Basic Communications
Overview of
communication technology.
Communications
Electronically exchanging data or
information.
Voice interactive communication
Data large volume batch transmissions
Image encoded graphics
Video streaming media
Telecommunications
History
Pre 1984
Local and long distance monopoly
1984 AT&T settlement
Intense long distance competition
1996 Telecommunications Act
Local access competition
Standard Telephone System
Analog
Switch
Analog
Digital
Digital
Network
Modem
Digital
Telephone Changes
Rapidly decreasing long distance rates
Value added telephone services
Cellular access
Flat rate long distance?
Data and voice convergence.
Issue: Access
Dedicated lines
Standard voice
Integrated Services Digital Network
Digital Subscriber Lines
Cable Modem
Wireless
Voice vs. Data
Voice
Delay Sensitive
Constant bit rate
Not error sensitive
Growth stable
(video ??)
Data
Delay insensitive
Variable bit rate
Error sensitive
Demand growing
Data Networks
NIC
LAN
Switch
Campus or
Router Metropolitan
Area
WAN
Public TELCO
POP
Packet Structure
Header(s)
Data Payload
Trailer
LAN Operating Protocols
(layer 2)
Ethernet
open standard, cheap, most common
Token Ring
IBM proprietary, high quality,
expensive
Others
Network Interface Cards
Build, send out and accept frames
Usually a daughter board on PC
Must match LAN and CPU
Require drivers to operate
Network Interface Cards
(NIC)
Ethernet
Carrier Sense Multiple Access/Collision
Detection
Trailer
Body
Listen before transmit
Contention access
Retransmit on collision
Header
Network Routing
Protocols for
internetworking.
Two major types
Packet switching (or datagram)
Usually layers 3 and 4
Circuit switching
Usually layers 1 and/or 2
Packet switching or
Datagram Protocols
Best effort
Frames take individual routes
Packet assembly devices needed
Error Control
Traffic Management
Buffering
Discard
Datagram Logic (IP)
Packet n
Packet 2
Packet 1
3
2
1
3
1
PAD
2
IP
Best Effort
Addressing
Variable packet lengths (1500 bytes or
less)
IPv4 vs IPv6
Frame and Header
TCP and UDP
Transmission Control
Protocol
Connection oriented
Assures that packets
arrive in order and
that they are correct.
User Datagram Protocol
Connectionless
Sends packets out
without confirming
that they arrive
Ethernet/TCP/IP Header
Structure
Circuit Protocols
All packets take the same route
No packet assembly device to reorder
packets
Normally layer 2 connection
May be permanent or switched
Allow guaranteed service quality levels
May be used to carry datagram protocols
Circuit Logic
Source
Destination
Setup
Message & ACK’s
Teardown
Internetworking
Technologies
Common WAN
technologies.
ISDN
Circuit
Switched
Data and
Voice
Service
Digital Subscriber Lines
DSL uses packet switching technology
that operates independent of the voice
telephone system, allowing the telephone
companies to provide the service and not
lock up circuits for long calls.
WAN Costs
Circuit Charges
Committed Bandwidth
Peak Bandwidth
Discard Priority
Latency
Representative Prices
per MB of traffic (Qwest, Dec. 98)
Frame Relay
Non-discard eligible
Discard eligible
4 cents
3 cents
ATM
Constant bit rate
Variable bit rate (real-time)
Variable bit rate (non real-time)
Available bit rate
Unspecified bit rate
2 cents
1.2 cents
.75 cents
.55 cents
.4 cents
Representative Prices
per port (Qwest, Dec. 98)
56 Kb Frame Relay
T-1 Frame Relay
T-3 Frame Relay
$190
$1,595
$3,190
Client/Server Architecture
An architecture in which the client
(personal computer or workstation) is the
requesting machine and the server is the
supplying machine, both of which are
connected via a network.
Client/Server Architectures
FAT CLIENT
FAT SERVER
SERVER PROCESSING
CLIENT PROCESSING
CENTRALIZED
STAND-ALONE
Client/Server
Scalability
Interoperability
User buy-in
Increased cost
Multi-tier
One Tier System
Two Tier Client/Server
Three Tier Client/Server
Application Issues
Interoperability (e.g. ODBC)
OS support
Multi-threaded or single threaded
Network impact (e.g. chattiness)
QoS demands
Delivery: centralized, clien/server, web
Application Management
Standards
Supported
Accepted
Prohibited
Version Control and Distribution
License Management
Virus detection and inoculation