Introduction to Computer Networks CSNETWK

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Questions and Answers

What are the three separate protocols involved in the store-and-forward method of sending, storing, and retrieving electronic messages in email applications?

POP (correct)

IMAP (correct)

HTTP

SMTP (correct)

What does DNS stand for?

Domain Name System

DNS Root Servers are responsible for managing top-level country domains.

False

DNS Caching improves response time by immediately returning a cached mapping in response to a query. Cached entries may be out-of-date and expire after some time known as ____.

TTL Signup and view all the answers

Define Network Protocols

Network Protocols govern all communication activities on the Internet and define the format, order of messages sent and received among network entities. Signup and view all the answers

What is a key advantage of using a layered approach in network architecture?

Reduces design complexity of a network Signup and view all the answers

The OSI model defines seven layers for network architecture.

True Signup and view all the answers

Encapsulation refers to packaging data into a suitable form to be transmitted over the network. Data has _______ information added to it as it passes through layers.

protocol Signup and view all the answers

Match the following layers with their descriptions:

Physical Layer = Transmission of bit patterns over a communications channel Application Layer = Contains protocols for user-oriented applications Transport Layer = Responsible for end-to-end connections between hosts Data Link Layer = Handles errors from physical transmission media Signup and view all the answers

What is the main function of Error Detection and Correction (EDC) bits?

Detect error in transmitted data Signup and view all the answers

Which type of bit parity is used to detect and correct single bit errors in a matrix?

Two-dimensional bit parity Signup and view all the answers

Ethernet CSMA/CD uses collision detection to reduce wasted channel time.

True Signup and view all the answers

CSMA stands for Carrier Sense Multiple ________.

Access Signup and view all the answers

Match the MAC Protocols with their descriptions:

TDMA = Time division multiple access FDMA = Frequency division multiple access CSMA/CD = Carrier Sense Multiple Access with Collision Detection Slotted ALOHA = Transmission with time slots for collision detection Signup and view all the answers

What are the components of the Internet?

All of the above Signup and view all the answers

Protocols such as HTTP, TCP, and IP control sending and receiving of messages on the Internet.

True Signup and view all the answers

What do RFC and IETF stand for in the context of Internet standards?

RFC stands for Request for Comments and IETF stands for Internet Engineering Task Force Signup and view all the answers

___ governs all communication activities in the Internet.

Protocol Signup and view all the answers

Match the following access network technologies with their descriptions:

Cable Based Access = Uses Frequency Division Multiplexing (FDM) Digital Subscriber Line (DSL) = Data over DSL phone line goes to internet, voice over DSL phone line goes to telephone net Wireless = Shared wireless access network connects end system to router via base station Enterprise Network = Used by companies, universities, etc., mix of wired, wireless link technologies Signup and view all the answers

What function does a host perform in network communication?

All of the above Signup and view all the answers

What is the main function of the Network (IP) Layer?

supervises host-to-host packet delivery Signup and view all the answers

What do routers do to IP datagrams passing through them?

Examine header fields Signup and view all the answers

Routing involves determining the ______ taken by packets from source to destination.

route Signup and view all the answers

Dynamic routing protocols continuously exchange network status updates with each other.

True Signup and view all the answers

Match the following network routing protocols with their descriptions:

Distance-Vector = Identifies distance and vector to reach a network Link-State = Creates a complete topology view of the network Interior Gateway Routing Protocol (IGRP) = Routing update mechanism with broadcast and multicast support Signup and view all the answers

What is the primary function of an Ethernet Switch?

store and forward Ethernet frames Signup and view all the answers

Ethernet switches require manual configuration before they can be used.

False Signup and view all the answers

Which of the following is a feature of using an Ethernet switch?

Full duplex communication Signup and view all the answers

What is the full form of DNS?

Domain Name System Signup and view all the answers

Which transport protocol is reliable and byte stream-oriented?

TCP Signup and view all the answers

UDP is a connection-oriented protocol.

False Signup and view all the answers

UDP segments may be __________ or delivered out-of-order to the application.

lost Signup and view all the answers

Match the following network layer functions with their descriptions:

Forwarding = Move packets from a router's input link to appropriate output link Routing = Determine the route taken by packets from source to destination Signup and view all the answers

What is the role of a router in a network?

To forward packets from one network to another based on routing decisions. Signup and view all the answers

What does each entry in a switch table typically contain?

MAC address of host, interface to reach host, time stamp Signup and view all the answers

Where does a switch learn the location of the sender when a frame is received?

Incoming LAN segment Signup and view all the answers

Switches usually learn which hosts can be reached through which interfaces.

True Signup and view all the answers

Switches are usually present in small _________ networks.

institutional Signup and view all the answers

Match the device to its description:

Router = Network-layer device Switch = Link-layer device NIC = Network Interface Card Signup and view all the answers

What does a Subnet Mask identify in an IPv4 address?

the network/host portion Signup and view all the answers

Which of the following IPv4 addresses is considered a Broadcast Address?

