mentor prep

Question 1

narrow waist of the internet

Answer 1

IP layer connects various networks and applications

IP remains consistent and universal across the entire network

Question 2

switching <-> routing

Answer 2

switching - forwarding packets at data link layer
routing - directing packets between different networks

Question 3

non-transparent fragmentation

Answer 3

packets are fragmented without informing the receiver

Question 4

transparent fragmenting

Answer 4

packets are reassembled at each hop

Question 5

avoiding fragmentation

Answer 5

notify the sender to send small packets

Question 6

distance vector routing

Answer 6

Nodes share their distance vector(the distances or cost to all of the nodes in the network) periodically to their neighbours

protocol example: RIP (Routing Information Protocol)

Question 7

count to infinity

Answer 7

a routing problem in distance-vector routing protocols like RIP (Routing Information Protocol). When a network node fails, nodes that rely on it may continuously increase their distance metric values (hop counts) to other destinations, leading to a situation where the network fails to converge.

Question 8

link state routing

Answer 8

a type of routing algorithm where routers exchange information about their directly connected links to build a complete network map

Question 9

OSPF

Answer 9

interior gateway protocol used within a single autonomous system (AS) to exchange routing information and determine the best paths (shortest paths) between routers

Question 10

BGP

Answer 10

an exterior gateway protocol used to exchange routing and reachability information between different autonomous systems on the internet

Question 11

IPv4 <-> IPv6

Answer 11

IPv4
- 32 bit
- ~4.3 billion addresses

IPv6
- 128 bit

Question 12

NAT

Answer 12

used to translate private IP addresses (used within a local network) to public IP addresses (used on the internet)
This allows multiple devices on a local network to share a single public IP address for communication with external networks

Question 13

transport layer manages:

Answer 13

data segmentation
error correction
and flow control
establishes connections
manages data transfer
provides reliable communication services

Question 14

three-way handshake

Answer 14

fundamental process used in TCP to establish a connection between two devices over an IP network
It ensures both ends are ready to send and receive data before actual data transmission begins, involving three steps: SYN, SYN-ACK, and ACK.

Question 15

purpose of using sliding window protocols

Answer 15

to manage transmission of frame and ensure reliable data transfer
They allow multiple frames to be sent before needing an acknowledgment for the first one, improving efficiency and ensuring that data is correctly received

Question 16

TCP <-> UDP

Answer 16

TCP ensures reliable and ordered data delivery through error checking, retransmission of lost packets, and flow control
UDP is a connectionless protocol that does not offer these features, making it faster but less reliable than TCP

Question 17

main function of DNS

Answer 17

To translate domain names to IP addresses

Question 18

HTTP as the narrow waist

Answer 18

HTTP is a foundational protocol that all other web protocols are built over

Question 19

802.11 protocol is in

Answer 19

the link layer

Question 20

IP is in

Answer 20

the network layer

Question 21

UDP is in

Answer 21

the transport layer

Question 22

IMAP is in

Answer 22

the application layer

Question 23

Ethernet is in

Answer 23

the link layer

Question 24

stop-and-wait

Answer 24

sliding window with window size =1

Question 25

Huffman encoding

Answer 25

lossless data compression algorithm assigns variable-length codes to input characters, with shorter codes for more frequent characters The process involves building a binary tree called the Huffman tree, where each leaf node represents a character from the input and its frequency. The resulting codes minimise the total length of the encoded message

Question 26

forward error correction

Answer 26

error control where the sender adds redundant data (error-correcting code) to the message this allows the receiver to detect and correct errors without needing a retransmission commonly include: Hamming codes, Reed-Solomon codes, convolutional codes

Question 27

QUIC

Answer 27

Quick UDP Internet Connections transport layer protocol developed by google provides security equivalent to TLS reduced connection and transport latency combines multiplexing, low-latency connection establishment and congestion control

Question 28

WebSocket

Answer 28

communication protocol providing full-duplex channels over a single TCP connection use for real-time web applications, allowing a persistent connection between the client and server for continuous data exchange without the overhead of HTTP request

Question 29

CDNs

Answer 29

Content Delivery Networks distributed networks of servers that deliver web content to users based on their geographic location improve the performance, availability, and security of web services by caching content at multiple locations, reducing latency and load on the origin server

