Summer exam Networks Flashcards
(150 cards)
1
Q
What are the five main components of a data communication system?
A
Sender, Receiver, Message, Transmission Medium, and Protocol.
2
Q
What is a computer network?
A
A system connecting two or more autonomous computers for data exchange via transmission media.
3
Q
List one major advantage and one disadvantage of computer networks.
A
Advantage: Resource sharing. Disadvantage: Security risks like data theft.
4
Q
What are the three modes of data flow?
A
Simplex, Half-duplex, and Full-duplex.
5
Q
What is the difference between point-to-point and multipoint connection?
A
Point-to-point is a dedicated link between two devices; multipoint shares one link among multiple devices.
6
Q
Define network topology.
A
The physical and logical layout of a network, describing how devices are connected.
7
Q
List four types of network topologies.
A
Bus, Ring, Star, and Mesh topologies.
8
Q
Which network topology is most commonly used in modern installations?
A
Star topology.
9
Q
What are PAN, LAN, MAN, and WAN?
A
Types of networks based on scale: Personal Area Network, Local Area Network, Metropolitan Area Network, Wide Area Network.
10
Q
Which topology offers the highest fault tolerance and redundancy?
A
Mesh topology.
11
Q
Give one example of a PAN device.
A
Bluetooth-enabled mouse or wireless printer.
12
Q
What is internetworking?
A
Connecting multiple networks together to form a larger network like the Internet.
13
Q
What are packet switches and what do they do?
A
Devices like routers and switches that forward data packets in a network.
14
Q
Name three real-world applications/devices that use Internet connectivity.
A
Internet refrigerator, IP picture frame, Amazon Echo.
15
Q
Which communication mode allows simultaneous transmission and reception?
A
Full-duplex mode.
16
Q
What are protocols in networking?
A
Rules followed in network communication systems, such as HTTP, FTP, SSL, etc.
17
Q
What are the key elements of a protocol?
A
Syntax, semantics, and timing.
18
Q
Why is a standardized protocol important?
A
To promote interoperability among different vendor equipment.
19
Q
What is the purpose of layering in network architecture?
A
To manage complexity and allow abstraction and modular design of network systems.
20
Q
Name the seven layers of the OSI model.
A
Application, Presentation, Session, Transport, Network, Data Link, Physical.
21
Q
Which OSI layer is responsible for reliable process-to-process delivery?
A
Transport Layer.
22
Q
What is the main function of the network layer in the OSI model?
A
Routing and logical addressing for packet delivery from source to destination.
23
Q
What is the difference between the OSI and TCP/IP model?
A
OSI has 7 layers; TCP/IP has 5 layers and is the de facto standard used on the Internet.
24
Q
Which TCP/IP layer corresponds to the physical transmission of bits?
A
Physical layer.
25
Which layer in the TCP/IP model is responsible for routing datagrams?
Network (Internet) layer.
26
What is encapsulation in TCP/IP?
The process of wrapping data with protocol headers at each layer of the TCP/IP stack.
27
Name four types of addressing in TCP/IP.
Physical, logical, port, and specific addressing.
28
Which TCP/IP layer is responsible for process-to-process delivery?
Transport layer.
29
What is the role of the data link layer in OSI?
Framing, physical addressing, error detection/correction, and flow control.
30
Which OSI layer handles formatting, translation, and encryption?
Presentation layer.
31
What is the main goal of switching networks?
To enable long-distance transmission through switched nodes by routing data from node to node.
32
What are the two main types of switching technologies?
Circuit-switching and Packet-switching.
33
What is a key characteristic of circuit switching?
A dedicated communication path is established and reserved for the entire call duration.
34
List the three steps in circuit switching communication.
Connection establishment, data transfer, and connection termination.
35
Why is circuit switching inefficient for bursty data traffic?
Because channel capacity is reserved regardless of actual usage, leading to resource underutilization.
36
What is the basic concept of packet switching?
Data is divided into packets that are transmitted independently without dedicated resources.
37
What is the store-and-forward technique in packet switching?
Each node stores the entire packet, checks for errors, and then forwards it to the next node.
38
What are two types of packet switching approaches?
Virtual circuits and datagrams.
39
How is a virtual circuit similar to circuit switching?
A path is pre-established and followed by all packets, but resources are not dedicated.
40
What is the role of the Virtual Circuit Identifier (VCI)?
To identify virtual circuits at each switch, allowing packets to be forwarded correctly.
41
What are the three phases of virtual circuit setup?
Setup request, setup acknowledgement, and teardown.
42
What is the main difference between virtual circuits and datagrams?
Datagrams are sent independently without a predefined route; virtual circuits use a fixed path.
43
Why can datagram delivery be out of order?
Because each packet may take a different path and encounter different delays.
44
List three types of delays in a communication system.
Propagation delay, transmission delay, and processing delay.
45
What is the main advantage of packet switching over circuit switching?
More efficient use of network resources, especially for bursty traffic.
46
What is the main goal of internetworking?
To connect multiple heterogeneous networks (LANs and WANs) to form a unified network like the Internet.
47
What are the three main issues in internetworking?
