Combined Flashcards
(110 cards)
1
Q
What is the Layered Network?
A
Packets travel on the network from the sending end system to the receiving end system.
Switching nodes decide which outgoing link should the packet take.
2
Q
What are the key characteristics of Circuit Switching?
A
- Fixed path
- No extra overhead
- Constant cost per time
- Problem: If 1 link fails, all circuits fail
3
Q
What are the key characteristics of Packet Switching?
A
- Data is sent in small packets of bits
- Routed independently
- Contains routing information: Source & Destination
- Charged for the amount of data sent
4
Q
What is Frequency Division Multiplexing (FDM)?
A
Assigning narrow frequency bands to specific users, transmitting at max rate of narrow band for as long as they want.
5
Q
What is Time Division Multiplexing (TDM)?
A
Assigning time slots to specific users, transmitting at max rate for a limited period of time.
6
Q
What is connection-oriented communication?
A
Maintains connection between sender and receiver pairs across multiple transmissions (e.g., SMTP, FTP, TCP).
7
Q
What is connectionless communication?
A
Each transmission is independent of the previous one (e.g., HTTP, UDP, IP, DHCP).
8
Q
How many unique IPV4 addresses are available?
A
2^32 unique addresses identifying each node in internet.
9
Q
What do IPV4 addresses encode?
A
Encoding of hierarchical arrangements of nodes into networks and subnetworks.
10
Q
What uniquely identifies application processes on a computer?
A
Port numbers (16-bit).
11
Q
What are the reserved port numbers range for well-known application processes?
A
Port numbers between 0 – 1023.
12
Q
What is a Socket in networking?
A
A software interface between application process (Layer 5) and protocol (Layer 4).
13
Q
What protocols are included in the TCP/IP Stack?
A
- Application: HTTP, DHCP, SMTP
- Transport: TCP, UDP
- Network: IP
- Data Link: Ethernet, ALOHA
- Physical: Bluetooth, Ethernet
14
Q
What is the typical socket life-cycle for UDP?
A
- Create
- Bind
- Transfer
- Close
15
Q
What is the typical socket life-cycle for TCP?
A
- Create
- Bind
- Connect
- Transfer
- Close
16
Q
What are the main differences between TCP and UDP?
A
- TCP: Reliable transport, Flow Control, Connection-oriented
- UDP: Unreliable transport, No Flow Control, Connection-less
17
Q
What does a network protocol specify?
A
A format for its PDU (Protocol Data Unit), for example, the request format for an HTTP request.
18
Q
What is HTTP classified as?
A
Connectionless and stateless.
19
Q
What is the sequence of events when URL is entered in a browser?
A
- Type URL in browser
- HTTP request message generated
- Open TCP socket
- DNS request made
- IP retrieved
- Send GET request to server
- Server sends HTTP response
20
Q
What is Round Trip Time (RTT)?
A
The measure of the latency of the network: the time it takes to receive a response after initiating a request.
21
Q
What is the difference between Non-persistent and Persistent connections?
A
- Non-persistent: Open TCP connection, send at most one object, close TCP connection
- Persistent: Open TCP connection, download multiple objects, close TCP connection
22
Q
What is Pipelining in networking?
A
Multiple requests sent over a single TCP connection without waiting for responses.
23
Q
What is Head of Line (HoL) blocking?
A
When the first request takes a long time to be served, causing other requests to wait.
24
Q
What is the function of Web Caches?
A
Improve page delivery speed and reduce traffic to the origin server.
25
What is a Conditional GET request?
Ensures the page served by the cache is up to date by checking with the origin server.
26
What are the types of Network Delays?
* Processing Delay
* Queueing Delay
* Transmission Delay
* Propagation Delay
27
What is the Total Delay at a Router?
Sum of processing, queueing, transmission, and propagation delays.
28
What is the Domain Name System (DNS)?
An application layer protocol used to obtain IP addresses from corresponding server names.
29
What is the purpose of local DNS servers?
Cache name-IP mappings to improve response time for DNS requests.
