- Networking protocols define the rules and conventions for communication across a network.
- Protocols define speed of transmission, error checking, async/sync etc.
- The protocols are established between sender and receiver before starting communication.
- This is done via a handshake.
- Data packets are exchanged between various routers.
TCP 3-way handshake
IP vs Mac address
A Mac address is provided by the NIC manufacturer and cannot be changed, but can be spoofed.
An IP address is typically assigned by a router, and allows for easier communication across the internet and within your local network.
IP addresses are more commonly used in networking applications.
- 32-bit IP addresses
- Around 4 billion possible IPs
- 8 bits form an octet. Each octet may represent any number between 0 to 255.
Reserved IP Ranges
A → 10.x.x.x /8 B → 172.16.0.1 - 172.31.255.255.255 / 16 C → 192.168.x.x /24
Link local 127.0.0.1
x.x.x.0 is a network address rather than a device address
Broadcast address x.x.x.255
- 128-bit IP addresses
- Initially, a network consisted of different classes
- Each class has a different structure of addressing
- Consider a large organisation; it will require class A addressing. In a single network, 2^24 hosts can be used. In total, only 2^7 such organisations can be addressed.
- In classless addressing, an IP address has an 8-bit suffix that specifies the number of bits allocated for network ID.
- For example, if the 8-bit suffix represents the number 14 and the remaining 18 bits represent the host ID.
- For example, 184.108.40.206/14 is represented in binary as given.
- A subnet mask is used to identify the two parts of an IP address.
- For example, a subnet mask 255.0.0.0 represents a network ID of 8 bits and a host ID of 24 bits. This is equivalent to a suffix /8 in classless addressing. (CIDR)
- When AND operation is performed between an IP address and its subnet mask, its network ID is obtained.
Public and private
- These addresses need not be registered on the internet registry.
- Private addressing for internal networks saves unique IPv4 addresses that can be used for routers and web servers that connect to the internet daily.
- Some public IP addresses are also identified using domin names.
- A DNS server translates the domain name to an IP address.
Static and Dynamic addressing
- Static IP addresses are assigned by the network administrator. When the device is in use, this address remains unused.
Dynamic IP Addressing
- An IP addressing can be used when the device is not used.
- The protocol responsible for this is dynamic host control protocol (DHCP)
Dynamic Host Control Protocol (DHCP)
DHCP also provides subnet masks and other automatic configuration details. This eliminates the problem of manual configuration.
Takes care of frequent changes in an IP address
Allocates private addresses within an internal network
Broadcast to all DHCP servers requesting an IP
A DHCP server offers an IP for a particular duration
Broadcasts a message confirming the request for IP
DHCP server that offered the IP address sends an acknowledgement and assigns the DHCP client the IP address.
- A port number is a 16-bit number attached to the IP address that is used to identify a process or application on a computer
- Using this number, an application running in the client system is accessed.
I am familiar with ports, so some information has been omitted.
NAT—Network Address Translation
- A network address translator provides external access to a privately addressed network as shown in the figure.
- 1 public IP is shared between all private IPs.
- Adds a layer of security
- Private IP addresses are not available to external servers
- Router tracks requests and reassigns them to the appropriate host
- Port numbers are assigned with a specific time frame
- Port forwarding is an application of NAT where port mappings are explicitly defined, allowing you to talk to services behind non-standard ports.
TCP/IP is a suite of communication protocols used to interconnect network devices of different manufacturers on the internet.
Source → Sender of the message
Destination → Receiver of the message
Packet sequence → The order of the message in which it should be reassembled
Data → Contents of the message
Error checking → Bits to make sure that the message has been received correctly
User Datagram Protocol (UDP)
- A protocol similar to TCP but operates at a faster rate
- UDP: message is sent in the form of chunks or called datagrams
- TCP: message is sent as segments
- Used for gaming and video calling over the internet
C → Create → POST R → Read → GET U → Update → PUT D → Delete → DELETE
Email Communications: SMTP, POP3, IMAP
- Send emails
- Retrieve mail from server
- Delete mail from server
- Retrieve message from server
- Leave mail on the remote server
SSH (Secure Shell Protocol)
Remotely access a terminal on another computer through a text interface
SSH is used by network administrators and developers
Typically runs on port 22
FTP (File Transfer Protocol)
- FTP defines the set of rules for transferring large files on the Internet
- The files required for a website are organised on a web server using this protocol.
- Users may have private access to upload the files. Other users may be given access to download these files.
VoIP (Voice over Internet Protocol)
- A set of protocols that enable you to make voice calls over the internet using UDP.