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What are the three separate protocols involved in the store-and-forward method of sending, storing, and retrieving electronic messages in email applications?
What are the three separate protocols involved in the store-and-forward method of sending, storing, and retrieving electronic messages in email applications?
What does DNS stand for?
What does DNS stand for?
Domain Name System
DNS Root Servers are responsible for managing top-level country domains.
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 Cached entries may be out-of-date and expire after some time known as ____.
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 Cached entries may be out-of-date and expire after some time known as ____.
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Define Network Protocols
Define Network Protocols
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What is a key advantage of using a layered approach in network architecture?
What is a key advantage of using a layered approach in network architecture?
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The OSI model defines seven layers for network architecture.
The OSI model defines seven layers for network architecture.
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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.
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.
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Match the following layers with their descriptions:
Match the following layers with their descriptions:
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What is the main function of Error Detection and Correction (EDC) bits?
What is the main function of Error Detection and Correction (EDC) bits?
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Which type of bit parity is used to detect and correct single bit errors in a matrix?
Which type of bit parity is used to detect and correct single bit errors in a matrix?
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Ethernet CSMA/CD uses collision detection to reduce wasted channel time.
Ethernet CSMA/CD uses collision detection to reduce wasted channel time.
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CSMA stands for Carrier Sense Multiple ________.
CSMA stands for Carrier Sense Multiple ________.
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Match the MAC Protocols with their descriptions:
Match the MAC Protocols with their descriptions:
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What are the components of the Internet?
What are the components of the Internet?
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Protocols such as HTTP, TCP, and IP control sending and receiving of messages on the Internet.
Protocols such as HTTP, TCP, and IP control sending and receiving of messages on the Internet.
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What do RFC and IETF stand for in the context of Internet standards?
What do RFC and IETF stand for in the context of Internet standards?
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___ governs all communication activities in the Internet.
___ governs all communication activities in the Internet.
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Match the following access network technologies with their descriptions:
Match the following access network technologies with their descriptions:
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What function does a host perform in network communication?
What function does a host perform in network communication?
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What is the main function of the Network (IP) Layer?
What is the main function of the Network (IP) Layer?
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What do routers do to IP datagrams passing through them?
What do routers do to IP datagrams passing through them?
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Routing involves determining the ______ taken by packets from source to destination.
Routing involves determining the ______ taken by packets from source to destination.
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Dynamic routing protocols continuously exchange network status updates with each other.
Dynamic routing protocols continuously exchange network status updates with each other.
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Match the following network routing protocols with their descriptions:
Match the following network routing protocols with their descriptions:
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What is the primary function of an Ethernet Switch?
What is the primary function of an Ethernet Switch?
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Ethernet switches require manual configuration before they can be used.
Ethernet switches require manual configuration before they can be used.
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Which of the following is a feature of using an Ethernet switch?
Which of the following is a feature of using an Ethernet switch?
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What is the full form of DNS?
What is the full form of DNS?
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Which transport protocol is reliable and byte stream-oriented?
Which transport protocol is reliable and byte stream-oriented?
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UDP is a connection-oriented protocol.
UDP is a connection-oriented protocol.
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UDP segments may be __________ or delivered out-of-order to the application.
UDP segments may be __________ or delivered out-of-order to the application.
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Match the following network layer functions with their descriptions:
Match the following network layer functions with their descriptions:
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What is the role of a router in a network?
What is the role of a router in a network?
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What does each entry in a switch table typically contain?
What does each entry in a switch table typically contain?
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Where does a switch learn the location of the sender when a frame is received?
Where does a switch learn the location of the sender when a frame is received?
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Switches usually learn which hosts can be reached through which interfaces.
Switches usually learn which hosts can be reached through which interfaces.
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Switches are usually present in small _________ networks.
Switches are usually present in small _________ networks.
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Match the device to its description:
Match the device to its description:
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What does a Subnet Mask identify in an IPv4 address?
What does a Subnet Mask identify in an IPv4 address?
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Which of the following IPv4 addresses is considered a Broadcast Address?
Which of the following IPv4 addresses is considered a Broadcast Address?
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Variable Length Subnet Masking is the process of obtaining additional bits from the ____________ of the host portion.
Variable Length Subnet Masking is the process of obtaining additional bits from the ____________ of the host portion.
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Match the following IPv4 communication types with their descriptions:
Match the following IPv4 communication types with their descriptions:
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DHCP allows a host to permanently obtain its IP address from the network server when it joins the network.
DHCP allows a host to permanently obtain its IP address from the network server when it joins the network.
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What are the major limitations of IPv4?
What are the major limitations of IPv4?
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Which of the following are examples of Private IPv4 Addresses?
Which of the following are examples of Private IPv4 Addresses?
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What is the address space size in IPv6?
What is the address space size in IPv6?
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ICMP is a messaging protocol used by hosts and routers to communicate hardware-level information.
ICMP is a messaging protocol used by hosts and routers to communicate hardware-level information.
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Which method does 802.11 use to avoid collisions?
Which method does 802.11 use to avoid collisions?
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Bluetooth operates in the 2.4-2.5 GHz ISM radio band.
Bluetooth operates in the 2.4-2.5 GHz ISM radio band.
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What does CSMA/CA stand for in the context of MAC Protocol?
What does CSMA/CA stand for in the context of MAC Protocol?
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In Cellular Networks, neighboring cells operate on different frequencies to avoid ___________.
In Cellular Networks, neighboring cells operate on different frequencies to avoid ___________.
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Match the following generations of mobile networks with their characteristics:
Match the following generations of mobile networks with their characteristics:
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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
- Types of DNS records:
- 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.
