2. Network Communication
• Recognize data
• Divide data into manageable chunk
• Add information to each chunk to:
– Determine where the data is coming from
– Identify where the data is going to
• Add timing and error checking information
• Put the data on the network and send it on
3. Why Networking Standards are needed?
• Standards provide a fixed way for hardware and/or
software systems to communicate.
• Need for standard protocols so that software/hardware
from different vendors could communicate
• Network operating systems follow strict rules (protocols)
to control how each of the previous tasks are
• For example, USB enables two pieces of equipment to
interface even though they are manufactured by different
• By allowing hardware and software from different
companies to interconnect, standards help promote
4. Types of Standards
There are two main types of standards:
• Formal: a standard developed by an industry
or government standards-making body
• De facto: standards that emerge in the
marketplace and are widely used, but lack
official backing by a standards-making body
5. The Standardization Processes:Three Steps
• Specification: developing the classification
and identifying the problems to be
• Identification of choices: identify solutions
to the problems and choose the “optimum”
• Acceptance: defining the solution, getting it
recognized by industry so that a uniform
solution is accepted.
7. American National Standards Institute (ANSI)
• ANSI is an organization composed of more
than 1000 representatives from industry in
addition to other fields, such as chemical and
nuclear engineering, health and safety, and
• ANSI also represents the United States in
setting international standards.
8. Electronic Industries Alliance (EIA)
• EIA is a trade organization composed of
representatives from electronics manufacturing firms
across the United States.
• EIA began as the Radio Manufacturers Association
(RMA) in 1924; over time it evolved to include
manufacturers of televisions, semiconductors,
computers and networking devices.
9. Institute of Electrical and Electronic Engineers
• The IEEE is an international society composed
of engineering professionals.
• Its goals are to promote development and
education in the electrical engineering and
computer science fields.
10. International Organization for Standardization (ISO)
• ISO is a collection of standards organizations
representing 130 countries.
• ISO’s goal is to establish international
technological standards to facilitate global
exchange of information and barrier-free trade.
11. International Telecommunication Union (ITU)
• The ITU is a specialized United Nations agency that
regulates international telecommunications, including
radio and TV frequencies, satellite and telephony
specifications, networking infrastructure, and tariffs
applied to global communications.
• It also provides developing countries with technical
expertise and equipment to advance those nations’
12. IEEE Networking Specifications
• 802.1 – Internetworking – Covers routing, bridging, and internetwork
• 802.2 – Logical Link Control – Relates to error and flow control over data
• 802.3 – Ethernet LAN – Covers all forms of Ethernet media and interfaces.
• 802.4 – Token Bus LAN – Covers all forms of Token Bus media and
• 802.5 – Token Ring LAN – Covers all forms of Token Ring media and
• 802.6 – Metropolitan Area Network (MAN) – Covers MAN technologies,
addressing, and services.
13. IEEE Networking Specifications
• 802.7 – Broadband Technical Advisory Group – Covers broadband
networking media, interfaces, and other equipment.
• 802.8 – Fiber Optic Technical Advisory Group – Covers use of fiber-optic
media and technologies for various networking types.
• 802.9 – Integrated Voice/Data Networks – Covers integration of voice and
data traffic over a single network medium.
• 802.10 – Network Security – Covers network access controls, encryption,
certification, and other security topics.
• 802.11 – Wireless Networks – Standards for wireless networking for many
different broadcast frequencies and usage techniques.
• 802.12 – High Speed Networking – Covers a variety of 100Mbps plus
technologies, including 100BASEVG-AnyLAN.
14. LAYERED TASKS
• Use of the concept of layers in our daily life.
• As an example, let us consider two friends who
communicate through postal mail.
• The process of sending a letter to a friend would be
complex if there were no services available from the
Sender, Receiver, and Carrier
16. THE OSI MODEL
• Established in 1947, the International Standards
Organization (ISO) is a multinational body dedicated
to worldwide agreement on international standards.
• An ISO standard that covers all aspects of network
communications is the Open Systems Interconnection
(OSI) model. It was first introduced in the late 1970s.
ISO is the organization.
OSI is the model.
17. Relationship of OSI Layers
• Each layer of the OSI model must communicate with the layer
above and below it
– For example, the Presentation layer must communicate
with the Application layer (one above) and the Session
layer (one below)
• As data passes down through the OSI layers, each layer
(except Physical) adds some information to the data
• When data reaches the receiving computer, the information
added by each layer of the OSI model is read and processed by
the corresponding layer on the receiving computer
• This is referred to as peer-layer communications
18. Relationships among Seven layers of the OSI model
Computer A Computer B
32. TCP/IP PROTOCOL SUITE
• The layers in the TCP/IP protocol suite do not exactly
match those in the OSI model.
• The original TCP/IP protocol suite was defined as
having four layers: host-to-network, internet,
transport, and application.
• However, when TCP/IP is compared to OSI, we can
say that the TCP/IP protocol suite is made of five
layers: physical, data link, network, transport, and
36. OSI Process
Places bits onto the network media
Data Link Layer
Packages data into frames
Adds FCS; adds physical addresses
passes to Physical layer
Add network addresses
passes data to Data Link Layer
adds sequencing info
passes data to Network layer
Adds a control frame to data that
indicates that you have the right to transmit data
passes data to Transport layer
encyrpts request (if necessary)
adds any codes required to implement formatting
passes request to Session layer
for data and sends
request to Presentation layer
Request for e-mail is received by Physical layer
on receiving computer
Request is passed up the layers of the OSI model
Each layer read, processes and removes info added by cooresponding layer on sending computer
User Requests Mail
37. In Next Figure a node with physical address 10 sends a
frame to a node with physical address 87. The two nodes
are connected by a link (bus topology LAN). As the figure
shows, the computer with physical address 10 is the
sender, and the computer with physical address 87 is the
39. Most local-area networks use a 48-bit (6-byte) physical
address written as 12 hexadecimal digits; every byte (2
hexadecimal digits) is separated by a colon, as shown
A 6-byte (12 hexadecimal digits) physical address.
40. Next Figure shows a part of an internet with two routers
connecting three LANs. Each device (computer or router)
has a pair of addresses (logical and physical) for each
connection. In this case, each computer is connected to
only one link and therefore has only one pair of addresses.
Each router, however, is connected to three networks (only
two are shown in the figure). So each router has three
pairs of addresses, one for each connection.
42. Next Figure shows two computers communicating via the
Internet. The sending computer is running three processes
at this time with port addresses a, b, and c. The receiving
computer is running two processes at this time with port
addresses j and k. Process a in the sending computer
needs to communicate with process j in the receiving
computer. Note that although physical addresses change
from hop to hop, logical and port addresses remain the
same from the source to destination.
44. Communication Functions according to the OSI Model
User applications ..
Session to transport
Layer and flow
deactivation of con.