1. Department of Electrical and Computer Engineering
ECE 4371, Fall, Introduction to Telecommunication Engineering/Telecommunication Laboratory
                                                           
Zhu Han
Department of Electrical and Computer Engineering
Class 22
Nov. 17th, 2014

2. Outline OIS Model TCP/IP Model Comparison Overall Architecture
Functionality
TCP/IP Model
Comparison

3. OSI Model The Open Systems Interconnection (OSI) model
A conceptual model
Partitioning it into abstraction layers
Characterizes and standardizes the internal functions of a communication system
“Open” denotes the ability to connect any two systems which conform to the reference model and associated standards
The primary Architectural model for inter-computer communications

4. History of OSI Model
International standard organization (ISO) established a committee in 1977 to develop an architecture for computer communication
Open Systems Interconnection (OSI) reference model is the result of this effort
In 1984, the OSI reference model was approved as an international standard for communications architecture

5. History of OSI Model
The OSI model is now considered the primary architectural model for inter-computer communications
The OSI reference model divides the problem of moving information between computers over a network medium into
SEVEN smaller and more manageable problems
This separation into smaller more manageable functions is known as layering

6. Advantages
Layer architecture simplifies the network design and adds flexibility
It is easy to debug network applications in a layered architecture network
We do not need to modify the entire host software to include more communication devices
The network management is easier due to the layered architecture
Network layers follow a set of rules, called protocol
Defines the format of the data being exchanged
The control and timing for the handshake between layers

7. OSI framework architecture
OSI had two major components:
An abstract model of networking, called the Basic Reference Model or seven-layer model
A set of specific protocols

8. OSI in Action
A layer serves the layer above it and is served by the layer below it.
A message begins at the top application layer and moves down the OSI layers to the bottom physical layer
As the message descends, each successive OSI model layer adds a header to it
Conversely, at the receiving end, headers are striped from the message as it travels up the corresponding layers

9. Communication Between Each Layer
At each level (N), two entities (layer N peers) exchange protocol data units (PDUs) by means of a layer-N protocol.
A service data unit (SDU) is the payload of a PDU, transmitted unchanged to a peer.
The SDU is a unit of data that is passed down from one OSI layer to the next-lower layer, and which the lower layer encapsulates into a PDU.
Layer N-1 adds a header or a footer, or both, to the SDU, composing a PDU of layer N-1.
The PDU at a layer N thus becomes the SDU of layer N-1.

10. Example – LTE-A NAS IP RRC PDCP RLC MAC PHY
To Evolved Packet Core
EUTRAN
To Radio
LTE-A Upper Layer Functionality
Medium Access Control (MAC)
Radio Link Control (RLC)
Packet Data Convergence Protocol (PDCP)
Radio Resource Control (RRC)
Non-Access Stratum (NAS)

11. Packet formatting • • • PDCP K-1 K K+1 RLC MAC Padding Transport block
SDU: Service data unit
PDU: Protocol data unit
Data from IP packets
PDCP SDUs
PDCP
PDCP PDUs
PDCP header
PDCP header
PDCP header
RLC SDUs
K-1 K
K+1
RLC
RLC PDUs
RLC header
MAC SDUs
MAC
MAC PDUs
MAC header
Padding
Transport block
PHY
• • •
Slot 0
Slot 1
Slot 2
Slot 17
Slot 18
Slot 19
subframe

12. Communication Between Each Layer

13. Communication Within Each Layer
At each level, two instances at one layer are connected by a horizontal connection on that layer.
Two entities (N-entity peers) interact by means of the N protocol by transmitting protocol data unit.

14. OSI Layer Functionality
Data unit
Layer
Function
Host layers
Data
7. Application
Network process to application
6. Presentation
Data representation, encryption and decryption, convert machine dependent data to machine independent data
5. Session
Interhost communication, managing sessions between applications
Segments
4. Transport
Reliable delivery of segments between points on a network.
Media layers
Packet/Datagram
3. Network
Addressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.
Bit/Frame
2. Data link
A reliable direct point-to-point data connection.
Bit
1. Physical
A (not necessarily reliable) direct point-to-point data connection.

15. Physical Layer
Provides physical interface for transmission of information
Defines rules by which bits are passed from one system to another on a physical communication medium
Covers all aspects for physical communication
Mechanical
Electrical
Functional
Procedural
Characteristics defined by physical layer
Voltage levels
Timing of voltage changes
Physical data rates
Maximum transmission distances
Physical connectors
And other similar attributes

16. Data Link Layer
Attempts to provide reliable communication over the physical layer interface
Handle errors by implementing an acknowledgement and retransmission scheme
Breaks the outgoing data into frames and reassemble the received frames
Implement flow control
Supports points-to-point protocol (PPP) as well as broadcast communication
The data link layer is divided into two sub-layers:
Media Access Control (MAC) layer
Responsible for controlling how computers in the network gain access to data and permission to transmit it.
Logical Link Control (LLC) layer
Controls error checking and packet synchronization.

