Download Advanced Networks Course Topics

Advanced Networks
‹ Lecturer:
‹ Web:
‹ E-mail:
‹ Course
Damian Bourke
www.comp.dit.ie/dbourke
[email protected]
Books -
» Internetworking with TCP/IP Vol 1: Principles,
Protocols and Architecture, 5th Edition
– Douglas Comer
– Prentice Hall
» Computer Networks, 4th Edition
– Andrew Tanenbaum
– Prentice Hall
1
Course Topics
‹
Introduction
» Historical Context for TCP/IP
and ATM
‹
‹ IP
‹
Protocol Architectures
Packet Switching
Technologies
» Concepts and protocols
associated with Frame Relay
and ATM
‹
High-speed LANs and
ATM
Common network
problems
» Congestion, traffic
management and queuing
» How TCP deals with these
problems
» ISO OSI and TCP/IP from an
application perspective
‹
and ATM
‹
Network applications
» Network APIs
» FTP, e-mail, browsers etc.
» Network programming
2
1
Introduction
‹
‹
Arpanet was intended to explore cooperative, distributed computing
using packet-switching technology
Some early ARPANET applications included TELNET and FTP:
» TELNET provided a common language for computer terminals to interact
with different computers
» FTP offered a similar open or common functionality allowing the transfer
of files from one computer to the another transparently
‹
However, the first real "killer app" for ARPANET was electronic mail
» In 1972 the first distributed mail service across multiple computers was
developed
» By 1973 three quarters of all ARPANET traffic was e-mail
– The popularity of e-mail necessitated the addition of more nodes and the use
of higher-speed links
‹
As ARPANET grew reliability and availability of the network became
important issues
3
The arrival of the internet
‹ Packet-switching
technology was also applied to
radio communications (aka Packet Radio) and to
satellite communications (aka SATNET)
» The integration of these three networks led to the
development of protocols for internetworking
» Internetworking is about creating a universal network
» This led to the development of the TCP and IP
protocols which form the basis for the modern Internet
‹ The
“killer app” for the internet was the World
Wide Web
4
2
The arrival of the WWW
‹ The
WWW started out in 1991 as a textoriented document reader
» Explosive growth came about with the
development of the first GUI browser, Mosaic
» This created more graphics-based and realtime traffic
» The resultant performance issues and the
protocols and techniques developed to address
them will be discussed in this module
5
The Arrival of ISDN
‹
‹
Early public telecommunications networks were based on
circuit switching technology using analogue
switching/transmission
These networks evolved to use digital
switching/transmission technologies
» Such networks are referred to as integrated digital networks
(IDN’s)
» The driving force behind this evolution was the need to provide
economic voice communications
» Fortunately IDN were also suitable for digital data services and
were referred to the Integrated Services Digital Network (ISDN)
6
3
ISDN
‹
An ISDN is:
"an integrated digital network in which the same digital switches and digital paths are
used to establish connections for different services; for example, telephony and data.”
‹
The key benefit of ISDN:
»
‹
‹
It can carry data services and voice services without any performance penalty for the voice
services
By the mid-1990s deployment of ISDN became widespread
An important development derived from ISDN was Frame Relay
»
»
»
This is a higher-speed packet switching network
Although initially part of ISDN it quickly became popular as a network technology in its own
right
In response to demand the ITU began developing Broadband-ISDN
“A broadband service or system is one that requires high-speed transmission channels
(greater than the primary rate ISDN).”
7
The Arrival of ATM
‹ The
factors that influenced the development of BISDN are as follows:
» The availability of high-speed transmission, switching
and signal-processing technologies
» Improved end-user computers with better data- and
image-processing capabilities
» Advances in software application processing
» Changing requirements of both user and operator
» Eventually Asynchronous Transfer Mode (ATM) was
developed as the transfer mode for implementing BISDN
8
4
ATM
‹
‹
ATM is another high-speed packet switching network technology
It achieves even greater speeds than FR
» Up to the Gbps range
‹
‹
With the arrival of ATM the ISDN has evolved into an end-to-end
packet-based network both at the user-network interface and within
the network itself
Today ATM is found in the following applications:
» Public network infrastructure: ATM enables public teleco’s to support
telephony, cable TV etc.
» ATM LAN: ATM can be used for Backbone LANs and as Switching Hub
for end systemsThis segment has been driven by the need for high-speed,
low-cost support within the local area.
