FIT1047
FIT1047 – Week 7 Part 1
Networks: Introduction
not the internet
but how does all this work?
400hours of video uploaded to YouTube every minute in 2018 2.19 billion daily active users on Facebook in 2018
144
Exabyte of world wide Internet traffic per month in 2018
3.63
trillion US$ in online sales in 2018 https://www.digitalcommerce360.com/article/us-ecommerce-sales/
1 Exabyte = 1073741708.03 Gigabytes ~ 109 GB
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Network components
Wireless Local Area Network (WLAN)
Local Area Network (LAN) switch
Wireless-client
circuit
circuit circuit
server
circuit
router Wired-client
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Hierarchical Network layout
High-speed WAN routers can carry traffic across the enterprise WAN backbone, medium-speed routers can connect buildings at each campus, and switches can connect user devices and servers within buildings
Campus A
Building C-1
Building C-2
Enterprise WAN Campus B Backbone
Core Layer
Campus C Backbone
Distribution Layer
Campus C
Edge(leaf) devices
Access Layer
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Network components
Client: gives users access to the network Server: stores data or software and makes
it available to the clients over the network Switch: connects computers in a LAN
Router: connects two or more networks Comm-Links: inter-connects network devices
Types of networks
Networks within an organisation:
• Local Area Network (LAN) (room, building):
a group of clients and servers that share a circuit
• Backbone Network (BN) (< a few km): high-speed connection between LANs
• Metropolitan Area Network (MAN) (> a few km): connect LANs and BNs across locations
• Wide Area Network (WAN):
same as MAN except longer distances
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The Monash Network
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The Monash Network
Guess the size of the Monash network:
A. 100 routers/switches, 5,000 computers
B. 500 routers/switches, 10,000 computers
C. 1,000 routers/switches, 25,000 computers
D. 2,000 routers/switches, 40,000 computers
E. 5,000 routers/switches, 100,000 computers
• Based on a common, standard set of protocols
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Source: Wikipedia / Opte project : https://en.wikipedia.org/wiki/Internet
The Internet
• A network of networks
• Connecting millions of networks
and billions of devices
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Data transmission rates
• Fundamental characteristic of a network: how many bits per second can it transmit?
• Typical transmission rates:
• 1 Mbps (million bits per second) from your home to your ISP (Internet Service Provider), 10-20 Mbps in the other direction
• 50-500 Mbps within your WLAN (wireless network)
• 1 Gbps in LANs (local area network, e.g. Monash lab)
• 10 Gbps in backbone networks
• Tbps (tera bits per second, 1012) in optical fiber networks
How long does it take?
Assume you want to send a 4k movie (50 GB) to a friend. How long does it take if you use your home ADSL connection?
A. At most 10 Minutes B. 10-12 hours
C. Around one day
D. Roughly one week E. About one month
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How long does it take?
• Typical ADSL upload speed: 1 Mbps
• 50 GByte = 400 Gbit = 400 000 Mbit
• 400 000 seconds = 4 days, 15 hours
• How about NBN? Advertised as 39 Mbps
• 400 000 Mbit / 39 Mbps = 2 hours 29 minutes
• And within the Monash network? 1 Gbps
• 400 Gbit / 1 Gbps = 6 minutes 40 seconds
http://www.meridianoutpost.com/resources/etools/calculators/calculator-file-download-time.php
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FIT1047
FIT1047 – Week 7
Networks: Layers and Protocols
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Layers and Protocols
How to transfer data
• Networks run on very diverse and complex hardware and software:
How can we make sure they all understand each other?
• Solution:
hierarchical layers of abstraction
each with well-defined tasks and interfaces
formal languages (protocols) within each layer • This is typical software engineering!
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Layers of Abstraction
Application
(manage user data)
Logical connections
(break up into packets, make sure they arrive)
Routing
(where should packets go?)
209.85.142.94
203.214.44.94 216.239.46.151
Low-level connections
packet
(computer-to-computer)
Hardware
packet
(cables, WIFI etc)
Layers of Abstraction
Application
(manage user data)
Transport
(break up into packets, make sure they arrive)
Network
Internet Model
(where should packets go?)
Data link
(computer-to-computer)
(cables, WIFI etc) FIT1047
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Physical
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Layers of Abstraction
Application
(manage user data)
Transport
Interface
(break up into packets, make sure they arrive)
Network
(where should packets go?)
