Before Diving into the network, I recommend you to read the Data communication sections first!! (It deals with the basic concept of Internet protocols, data link layer and Physical Layer)
Then, Let’s get started!
First, What Is the OSI Model?
The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to communicate over a network
- Application Layer (top of the layer)
- Presentation Layer, Session Layer
- Transport Layer
- ✨Network Layer✨ -> part1 cover this!
- Data Link Layer
- Physical Layer (Layer 1, bottom of the layer)
the standard model of network = router + switch -> LAN (A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home.)
Router
Use of a router
• connecting different LAN(sub network)s • determining the effective datagram transmission path through other routers on the outside network (routing algorithm) • Forwarding datagrams based on IP address ‘range’ information • Router has at least two ports Assign 2 IP addresses when using 2 ports: 1 external address and 1 internal address
e.g.
10.5.0.2(external) 192.168.0.1(internal)
• A host exists on the LAN with an IP address of up to 192.168.0.3 – 8
Warning ⚠ 99% of this contents based on DDWU Network lecture by Professor sc, Lim So Please do not use my work without permission
Subnet mask
Masking is used to get some bits of the given data
Mask and remove 4 bits from the back Masking “11111111” with “11110000” -> “11110000” (AND) Masking “10101010” with “11110000” -> “10100000”
Subnet(=LAN) mask • Used to determine if a given IP address belongs to the same subnet or not
e.g. suppose you have 255.255.255.0 as a subnet mask This subnet mask shows that the first 24 bits are all 1 and The rest of the bits are all 0 With this mask value, turn on the value of the first 24 bits of the IP address and turn off the next 8 bits (AND bit operation) 203.89.56.12 & mask -> 203.89.56.0 203.89.56.32 & mask -> 203.89.56.0 203.89.57.32 & mask -> 203.89.57.0
If IP addresses A and B have the same value after masking , it is determined that they are on the same subnetreference examples)