Intro to computing networks Midterm 1 review

#midterm

What is the internet?

A network of networks where different internet service providers (ISPs) are connected. Global network of interconnected computers and devices that communicate using standard protocols enabling the global exchange of data.

What is the physical view of the internet?

The infrastructure and hardware that comprise the network. E.g. routers, servers, data centers, fiber optic cables, satellite links etc. Tangible: physical elements that allow data transmission and communication between devices and networks.

What is the service view of the internet?

The infrastructure that provides a variety of services to applications. E.g. World Wide Web, VoIP, email, online games, and social networks. It also includes a programming interface, which allows applications to connect to the internet and facilitates the seamless exchange of data.

What is a network protocol?

A set of rules or formats that a host computer should follow to communicate with another computer.

Formal standards and policies comprised of rules, defining communication between two or more devices over a network; also governing the end-to-end processes of timely, secure, and managed data or network communication.

List five network protocols:

IP - Internet Protocol

SSH - Secure Shell

FTP - File Transfer Protocol

SMTP - Simple Mail Transfer Protocol

HTTP - Hypertext Transfer Protocol

Internet Protocol (IP)

defines the set of rules that commands how the data should be delivered over the internet.

Secure Shell (SSH)

establishes a secure connection between two computers so t hat they can communicate with each other.

File Transfer Protocol (FTP)

used to transfer data files between different computers using the internet.

Simple Mail Transfer Protocol (SMTP)

used to send email messages.

Hypertext Transfer Protocol (HTTP)

used to interact with web resources transmitting hypertext messages between clients and servers.

What is a network edge?

A device or local network that connects to the internet where the edge is close to the devices it is communicating with and is the entry point to the network. The network edge is a security related boundary for which the network administrator must provide solutions.

What is an access network?

a type of network which connects an end system to the immediate router on a path from the end system to any other distant end system.

What is a network core?

Network core provides multiple services to connect users to interconnect by access network. It delivers routes to exchange information among various sub-networks.

Bandwidth

the maximum rate or capacity of the channel or path through which data is transmitted in a network connection. It is measured in bits per second (bps).

Data rate

the rate at which data is transmitted or amount of data transmitted during a specified time period over a network. It is also measured in bits per second (bps).chat

Physical Media

The actual physical environment through which data travels. The two categories of physical media is Guided and Unguided Media.

Guided Media

the physical links through which signals are confined to a narrow path. Guided media are made up of an external conductor (usually copper) bounded by jacket material. Guided media offers high speeds, good security, and low cost.

However, sometimes they cannot be used for distance communication.

Unguided Media

the information is transmitted by sending electromagnetic signals through free space and hence the name unguided media. All unguided media transmissions are classified as wireless transmissions.

Wireless transmission can be used as the medium in both LAN and WAN environments.

Guided Media Examples:

• Coaxial Cable

• Twisted Pairs Cable

• Fiber Optic Cable

Unguided Media Examples:

• Radio waves

• Microwaves

• Infrared

Coaxial Cable

• It has more insulation than most other cables.

• It contains two conductors that are parallel to each other.

Twisted Pairs Cable

• It is made up of pairs of cables that are twisted to each other.

• Installation is very easy.

Fiber Optics Cable

• It carries data in the form of light.

• It has more bandwidth compared to copper.

Radio Waves

• They are omnidirectional

• Sending and receiving antenna are not aligned i.e., sending antenna can be received by any receiver antenna.

Microwaves

• They are Unidirectional

• Sending and receiving antenna are aligned

Infrared

• it is used for short range data transmission.

• It cannot penetrate through walls.

Forwarding

the process of moving packets from a router’s input to the appropriate output. It decides the output by examining the destination address, facilitated through a forwarding table.

Routing

Routing is the process of determining the route taken by packets from the source to the destination within the network. Routing utilizes algorithms to compute the best paths based on network conditions.

Packet Switching

• Does not require any dedicated path to send data from source to destination

• It can follow any path throughout the session

• Data is processed and transmitted at the source as well as at each switching station

• It supports store and forward transmissions

• Packet switching is less reliable

Circuit Switching

• Circuit switching requires a dedicated path before sending data from source to destination

• Same path is followed throughout the session

• Data to be transmitted is processed at the source itself

• It does not do store and forward transmissions

• Circuit switching is more reliable

FDM (Frequency Division Multiplexing)

• In this technique, the channel is divided between multiple users

• In FDM, each signal uses a small portion of bandwidth all the time

• FDM works with only analog signals

TDM (Time Division Multiplexing)

• In this technique, the time is divided between multiple users

• In TDM, each signal uses all the bandwidth some of the time

• TDM works with digital signals as well as analog signals

What is an internet exchange point (IXP)?

