T01 - Overview of Computer Network
Transcript of T01 - Overview of Computer Network
-
7/27/2019 T01 - Overview of Computer Network
1/16
1
ECTE 182Internet Technology 1
Topic 01
An Overview of Computer
Network
What is a computer network?
Simple and general answer : A computer networkis a group of computers that are interconnected toshare hardware, software and data.
But then
How do we connect these computers together ?
How does these computers communicate with each other?
How can we make sure the communication is smooth andflawless ?
How do we make sure the communication is private andsecure ?
The study of networking courses is generally tounderstand the above questions and to answerthem.
ECTE182 2
-
7/27/2019 T01 - Overview of Computer Network
2/16
2
Data Communications
The essence of computer network is to allow datacommunications.
Goal: convey information
How to do it?
Hand signal, smoke, light, .?
Characteristics
Delivery/Reliability
Accuracy
Timeliness
Jitter
ECTE182 3
Whats a computer network?Establishing a communication channel
ECTE182 4
Wired (copper, fiber)
Wireless (electromagnetic, infra-red)
Information
-
7/27/2019 T01 - Overview of Computer Network
3/16
3
A home network
ECTE182 5
Internet
Service Provider
- Wireless (IEEE 802.11a/b/g/n,
Bluetooth, USB (wired/wireless))- Wired (Firewire, USB, Ethernet(10/100/1000/10000 Mbps)).
ADSL, Cable Modem, Dial-Up,WiMAX (IEEE 802.16)
(56 Kbit/s 40 Mbit/s)
Internet structure: network of networks
Tier-2 ISPs: smaller (often regional) ISPs
Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
ECTE182 6
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISPTier-2 ISP
Tier-2 ISP
Tier-2 ISP
Tier-2 ISP pays tier-1
ISP for connectivity to
rest of the Internet
i.e., tier-2 ISP is
customerof tier-1
provider
Tier-2 ISP
Service Level Agreement
Throughput, Delay, Jitter,
Loss
-
7/27/2019 T01 - Overview of Computer Network
4/16
4
Internet structure: network of networks
A packet passes through many networks!
ECTE182 7
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
localISP
localISP
localISP
localISP
localISP
Tier 3ISP
localISP
localISP
localISP
Problems?
Network of NetworksAnother View
ECTE182 8
LAN Local Area Network
MAN Metropolitan Local Area Network
WAN Wide Area Network
Wide Area Network
MAN
MAN
MAN
MAN
LAN
LAN
LAN
LAN
LAN
LAN
LANLAN
LAN
LAN
LAN
LAN
PAN Personal Area Network
-
7/27/2019 T01 - Overview of Computer Network
5/16
5
Category of Networks
Body Area Networks
Personal Area Networks
Local Area Network
Privately owned, links computer in a single building oroffice
Fixed transmission media and topology; e.g., WirelessLANs
Metropolitan Area Network
Covers a town or city
E.g., cable TV, wireless MANs (WiMAX)
Wide Area Network
Between continents
Satellites or oceanic fiber links.
ECTE182 9
Physical StructureTypes of Connection
ECTE182 10
Point-to-Point
Multipoint
-
7/27/2019 T01 - Overview of Computer Network
6/16
6
ys ca ruc ureTopology
ECTE182 11
Each computer has a dedicated line to allstations
Number of links: N(N-1)/2, N is # of nodes. Lots of cabling Dedicated line, simultaneous transmissions Good fault tolerance Good privacy
Mesh
Star Hub relays data from all stations No point-to-point communications
Cheaper than mesh Single point of failure Easy to isolate link fault
Hub
ys ca ruc ureTopology
ECTE182 12
Backbone laid on most efficient path Less cabling than mesh or star Break in backbone link disables the network Difficult to isolate fault Only one station can be using the backbone
at any given time bus is a shared resource
Bus
Ring Messages goes from station to station in onedirection
Each station repeats received message Only one station can be transmitting at any giventime.
Simpler fault isolation
-
7/27/2019 T01 - Overview of Computer Network
7/16
7
Physical StructureTopology
ECTE182 13
Hybrid
Hub
Local Area Networks
ECTE182 14
Dedicated
Shared
-
7/27/2019 T01 - Overview of Computer Network
8/16
8
Break
ECTE182 15
Information Flow
ECTE182 16
simplex
Half-Duplex
Time t1
Time t2
Duplex
-
7/27/2019 T01 - Overview of Computer Network
9/16
9
Packets
ECTE182 17
0010110101010101010101
Packet
Your dataInserted byprotocol
information
Header Payload
Packet
Analogy
Given a 500 page book, and 1000 standard90x140mm envelopes.