30
What is a Resource Record (RR) in DNS?
A 4-tuple consisting of (name, value, type, ttl).
31
What are the two types of DNS queries?
* Recursive query
* Iterative query
32
What does a recursive query do?
Puts the burden of name resolution on the contacted name server.
33
What does an iterative query do?
Puts the majority of the load on the local DNS server.
34
What is the purpose of a DNS query?
To obtain the IP address associated with a hostname
35
What does an NS record do in the DNS hierarchy?
Pushes the query along to the next level of the DNS hierarchy
36
What is a CNAME record?
A record that allows multiple aliases to point to one canonical hostname
37
What is load distribution in DNS?
Using multiple IP addresses corresponding to the same host alias name to distribute client requests
38
Fill in the blank: You register a domain name with a _______.
[DNS registrar]
39
What information do you provide when registering a domain name?
Names and IP addresses of authoritative name servers
40
What is the example provided for a new startup's DNS registration?
networkutopia.com
41
What does Peer-to-Peer (P2P) architecture lack?
An always-on central server
42
True or False: In P2P, the server imposes a minimum download time based on file size and speed.
True
43
What is the overall worst-case download time in a P2P setup?
max(F/N, F)
44
What is the BitTorrent protocol's chunk request strategy?
Rarest chunk first strategy
45
What is a DHT in the context of P2P?
Distributed Hash Table used for peer discovery
46
True or False: Peers in a DHT maintain knowledge of their successors.
True
47
What is the minimal functionality of the transport layer?
Breaks messages into segments and passes them to the network layer
48
What are Protocol Data Units (PDUs)?
Different parts of the message exchanged by each layer
49
What distinguishes UDP from TCP?
UDP is unreliable and unordered, while TCP is reliable and ordered
50
Fill in the blank: Demultiplexing in transport layer uses _______ to direct segments to correct sockets.
[port numbers]
51
What is the checksum used for in TCP/UDP?
To detect errors in transmitted segments
52
What is the Two Generals paradox about?
The uncertainty in coordinating simultaneous actions between two parties
53
What does the Stop and Wait Protocol fail to recover?
Lost data
54
What does a NAK-free protocol achieve?
Simplifies the protocol by eliminating NAKs
55
What is the purpose of a timeout in reliable data transfer?
To retransmit packets that are not acknowledged
56
What is the difference between Go-Back-N and Selective Repeat protocols?
Go-Back-N retransmits all packets after a lost packet, while Selective Repeat only resends the lost packet
57
What is the main feature of TCP regarding network congestion?
Reduces window size if congestion is detected
58
What does the network layer deliver from source to destination?
Datagrams
59
What is the role of forwarding tables in the network layer?
To determine where to pass datagrams
60
What constitutes the data plane of the network layer?
Forwarding datagrams based on forwarding tables
61
What is routing in the context of the network layer?
Filling forwarding tables using pathfinding algorithms
62
What is the primary function of routers in the network layer?
Routers store and forward datagrams using a forwarding table.
63
What is the difference between the data plane and the control plane in the network layer?
The data plane forwards datagrams according to forwarding tables, while the control plane is responsible for filling those tables through routing.
64
What are the most important fields in an IP Datagram format?
* Source IP address
* Destination IP address
* Upper layer protocol
* TTL
65
What is the purpose of the DHCP protocol?
To dynamically allocate IP addresses to clients.
66
What is the process of IP address allocation via DHCP?
* Host broadcasts DHCP discover message
* DHCP server responds with DHCP offer message
* Host requests IP address with DHCP request message
* DHCP server sends back the address with DHCP ack message
67
What is the destination IP address used by a client when broadcasting a DHCP discover message?
255.255.255.255
68
What is an interface in the context of IP address allocation?
A connection between a host/router and a physical link.
69
What defines a subnet?
A set of interfaces that can reach each other without passing through a router.
70
What are the two parts of an IP address hierarchy?
* Network ID
* Host ID
71
What was the purpose of classful IP addressing?
