Python Notes for mca i year students osmania university.docx
01 overview[1]r
1. Data and Computer
Communications
Chapter 1 – Data Communications,
Data Networks, and the Internet
Ninth Edition
by William Stallings
Data and Computer Communications, Ninth
Edition by William Stallings, (c) Pearson
Education - Prentice Hall, 2011
2. Data Communications, Data
Networks, and the Internet
“The fundamental problem of
communication is that of reproducing at
one point either exactly or approximately a
message selected at another point”
- The Mathematical Theory of
Communication,
Message Claude Shannon
Message
3. Technological Advancement
Driving Forces
Traffic • Development of
growth at new services
a high &
steady • Advances in
rate technology
4. Changes in Networking
Technology
* Emergence of high-speed LANs
* Corporate WAN needs
* Digital electronics
5. Convergence
The merger of previously distinct telephony
and information technologies and markets
Layers:
• applications
• these are seen by the end users
• enterprise services
• services the information network supplies to support
applications
• infrastructure
• communication links available to the enterprise
7. Benefits
Convergence benefits include:
Efficiency Effectiveness Transformation
• better use of • the converged • enables the
existing environment enterprise-wide
resources, and provides users adoption of
implementation with flexibility, global
of centralized rapid standards and
capacity standardized associated
planning, asset service service levels
and policy deployment and
management enhanced
remote
connectivity
and mobility
11. Transmission Lines
Capacity
The basic building block of
any communications facility
is the transmission line.
Reliability
The business manager is
concerned with a facility Cost
providing the
required capacity, Transmission
with acceptable reliability,
Line
at minimum cost.
12. Two mediums currently driving
the evolution of data communications
transmission are:
and
13. Networking
Advances in technology have led to greatly
increased capacity and the concept of
integration, allowing equipment and
networks to work simultaneously.
Voice Data
Image Video
14. LANs and WANs
There are two broad categories
of networks:
Local Area Networks (LAN)
Wide Area Networks (WAN)
15. Wide Area Networks (WANs)
Span a large geographical area
Require the crossing of public right-of-ways
Rely in part on common carrier circuits
Typically
consist of a number of
interconnected switching nodes
16. Wide Area Networks
Alternative technologies used include:
Circuit switching
Packet switching
Frame relay
Asynchronous Transfer Mode (ATM)
17. Circuit Switching
Uses a dedicated communications path
Connected sequence of physical links
between nodes
Logical channel dedicated on each link
Rapid transmission
The most common example of circuit
switching is the telephone network
18. Packet Switching
Data are sent out in a sequence of small
chunks called packets
Packets are passed from node to node
along a path leading from source to
destination
Packet-switching networks are commonly
used for terminal-to-terminal computer and
computer-to-computer communications
19. Frame Relay
Developed to take advantage of high data
rates and low error rates
Operates at data rates of up to 2 Mbps
Rate of errors dramatically lowered thus
reducing overhead of packet-switching
20. Asynchronous Transfer Mode
(ATM)
Referred to as cell relay
Culmination of circuit switching and packet
switching
Uses fixed-length packets called cells
Works in range of 10’s and 100’s of Mbps
and in the Gbps range
Data rate on each channel dynamically set
on demand
23. The Internet
Internetevolved from ARPANET
Developed to solve the dilemma of
communicating across arbitrary, multiple,
packet-switched network
TCP/IP provides the foundation
28. Summary
Trends challenging data communications:
• traffic growth
• development of new services
• advances in technology
Transmission mediums
• fiber optic
• wireless
Network categories:
• WAN
• LAN
Internet
• evolved from the ARPANET
• TCP/IP foundation
Notes de l'éditeur
Changes in networking technology include a growing need for high-speed LANs in the business environment to support requirements like Centralized server farms, Power workgroups, and High-speed local backbones. Changes in corporate data traffic patterns are driving the creation of high-speed WANs. Rapid conversion of consumer electronics to digital technology is having an impact on both the Internet and corporate intranets, dramatically increasing the amount of image and video traffic carried by networks.
ConvergenceConvergence refers to the merger of previously distinct telephony and information technologies and markets. We can think of this convergence in terms of a three-layer model of enterprise communications: Applications: These are seen by the end users of a business. Convergence integrates communications applications, such as voice calling (telephone), voice mail, e-mail, and instant messaging, with business applications, such as workgroup collaboration, customer relationship management, and other back-office functions. With convergence, applications provide features that incorporate voice, data, and video in a seamless, organized, and value-added manner. One example is multimedia messaging, which enables a user to employ a single interface to access messages from a variety of sources (e.g., office voice mail, office e-mail, beeper, and fax).Enterprise services: At this level, the manager deals with the information network in terms of the services it supplies to support applications. The network manager needs design, maintenance, and support services related to the deployment of convergence-based facilities. Also at this level, network managers deal with the enterprise network as a function-providing system. Such management services may include setting up authentication schemes; capacity management for various users, groups, and applications; and QoS provision.Infrastructure: The infrastructure consists of the communication links, LANs, WANs, and Internet connections available to the enterprise. The key aspect of convergence at this level is the ability to carry voice and video over data networks, such as the Internet.
Stallings DCC9e Figure 1.3, based on [MILL05], illustrates the three layers and their associated convergence attributes. In simple terms, convergence involves moving voice into a data infrastructure, integrating all the voice and data networks inside a user organization into a single data network infrastructure, and then extending that into the wireless arena. The foundation of this convergence is packet-based transmission using the Internet Protocol (IP). Convergence increases the function and scope of both the infrastructure and the application base.
Convergence brings many benefits, including simplified network management, increased efficiency, and greater flexibility at the application level. For example, a converged network infrastructure makes it easier to add applications that combine video, data, and voice. [POL07] lists the following three key benefits of convergence: Efficiency: Provides a double-digit percent reduction in operating costs through the convergence of legacy networks onto a single global IP network, better use of and reduction in existing resources, and implementation of centralized capacity planning, asset management, and policy management.Effectiveness: The converged environment has the potential to provide users with great flexibility, irrespective of where they are. Such a company-wide environment provides for rapid standardized service deployment and enhanced remote connectivity and mobility.Transformation: Convergence also enables the enterprise-wide adoption of global standards and associated service levels, thus providing better data, enhanced real-time global decision-making processes, and improved execution in business planning and operations. This leads to greater agility for the enterprise in providing new services to its customers and employees.
One of the basic choices facing a business user is the transmission medium. Changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications. Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression.
Networks are currently classified into two broad categories: Local Area Networks (LANs) and Wide Area Networks (WANs).
Traditionally, WANs have been implemented using one of two technologies: circuit switching and packet switching. More recently, frame relay and ATM networks have assumed major roles.
Stallings DCC9e Table 1.2 lists Internet terminology.