17. Network Layer
Implements routing of frames (packets) through the network
Defines the most optimum path the packet should take from the source to the destination
Defines logical addressing so that any endpoint can be identified
Defines how to fragment a packet into smaller packets to accommodate different media
Handles congestion in the network

18. Transport Layer
Provide a reliable mechanism for the exchange of segment between two processes in different computers
Ensures that the data units are delivered error free and in sequence
Ensures that there is no loss or duplication of data units
Provides connectionless or connection oriented service
Provides for the connection management
Compare it with a Post Office
Deals with the dispatch and classification of mail and parcels sent

19. Session Layer Provides
Mechanism for controlling the dialogue between the two end systems
Defines how to start, control and end conversations between applications
Responsible for terminating the connection
Full-duplex, half-duplex, or simplex operation
Check-pointing mechanism
If a failure of some sort occurs between checkpoints, all data can be retransmitted from the last checkpoint
Any necessary log-on or password validation is also handled by this layer

20. Presentation Layer
Defines the format in which the data is to be exchanged between the two communicating entities
Transforms data into the form that the application accepts
Handles data compression and data encryption (cryptography)

21. Application Layer
The highest level of OSI model, closest to the end user,
Both the OSI application layer and the user interact directly with the software application
Contains management functions to support distributed applications
Examples are applications such as file transfer, electronic mail, remote login etc.

22. Outline OIS Model TCP/IP Model Comparison Overall Architecture
Functionality
TCP/IP Model
Comparison

23. TCP/IP Model The main design goal of TCP/IP
The Internet protocol suite
Named for two of its most important protocols:
Transmission Control Protocol (TCP) and the Internet Protocol (IP)
The networking model and a set of communications protocols used for the Internet and similar networks.
The main design goal of TCP/IP
Build an interconnection of networks (internetwork or internet)
Provided universal communication services over heterogeneous physical networks.

24. Transport Layer (TCP/UDP)
TCP/IP Model
The TCP/IP model does not consider the specifics of formatting and presenting data, and does not define additional layers between the application and transport layers as in the OSI model (presentation and session layers).
Organized into four abstraction layers
Application Layer
Application programs using the network
Transport Layer (TCP/UDP)
Management of end-to-end message transmission,
error detection and error correction
Network Layer (IP)
Handling of datagrams : routing and congestion
Data Link Layer
Management of cost effective and reliable data delivery,
access to physical networks

25. Advantages
The enabling of communication between hosts on different networks, perhaps separated by a large geographical area.
The creation of a standardized abstraction of the communication mechanisms provided by each type of network.
Each physical network has its own technology-dependent communication interface, in the form of a programming interface that provides basic communication functions (primitives).
The protocol stack allows for division of labor, ease of implementation and code testing, and the ability to develop alternative layer implementations.
A layer provides a service for the layer directly above it and makes use of services provided by the layer directly below it.

26. TCP/IP Model
ECE 4371 Fall 2008

27. Data-Link Layer
Also called the link layer or the network interface layer
The interface to the actual network hardware.
This interface may or may not provide reliable delivery, and may be packet or stream oriented.
In fact, TCP/IP does not specify any protocol here, but can use almost any network interface available, which illustrates the flexibility of the IP layer.
ECE 4371 Fall 2008

28. Network Layer Also called the internetwork layer or the inter layer
Provides the “virtual network” image of an internet (this layer shields the higher levels from the physical network architecture below it).
Internet Protocol (IP) is the most important protocol in this layer.
It is a connectionless protocol that does not assume reliability from lower layers.
IP does not provide reliability, flow control, or error recovery.
These functions must be provided at a higher level.
ECE 4371 Fall 2008

29. Transport Layer
The transport layer provides the end-to-end data transfer by delivering data from an application to its remote peer.
Multiple applications can be supported simultaneously.
The most-used transport layer protocol is the Transmission Control Protocol (TCP),
Provides connection-oriented reliable data delivery, duplicate data suppression, congestion control, and flow control.
ECE 4371 Fall 2008

30. Application Layer
The application layer is provided by the program that uses TCP/IP for communication.
An application is a user process cooperating with another process usually on a different host (there is also a benefit to application communication within a single host).
Examples of applications include Telnet and the File Transfer Protocol (FTP).
ECE 4371 Fall 2008

31. Outline OIS Model TCP/IP Model Comparison Overall Architecture
Functionality
TCP/IP Model
Comparison

32. Comparison with OSI model
In the TCP/IP model of the Internet
Protocols are not designed into strict layers as in the OSI model
Compared with the OSI layering scheme in the following way:
Application layer includes the OSI application layer, presentation layer, and most of the session layer
Its end-to-end transport layer includes the graceful close function of the OSI session layer as well as the OSI transport layer
The network layer is a subset of the OSI network layer
The link layer includes the OSI data link and physical layers, as well as parts of OSI's network layer.
Network
Link

33. Comparison with OSI model
Examples of application-layer implementations also include:
On OSI stack:
FTAM File Transfer and Access Management Protocol
X.400 Mail
Common Management Information Protocol (CMIP)
On TCP/IP stack:
Hypertext Transfer Protocol (HTTP)
File Transfer Protocol (FTP)
Simple Mail Transfer Protocol (SMTP)
Simple Network Management Protocol (SNMP)

34. Outline Thank You! OIS Model TCP/IP Model Comparison
Overall Architecture
Functionality
TCP/IP Model
Comparison
Thank You!