Question 30

SMTP

Answer 30

Used to send emails from a client to a server or between servers

Question 31

IMAP

Answer 31

Used by email clients to retrieve messages from a mail server, allowing for the management of emails directly on the server

Question 32

max-min fairness

Answer 32

an allocation principle used in network resource management It aims to maximise the minimum resource allocation among all users Resources are allocated in such a way that no user can receive more without reducing the allocation of another user who has an equal or smaller allocation

Question 33

route aggregation

Answer 33

or route summarisation a method used to combine multiple IP address routes into a single route reduces the size of the routing table and improves the efficiency of the routing process by representing a block of IP addresses with a single entry

Question 34

two armies problem

Answer 34

demonstrates the impossibility of achieving guaranteed coordination in the presence of communication uncertainty, as neither side can be sure that their messages have been received and acknowledged

Question 35

network layer

Answer 35

third layer in the OSI model responsible for logical addressing, routing, and forwarding of packets across different networks key functions: determining the best path to the destination and handling packet switching and routing through intermediate routers

Question 36

link state routing

Answer 36

a type of routing protocol in which routers share information about their directly connected links and build a complete map of the network topology Each router independently calculates the best path to every destination using algorithms like Dijkstra's Examples include OSPF (Open Shortest Path First) and IS-IS (Intermediate System to Intermediate System)

Question 37

sliding window protocols

Answer 37

used in data transmission to control the flow and ensure reliable delivery of packets. The sender can send multiple frames before needing an acknowledgment for the first one, maintaining a "window" of frames that can be sent This improves efficiency and throughput compared to stop-and-wait protocols

Question 38

ECN and RED

Answer 38

methods to signal congestion both require transport layer to do it

Question 39

ECN (explicit network notification)

Answer 39

works by marking packets instead of dropping them when it predicts the onset of congestion. However, for ECN to work effectively, the transport layer protocols must be able to recognize these marked packets and react accordingly (usually by reducing the sending rate), meaning they must take action to prevent further congestion

Question 40

RED (Random early detection)

Answer 40

works by randomly dropping packets before actual congestion occurs, based on average queue size. This triggers transport layer protocols' built-in loss recovery and congestion control mechanisms (for example, TCP will reduce its sending rate when it detects packet loss), meaning that, in a sense, it also requires action from the transport layer to prevent congestion

Question 41

pure store-and-forward routers

Answer 41

they wait until they have received the entire packet before forwarding it. Therefore, it's possible that the first bytes of a packet are forwarded while the last bytes are still arriving at the router. This behaviour contrasts with cut-through switching, where forwarding begins as soon as the destination address is read, without waiting for the entire packet to arrive

Question 42

IP encapsulation or IP tunnelling

Answer 42

an IP packet is encapsulated within another IP packet. The TTL (Time To Live) value of the inner datagram will not be decremented at each hop; instead, the outer TTL value will be decremented. This is because each router along the path decrements the TTL of the outer packet, while the inner packet remains unchanged until it reaches the final destination

Question 43

SMTP, the simple mail transfer protocol, can be used for both sending and receiving of email, but we also use protocols like POP3 and IMAP for receiving

Question 44

Distance vector routing typically requires less memory and computational resources than link state routing. This is because in distance vector routing, a router only needs to know the next hop and distance or cost for each destination, which is a smaller amount of information than link state routing requires.

Question 45

sink tree

Answer 45

A sink tree (/source tree) for a destination is the union of all shortest paths towards the destination

Question 46

forwarding table

Answer 46

lists next hop for each destination

Question 47

dv <-> ls

Answer 47

dv - slow convergence - excellent scalabilty ls - fast convergence - modereate scalability

Question 48

aggreagtion

Answer 48

Externally join multiple more specific prefixes → one large/less specific prefix

Question 49

ARP

Answer 49

Communication protocol used for discovering the link layer address, (e.g. MAC address) associated with a given network layer address, (e.g. IPv4 address)

Question 50

DHCP

Answer 50

Network managmement protocol used on IP Networks for autmatically assigning IP addresses and other communication paramters to devices connection to the network.

Question 51

discovery

Answer 51

used by IP Find the largest packet that fits on the network path and use it