Networking Concepts Quiz

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Questions and Answers

What type of device is a router classified as at the network layer?

Ethernet switch

Packet switch (correct)

Hub

Bridge

Which of the following statements about hosts in a network is true?

Hosts can forward IP datagrams.

Hosts usually connect multiple interfaces at a time.

Hosts operate at the data link layer.

Hosts typically use a single network interface at a time. (correct)

What is the primary function of routers in a network?

To operate at the application layer

To provide wireless access to devices

To establish circuit-switching connections

To forward datagrams between networks (correct)

In IP routing, what is the role of the routing table?

To store the paths and next router for datagrams Signup and view all the answers

What type of switch operates at the data link layer?

Ethernet switch Signup and view all the answers

What is the main purpose of transport protocols in the Internet?

To send data between application processes on source and destination hosts Signup and view all the answers

Which of the following statements correctly describes Transmission Control Protocol (TCP)?

It includes features for error control and flow control. Signup and view all the answers

How is a transport protocol identified in communications?

By an 8-bit protocol number in the IP header Signup and view all the answers

What role do ports play in Internet communications?

They identify application processes on a host. Signup and view all the answers

Which of the following is NOT a feature of the Transmission Control Protocol?

Streamlined design for minimal data overhead Signup and view all the answers

What is the primary role of a WAN?

To interconnect LANs over a larger distance Signup and view all the answers

What technology is commonly used to connect LANs of similar types?

Bridges Signup and view all the answers

Which layer do WANs typically operate at?

Layer 1 and 2 Signup and view all the answers

What is the main purpose of internetworking?

To allow independent communication between different networks Signup and view all the answers

What type of connection does a WAN's point-to-point link often utilize?

Network-based packet or circuit switching Signup and view all the answers

Which of the following best describes an internetworking protocol?

It facilitates data delivery across different types of networks Signup and view all the answers

Which statement is true regarding LANs?

They can use routers to connect to WANs Signup and view all the answers

Which component is essential for interconnecting a WAN to a LAN?

A device that supports both LAN and WAN technologies Signup and view all the answers

Which range of port numbers is classified as well-known ports?

0–1023 Signup and view all the answers

For web browsing, which transport protocol is most commonly utilized?

TCP Signup and view all the answers

What system manages port assignments on a host?

Operating System Signup and view all the answers

Which of the following is a registered port number?

3306 Signup and view all the answers

What range of port numbers do clients typically use for dynamic ports?

49152–65535 Signup and view all the answers

Which of the following applications would NOT commonly use TCP for its operation?

DNS resolution Signup and view all the answers

Which port number is assigned to SSH by default?

22 Signup and view all the answers

What is the highest number in the range for well-known ports?

1023 Signup and view all the answers

What is the primary purpose of the IP Datagram in Internet networking?

To encapsulate data for transmission over a network. Signup and view all the answers

Which IP address range is classified as a private IP range?

192.168.0.0—192.168.255.255 Signup and view all the answers

What does the source address represent in an IP Datagram?

The address where the data originated from. Signup and view all the answers

What is a loopback address and its purpose?

An address used for local testing, primarily 127.0.0.1. Signup and view all the answers

What is indicated by the destination address in a directed broadcast?

A broadcast to all devices in a specific subnet. Signup and view all the answers

Which of the following subnet masks corresponds to a /24 notation?

255.255.255.0 Signup and view all the answers

In the context of network addressing, what is meant by a startup source address of 0.0.0.0?

It signifies that the device has not yet assigned itself an IP address. Signup and view all the answers

Which of the following defines a unicast communication?

Data sent from one sender to one receiver directly. Signup and view all the answers

What range do the address 172.16.0.0—172.31.255.255 fall under?

Private IP range. Signup and view all the answers

To which category does the IP address 255.255.255.255 belong?

Local broadcast address. Signup and view all the answers

What does the CWR flag in a TCP segment indicate?

Congestion Window Reduced Signup and view all the answers

During the TCP three-way handshake, what does the second segment sent by B contain?

Flags=SYN,ACK Signup and view all the answers

What is indicated by the SYN flag in a TCP segment?

Synchronized the sequence numbers Signup and view all the answers

Which of the following is NOT a purpose of TCP segment flags?

Initiate a secure connection Signup and view all the answers

Which control method is primarily used in TCP for error control?

Go-Back-N style Signup and view all the answers

What happens when the FIN flag is set in a TCP segment?

No more data will be sent from the sender Signup and view all the answers

What aspect of TCP affects the speed of data transfer?

Flow control techniques Signup and view all the answers

What is the function of the PSH flag in a TCP segment?

To prompt the receiver to push buffered data to the application Signup and view all the answers

What does the presence of lost segments indicate during data transfer in TCP?

Network is saturated and sender should reduce speed Signup and view all the answers

Which protocol is NOT related to the Application layer protocols mentioned?