11111111 Signup and view all the answers

Variable Length Subnet Masking is the process of obtaining additional bits from the ____________ of the host portion.

leftmost or most significant bits Signup and view all the answers

Match the following IPv4 communication types with their descriptions:

Unicast = one to one communication Broadcast = one to all Multicast = one to a selected group Signup and view all the answers

DHCP allows a host to permanently obtain its IP address from the network server when it joins the network.

False Signup and view all the answers

What are the major limitations of IPv4?

IP address depletion, internet routing table expansion, lack of end-to-end connectivity Signup and view all the answers

Which of the following are examples of Private IPv4 Addresses?

All of the above Signup and view all the answers

What is the address space size in IPv6?

128-bit Signup and view all the answers

ICMP is a messaging protocol used by hosts and routers to communicate hardware-level information.

False Signup and view all the answers

Which method does 802.11 use to avoid collisions?

CSMA/CA Signup and view all the answers

Bluetooth operates in the 2.4-2.5 GHz ISM radio band.

True Signup and view all the answers

What does CSMA/CA stand for in the context of MAC Protocol?

Carrier Sense Multiple Access with Collision Avoidance Signup and view all the answers

In Cellular Networks, neighboring cells operate on different frequencies to avoid ___________.

interference Signup and view all the answers

Match the following generations of mobile networks with their characteristics:

1G = Analog voice with limited capacity 2G = Increased voice capacity and initial TDMA technologies 3G = Evolved for data with high-speed internet access 4G LTE = Delivers more data capacity with faster browsing 5G = Goal of 10x peak bitrate, 10x lower latency, 100x traffic capacity over 4G Signup and view all the answers

Study Notes

Introduction to Computer Networks

Components of the Internet:
- Billions of connected computing devices (hosts)
- Packet switches (routers, switches) forward packets (chunks of data)
- Communication links transmit data

The Internet

A network of networks through interconnected ISPs
Protocols control sending and receiving of messages
Examples: HTTP (Web), streaming video, Skype, TCP, IP, WiFi, 4G, Ethernet
Standards are set by RFC (Request for Comments) and IETF (Internet Engineering Task Force)
Infrastructure that provides services to applications
- Provides programming interface to distributed applications
- Offers service options, analogous to postal service

Internet Structure

Network Edge: hosts (clients and servers)
Access Networks, Physical Media: wired, wireless communication links
Network Core: interconnected routers, network of networks

Access Networks

Cable Based Access: uses Frequency Division Multiplexing (FDM)
Digital Subscriber Line (DSL): uses existing telephone line to central office DSLAM
Wireless:
- Shared wireless access network connects end system to router via base station (access point)
- Wireless Local Area Networks (WLAN)
- Wide-Area Cellular Access Networks

Host

Sends packets of data
Sending function:
- Takes application message
- Breaks into smaller chunks (packets) of length L bits
- Transmits packet into access network at transmission rate R

Network Core

Mesh of interconnected routers
Packet-switching:
- Hosts break application-layer messages into packets
- Forward packets from one router to the next across links on path from source to destination
- Each packet transmitted at full link capacity
Functions:
- Forwarding: local action, moves arriving packets from router's input link to appropriate router output link
- Routing: global action, determines source-destination paths taken by packets

Circuit Switching

End-end resources allocated to, reserved for "call" between source and destination
Methodologies include FDM and Time Division Multiplexing (TDM)

Internet Standard

Tested specification that is useful to and adhered to by those who work with the internet
Formalized regulation that must be followed

Layered Network Design

Protocols govern all communication activities on the internet
Define the format order of messages sent and received among network entities, and actions taken on message transmission and receipt
Formal specification that defines how devices are to behave or communicate with each other

OSI Architecture

Provides detailed set of standards for describing a network
Framework for development of network protocol standards
Defines and codifies the concept of layered network architecture
Layers:
- Application (7)
- Presentation (6)
- Session (5)
- Transport (4)
- Network (3)
- Data Link (2)
- Physical (1)

TCP/IP Suite

Transmission Control Protocol/Internet Protocol
Layers:
- Application
- Transport
- Internet
- Network Interface

Encapsulation

Packaging data into a suitable form to be transmitted over the network
Data has protocol information added to it as it is passed down through the OSI or TCP/IP layers

Network Applications

Client-Server Model
Peer-to-Peer Architecture
Process Communicating
Sockets
Addressing Processes

Web and HTTP

HTTP: Hypertext Transfer Protocol
Uses web address/URL as a reference to a web server
Uses TCP
HTTP messages: request, response
HTTP Cookies

Web Caching

Goal: satisfy client requests without involving origin server
User configures browser to point to a (local) Web cache
Browser sends all HTTP requests to cache

Email Application Protocols

SMTP (Simple Mail Transfer Protocol): sending
POP (Post Office Protocol): retrieving
IMAP (Internet Message Access Protocol): retrieving### DNS Security and Management
DNSSEC provides security features such as authentication and message integrity.
ICANN (Internet Corporation for Assigned Names and Numbers) manages the root DNS domain.