Addressing scheme differences, maximum packet size, timeout, and routing techniques.
48
What is a repeater and what layer does it operate on?
A repeater is a physical layer device that regenerates weak signals to extend the LAN.
49
What is a hub and how is it different from a repeater?
A hub is a multi-port repeater used to create hierarchical networks and connects devices via RJ-45 ports.
50
What are the limitations of hubs?
They cannot link dissimilar segments, don't isolate/filter packets, and can't join segments with different access methods.
51
What function does a bridge perform?
It connects LAN segments and filters traffic based on MAC addresses by using a forwarding table.
52
What is bridge learning?
The process of dynamically building a forwarding table by observing source MAC addresses on incoming frames.
53
What is the filtering rule of a bridge?
Drop if src and dest are on same port; forward if on different ports; flood if dest not in table.
54
What layer does a router operate at?
A router operates at Layer 3 (Network Layer) and determines packet routing.
55
What is the difference between a bridge and a router?
A bridge connects segments within a LAN using MAC addresses; a router connects different LANs/WANs using IP addresses.
56
What is the role of a gateway in networking?
A gateway operates above Layer 3 and can analyze application-layer data, useful for firewalls and protocol conversion.
57
What does a backbone network do?
It connects several LANs together, allowing them to communicate, usually using a star topology.
58
Which device is used to extend the physical length of a LAN?
Repeater.
59
Which device can be used to connect two LANs with filtering capability?
Bridge.
60
Which device can be used to implement a firewall based on content?
Gateway.
61
What is the TCP/IP protocol suite?
A set of communication protocols used for the Internet, initially developed by ARPA in the 1970s.
62
What are the most important members of the TCP/IP protocol family?
TCP, UDP, and IP.
63
What type of service does IP provide?
Connectionless, unreliable delivery of datagrams.
64
What is encapsulation in networking?
The process of adding headers (and sometimes trailers) to data as it moves down the protocol stack.
65
What is the role of TCP?
Provides a reliable, connection-oriented transport service with error checking and packet reassembly.
66
How does TCP ensure reliability?
By retransmitting lost packets and assembling packets in the correct order at the receiver.
67
What is UDP and how does it differ from TCP?
UDP is a connectionless, unreliable transport protocol with no error control, faster and simpler than TCP.
68
What is the size of a port address in TCP/IP?
16 bits.
69
What is the minimum and maximum size of an IPv4 header?
Minimum is 20 bytes (5x4), maximum is 60 bytes (15x4).
70
What does the TTL field in an IP header do?
Limits packet lifetime by decrementing at each hop; if it reaches 0, the packet is discarded.
71
What is non-transparent fragmentation?
Fragments are not reassembled by intermediate routers; they are reassembled at the destination.
72
What does the M (More Fragments) flag indicate?
Whether there are more fragments after the current one; M=0 indicates last fragment.
73
What is the function of the 'Don't Fragment' (DF) bit in IP headers?
Prevents intermediate routers from fragmenting the packet.
74
What is the HLEN field in an IP header?
Header Length field in 32-bit words; minimum value is 5.
75
What is the format of an IP datagram?
It includes fields like version, HLEN, total length, ID, flags, fragment offset, TTL, protocol, source and destination IP, and options.
76
What is the length of an IPv4 address?
32 bits.
77
What does a subnet mask do?
It separates the network portion from the host portion in an IP address.
78
What are the five classes of IP addresses?
Class A, B, C (Unicast), D (Multicast), and E (Reserved).
79
What is the purpose of classful addressing?
To categorize IP addresses into predefined classes based on address size.
80
What address range is reserved for loopback addresses?
127.0.0.0 to 127.255.255.255.
81
What is the default network address?
0.0.0.0
82
What does the broadcast address 255.255.255.255 represent?
A broadcast to all machines on the local network.
83
What is the purpose of Network Address Translation (NAT)?
To map private IP addresses to public IPs for Internet access.
84
What is Static NAT?
Maps a single private IP address to a single public IP address (1-to-1).
85
What is Dynamic NAT?
Maps multiple private IPs to a pool of public IPs.
86
What is VLSM?
Variable-Length Subnet Masking allows subnets of different sizes in the same network.
87
Why is VLSM more efficient than traditional subnetting?
It removes class boundary restrictions and allows subnetting to any size.
88
What does NAT offer in terms of security?
Devices inside the local network are not directly visible to the outside world.
89
Which IP address class does 10.40.120.29 belong to?
Class A.
90
How does a NAT router modify packet headers?
It replaces the source IP and port with a public IP and port number, then restores them on reply.
91
What are the two parts of an IPv4 address?
A network number and a host number.
92
What does dotted decimal notation refer to?
It expresses a 32-bit IPv4 address in four octets separated by dots for human readability.
93
What is hierarchical addressing in IP?
An IP address includes a network number (assigned by a central authority) and a host number (assigned by local admin).
94
What does a subnet mask do?
It separates the network and host portions of an IP address.
95
Which IP address class is used for multicast?
Class D.
96
What does the IP address 127.0.0.1 represent?
Loopback address for local testing on a device.
97
Why is NAT (Network Address Translation) used?
