8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 1/21
Topics Covered
Network SoftwareOSI Reference Model
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 2/21
Network Software
Basic activities :• reliability (error correction, messages order preservation),• flow control,• addressing (to refer to users),• connection and disconnection,• routing.
Secondary activities :• take the heterogeneity of the network into account,•
synchronization of the transmission,• multiplexing- de multiplexing,• error recovery,• congestion control,• failure management,
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 3/21
Layers, Protocols & Interfaces
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 4/21
Design issues for layers
• Identifying senders & receivers
• Rules of Data transfer
• Error control• Sequencing
• Speed regulation
• Inability to process long messages
• Multiplexing
• Routing
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 5/21
Interfaces & services
Service Provider
Service User Peer Entities
SAP-Service Access Point
IDU-Interface Data Unit
SDU-Service Data Unit
PDU-Protocol data UnitICI-Interface Control Information
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 6/21
Types of services
Connection-oriented services
Connectionless services
Service Primitives
Services/Protocols Relations
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 7/21
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 8/21
OSI Reference model
(7 layered )
• Principles
1. Different level of abstraction.
2. Well defined function.3. Defining international standard protocols.
4. Minimum information flow across interfaces.
5. No. of layers.
Not a network Architecture
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 9/21
OSI Model
Medium/Channel
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 10/21
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 11/21
Physical Layer
• Transmitting raw bits over a communication
channel.
• Design issues :Mechanical
Electrical
Procedural
• Protocols: Fast Ethernet, RS232, and ATM
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 12/21
Data Link Layer
• Handles errors in the physical layer
• Frame boundaries: special bit patterns
• Problem of damaged, lost & duplicate frames.
• Speed matching
• Transmission in both directions
• Broadcast n/w s
Data Link layer
MAC
Medium Access Layer
LLC
Logical Link Layer
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 13/21
Network Layer
• Controlling the operation of the subnet.
• Switching & Routing: Virtual circuits
• Congestion control
• Heterogeneous networks
• Billing purpose
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 14/21
Transport Layer (End to End layer)
• Insulates the upper layers
• Efficient transfer of data between layers.
• Establishing two types of connections:
network connections
transport connections
• Type of service to the service layer.
• Supports multiprogramming
• Flow control
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 15/21
Session Layer
• Establish the sessions.
• Dialogue control
• Token management
• Synchronization
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 16/21
Presentation Layer :compatibility problems
Application Layer : supports end user processes
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 17/21
Data Transmission
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 18/21
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 19/21
ENCAPSULATION
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 20/21
Criticism of the model
• It was not the right moment
• It was not the right technology
• It was not the right implementation
• It was not the right policy
8/14/2019 Network Software & OSI Model
http://slidepdf.com/reader/full/network-software-osi-model 21/21