Computer Networks Flashcards
Computer Network definition
collection of nodes connected by a communication link
Why setup a computer network?
Resource/Database/Software sharing
Key performance parameters of Computer Networks
-Bandwidth
-Delays
-Error rate
Components of Computer Networks?
-Hosts
-Central connecting devices
-Apps use the network to provide a service
-Links are channels that connect nodes
Network Types
-Personal Area Networks
-Local Area Networks
-Metropolitan Area Networks
-Wide Area Networks
Personal Area Networks factors?
-Smallest
-Bluetooth, infrared enabled devices
-Connect up to 10 meters
-Wireless mouse, keyboards, headphones, printers, tv remotes
Local Area Network factors?
-Privately owned network - home, office, campus
-Connect up to a few kilometers
-Worst case transmission time bounded and known in advance
-Different topologies can be implemented
-LAN uses ethernet or wireless network(WLAN
-LAN is relatively fast
Metropolitan Area Network factors?
-Connection over entire city
-MAN can connect several LANs
-Ex - interconnecting several LANs on campus
-MAN uses Asynchronous Transfer Mode (ATM) and Fiber Distributed Data Interface (FDDI)
Wide Area Network factors?
-Long distance transmission of data, voice, image and information
-Connectivity range up to countries, continents, entire planet
-Slower than LAN
-Some WAN use ATM, Frame Relay, and synchronous optical network
-Enterprise network is a WAN owned by a company
What is a Network Topology?
-Physical and logical layout of a computer network
-Determines how various components communicate and connect
-Choice of topology depends on the following factors:
- # of devices
- Application
- Data transfer rate
- Response time
- Cost
What are the types of Network Topologies?
- Bus
- Star
- Tree
- Ring
- Mesh
What is Bus Topology?
-Linear configuration in which all network devices are connected to a common bus
- Full duplex communication is possible between devices and taps
- Data sent by one node can be seen by others
- Example: Ethernet LAN
Pros/Cons of Bus Topology?
Pros:
- Cheap, easy to implement
-less cabling required, shared link reduces cost
- Expandable - devices can be added/removed without disruption
Cons:
- One device can transfer data at a time
-access control required to avoid data collision
- Signal strength becomes an issue for long distances
- Common bus failure can crash network
- Security risk - other devices can see data
What is Star Topology?
- Central device to which remaining nodes are connected
- Each node has direct access to the central device via point to point links
- Central device can operate in either broadcast mode (hub/multiport transmission of data to all nodes) or unicast/frame switching mode (perform switching/routing function using a switch)
- Example: High speed LAN
- looks like a snowflake (central device)
What are the pros and cons of Star Topology?
Pros:
- Scalable, high speed, easy to maintain.
- # of links = # of nodes
- Individual node failure doesn’t impact overall network
- Troubleshooting, modification is easy
Cons:
- Single point of failure exists in the form of central device
- Network size is limited by number of I/O ports on device
What is Tree Topology?
- (Hierarchical topology) a hybrid of star and bus
- Network divided into multiple layers
- Highest layer contains central node
- Middle layer contains distribution nodes
- Lower layer (access layer) contains end-nodes
Pros/cons of Tree Topology?
Pros:
- Scalable
- Flexible
- Easy maintenance, layered control of devices
Cons:
- Expensive to implement
- Single point of failure in the form of central node
- looks like binary tree
What is Ring Topology?
- Circular config
- Each network device is connected to the 2 adjacent devices
- Data is transmitted in one direction reducing chances of collision
- Implementation requires use of token passing protocol
Pros/cons of Ring Topology?
Pros:
- Simple installation with less cabling
- Troubleshooting is easy
- All devices have equal network access
Cons:
- Not very scalable
- Single mode of failure possible
- Transmission of data is slower than star, data travels through loop
What is Mesh Topology?
- Involves interconnecting all network devices with each other via point to point links
- Fully connected mesh with ‘n’ devices has n(n-1)/2 cables
- Each device must have (n-1) I/O ports
Pros/Cons of Mesh Topology?
Pros:
- High speed, no congestion issues
- Very high reliability/redundancy/security
- Individual node failure doesn’t impact network
Cons:
- Very expensive (cabling expensive)
- Poor expandability - addition of new node requires multiple links
- Rarely used in practice
