all normal devices have a private IP. With a private IP, we cannot access the internet. So, we use a NAT (in Router) which converts our private IP to the router's public IP. Using this public IP, we can communicate in the internet.
It converts both private to public as well as public to private
Subnet mask
Each IP address contains two parts:
Network address
The part which identifies, which local network you belong to
Host address
The part which identifies the specific device within the network
example: 10.20.30.40/16
=> 16 is the subnet mask i.e., 255.255.0.0 (16 bits will be 1 and rest will be 0)
=> first 16 bits is the network address => 10.20.0.0
=> rest 16 bits is the host part => 30.40
=> All the device in the network will have address in the form 10.20.x.x
DHCP Server
Dynamic Host Configuration Protocol
IPs can be assigned statically or dynamically.
Static IP means, we assign the IP for a device on our own, this includes the IP address, subnet mask and default gateway. This should be done carefully so that, there is no two devices in the same network having the same IP address. Which is tiresome.
Therefore we use a dedicated server for that, called DHCP server which dynamically assign these values for each device connected to that network. Also, IPs are assigned in lease, i.e., the IP assigned to a device will be revoked after a period of time to prevent IP range exhaustion (A DHCP server will be given only a range of IPs to be assigned). There is option to assign the same IP to a device all the time by maintaining a address reservation table in DHCP server (mainly for devices like printer, routers, servers etc)
Band Width
It is the maximum theoretical capacity of a channel
Unit is Mbps, Gbps...
Throughput
Actual data rate achieved over the network
Utilization of the bandwidth
Unit is same as Bandwidth
Input Traffic
The data offered to the network (traffic entering the network)