Title: CSCI-690 Computer Networks: Shrinking the globe one click at a time Lecture 2
1CSCI-690Computer NetworksShrinking the globe
one click at a timeLecture 2
2Major sources of the slides for this lecture
- Slides from Tanenbaums and William Stallings
website are used in this lecture
3Mankind and Communication
- O mankind! We have created you from a single
(pair) of a male and female, and have made you
into nations and tribes, so that you may know
each other Quran 49.13 - When one ponders over how we get to know each
other certain thoughts come to mind. - As we venture outside our own region or domain,
we tend to follow certain protocols that allow us
to communicate with each other. - Try to use common language that both parties
understand - Sign language
- Draw pictures, use hand gestures
- In short we find a command ground or similar
footing which to build a communication platform
on, even though we may come from diverse cultures
and background
4Mankind and Communication
- Just as we have diversity in mankind, we have
disparate, ever-evolving communications networks - These networks are evolving towards providing
seamless connectivity between different platforms
and applications so that they cater to our
insatiable need to communicate - An integral component of networking is PROTOCOLS
5OSI A Model developed by International Standards
Organization (ISO)
- Open Systems Interconnection
- Developed by the International Organization for
Standardization (ISO) has seven layers - Is a theoretical system delivered too late!
- TCP (Transmission Control Protocol) /IP is the de
facto standard
6Networking Reference Models
- The OSI Reference Model
- The TCP/IP Reference Model
7TCP/IP Protocol Architecture
- developed by US Defense Advanced Research Project
Agency (DARPA) - for ARPANET packet switched network
- used by the global Internet
- protocol suite comprises a large collection of
standardized protocols
8OSI vs. TCP/IP
- The OSI TCP/IP reference model.
9Reference Models
- Protocols and networks in the TCP/IP model
initially.
10Key Elements of a Protocol
- syntax - data format
- semantics - control info error handling
- timing - speed matching sequencing
11Simplified Network Architecture
12TCP/IP Layers
- no official model but a working one
- Application layer
- Host-to-host, or transport layer
- Internet layer
- Network access layer
- Physical layer
13Physical Layer
- concerned with physical interface between
computer and network - concerned with issues like
- characteristics of transmission medium
- signal levels
- data rates
- other related matters
14Network Access Layer
- exchange of data between an end system and
attached network - concerned with issues like
- destination address provision
- invoking specific services like priority
- access to routing data across a network link
between two attached systems - allows layers above to ignore link specifics
15Internet Layer (IP)
- routing functions across multiple networks
- for systems attached to different networks
- using IP protocol
- implemented in end systems and routers
- routers connect two networks and relays data
between them
16Transport Layer (TCP)
- common layer shared by all applications
- provides reliable delivery of data
- in same order as sent
- commonly uses TCP
17Application Layer
- provide support for user applications
- need a separate module for each type of
application
18Operation of TCP and IP
19Addressing Requirements (will discuss at length
in later lectures)
- two levels of addressing required
- each host on a subnet needs a unique global
network address - its IP address
- each application on a (multi-tasking) host needs
a unique address within the host - known as a port
20Operation of TCP/IP
21Transmission Control Protocol (TCP)
- usual transport layer is (TCP)
- provides a reliable connection for transfer of
data between applications - a TCP segment is the basic protocol unit
- TCP tracks segments between entities for duration
of each connection
22TCP Header
23User Datagram Protocol(UDP)
- an alternative to TCP
- no guaranteed delivery
- no preservation of sequence
- no protection against duplication
- minimum overhead
- adds port addressing to IP
24UDP Header
25IP Header
26IPv6 Header
27TCP/IP Applications
- have a number of standard TCP/IP applications
such as - Simple Mail Transfer Protocol (SMTP)
- File Transfer Protocol (FTP)
- Telnet
28Some TCP/IP Protocols
29Network Design Software Hardware
- Protocol Hierarchies
- Design Issues for the Layers
- Connection-Oriented and Connectionless Services
- Service Primitives
- The Relationship of Services to Protocols
30Design Issues for the Layers
- Addressing
- Error Control
- Flow Control
- Multiplexing
- Routing
31Connection-Oriented and Connectionless Services
- Six different types of service.