A physical location where Internet infrastructure organizations such as Internet Service Providers (ISPs) and Content Delivery Networks (CDNs) connect with one another.

These locations are on several networks’ edges, allowing network providers to share transit outside of their own. By establishing a presence inside an IXP site, companies may decrease their path to transmit from other participating networks, cutting latency, improving round-trip time, and perhaps saving costs.

What is a peering link?

The practice of connecting and exchanging traffic between two internet networks is known as peering. It allows them to send traffic across each other’s customers without having to pay a third party to do so on their behalf through the internet.

Four sources of packet delay

• Processing delay

• Queuing delay

• Transmission delay

• Propagation delay

Processing delay

the time required to process a packet to check for bit errors, to determine output links, etc. It occurs at any intermediate router, and they are on the order of 10^-6 seconds or less often negligible

Queuing delay

the time spent waiting in a queue at any point along the route (depending on the intensity of the traffic) in the order of 10^-6 to 10^-3

Transmission delay

the time to send out all the packet bits; on the order of 10^-6 to 10^-3 seconds. Negligible for transmission rates >= 10Mbps; significant for large packets sent over low-speed links.

L/R

Propagation delay

(d/s) the time for one bit to propagate from source to destination at the propagation speed of the link. Depending on the physical medium of the link, they are on the order of 10^-6. Negligible for two routers on the same LAN; significant for two geostationary satellites.

Traffic Intensity

Average occupancy of a server or resource for a specific period. (La/R). 0 = small 1 = large >1 = infinite

traceroute

a utility that records the route, also calculates and displays the amount of time each hop took. Uses TTL (time to live packets)

Latency

the time it takes for a packet to get from source to destination. It is measured in units of time

Throughput

actual rate at which bits are transferred between sender and receiver. Throughput is measured in kilobits per second, mbps or Gbps

Instantaneous throughput

the rate at which the bits are transferred at a given point of time between sender and receiver

Average throughput

the rate at which the bits are transferred over a longer period of time between sender and receiver.

What are the seven Layers of the ISO-OSI reference model?

• Application Layer

• Presentation Layer

• Session Layer

• Transport Layer

• Network Layer

• Data-link Layer

• Physical Layer

Encapsulation

a process of adding information to the message as headers so that the messages can be routed from the source application to destination application. Data is encapsulated on the senders side then built up from each preceding layer

Atleast three types of network attacks:

• Malware (Malicious software)

• DDOS (Denial of service attack)

• Sniffer Attack (reads packets)

• Identity spoofing (IP attack)

• Cross-Site scripting (embedded scripts on websites)

• Phishing (sending fake emails)

Client server

• Requests for service and server responds with the service

• As the num of client requests increase the server capacity must be increased using up resources and hence not self-scalable

• focuses on sharing the information

• when several clients request the services simultaneously, servers can get bottlenecked

• expensive to implement

P2P

• each peer can request services and also provide

• is self-scalable

• focuses on connectivity

• each peer has its own data

• not bottlenecked since services are provided by multiple peers

• less expensive to implement

Process

a program or application that runs within a host. Processes can communicate with each other over a network using various mechanisms such as sockets.

Inter process Communicatioon (IPC)

is a mechanism where two processes communicate withing the same host by exchanging the messages

Socket

FTP

File transfer ptorocol client and server uses TCP

TFTP

Trivial file transfer protocol uses UDP

HTTP

uses tcp

SMTP

tcp

DNS

udp

TCP

• is a connection oriented protocol. When a file or message is sent, it will be delivered for sure unless there is no fail in connection

• Flow control: TCP does not overwhelm the receiver

• Congestion control: TCP would throttle the data when the network is ovberloaded

• Slower than UDP

UDP

• connectionless protocol you dont know if itll get there and could get lost on the way

• no flow control

• no congestion control

• faster than TCP

Persistent HTTP

can request multiple objects over single TCP

Does not need repeated connection

an avg of one RTT per each object

Nonpersistent HTTP

at most one object can be requested over TCP

each object must establish a new connection

avg of 2 RTT per object