To map private IP addresses to public IPs and conserve global IP address space.
98
What is Static NAT?
A one-to-one mapping between private and public IP addresses.
99
What is the primary benefit of using NAT?
It allows multiple devices to share a single public IP and improves security by hiding internal addresses.
100
Which communication mode allows simultaneous send and receive?
Full-duplex.
101
Which topology is the most expensive to implement?
Mesh topology.
102
How many layers are there in the OSI model?
Seven layers.
103
An IP address belongs to which OSI layer?
Network layer.
104
What is the minimum size of an IP header?
20 bytes.
105
What class does the IP address 179.36.25.29 belong to?
Class B.
106
What is the difference between forwarding and routing?
Forwarding is moving packets based on routing tables, while routing is building those tables by exchanging network information.
107
What is direct delivery in packet delivery?
When the destination is on the same physical network as the sender.
108
What is indirect delivery in packet delivery?
When the packet goes through routers to reach a destination on a different network.
109
What is the 'next-hop' method in forwarding?
A forwarding technique where only the address of the next hop is stored in the routing table.
110
What does a routing table contain?
Information that helps a router determine the best path to forward packets.
111
What are the advantages of static routing?
Easy to configure, no extra resources needed, and more secure.
112
What are the disadvantages of static routing?
Manual reconfiguration for network changes and poor scalability.
113
What is dynamic routing?
Routing where routers automatically share and update routing information and select the best path dynamically.
114
Name two intradomain routing protocols.
RIP and OSPF.
115
What is BGP used for?
Border Gateway Protocol (BGP) is used for inter-domain routing between autonomous systems.
116
What is an autonomous system (AS)?
A group of networks and routers under one administrative control.
117
How does dynamic routing handle topology changes?
It automatically updates routing tables and recalculates the best path.
118
What are some metrics used for path selection in routing?
Hop count, filtering, delay, bandwidth, and policies.
119
What is the role of a router in IP routing?
To forward packets based on destination IP addresses and routing tables.
120
What does forwarding depend on?
Forwarding depends on the information stored in routing tables and the destination IP address.
121
What are the two levels of addressing required for packet delivery?
Logical (IP) and physical (MAC) addresses.
122
What is the function of ARP?
It maps a logical IP address to its corresponding physical MAC address.
123
What does RARP do?
It maps a known physical address (MAC) to a logical address (IP), useful for diskless machines.
124
What is the purpose of DHCP?
To dynamically assign IP addresses to hosts when they join a network.
125
What service does TCP provide?
Connection-oriented, reliable, full-duplex, byte-stream service.
126
What are some reliability mechanisms in TCP?
Checksum, Positive Acknowledgement (ACK), Timeouts, Flow Control.
127
How does TCP establish a connection?
Using a three-way handshake with SYN, SYN-ACK, and ACK segments.
128
What is the purpose of RWND in TCP?
Receiver Window Size advertises how much data the destination can accept.
129
What does UDP provide?
Connectionless, unreliable, datagram service with minimal overhead.
130
What features does UDP add beyond IP?
Checksum and Port Numbers.
131
Why are port numbers needed in transport layer?
To uniquely identify processes at each end of a communication.
132
What are well-known port numbers?
Port numbers from 0 to 1023 assigned to commonly used services.
133
What does DNS do?
Maps hostnames to IP addresses and vice versa.
134
What are the key components of DNS architecture?
Root servers, TLD servers, and authoritative DNS servers.
135
What is the difference between recursive and iterative DNS queries?
Recursive: server resolves completely; Iterative: server refers client to next server.
136
What are the six main network security services?
Confidentiality, Integrity, Authentication, Nonrepudiation, Access Control, and Availability.
137
What is the main goal of cryptography in network security?
To ensure the confidentiality, integrity, and authenticity of messages.
138
In the security communication model, who are Alice, Bob, and Eve?
Alice and Bob are the communicating parties; Eve is the adversary trying to intercept or alter communication.
139
What is the purpose of symmetric key cryptography?
To use the same key for both encryption and decryption.
140
What is the purpose of public-key cryptography?
To use a public key for encryption and a private key for decryption, enhancing secure communication.
141
What is message integrity?
Ensuring the message has not been tampered with during transmission.
142
What is a digital signature used for?
To provide message integrity, authentication, and nonrepudiation.
143
What are the components of a digital signature system?
A private key for signing and a public key for verification.
144
What is the main purpose of SSL/TLS?
To secure communication over the Internet by providing encryption, integrity, and server authentication.
145
What is the SSL handshake?
A process where the server and client authenticate each other and agree on a session key.
146
What is HTTPS?
HTTP over TLS, which encrypts all HTTP traffic between browser and server.
147
What is SSL stripping?
An attack that downgrades a secure HTTPS connection to an insecure HTTP one.
148
What is HSTS and how does it help?
HTTP Strict Transport Security forces browsers to use HTTPS, preventing SSL stripping.
149
What are some issues with HSTS?
Vulnerability on the first visit and privacy risks from stored HSTS information.
150
How does a browser validate a server's certificate in HTTPS?
By checking it against trusted Certificate Authorities (CAs) and ensuring it hasn't been revoked.
