ICT 390 {quiz 1}

Before Midterms

What is computer Networks

• An interconnected collection of autonomous computers

  • Autonomous: function on their own

    • exclude from the definite situation where there is a clear master/slave relationship

    • have memory, processing capability and run on their own

  • interconnected: connected to each other

    • The computers have the ability to exchange information

    • mode of connection doesn’t matter as long as they can exchange information

All Network Management must be……….

handled personally

What is another definition Computer Networks

• Collection of computers(hosts) and devices connected together:

  • 4 components:

    • Hosts - computers/servers/smart devices

    • links (wireless, wired satellites, twisted pair, fiber, coax)

    • switches/routers

    • network interface

What is Distributed Systems:

• Existence of multiple autonomous computers that are not visible to the user:

  • i.e: transparent

• The Software decides which processor to select to execute command and determine where files needed need to retrieve and move to the destination

• Like user using a Virtual processor 

  • user of a distributed system is not aware of the existence of multiple processors

• Everything upon typing with a disturbed system is done Automatically

• Nothing is done explicitly and everything is done automatically without user’s knowledge

• Software give it this high degree of cohesiveness and transparency

World Wide web is a computer Network? True or False

False, because it is a software running over the computer network

What are the different types of software: list example

• Application software: Excel, powerpoint

• System software: OS, Firmware, device driver

What does the NIC do?

converts fiber light (optical) to electricity: conversion not fast not enough so bandwidth is lost, slowing down the speed

2 reason for things to slow down

• 1) Conversion: opto electronic device not converting light to electricity fast enough

• 2) data copy: slows down by every copy due to memory not being fast enough

What is the network interface?

• 1) Its a NIC (network interface card)

• 2) software for a NIC

  • for a device driver to work -> manages the hardware

list two things that are transparent to the user

Network and transport

___ access to both local and remote access

ubiquitous

List two thing about Point to point connection

1. Not scalable

2. as number of link increases, number of link increases exponentially

Example of shared medium/Multiple point access and the downside

1. wireless transmission sharing airwave

   1. risk of having a bottleneck

What is Switch Networks

1. One source going through various links such as switches and routers

2. Collection of Networks joined together

   1. INTERNETWORKS

      1. Networks of Networks

What does ARPANET stand for

Advance Research Project Agency Networks

What was ARPANET?

• A small Network connecting university, research labs, and government agency

  • Primary apps: email

  • ftp: file transfer protocol

• Today:

  • We have a global world wide network:

    • 1 billion host

    • 5 billion users

What is the internet?

1. A huge collection of heterogeneous networks devices

2. Hierarchily structured

   1. fully distributed, no centralized control

List the diffrrent types of area networks: List its effects too

BAN: body area network: Stuff on your body, Military application

PAN: personal area network: Bluetooth (short distance)

LAN: Local Area Network: Printers, computer, {ethernet}

CAN: Campus Area Network: University Campuses, multiple connected building

MAN: Metropolitan Area Network: Network covering a city

WAN: Wide Area Network: Internet

---

• Coverage Increases

• Delay increases

• Network performance decreases

Meaning of being Connected to the Internet:

1. must have a IP (internet protocol) Address

2. Must run TCP (Transmission control protocol) IP Stack

3. must be able to communicate with any other hosts on the internet

Whos carrying most of the internet traffic

ISPs are carrying most of the internet traffic

What is a packet?

• Small Chuck of data

  • 48 bytes ~ 150 bytes

What does a packet carry? How does it travel?

• Each packet carries information that is used to route it to its destination

• Packets travel along different links/networks with different speeds.

What are the benifts and downside of packets?

• We can achieve flexible, adaptive routing

  • packets can use different routes

  • Performance may degrade ⇒ hit congested internet links

What does a packet contain?

Header, Data, Trailer

• Header contains: Source and destination address

• Trailer contains: Error control information

How does Packet Switching Work?

