Network protocols

Last updated May 26, 2023 Edit

• Compsci
• Theory
• Networking

• 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.

• 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.
• 192.123.45.94

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
• fc00:bbbb:bbbb:bb01::34:4e8e

• 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, 172.45.9.3/14 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.

• 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 IP addresses are assigned by the network administrator. When the device is in use, this address remains unused.

• An IP addressing can be used when the device is not used.
• The protocol responsible for this is 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.

• 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

• 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

• Send emails

• Retrieve mail from server
• Delete mail from server

• Retrieve message from server
• Leave mail on the remote server

• 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 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.

• A set of protocols that enable you to make voice calls over the internet using UDP.

Networking