IP Signup and view all the answers

Study Notes

Course Information

Course Number: CS461
Course Title: Computer Networks
Topic: Internet and Transport Protocols
Covered Topics: Internet, Internetworking, IP, IP Addresses, Internet Apps, TCP, Application

Course Content includes: Internetworking, The Internet Protocol, IP Addressing, Internet Applications, Transmission Control Protocol, Application Layer Protocols, LANs and WANs, and Connecting Multiple LANs and WANs
Various concepts and topics regarding Computer Networks are covered in CS461

LANs and WANs

LANs (Local Area Networks):
- Different types, topologies, and technologies.
- Operate at layers 1 and 2 (Physical and Data Link Layer) using switches and hubs.
- Connected by bridges
WANs (Wide Area Networks):
- Connect LANs over a large distance.
- Employ point-to-point links (e.g., ADSL, PDH) or networks (e.g., ATM, SDH, telephone) using packet or circuit switching.
- Devices connecting WAN to LAN need to support both technologies.
- Primarily operate at layers 1 and 2.

Connecting Multiple LANs and WANs

Organizations require various network technologies.
Aim: allow any computer to communicate with any other computer, regardless of their LAN/WAN connection.
Internetworking: connecting the many types of networks (LANs/WANs) together.
An internetworking protocol supports data delivery across different networks.
Example: Internet Protocol (IP)

Internetworking with Routers

Internetworking is accomplished using routers.
Routers connect two or more LANs or WANs.
Routers are packet switches that operate at the network layer.

The Internet Protocol (IP)

The core internetworking protocol for the Internet.
Implemented in hosts and routers.
Features:
- Datagram packet switching
- Connectionless
- Addressing
- Fragmentation-and-reassembly
IP version 4 (IPv4) is most prevalent; IPv6 is available.
IP does not provide:
- Connection control
- Error control
- Flow control (TCP)
- Status reporting (ICMP)
- Priority, QoS (DiffServ, IntServ)
- Security (IPsec)

Terminology

Routers: Nodes connecting networks (LANs/WANs); operate at the network layer.
Subnetworks: Individual networks (LANs and WANs).
Internetworking: Connects two or more networks using routers, creating an internetwork/internet.
The Internet: A global internetwork using IP.
Routing: Locating a path from source to destination across a network.
Forwarding: Moving data along a network path.
Packet Switch: A generic device performing switching in a packet switching network; routers are packet switches at the network layer.
Circuit Switch: A generic device performing circuit switching in a circuit switching network
Ethernet switch: An IEEE 802.3 switch (Ethernet, Fast Ethernet, or Gigabit Ethernet) that operates at the data link layer.

IP Datagram

Variable-length header and variable-length data.
Header (20 Bytes): Required fields and optional fields (may reach 60 bytes).
Data: Multiple of 8 bits. Max size: 65,536 bytes.
Field details include Version, Header Length, DiffServ/ECN, Identification, Time to Live, Protocol, Flags, Total Length, Fragment Offset, Header Checksum, Source IP Address, Destination IP Address, Options, Padding.

IP Datagram Fields

Version (4 bits): Current value = 4 (IPv4)
Header Length (4 bits): Measured in 4 byte words.
DiffServ (6 bits): Used for quality of service.
ECN (2 bits): Used for congestion notification.
Total Length (16 bits): Length of the entire datagram (including the header) measured in bytes.
Identification (16 bits): Sequence number for datagrams.
Flags (3 bits): Used for fragmentation and reassembly.
Fragment Offset (13 bits): Information about fragmented packets.
Time To Live (8 bits): Datagram lifetime.
Protocol (8 bits): Identifies the next higher layer protocol.
Header Checksum (16 bits): Error-detecting code.
Source and Destination Addresses (32 bits each): IP addresses of source and destination hosts.
Options: Variable-length fields.
Padding: Ensures datagram length is a multiple of 4 bytes.
Data: Variable length containing data to be transmitted.

IP Routing and Forwarding

Routing Tables: Store destination addresses and next node. Created manually or by routing protocols.
Routing Protocols: Collect network information, calculate least cost paths, and update routing tables. Adaptive protocols (OSPF, RIP, EIGRP, BGP).
Forwarding: Routers relay IP datagrams from the source to the destination host, based on destination addresses in routing tables.

Other Features

IP includes:
- Fragmentation and reassembly (fragmentation on source and reassembly on destination).
- Time to Live (TTL).
- ICMP (error reporting, ping).
- ARP (mapping IP addresses to Ethernet addresses).
- IPv6
- Multicasting
- Quality of Service (DiffServ)
- Mobility (Mobile IP)
- Security (IPsec)

IPv4 Addresses

32 bits long
Split into network and host portions
Network portion: identifies the subnet.
Host portion: identifies the specific device (host/router) within that subnet.
All subnets have unique network portions.
Devices in the same subnet have the same network portion but different host portions.
Classful, subnet, and classless addressing schemes (focus on classless addressing)
Why split? Allows hierarchical addressing, making routing in the Internet scalable.