Domain Name System Hierarchy

Top-Level Domain (TLD) Servers are responsible for managing top-level domains such as .com, .org, .net, .edu, .aero, .jobs, .museums, and country domains like .cn, .uk, .fr.
Network Solutions is the authoritative registry for .com and .net TLDs.
Educause is the authoritative registry for .edu TLD.

DNS Server Types

Authoritative DNS Servers: organizations' own DNS servers, providing authoritative hostname to IP mappings for their named hosts.
Local DNS Name Servers: return replies from local cache or forward requests to the DNS hierarchy for resolution.
Each ISP has a local DNS name server.

DNS Query Process

Iterated Query

Contacted server replies with the name of the server to contact.
"I don't know this name, but ask this server."

Recursive Query

Puts the burden of name resolution on the contacted name server.
Heavy load at upper levels of the hierarchy.

DNS Caching

Once a name server learns a mapping, it caches the mapping and immediately returns a cached mapping in response to a query.
Caching improves response time.
Cache entries timeout (disappear) after some time (TTL).
TLD servers are typically cached in local name servers.
Cached entries may be out-of-date if a named host changes its IP address.

DNS Resource Records

Name servers store Resource Records (RRs).
Format: [name, value, type, TL].
Type=A: name is hostname, value is IP address.
Type=NS: name is domain.### DNS and Application Layer Protocols
DNS (Domain Name System) is a protocol used for translating domain names to IP addresses
- Types of DNS records:
  - A record: maps hostname to IP address
  - NS record: maps domain name to name server
  - MX record: maps domain name to mail server
  - CNAME record: maps alias to canonical name
Authoritative name server: a DNS server that has the authority to resolve a domain name
Types of DNS queries:
- Recursive query: a DNS client asks a DNS server to resolve a domain name
- Iterative query: a DNS client asks a DNS server to resolve a domain name, and the server recursively queries other servers
DNS message format:
- Header: contains flags and question count
- Question section: contains the domain name being queried
- Answer section: contains the resolved IP address

DHCP and FTP

DHCP (Dynamic Host Configuration Protocol):
- Assigns IP addresses to clients dynamically
- Leases IP addresses for a certain period
- Clients request IP address renewal when lease is about to expire
DHCP message format:
- DHCPDISCOVER: client broadcasts to find DHCP server
- DHCPOFFER: server responds with IP address offer
- DHCPREQUEST: client requests IP address
- DHCPACK: server confirms IP address allocation

P2P Network Applications

P2P (Peer-to-Peer) network: allows peers to act as both clients and servers
Characteristics:
- Decentralized: no always-on server
- Self-scalability: new peers bring new service capacity
- Intermitently connected peers with changing IP addresses
Examples:
- P2P file sharing (BitTorrent)
- Video streaming (KanKan)

Video Streaming and CDNs

Video streaming challenges:
- Scalability: handling high traffic and bandwidth demands
- Heterogeneity: different devices and bandwidths
Distributed, application-level infrastructure:
- Content Delivery Networks (CDNs)
- Cache servers at edge of network
- Reduce latency and improve QoS

Socket Programming

Socket: endpoint for communication between two devices
Socket types:
- Connection-oriented socket
- Connectionless socket
Socket programming:
- Create socket and bind to port number
- Listen for incoming connections
- Accept incoming connections
- Send and receive data

Transport Services and Protocols

Transport services:
- Connection-oriented: guaranteed delivery
- Connectionless: best-effort delivery
- Reliable: error-free delivery
- Unreliable: error-tolerant delivery
Transport protocols:
- TCP (Transmission Control Protocol)
- UDP (User Datagram Protocol)

Multiplexing and Demultiplexing

Multiplexing: combining multiple data streams into one stream
Demultiplexing: separating combined stream into individual streams
Types of multiplexing:
- Frequency Division Multiplexing (FDM)
- Time Division Multiplexing (TDM)

TCP and UDP

TCP (Transmission Control Protocol):
- Connection-oriented
- Reliable, in-order delivery
- Congestion control and flow control
- Three-way handshake for connection establishment
UDP (User Datagram Protocol):
- Connectionless
- Best-effort delivery
- No congestion control or flow control
- No handshaking for connection establishment

Routing and Forwarding

Network layer functions:
- Forwarding: moving packets from input link to output link
- Routing: determining route taken by packets from source to destination
Routers:
- Computer with CPU, OS, and memory
- Examines header fields in IP datagrams
- Forwards datagrams to output ports

IPv4 Addressing

IPv4 address:
- 32-bit identifier associated with each host or router interface
- Divided into network and host portions
- Uses dotted-decimal notation
IPv4 datagram format:
- Header contains source and destination IP addresses
- Payload contains data being transmitted

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Description

Learn about the components of the internet, including hosts, packet switches, and communication links, and understand how they interact to form a network of networks.