9.1 Networking Flashcards
Topology
The structure of a network
Physical Topology
The actual architecture of a network
Physical Star Topology
- Each client has a direct connection to the central hub
- the hub receives packets for all the clients and delivers them to the correct recipient
- A server can be added by directly connecting it to the hub
Advantages of Physical Star Topology
- Packets are sent directly to their recipient
- Other clients cant see the packets being sent
- Easy to add and remove clients
- No collisions as each cable connects only one device
- Failure of one cable doesnt effect the whole network
Disadvantages of Physical Star Topology
- Central Hub Fails = Entire system fails
- Expensive (a lot of cabling)
Physical Bus Topology
- Clients are connected to a single cable called the backbone.
- A terminator is placed at either end of the backbone
- The server can be connected to the backbone like a client
Advantages of Physical Bus Topology
- No central hub reducing chance of network failure
- No central hub means cheaper
- Little cabling is required (inexpensive)
Disadvantages of Physical Bus Toplogy
- Clients can see all the packets being sent on the backbone, including ones not intended for them
- Risk of collisions
- Backbone failure = Entire system fails
Logical Network Topology
Flow of data packets within a network
Logical Bus Network
Delivers packets to all clients
Logical Star Network
Delivers packets only to the recipient
Physical Star, Logical Bus
Running a bus protocol on the physical star network allows the hub to distribute packets to all connected clients, making it act like a bus network
Host
Device which provides services
Usually a server
Examples of services a host provides
File storage, printer sharing, internet access
Client Server Networking
- Use one or more central servers to provide services to clients on the network
- Connected to the network the same way as clients, but are more powerful machines
How Client Server Networking Works
- Clients on the network request services from the server which then responds with the services
Advantages/Disadvantages of Client Server Networking
ADVANTAGES
- Allows for central management
- Improved security
DISADVANTAGES
- Fair degree of expertise to setup and manage
Peer to Peer Networking
Services are provided by the clients themselves and every client has equal status
Advantages and Disadvantages of Peer to Peer Networking
ADVANTAGES
- More cost effective
- Easier to set up and maintain
DISADVANTAGE
- All clients providing services must be running at all times
Wireless Networking
Allow clients to communicate within a network without physically being connected to it.
Structure of a Wireless Network
- A wireless access point that connects to a wired network
- A Wireless network adapter in the devices connected to the network
WIFI
A Wireless Local Area Network that is based on international standards.
WPA/WPA2
- Data is encrypted using WPA or WPA2.
- WPA stands for wifi protected access
- requires a new wireless client to enter a password to connect to the network
SSID
- Disabling SSIID Broadcast improves security
- Stands for Service Set Identifier
- Stops wireless device within the range of the network from seeing the network is available, and requiring clients to know the SSID to connect.
MAC Address Filtering
- Wireless networks can be protected by using MAC address filtering.
- Stands for media access control
- They are addresses assigned to every wireless device by their manufacturer.
- Using MAC Address whitelists allows only certain MAC Addresses to join the network
- Using MAC Address blacklists bans certain MAC Addresses from joining the network.
CSMA/CA
- Stands for Carrier Sense Multiple Access With Collision Avoidance
- Avoids data collisions in wireless networks caused by multiple devices communicating simultaneously.
How does Carrier Sense Multiple Access With Collision Avoidance
- A device listens to its communication channel to check if it’s idle.
- If yes, data is transmitted.
- If not, the device waits a random period of time before trying again.
- An exponential backoff algorithm increases the time for each wait period.
Effectiveness of CSMA/CA
- Good at avoiding collisions in small networks
- Cannot overcome hidden nodes as they cannot see if there is communication.
How to Get Around Hidden Nodes in CSMA/CA
-The protocol request to send/clear to send is used.
- Once the device has checked if the communication channel is clear, it sends a request to send message to the server.
- If the server is Idle, it’ll send back a clear to send. Transmission starts.
- If the server doesn’t send a clear to send the device waits a random period of time as the server is busy with a hidden node.