» ATM WAN: Providing high-speed, long distance connectivity for private
and public enterprises
9
Low-speed LANs
‹
‹
PCs have become an essential tool for the office worker
The original LANs that interconnected these PCs provided
very basic connectivity services such as:
» Interconnecting PCs and terminals to mainframes running
corporate applications
» Providing workgroup connectivity across the organization
‹
Consequently traffic patterns were relatively light
» Mainly used for file transfer and e-mail
» Ethernet and Token Ring are well suited to this environment
10
5
The emergence of High-speed LANs
‹
Since the 1990s, two trends have affected traffic patterns:
» High Spec PCs: The speed and computing power of PCs have improved
significantly;
– A typical PC comprises high-speed processors (hundreds of MHz), RAM of
64MB+ and GB hard drives
– These platforms are needed to support graphics-intensive applications and
GUI’s
» Network Computing: LANs have become an essential computing
platform with greater emphasis on network computing:
– The client-server model for computing has become a dominant architecture
– This has given rise to Web-focused intranets
‹
These trends have led to:
– An increase in the volume of data across LANs
– A lower tolerance for delay on data transfers.
‹
The 1st generation of 10-Mbps Ethernets and 16-Mbps Token Rings
could not support these requirements
11
The need for High-speed LANs
‹
Typical application of higher-speed LANs:
» Centralized server farms: Here client applications draw huge
amounts of data from centralized servers, called server farms
– e.g. a colour publishing application comprising networked servers
holding Gbytes of image data
» Power workgroups: Here small numbers of cooperating users
share massive data files across the network
– e.g. software development groups that run tests on new software
versions, computer-aided design (CAD) companies running
simulations of new designs etc.
» High-speed local backbone: As the user base grows the number of
LANs proliferate. High-speed interconnection is necessary to
maintain performance
12
6
Corporate WAN Requirements
‹
The same factors that have affected LANs have also affected corporate
WANs:
» In the early 1990s, many organizations adopted a centralized data
processing model
– Here high-end mainframes housed the corporate applications. These
mainframes were located at a small number of regional offices
» More recently many organizations have:
– Brought the processing power to the end-user with high-spec PCs,
workstations, and servers
– Changed the nature of the application structure adopting a client-server
approach and intranet/internet computing
‹
These trends lead to more data being transported off premises
» Originally 80% of the traffic remained on the LAN and about 20% went
across the WAN
» Nowadays a greater percentage of the traffic goes into the WAN
environment
13
QoS on The Internet
‹
‹
The Internet Protocol (IP) is as low as most people tend to conceptualize
networks
IP was designed to provide a best-effort, fair delivery service
» Here all packets are treated equally
» In the event of congestion packets are simply dropped at random (this is seen as
‘fair’)
‹
These days a lot of traffic is derived from real-time, multimedia, and
multicasting applications:
» IP has proven woefully inadequate at coping with these applications
– However, many companies have spent millions of dollars installing IP-based internets
» ATM is the only networking scheme designed to support different types of traffic
» To start using ATM would require either replacing the existing IP-based
configurations or constructing secondary ATM network infrastructures
» Both of these options are expensive
‹
In order to appreciate the networking issues faced by organisations it is
important to understand the different types of traffic
14
7
Elastic and Inelastic traffic
‹
Traffic on an internet can be classified as either elastic or inelastic
» Elastic traffic can cope with large changes in delay and throughput across an
internet:
– Examples include file transfer, electronic mail, remote logon, network management, Web
access etc.
– This is the traditional type of traffic for which internets were designed
– But even amongst these applications there can be differences in requirements
» Inelastic traffic does not tolerate changes in delay and throughput across an
internet:
– Examples include real-time voice and video
– Inelastic traffic generally has specific requirements in the areas of: Throughput, Delay,
Delay variation and Packet loss
– These requirements are very difficult to address in a typical IP-based internet
environment. These networks typically have variable queuing delays and congestion
losses
‹
It is clear that both types of traffic need to be supported:
» Inelastic applications need to be given preferential treatment without affecting the
traditional elastic traffic which must continue to be supported
15
Delay sensitivity versus Criticality
CEO Videoconferencing
VoIP
N/W
Monitoring
Financial
Transactions
Unicast
Radio
Public
Web Traffic
Corporate
Web Traffic
N/W
Management
Push News
Personal
e-mail
Business
e-mail
Server
Backups
16
8
Delay sensitivity versus Criticality
17
9