32Service Primitives
- Five service primitives for implementing a simple
connection-oriented service.
33Service Primitives (2)
- Packets sent in a simple client-server
interaction on a connection-oriented network.
34Starting from the bottom layer of the TCP/IP
working model
- Physical Layer
- Getting into the Fundamentals
35The Theoretical Basis for Data Communication
- Fourier Analysis
- Bandwidth-Limited Signals
- Maximum Data Rate of a Channel
36Bandwidth-Limited Signals
- A binary signal and its root-mean-square Fourier
amplitudes. - (b) (c) Successive approximations to the
original signal.
37Bandwidth-Limited Signals (2)
- (d) (e) Successive approximations to the
original signal.
38Guided Transmission Data
- Magnetic Media
- Twisted Pair
- Coaxial Cable
- Fiber Optics
39Twisted Pair Widely used in Telephony and
Ethernet cabling
- (a) Category 3 UTP.
- (b) Category 5 UTP.
40Coaxial Cable Primarily used in Cable networks
41Fiber Optics Widely used in high speed networks
- (a) Three examples of a light ray from inside a
silica fiber impinging on the air/silica boundary
at different angles. - (b) Light trapped by total internal reflection.
42Transmission of Light through Fiber
- Attenuation of light through fiber in the
infrared region.
43Fiber Cables
- (a) Side view of a single fiber.
- (b) End view of a sheath with three fibers.
44Fiber Cables (2)
- A comparison of semiconductor diodes and LEDs as
light sources.
45Fiber Optic Networks
- A fiber optic ring with active repeaters.
46Wireless Transmission
- The Electromagnetic Spectrum
- Radio Transmission
- Microwave Transmission
- Infrared and Millimeter Waves
- Lightwave Transmission
47The Electromagnetic Spectrum
- The electromagnetic spectrum and its uses for
communication.
48Radio Transmission
- (a) In the VLF, LF, and MF bands, radio waves
follow the curvature of the earth. - (b) In the HF band, they bounce off the
ionosphere.
49Politics of the Electromagnetic Spectrum
- Industrial, Scientific and Medical (ISM) bands in
the United States. Originally reserved
internationally for the use of RF electromagnetic
fields for industrial, scientific and medical
purposes other than communications.
50Lightwave Transmission
- Convection currents can interfere with laser
communication systems. - A bidirectional system with two lasers is
pictured here.
51Communication Satellites
- Geostationary Satellites
- Medium-Earth Orbit Satellites
- Low-Earth Orbit Satellites
- Satellites versus Fiber
52Communication Satellites
- Communication satellites and some of their
properties, including altitude above the earth,
round-trip delay time and number of satellites
needed for global coverage.
53Communication Satellites (2)
- The principal satellite bands.
54Public Switched Telephone System
- Structure of the Telephone System
- The Politics of Telephones
- The Local Loop Modems, ADSL and Wireless
- Trunks and Multiplexing
- Switching
55Structure of the Telephone System
- (a) Fully-interconnected network. (Mesh network)
- (b) Centralized switch.
- (c) Two-level hierarchy.
56Structure of the Telephone System (2)
- A typical circuit route for a medium-distance
call.
57Major Components of the Telephone System
- Local loops
- Analog twisted pairs going to houses and
businesses - Trunks
- Digital fiber optics connecting the switching
offices - Switching offices
- Where calls are moved from one trunk to another
58The Local Loop Modems, ADSL, and Wireless
- The use of both analog and digital transmissions
for a computer to computer call. Conversion is
done by the modems and codecs (CoDecoder).
59Modems
- (a) A binary signal
- (b) Amplitude modulation
- (c) Frequency modulation
- (d) Phase modulation