Zusammenfassung der Ressource
CHP 7: Computer Network (7.1 Internet
protocols and network hardware)
- Internet Protocols: a set of rules use for transferring data
and communication between computers
- Layer 1: Physical [data is transfer bit by
bit]
- modems
- Layer 2: Data link [act upon request from both
network layer and physical layer]
- WiFi
- Ethernet: set of protocols used to operate
LAN
- Hardware: PC, printer, server, hubs, switches, routers,
cables
- Layer 3: Network/Internet [responsible for
forwarding packets]
- Internet Protocol
(IP)
- Layer 4: Transport [dividing data into smaller
packets]
- transmission control protocol
(TCP)
- user datagram protocol
(UDP)
- Layer 5: Application [deliver services to Internet
layer]
- file transfer protocol
(FTP)
- hypertext transfer protocol
(HTTP)
- telecommunication network
(Telnet)
- secure shell
(SSH)
- parts that makes up a
network
- TCP/IP
- TCP makes sure that data is transmitted accurately (faster than UDP because
of connection-oriented service), soit's preferred for real-time applications)
- IP (four bytes of data) makes sure it delivers all the small
packets to the correct address using IP addresses
- handshaking: rate of data transfer, type of
data, solutions between computers are agreed
- parity check: must be an even
number of 1s in the code (eg.
10010101)
- If there's an odd number of 1s in
the code: the parity bit (the first
number in the code) will have to
change to 1
- UDP: limits the speed of data transfer
- Disadvantage: cannot check whether the
data as sent or not, data packets sent in
wrong order
- advantage: reduce loss of data, slower than
TCP. suitable for Internet telephony and
video-on-demand systems
- FTP uses TCP/IP to transmit data for
downloading through Internet
straight from the server.
- HTTP uses TCP/IP to transmit data
through Internet (what you see on a
webpage).
- Telnet use for gaining access to another computer and use software and
data from that computer. Happens on Internet or LAN.
- The commands are made from the remote
computer but the results will be shown on the
user's screen.
- SSH is more secure than Telnet and FTP so it use for securing data
transfer between devices. The password encrypted will allow the server
to provide service.
- Hardware
- network hub: allows multiple computers to be connected and form a network. It doesn't read the data transmitted but will
send too ALL computers in the network. Congestion might happen resulting to a slower data transfer.
- Passive hub: It doesn't amplify the signal, it just sends the data packets.
- Active hub: amplify signals to prevent interruption while
transmitting data. Use mostly in huge networks.
- switches: better than hubs because data transferred will not block up and it is
faster. It stores every address of every device connected to it.
- disadvantage: it will not know the senders address but will know the
receiver address.
- How it works: When the receiver got the data packets, it will send an acknowledgement back to the
sender's address. The address stored are called media access control (MAC) NOT IP.
- routers: allows data to be transfer in between
different types of networks to be able to
connect to the Internet. It has firewalls to
provide network network. This hardware will
inspect every packets of data transferred.
- How it works: When data is transfer, it will go
through switches and match up the MAC
address. If MAC address does not match then it
will move on to another switch.
- servers runs many aspects of a
computer to be part of the Internet.
- file servers are use for storing documents,
videos, etc. It allows users to save the data
rather than a physical copy in their computers.
- Applications servers allows users to save data onto their hard-disks.
- cables
- twisted pair: two conducting wire twisted around each
other, reduces data loss
- suitable for Ethernet and Local Talk networks
- coaxial cables: conducting wire covered with
non-conducting layer and covered in conducting material
and a PVC jacket.
- fibre optic: cables: individually coated with
plastic resin and a plastic layer.
- network interface cards (NIC) slides in the motherboard to enable connection with the
server or other computers. It identifies the IP address for data transfers.