Representing IPv4 Addresses

Written in dotted decimal notation (e.g., 192.168.1.1).
Each part represents a byte.

Classless IP Addressing

Subnet masks or address masks identify the split between network and host portion in an IP address.
32 bits long
Bit 1 in the mask indicates network portion; Bit 0 indicates host portion.
Represented in dotted decimal form or shortened form (counting the number of 1 bits from left).

Special Case IP Addresses

Network Address: All bits in the host portion are 0 (identifies a subnet).
Directed Broadcast Address: All bits in the host portion are 1 (sent to all hosts on a specific subnet).
Local Broadcast Address: Identifies all hosts on the current subnet.
Loopback Address: Identifies the current host (e.g., 127.0.0.1, also called localhost).
Start-up Source Address: Identifies a host that does not yet have an assigned address (all bits are 0).
Selected Addresses: Reserved for private networks (not connected to the Internet; behind NAT). Ranges include 10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255, 192.168.0.0-192.168.255.255

Obtaining an IP Address

IANA (Internet Assigned Numbers Authority) manages IP address assignment.
IANA delegates IP network ranges to regional and national authorities.
Organizations obtain addresses from national/local registries.
Organizations can freely assign addresses within their allocated block.
Manual IP configuration is possible, but automatic configuration via protocols like DHCP is more common.

Internet Applications

Most follow a client/server model.
Server waits for client to initiate communication.
Client initiates communication. Data can flow in both directions.
Examples: web browsers, email clients, instant messaging clients, and various other applications.

Issues with Client/Server Applications

How to simplify application programming without needing in-depth communication details?
Employing transport protocols (e.g., TCP and UDP) to implement common functions across applications.
Facilitating communication between applications written in different languages and operating systems using common APIs like Sockets.
Distinguishing various applications residing on the same computer utilizing port numbers.

Transport Protocols

Transfer data between application processes at different hosts
End-to-end communications
Transmission Control Protocol (TCP):
- Widely used, connection-oriented, error control, flow control, and congestion control.
- Connection-oriented: Establishes a connection before data transfer.
- Stream-oriented: Treats data as a continuous stream of bytes; uses sequence numbers.
- Full duplex: Data can flow in both directions.
- Flow and error control: Go-Back-N style.
User Datagram Protocol (UDP): Older protocol, connectionless
- Domain-specific protocols
Other transport protocols: SCTP, DCCP

TCP Segment

Header (20 bytes): Includes source and destination ports, sequence numbers, acknowledgment numbers, window size (flow control), checksum (for error checking), and urgent pointer (for critical data).
Optional fields and padding
Fields detailed as follows: Length, Reserved, Flags, Advertised Window, Checksum, Urgent Pointer, Options and padding

TCP Segment Fields

Source/Destination ports Sequence/Acknowledgement numbers Header Length Window: flow control Checksum: error checking Urgent pointer: critical data Options: features like maximum segment size and window scaling

TCP Segment Flags

CWR: Congestion window reduced
ECE: Explicit congestion notification echo
URG: Urgent data (use urgent pointer field)
ACK: Acknowledgement (use ACK field)
PSH: Push function
RST: Reset connection
SYN: Synchronize sequence numbers
FIN: No more data from sender

TCP Connection Establishment (3-way handshake)

Initiator selects Initial Sequence Number (ISNA).
B acknowledges ISNA and selects its own Initial Sequence Number (ISNB); also includes acknowledgement(ACK).
After 2 way handshake, data transfer can start; optionally the 3rd segment can contain data.

TCP Data Transfer

Segments hold varying amounts of data.
ACK flags used for acknowledgement. Piggybacking of ACK are common.
Speed depends on flow control (sliding window), error control (Go-Back-N), and congestion control (sender slowing down during congestion).

Application Layer Protocols

Various protocols support different applications.
Examples: HTTP, FTP, SMTP, SSH, Telnet, BitTorrent, SIP, IMAP, RDP, SMB.
Protocols for network operation: DNS, DHCP, BOOTP, NTP, SNMP.

Port Numbers

Ports are 16-bit whole numbers used to identify applications on a host
Source/destination port number is included in transport layer header
Well-known ports (0-1023): Commonly used by server applications: e.g., http = 80, https = 443, ftp = 20/21, smtp = 25, dns = 53, ssh = 22, dhcp = 67/68.
Registered ports (1024-49151): Reserved for specific servers by convention
Dynamic ports (49152-65535): Assigned dynamically to client applications by the OS.

Additional Topics

Unicast
Directed Broadcast
Local Broadcast
Startup Source Address

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Test your knowledge on essential networking concepts, including routers, transport protocols, and the role of WANs. This quiz covers various aspects of network layers, internetworking protocols, and their functionalities within a networked environment.