1. Telemedicine

2. BREAK THE THINGS UP To solve a big problem:
You have to break it to small problems.
Sub activities.
Different Layers or Levels.
Hierarchy
Manager for every department
Requests from the lower layers
Giving service to upper layers

3. Network Hierarchy Different layers  Different duties
Different Networks  Different names, contents, layers…
Every layer is a Virtual Machine
Requests and Responses for every layer
For every layer:
Service TO upper layer
Requests FROM upper layer
Requests to lower layer
Service FROM lower layer
Hiding the details  Object Oriented Programming

4. Example: Manager of a company
Manager  Second Manager  …  Employee
Manager doesn’t know about the details of lower layers
The same goes from bottom to top.
It is a good thing…
Maybe we want to upgrade some layers…
Other layers will not notice the upgrade  good thing

5. IMPORTANT EXAMPLE
Queen to Queen :D.

6. Keywords
a protocol is a standard used to define a method of exchanging data over a computer network.
Protocol of the story: Invitation between two kings.
Peer  two peers connect to each other with a protocol.
In a protocol the connection is not a real connection.
The real connection is between the king and the translator.

7. Keywords
Interface  How the upper layer should have a connection with the lower layer.  king with translator.
Physical Medium  Making the REAL connection  The bird.
Protocol Stack  How you make a connection with others  Hand shaking, Bowing down or …
Network Architecture
Header and Trailer  The number of the message in the king example.  MUST COME AT THE VERY BEGINNING

8. Keywords

9. Important Notices Virtual connection  Protocol
Real connection  Interface
Hardware implementation in lower layers
Due to the big volume of messages
First and Second Layer are Hardware Implemented  IC (Sometimes)

10. Important Notices in Implementation
Reliability
Making sure the components are working the right way
E.g. the birds may get killed by other birds.
Error
Noise
Error Detection  Ask to send again
Error Correction  Difficult
Redundancy
Routing  Different Paths  Maybe some are better

11. Important Notices in Implementation
Scalability
Predict the future  Growth rate…
internetworking  Different technologies  How to connect them?
High traffic  How to maintain good quality?
Protocol Layering
Addressing
Identifying Sender and Receiver
New and quality Services  Somehow a scalability problem

12. Important Notices in Implementation
Resource Allocation
Sharing the resources  E.g. Band allocation
Dynamic allocation
Flow Control
Real Time Services
Congestion
Quality of Service (QoS)

13. Important Notices in Implementation
Security
Confidentiality
Authentication
Integrity
Cryptography

14. Connection Services Connection-Oriented Connection less
E.g. Telephone Network
Keeping the order of data
Negotiation between the two side of connection
Circuit  A close path between sender and receiver
Connection less
E.g. Internet (Web browsing, …)
Post Network  From different paths the message is delivered
Specific address for every message
Switching and routing of packet
Cut Through Switching
Store and Forward Switching

15. Switching

16. Packet Switching
The network layer is designed as a packet-switched network. This means that the packet at the source is divided into manageable packets, normally called datagrams. Individual datagrams are then transferred from the source to the destination. The received datagrams are assembled at the destination before recreating the original message.

17. Connection-Oriented and Connectionless Services
Layers can offer two types of services to the layers above: connection oriented services and connection-less services
Connection oriented services
Reliable message stream (sequence of pages)
Reliable byte stream (remote login, file transfer, etc..)
Unreliable connection (digitized voice or video)
Connection-less
Datagram service
Acknowledged datagram service
Request-reply service

18. Connection-Oriented and Connectionless Services

19. Service Primitives
A Service is formally specified by a set of primitives

20. Service Primitives
Five service primitives for implementing a simple connection- oriented service.

21. Protocol vs Service
Queen requests a service from the king (sending an invitation)
Queen doesn’t know the protocol between the two kings
The 2 kings may change the connection protocol, if the service requested by queen has not changed

22. Protocol vs Service
Service – set of primitives (operations) that a layer provides to the layer above it. Relate to the interfaces between layers.
Protocol – set of rules governing the format and meaning of packets exchanged by peer entities within a layer. Relate to the packets that are sent between peer entities between different machines.