Host Name
…
…
www.inq7.net
…
IP Address
…
…
128.171.17.13
…
DNS Request Message
Originating Host and DNS Host
“What is the IP address www.inq7.net?”
DNS Response Message
“The target’s IP address is 128.171.17.13”
PROTOCOLS
is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate.
it control all aspects of data communication, which include the following:
how the physical network is built
how computers connect to the network
how the data is formatted for transmission
how that data is sent
how to deal with errors
How Protocols Work?
Protocols at the sending computer:
Break the data into smaller sections, called packets, that the protocol can handle.
Add addressing information to the packets so that the destination computer on the network can determine that the data belongs to it.
Prepare the data for transmission through the NIC and out onto the network cable.
Protocols at the receiving computer carry out the same series of steps in reverse order.
Take the data packets off the cable.
Bring the data packets into the computer through the NIC.
Strip the data packets of all the transmitting information that was added by the sending computer.
Copy the data from the packets to a buffer for reassembly.
Pass the reassembled data to the application in a usable form.
Network Fundamentals
Network:
Is a collection of computers, printers, switches, routers, and other devices that are able
to communicate with each other over a transmission medium.
Local Area Network:
are high speed, low-error data networks that covers a relatively small geographic area.
What is the Internet?
is a group of networks linked together with routers in a way that allows an application
program on any station on any network to be able to communicate with the application
program on another station on any other network.
Internet Elements:
Multiple networks
Router
Route
Packets
How networks send data?
Packets are basic units for network communication
Send the original, disassembled data in small chunks.
Reassemble the data in the proper order when it reaches its destination.
Check the data for errors after it has been reassembled.
Packet goes from source host to destination host across multiple networks.
Within a single network, the packet is carried in the data field of that network’s frame,
probably across multiple switches.
The first router removes packet from first network’s frame, sends back out in a frame with
the second network’s frame format.
The second router removes packet from second network’s frame, sends back out in a frame
with the third network’s frame format.
Host Addresses and Host Names:
Host IP Address
Official address of host on the Internet
Every host must have an IP address, including client PCs
32 bits long
Often expressed in dotted Decimal Notation for human reading (e.g., 202.78.93.13)
Host Name
Several labels separated by dots (www.uic.edu.ph)
Like nickname; easy to remember
Not the official address of the host
Domain name system (DNS)
DNS is a system used on the Internet for translating names of domains and their publicly
advertised network nodes into IP addresses.
You cannot send messages to a host if you only know its host name
Computer must know its official address (IP Address)
DNS provides a way of finding a host’s IP address if only its host name is known
