of the destination end system and then pops the packet into the network.

Question 9

What is a subnet?

Answer 9

Device interfaces that can physically reach each other without passing through an intervening router

Question 10

How does a host get an IP address?

Answer 10

Hard-coded by sysadmin in the config file. DHCP-Dynamic Host Configuration Protocol: dynamically get address from a server

Question 11

What is NAT?

Answer 11

Network address translation.

Question 12

Differences between IPV6 and IPV4

Answer 12

IPv4 is 32-Bit IP address whereas IPv6 is a 128-Bit IP address. IPV4 bits are separated by a dot(.) whereas IPV6 bits are separated by a colon(:). IPv4 is a numeric addressing method whereas IPv6 is an alphanumeric addressing method. IPv4 offers 12 header fields whereas IPv6 offers 8 header fields. IPv4 supports broadcast whereas IPv6 doesn’t support broadcast. IPv4 has checksum fields while IPv6 doesn’t have checksum fields. IPv4 supports VLSM (Variable Length Subnet Mask) whereas IPv6 doesn’t support VLSM. IPv4 uses ARP (Address Resolution Protocol) to map to MAC address whereas IPv6 uses NDP (Neighbour Discovery Protocol) to map to MAC address.

Question 13

What are the possible Internet transport protocol services that can be provided to applications?

Answer 13

UDP- has a very low overhead for both header size and protocol logic, which means that both the packet transmissions and receptions consume less energy, and each packet has more room for application-layer data
TCP- provides a reliable byte stream and reduces the application complexity at the cost of a larger header size and more complex transport layer protocol logic .

Question 14

The differences between Non-persistent HTTP and persistent HTTP

Answer 14

After the client receives the object with non-persistent, the connection is immediately closed.

Question 15

Disadvantages of Non-Persistent HTTP

Answer 15

Requires 2 RTTs per object.
OS overhead for each TCP connection.
Browsers open parallel TCP connections to fetch referenced objects

Question 16

Advantages of Persistent HTTP

Answer 16

Lower CPU and memory usage because there are less number of connections. Allows HTTP pipelining of requests and responses.
Reduced network congestion (fewer TCP connections).

Question 17

How DNS application work?

Answer 17

1- Requesting Website Information- If it is present locally, then the website will be displayed. If our computer does not have the information, it will perform a DNS query to retrieve the correct information
2- Contact the Recursive DNS Servers
3- Query the Authoritative DNS Servers
4- Access the DNS Record
5- The Recursive DNS server has the information and returns the A record to your computer.

Question 18

How do Email applications work?

Answer 18

The email gets sent by the client to an outgoing mail server via Simple Mail Transfer Protocol. The SMTP server is like your local post office, which checks your postage and address and figures out where to send your mail. It doesn’t understand domains, though. They’re a sort of abstract thing, so the SMTP server contacts a Domain Name System server. The DNS server is a sort of phone or address book for the internet; it translates domains like “arrakis.com” to an IP address like “74.238.23.45.” Then, it finds out if that domain has any “MX” or mail exchange servers on it and makes a note of it. This is like your post office consulting maps of where your mail is supposed to go, calling their local post office, and checking to see if your friend has a mailbox or P.O. box to receive mail.

Question 19

Give examples of applications that use such transport protocols (TCP and UDP)

Answer 19

TCP- browser, email, FTP. UDP- live broadcasts and online games

Question 20

What is the purpose of the receiver window?

Answer 20

A variable that advertises the amount of data that the destination site can receive.

Question 21

What is the difference between the sequence number and acknowledgement number in TCP?

Answer 21

The sequence number is the byte number of the first byte of data in the TCP packet sent. The acknowledgement number is the sequence number of the next byte the receiver expects to receive.

Question 22

Why do we need the checksum bits in the TCP or UDP segments?

Answer 22

In order to determine whether the received data is corrupted along the network

Question 23

Why do we need the ‘A’, ‘S’ and ‘F’ bits in the TCP segment?

Answer 23

It is the control bits. They are used to establish connections, send data and terminate connections

Question 24

Benefits of TCP

Answer 24

Performs error checking and attempts error recovery.

Question 25

Benefits of UDP

Answer 25

Faster because integrity is checked at the arrival time using checksum.

Question 26

How does TCP work?

Answer 26

First, it orders packets by numbering them. Second, it error-checks by having the recipient send a response back to the sender saying that it has received the message. If the sender doesn’t get a correct response, it can resend the packets to ensure the recipient receives them correctly.

Question 27

How does UDP work?

Answer 27

When an app uses UDP, packets are just sent to the recipient. The sender doesn’t wait to make sure the recipient received the packet—it just continues sending the next packets. If the recipient misses a few UDP packets here and there, they are just lost—the sender won’t resend them. Losing all this overhead means the devices can communicate more quickly.