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Shortest Path Algorithm
Dijkstra Algorithm. Weighted edges and resourse hungry to create
Shortest Path Advantages   Shortest Path Disadvantages
This algorithm makes allows the network to use the shortest path between any two nodes minimising delay.   This algorithm is very resourse heavy to search
Packet switching network Virtual Circuit
This is where all the packets are sent along the same routing path and this means that the packets cant arrive out of order.
Packet Switching Network Four sources of delay
1. Nodal processing 2.Queuing 3. Transmission delay 4.Propagation delay
Packet Switching Network Difference between datagram and VC
The VC sends all along the same path and this is most suited to things like skypes video and voice calling to reduce distortion. The Datagram sends packets by different paths to be reordered and reassembled at the other end, likely use in P2P
Jitter
Jitter comes about by changes in the environment in the transfer medium, for instance a change in electric interfearance around he line. This means that the realtime application may experiance distortion as packets arrive out of order or they have a gap due to increased delay.
NAT
Network Address Translation Converts an external IP to an internal IP in a network. This allows less IPV4 addresses to be assigned to end users. This meant that there would be a great reduction in external assignmnets and thus saving IPV4.
Types of WWW Document
Static - This is where the page is manually created by a developer and the information has to be changed by a developer each time to be updated. This is usually used for web pages that contain informantion that does not change often. Every request to the webserver responds with the same document. Dynamic- This is an adaptive page that will change depending on the users actions. This is generally done without further requests to the webesrver. every request creates a new document Active- This is a program that the web server sends to the client and the client must run it locally.
the two army problem
This is where two armies are in a war, one army splits their forces and forms a pincer movement. If both sides of the pincer attack at the same time then this army will win. They both set up camp and then the problem is how to communicate to the other party when they will attack. If they send a messenger and the messenger does not arrive in time then they will attack alone and lose. This is like the connectionless service and hence we call it unreliable as we dont actually know if the message was sent and received.
OSI Model
7. Application 6. Presentation Layer 5.Session Layer 4.Transport 3.Network 2.Data link 1.Physical
Application Layer
This is where the user interacts and initiates any netowrking related activity from the operation System.
Presentation Layer
This layer is in charge of converting all of the data into a standard set that the other layers understand.
Session Layer
Establishes maintains and ends communication with the receiving device
Transport Layer
This maintains the flow control, provides error checking and recovery. Flow control is taking all of the data from all sources and converting it into one stream of data.
Network Layer
this is where the method of transmission is determined. This is in charge of addressing, routing and protocols.
Data Layer
The physical protocol is assigned to the data and this deals with the packet sequencing.
Physical Layer
This is concerned wit the voltage levels, connections and timing.
Addressing
Port: This is an application specific communications construct which allows computers to communicate effectively. Logical: This is where something (memory) apppears to reside from the perspective of an application. Physical: This is the address that corresponds with address for the specific memory on the addressing bus.
Differences between TCP and UDP
TCP implements Flow control so the data is sent accuratly to the receiving computer. This method is reliable but slow. This is generally used for webpages and databases. UDP is only concerned with speed. There is no flow control and this is usually used for non essential appliactions like streaming media across the internet/
Capabilities provided by multi-service Core in the Next Generation Network
1. Allows a heighrachy of charging systems to support local, reginal international and interconnect acounts. 2. Support for a layered security model with centeralised administration with passive and active monitoring capabilities. 3.Support for tighter QOS specifications for performance improvements in various data connections.
JPEG
1. DCT 2. Quantisation 3. Compression First you find the value of the pixel in the top left corner, then a table i created and it shows the changes from this initial colour. Once the table is competed then quantisation is used to reduce the number of bits needed to represent the table. then compression is used to remove the redundant zeros.
Connection orientated VS Connectionless
connection oriented makes a handshake to establish a connection and make sure the device is ready to receive. always bi-directional. connectionless will just send the data regardless and hope the other end receives and understands the data.
equal cost multipath routing
if there are multiple best paths the tie for the top position in the routing table, packets ay be sent via different paths to balance the loading in the network which should improve the bandwidth per pipe.
Link State routing
This is opposed to the distance metric as the distance metric only focuses on how many hops it takes to get to the destination while linked state calculates the states of the outgoing links and chooses the fastest and most suited link. This means that linked state will take a longer option with faster transitions rather than a short one with slow transmissions.
Distance Vector Routing
This is where the router will find the path with the shortest number of hops to reach it's destination.
Security in the OSI layers
1. Application- Firewall and Anti-virus 2. Session - Authentication checks to make sure the session is correst 3. Datalink - Encryption so when transmitted people can't intercept it.
Repeater
What comes in, it will rebroadcast along its output lines.
Router
This takes packets from one network and transmits them to another network to their destination according to inbuilt protocols.
Switch
Takes the packet received and finds the correct recipient and then sends it to them.
Hub
This receives a packet and retransmits it across all its output lines. The terminals that i was not meant for will trash it on arrival.
Bridge
This is a way of connecting more than one Local Area Networks together.
Proxy Server
This is used to route all internet traffic from one terminal or network through another to appear as if the traffic origonated from the proxy server. thus annonnimity,another use is to block certain traffic from leaving a network by having proxy filters.
POP3 Advantages Disadvantages
Straight foward, Faster   If you lose an email then it is gone forever  
Imap Advantages Disadvantages
More Redundant, Keeps a copy of everything on the server. Slower, takes up more space
POP3 Description
PassThrough tech, the server holds the mail until you request it and then when you do it will send the mail to you.
IMAP Description
This is a Syncing server, It holds the mail on the server and when you request new mail it will send a copy of the mail while keeping a copy on the server. If you delete or compose on your client then these actions will be performed automatically on the server copies.
Internet Assigned Number Authority
3 groups
  • System   -  IETF
  • User       -  IANA
  • Dynamic -   NOT
Public Vs Private key encryption
Private - Both parties have a copy of the encryption/decryption algorithm and they use these to send messages. Public - There is only one private key that will decrypt the message if it is encoded with the persons public key. The user sends out the public key to others so they can use it to encrypt data for them.
Digital Signature
Used to prove someones identity through the decryption process. If they are unable to provide they are not trustworthy.
IPV4 to IPV6
To ease the transition there are a few options for networks. There can be Duel stacks or tunneling. Duel Stacks is where IPV4 and IPV6 can coexist where tunneling is where the non supported addressing version is encapsulated within the supported version.
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