•  Each intermediate node - (switch/routes) buffers incoming packets, processes it and forwards packets

  • ⇒ Store and forward

What are the issues of packet switching

1. Resource sharing (multiple users sharing resources | e.g links)

   1. circuit sharing (e.g plain old telephone)

   2. Packet switching (Internet)

   3. fiber to neighborhood ⇒ split between houses

2. Addressing and routing

3. reliability and recovery guaranteed end-to-end delivery

4. Traffic management ⇒ managing and policing networks

Give a example of what uses a Packet Switching

Internet

List all the feature of Packet Switching

1. Store and forward approach:

   • an intermediate stores and  buffers incoming packet, processes it, and forwards it

2. Adaptive/ routing flexible

   • packages can choose alternative paths

3. performance may degrade along congested routes

1. Packet from different sources are interleaved

2. efficient use of resources ⇒ Links are used on demand

What is Statistical Multiplexing?

• No reservation made

• a technique  that assumes not all attached devices are used at their maximum speed

  • as a result, the capacity of the output line is less than the sum of all the inputs 

• can support Bustly traffic, compared to circuit switching at a constant rate 

  • ⇒ can use unused links to accommodate this

1. High peak 2. Short Duration

List a example of what uses Circuits Switching?

Plain Old telephone System (POTS)

How does circuit switching work?

1. Set up a connection path ( circuit ) from source to destination

2. Circuit remains throughout the lifetime of the connection

3. Bit-orientated: all bytes follow the same dedicated path

   1. if one chain breaks, the whole path breaks

4. Guaranteed resources: links are reserved once a successful connection is established

• Dedicated circuits to individual users

• While A talks to C, B cannot talk to D.

• Typical phone call: POTS -> user speaks less than 35%

Diffrences between Circuit switching and Packet Switching?

CIRCUIT SWITCHING	PACKET SWITCHING
Resources are statically reserved unused resources go wasted	Resources are used on-demand unused resources can be used by other sources
Data is delivered in the same exact order as it was transmitted.	2) Possible out of order delivery.
Charging:  based on connection time and distance	3) Charging: based amount of data
can choose any format for the data transfer carrier does not care img voice text	4) Format of the data sent is determined by the carrier Internet protocol packet format

Reliablity and recovery and its consequences

Reliability and recovery	Consequences
⇒ Many things can go wrong in a network	⇒ Packet can get delivered out of order
bits can be flipped due to signal interference	Packet delivered to the wrong address
packet loss (buffers are full)	Packets are lost
Packet delays (Packet waiting inside buffers)	packet are delayed, may also get duplicate packets
eavesdroping
Link / node failure

What should be implemented for recovery

For packet lost: Implement a hop-by-hop solution or end-to -end solution

⇒ Error recovery solution

What is Re-transmission Schemes

• e.g: receiver asking a resend due to not being able to open file

• e.g: No point of re-transmission during live video conference because the sender may have moved to something else.

Network Perfomace Metrice: What is bandwidth and what is Throughput

Network Performance Metrics:

Bandwidth: Bit rate of transmission units: Kbits/s, Mbits/s, Gbits/s 10^3,     10^6,     10^9

Throughput: effective bit rate Efficiency:(Throughput/Bandwidth) *100  drops due to data copy

What is Latency

• Latency: Time it takes for a packet to transfer from source to destination

What is RTT and whats it stand for?

RTT stands for Round Trip Time

Round Trip Time: time it takes to reach its destination and back to the source

• Clocks are not synchronized so use the same clock 

End to end Delay. describe: Transmision delay, Propagation Delay, Queuing delay and Processing Delay

• Transmission delay: Time it takes to transmit a packet

• Propagation delay: Time it takes to travel along medium

  • Depends on: 

    • Distance

    • Communication Medium

  • S=D/T      T=D/S

• Queuing Delay: Buffering time, waiting insider buffer

• Processing delay: Time it takes to process a packet