Please enable JavaScript.
Coggle requires JavaScript to display documents.
(Network Architecture, Network performance, :) - Coggle Diagram
Network Architecture
Types of servers
-
-
Authentication (login) server - checks usernames and passwords - a user must be logged in before they can request services from other servers
-
-
File server - manages file access rights/permissions (read, write and delete, execute)
-
-
-
Peer to peer examples
Typically, peer-peer architecture is used for LANS.
-
They can support up to a maximum of 10 workstations – hence why they aren’t suitable for larger organisations.
The peer-to-peer architecture is sometimes used on the internet for sharing files such as music and videos (sometimes illegally).
The internet is a huge WAN. In order to use peer-to-peer architecture, a special type of software such as Bittorrent has to be installed on each of the peer computers:
- Peers allow other peers access to files in a shared folder on their hard drive.
- When one peer requests a file, they get “bits” of the file from several other peers.
- These means that lots of peers share the workload so there is little effect on the speed of the connection.
- If a file was stored on just one server and lots of clients requested access at the same time, this would put a strain on the server and slow down the connection.
BitTorrent technology is perfectly legal - it is only illegal to use it if you are downloading a copyrighted file e.g. a TV programme, film or song that was recorded in the last 70 years. There are many legal uses of BitTorrent.
-
-
-
Cost
-
Expensive
- Need to pay for hardware (e.g. servers), licences for a network operating system and specialist staff.
-
Relatively cheap
- No specialist hardware or staff. Can use a standard operating system.
-
-
Backups
-
Backups can be made centrally from the file server, rather than having to go to each workstation.
-
-
-
-
-
Server
Servers are powerful computers that control access to files, resources and services on a network.
They ‘serve’ files, resources and services to users whenever they are requested by clients.
-
Peers
All the computers on a peer-to-peer network are called peers - this is because they have equal status.
Each peer can act as a server (serving resources to other peers) or a client (requesting resources from other peers)
Network performance
Latency
-
-
-
-
On a small LAN, latency is not really a problem as all of the nodes are near to one another.
But on larger networks, e.g. WANs, latency can become more of an issue.
Every cable, switch and router on the network adds a delay (latency), to the connection
-
Hubs cause more latency than switches because they send data packets to every single node they are connected to.
-
-
Client server networks can be prone to high latency if several clients request resources from the same server at the same time
-
Also, multiple copies of popular resources can be stored on several servers
Small peer to peer networks have low latency because here are few nodes (peers) but latency increases as more nodes are added
-
-
The star topology reduces latency because node A does not have to go through lots of other nodes to communicate with node B - it simply goes through the central node
A partial mesh topology has a higher latency because node A may have to go through several nodes to communicate with node B
Transmission Media
-
-
-
-
There are different types of copper cable. More expensive cables can carry additional data at a faster speed.
-
On WANs, fibre optic cables are often used.
-
-
-
Wireless technology, or Wi-Fi can be used to transmit data over a LAN.
However, Wi-Fi has a lower bandwidth compared to Ethernet cables. Less data can be supported and it may be transmitted at a slower rate, thus affecting network performance.
-
-
Bit errors
An error can happen when, for example, a binary 1 is sent across the network, but instead, a binary 0 is received.
-
-
If a cable, or switch, is placed in close proximity to electrical equipment e.g. motors, then interference from the equipment may cause the bits to flip randomly.
-
-
As the cable length gets longer, the signal can become too weak and errors can begin to creep in.
The ‘error rate’ is the number of bit errors divided by the number of bits successfully transmitted in a given period of time.
-
-
-
Numbers of users
-
-
However, bandwidth isn’t always shared equally.
(The ‘contention ratio’ is used to measure the ratio of users compared to the available bandwidth.) - probably don't have to know this
Bandwidth
Bandwidth describes how much data can be transferred over the network in a given time - it is the maximum number of bits that can be transmitted per second.
-
Network performance
Network performance refers to how well data (in the form of packets) is transmitted throughout the network.
-
-