Networks Flashcards
What is a network?
Connected devices that can communicate, share resources and data
What are protocols?
Rules and standards that govern how networks should function and communicate
What is a topology?
Theoretical arrangement of the comments of a networks. Actual arrangement is influenced by physical factors and cost
Draw a ring, bus, star and mesh topology and explain the +/- of each
Picture can be found in photo Library
Star: + no data collisions, fast, robust, cheap +hub can be node switch etc, can be split into segments
Ring: +few collisions due to one way traffic, fast, one cable (cheap), passes through NIC of each node
- if one node fails the whole network could
Mesh: +Decentralised, wired or wireless, no single point of failure, no need for Internet and directly communicate, Good for communication
- lots of expensive cable
Bus: + simple, cheap (one cable)
- lots of collisions, if the cable breaks so does the network, slow with heavy traffic
What is a LAN?
Local Area Network. Nodes connected are geographically close
Benefits/properties of LAN?
- organisation owns infrastructure
- allows communication
- Allows peripherals to be shared
- Allows data to be shared
- Can log on from any connected computer
- easy upgrade and virus scans
- Can run a program simultaneously on multiple devices
1) What is a WAN?
2) What is a MAN?
1) Wide Area Network - result of joining multiple LANs via satellite, fibre optics cables, telephone cables, or a mixture - nodes a re geographically distant
2) Metropolitan Area Networks, provide WAN services in a city
Properties of WAN?
- infrastructure owned by 3rd party
- Same properties as WAN but it allows it at a much further distance
What is a SAN? Give an example
Storage Area Network - used for large scale storage of data in data centres
Email servers, databases and high usage file servers
What Is a PAN?
Personal Area Network - Used for transmission among devices such as computers, smartphones and tablets - can also be used to connect to high level networks or Internet
Advantages and disadvantages of cloud storage?
\+Data moves off site \+Maintained by third party \+Cheaper \+scalability -Loss of control -Security issues (?)
What are the properties of a peer-peer network?
- All nodes have = status
- All share files and peripherals
- each node can be accessed by another peer
- speed decreases due to lots of collisions
- Implemented over Internet
- Used for legal and illegal file sharing
What are the properties of a client-server network?
- Traditional architecture
- Dedicated high spec machine is server
- centralised data storage
- Allows processing of shared files, printing, Internet access
- manages security
- Clients request access to services from the servers (file server, web server, printer server etc)
What are data centres?
Multiple servers stacked together
What are virtualised servers? +/-
One server is split into multiple “virtual servers” using cloud computing.
+Efficient
+Lower energy consumption
What is the OSI and why was it created?
- Open systems interconnection evolved to create a standard of communication between different device types. Describes protocols that allow comps with different architectures to be linked together so that they can share data and communicate with each other
- just a model
Describe the 7 layers of the OSI
Application - Network aware applications. what the user interacts with (email, web browsing etc)
Presentation - converts data between formats required for different applications +transmission over network. Eg: Compression, encryption and translation
Session - Controls communication between connected devices. Starts connections, manages them and terminates them. User login rights, file/folder perms
Transport - Guarantees end to end delivery of data. Make sure data is present and that it gets to destination
Network - Transmits and routes data via shortest possible path across network. Shortest time not distance
Data Link - decides whose turn it is to send/receive data
Physical - Physical properties of network (cable, bit encoding, transfer rates etc)
What is the TCP/IP stack?
- A suite of protocols that describes how data is sent over a network
- Not just a model
Four layers of the TCP/IP stack?
Application - Production, communication and reception of data, makes sure data in correct format
Transport - Session layer + responsible for providing constant flow
Internet - provides links to transmit datagrams across different networks
Link - Passing Datagrams to local and physical network. Allows network hardware Independence therefore allowing it to operate over any transmission medium such as copper wire, optical fibre etc
What does PDU mean?
- Protocol Data Unit - Term used to describe data on any given layer of the stack
- Application = data
- Transport = Segment/Datagram
- Internet = Datagram
- Network access layer = frame/bits
What term is used to describe data on all levels instead of there associated PDU?
Packet
How do each of the four layers identify the source and destination address of data?
Application - just data no addressing needed
Transport - Data broken into segments that use ports to identify services
Internet - Devices have unique IP address, IP datagrams use IP address to reach correct destination
Link - Ethernet splits packets into frames. Frames use MAC address of device to reach it
What devices are used on each layer of the TCP/IP stack and OSI and what do they do?
- Physical = devices that extend the physical network (repeaters/transceivers)
- Data Link = Devices that make decisions based on MAC address of sender/recipient (bridges forwards frames to destination MAC address and switches which are bridges with multiple ports)
- Internet/Network = devices examine data packets and make decisions based on IP address of sender/recipient (Router examines contents and finds appropriate network to route data to based on IP)
- Transport = devices examine segments and make decision base on port number. Firewalls use port numbers
- Application = devices examine contents of data and make decision based on content (Checking email for spam). Application layer gateway
What is a Datagram?
A self contained unit of data that is the basic unit of data used in transmission. Allows data to be treated independently from one another which increases reliability