Data link
(computer-to-computer)
Interfaces define how each layer “talks” to the one above and below.
Physical
(cables, WIFI etc)
Layers of Abstraction
Computer 1
Protocol
Computer 2
Application Transport Network Data Link Physical
Application Transport Network Data Link Physical
Protocols define how the same layers communicate between different computers.
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ADSL
Wi-Fi
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Layers of Abstraction
Application Transport Network Data Link Physical
Switch
Router
Switch
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Message Encapsulation
Application Transport Network Data Link Physical
Message Segment Packet
HTTP www.youtube.com PDU contains:
Protocol Data Unit
(PDU)
Frame Bit
• Protocol-specific information
• Addresses TCP
(sender/receiver)
• Error detection codes IP
Ethernet
• Special start and end
symbols
• The Internet model has five layers
Summary
• Networks consist of clients, servers, switches, routers, and other circuit hardware (e.g. cables)
• LANs connect computers directly with each other
• Each layer encapsulates the message and adds its own PDU
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FIT1047
FIT1047 Week 7
Computer Networks: Application Layer
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Layers of Abstraction
Switch Router Switch
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Architectures
client server
Application Architectures
Presentation logic
The user interface. Controls the application.
Application / business logic
Defines what the application does.
Who(Client/Server) does what.. ? ?
Data access logic
Defines how the application manages its data.
Data storage
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Where the data is kept, e.g. files or data base.
client server
Server-based Architecture
“dumb” terminal
Presentation logic Application / business logic Data access logic
Data storage
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Client sends keystrokes to the server, displays text according to server’s instructions.
Problems:
Server can become a bottleneck. Upgrade expensive and “lumpy”.
client server
Client-based Architecture
Presentation logic Application / business logic Data access logic
Data storage
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All the logic is performed by the client. The server stores the data.
Problems:
All data must travel back and forth between server and client.
client server
Client-Server Architecture
Presentation logic Application / business logic
Data access logic Data storage
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Balance the processing load between
client and server.
client server
Thin-Client Architecture
Presentation logic
Application / business logic Data access logic
Data storage
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Server handles most of the application logic.
Advantage:
Only one server needs updating.
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client client
Peer-To-Peer Architecture
Presentation logic Application / business logic
Data access logic Data storage
Presentation logic Application / business logic Data access logic
Data storage
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All computers act as both clients and servers.
Use local logic to access data stored on another computer.
Question: Google Drive
• Monash pays Google to provide vital services such as email, calendars,
and Google Drive, a cloud-based file storage. • Which architecture does Google Drive use? A. Client-based
B. Thin client-server
C. Server-based
D. Client-server
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World Wide Web
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WWW
• Based on two main technologies:
• HTTP is the protocol for communication between
browser and server
• HTML is the format in which web pages are described
HyperText Transfer Protocol (HTTP) • Defines how web browsers talk to web servers
• Invented in 1989 by Tim Berners-Lee at CERN:
“How will we ever keep track of such a large project?”
• Based on two innovative ideas:
• Hypertext:
A document containing links to other documents
• Uniform Resource Locators (URLs):
A standard for identifying links to other documents
• HTTP defines how documents are requested and transferred FIT1047
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Request – Response-Cycle
Request
HTTP www.youtube.com
Internet
HTTP
…
Response
client: server:
GET /~guidot/test.html HTTP/1.1 Host: www.csse.monash.edu
Request line
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Basic HTTP session
HTTP/1.1 200 OK
Date: Thu, 05 Mar 2015 08:30:48 GMT Server: Apache/1.3.26 (Unix) Transfer-Encoding: chunked Content-Type: text/html
Req. header Response
Response body
Guido Tack
status(http=status codes)
Response header
,
Server: Apache/1.3.26 (Unix) Transfer-Encoding: chunked
Basic HTTP session
Content-Type: text/html
Guido Tack
client:
Host: www.csse.monash.edu
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GET /~guidot/images/guido3.jpg HTTP/1.1
client:
GET /~guidot/images/guido3.jpg HTTP/1.1 Host: users.monash.edu
server:
HTTP/1.1 200 OK
Date: Thu, 05 Mar 2015 08:31:23 GMT
Server: Apache/1.3.26 (Unix)
Last-Modified: Tue, 20 Nov 2012 03:29:22 GMT Accept-Ranges: bytes
Content-Length: 15681
Content-Type: image/jpeg
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