To divide IP addresses into classes with fixed lengths for Network and Host IDs.
72
What does CIDR stand for and what is its purpose?
Classless Inter-Domain Routing; it allows for more flexible IP address allocation.
73
What is a subnet mask?
A binary number that selects only the network ID under bitwise AND.
74
What is NAT and what is its main function?
Network Address Translation; it maps local networks to the wider internet.
75
What problem does NAT attempt to solve when multiple devices request from the same destination?
It uses port numbers to ensure unique identification for requests.
76
What is the time complexity of Dijkstra’s algorithm?
O(E + N log N) worst case for N nodes and E edges.
77
What is the main characteristic of Link State Algorithms?
Each router maintains the complete network topology and link costs.
78
What is the Distance Vector Algorithm's approach to routing?
It focuses on routing from the current router by assuming neighbors have found best paths.
79
What is OSPF and where is it used?
Open Shortest Path First; used for intra-AS routing.
80
What is BGP and what is its significance?
Border Gateway Protocol; it is the de-facto inter-AS routing protocol.
81
What is the primary responsibility of the link layer?
To transfer frames from one node to a physically adjacent node over a link.
82
What are the three main services provided by the link layer?
* Framing
* Addressing
* Medium Access
83
What is a MAC address?
A unique 48-bit address assigned to each device, allowing it to be identified on a network.
84
How does the link layer perform IP to MAC translation?
Using the Address Resolution Protocol (ARP) to map IP addresses to MAC addresses.
85
What is the purpose of the ARP table?
To store IP to MAC address mappings.
86
What happens when an IP datagram needs to be sent to another subnet?
The source node creates a link-layer frame with the next-hop router's MAC address as the destination.
87
What does a node do when it creates an IP datagram?
Creates an IP datagram with IP source A and IP destination B
88
What is the role of a switch in a network?
Forwards the frame to the appropriate outgoing interface based on the destination MAC address
89
True or False: A switch operates at layer 1 of the OSI model.
False
90
What distinguishes a switch from a hub?
A switch forwards frames based on MAC addresses, while a hub broadcasts to all outgoing links
91
What does a forwarding table in a switch map?
Maps MAC addresses to outgoing interfaces
92
What happens when a frame arrives at a switch with an unknown destination MAC?
The frame is broadcast to all interfaces
93
Fill in the blank: The types of connectors include T-type, hub/repeater, switch or bridge, and ______.
router
94
What are the two types of links mentioned?
* Point to Point
* Broadcast
95
What is the purpose of multiple access protocols?
To determine which node can transmit on a shared channel and when
96
What is an ideal multiple access protocol characterized by?
* Fully decentralized
* Simple and inexpensive to implement
* R/M bps for each node
97
What type of access protocol divides the channel into smaller sub channels?
Channel Partitioning
98
Describe TDMA.
Accesses channels in rounds with each node having a set length slot
99
What is the limitation of FDMA?
Always limited to R/N bits for N users, even if others are idle
100
What are the assumptions of Slotted ALOHA?
* All frames are of equal size
* Time is divided into slots
* Nodes transmit at the beginning of a time slot
101
What happens if a collision occurs in Slotted ALOHA?
The node retransmits the frame in the next slot with a probability of P
102
True or False: Pure ALOHA uses time slots.
False
103
What is the operation of Simple CSMA?
Listen before you transmit; if idle, send the entire frame
104
What does CSMA-CD stand for?
Carrier Sense Multiple Access with Collision Detection
105
What is the purpose of the jam signal in CSMA/CD?
Notifies all devices of a collision
106
What is the backoff strategy used in CSMA/CD after a collision?
Binary exponential backoff
107
What is the polling protocol?
A master node invites other devices to transmit in turn
108
What is a disadvantage of the polling protocol?
Single point of failure due to the master node
109
What is the function of token passing in a network?
The device holding the token can send frames while passing it to the next device
110
What are the disadvantages of token passing?
* Single point of failure
* Token overhead
* Latency issues
