4.9 - TCP/IP layer Flashcards
What is the TCP/IP layer?
TCP (transmission control protocol / internet protocol) is used in all parts of the internet to enable different devices to communicate.
What are the layers of TCP/IP?
Application - Selects and uses the correct protocol to transmit data. The layer interacts with the user application software like a web browser.
Transport - Establishes end to end communication between the sender and receiver. This layer also splits the data into packets. Each packet has sequence number which identifies a packets position in relation to other packets that form part of the same message. Also adds the port number to specify which protocol to use.
Network - Provides the correct IP address for each packets source and destination. Routers work within the network layer, using the IP addresses on a packet to send it to its destination.
Link - Controls physical connections between pieces of hardware in a network. Adds MAC addresses to packets which it receives from the network layer. MAC addresses are unique to the device and change with every hop through a network.
What is a socket address?
IP address combined with a port number
e.g: 114.26.20.199:80
Socket address identifies which of the applications on the recipient device a packet should be sent to.
What is IPV4?
IPV4 IP addresses are dotted quad numbers, meaning that they consist of four parts that are separated by dots. This allows for slightly over 4 billion unique IPV4 addresses (256^4
).
What is IPV6?
IPV6 IP addresses are formed of eight blocks separated by colons. Each block contains four hexadecimal characters. IPV6 uses 128 bits which compared to IPV4’s use of 32 bits allows for far more unique permutations.
What is a public IP address?
A public IP address is routable and globally unique
What is a private IP address?
A private IP address is non routable and not globally unique. Millions of devices can have the same private IP address
What is the DHCP?
DHCP (Dynamic Host Configuration Protocol) is a protocol used to assign private IP addresses to devices as they join a network. It uses a pool of available IP addresses to allocate new ones for the duration of their session. Once a device leaves the network, the IP address that the device was using is returned to the pool for allocation to a new device.
What is the NAT?
NAT (Network Address Translation) is used to map private non routable IP addresses to public routable ones for network communication.
What is Port Forwarding?
Port Forwarding is used when a client needs to communicate to a server that is connected to a private network.
The client sends packets to the public IP address of the router belonging to the server’s private network. The packets sent by the client contain the port number of the application running on the server that the client wishes to access. The private networks router then forwards packets to the server using NAT.