Problem:
How do you send the book to your friend Bill Gates atMicrosoft Corp, One Microsoft Way, Washington, USA?
Assume free postage and handling.
ECTE182 18
-
7/27/2019 T01 - Overview of Computer Network
10/16
10
Packets/Envelopes
Header information
Source address
Destination address
Time to live
Length of header and payload
Timestamp
Security information
Packet type
ECTE182 19
The InternetA Packet Switched Network
ECTE182 20
Your
ISP
Telstra
Sprint
Level-3
-
7/27/2019 T01 - Overview of Computer Network
11/16
11
Whats a protocol?
human protocols:
whats the time?
I have a question
introductions
specific msgs sent
specific actions taken when msgs received, or otherevents
ECTE182 21
network protocols:
machines rather thanhumans
all communicationactivities in Internetare governed byprotocols
protocols define format, order
of msgs sent and received
among network entities,
and actions taken on msg
transmission, receipt
Whats a protocol?
ECTE182 22
Hi
HiGot thetime?
2:00
connectionreq
connectionresponse
Get http://www.uow.edu.au
time
Human Computer
-
7/27/2019 T01 - Overview of Computer Network
12/16
12
What does a protocol specify?
A set of rules that govern data communications
Syntax.
Fields in the header, and their size.
Semantics
The meaning of each bit in the packet
Timing
When data should be sent, and how fast?
ECTE182 23
A simple protocol
ECTE182 24
Computer-A Computer-B
Filename: ecte182.zip
Got it!
Heres bit 1 to 1000Got it!
Heres bit 1001 to 2000
I only received bits1001 to 1500
Heres bit 1500 to 2000again
-
7/27/2019 T01 - Overview of Computer Network
13/16
13
A Routing Example
ECTE182 25
YourISP
Optus
Telstra
AT&T
R
R
R
Sprint
Level3
Google
RR
R
R
R
R
R
RR
Routing Problems How to get to Google? Which way is the bestroute? How to find out which way is best?
R Router
search: ecte182
Who standardize protocols?
Why do it?
To ensure interoperation between machines developed by
different vendors.
E.g., Bluetooth, Motorola Samsung
Standards creation committees
International Organization for Standardization (ISO)
International Telecommunication Union Telecommunication
Standards Sector (ITU-T)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
Electronic Industries Association (EIA)
Internet Engineering Task Force (IETF)
ECTE182 26
-
7/27/2019 T01 - Overview of Computer Network
14/16
14
IETF (www.ietf.org)
Protocol engineering and development arm of the Internet
Society ( founded in 1992 to provide leadership in Internetrelated standards, education, and policy)
Includes designers, operators, vendors and researchers. Open
to anyone
Produces two types of document
Internet drafts - no formal status
Request For Comment (RFC) are official documents.
ECTE182 27
IETF Working Group
This is where the IETF primarily get its work done
Working group focused by charter agreed betweenchair(s) and area director restrictive charters with deliverables and milestones
working groups closed when their work is done
Charter approved by Internet Engineering SteeringGroup (IESG) with IAB (Internet Architecture Board)advice
Area Director with IESG has final say on charter &chair(s)
ECTE182 28
-
7/27/2019 T01 - Overview of Computer Network
15/16
15
IETF Working Group
rough consensus and running code...
no formal voting
- can do show of hands - but no count
does not require unanimity
disputes resolved by discussion
mailing list and face-to-face meetings
most work happens on mailing lists
all decisions must be verified on mailing list
face-to-face discussion to resolve disagreements
ECTE182 29
Source: IETF Slides presented to newcomers.
ICANN
Internet Corporation for Assigned Names and Numbers
(ICANN) manages
IP addresses
Uniqueness
Domain names
.com, .edu, .net, etc
Port numbers
ECTE182 30
-
7/27/2019 T01 - Overview of Computer Network
16/16
SummaryKey Concepts
Internet Network of Networks
Topologies: mesh, bus, star, hybrid
Simplex, half-duplex, full duplex
LAN, MAN, WAN
Packets
Packet switched networks
Protocols
Standardization
ECTE182 31