Telemedicine

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

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

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

IMPORTANT EXAMPLE Queen to Queen :D.

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.

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

Keywords

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)

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

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

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)

Important Notices in Implementation Security Confidentiality Authentication Integrity Cryptography

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, Email…) 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

Switching

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.

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

Connection-Oriented and Connectionless Services

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

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

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

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.