WK1 Local and Network Wide Communication Flashcards
IP stands for
Internet Protocol
What is An internet protocol address (IP address)
An internet protocol address, or IP address, is a unique string of characters that identifies a location of a device on the internet.
Each device on the internet has a unique IP address, just like every house on a street has its own mailing address.
Key takeaway: Security analysts can use packet capturing tools, or PCAP, to inspect packets while they’re in transit. Analyzing the different fields in an IP address packet can be used to find out important security information about the packet. Some examples of security-related information found in IP address packets: where the packet is coming from, where it’s going, and which protocol it’s using. Understanding the data in an IPv4 data packet will allow you to make critical decisions about the security implications of packets that you inspect.
What are the are two types of IP addresses
- IP version 4, or IPv4,
- IP version 6, or IPv6.
IPv4 addresses are written as four, 1, 2, or 3-digit numbers separated by a decimal point. In the early days of the internet, IP addresses were all IPV4. But as the use of the internet grew, all the IPv4 addresses started to get used up, so IPv6 was developed.
IPv6 addresses are made up of 32 characters. The length of the IPv6 address will allow for more devices to be connected to the internet without running out of addresses as quickly as IPv4.
Public IP address
IP addresses can be either public or private. Your internet service provider assigns a public IP address that is connected to your geographic location. When network communications goes out from your device on the internet, they all have the same public-facing address. Just like all the roommates in one home share the same mailing address, all the devices on a network share the same public-facing IP address.
Private IP address
Private IP addresses are only seen by other devices on the same local network. This means that all the devices on your home network can communicate with each other using unique IP addresses that the rest of the internet can’t see.
MAC address
A MAC address is a unique alphanumeric identifier that is assigned to each physical device on a network.
When a switch receives a data packet, it reads the MAC address of the destination device and maps it to a port. It then keeps this information in a MAC address table.
Think of the MAC address table like an address book that the switch uses to direct data packets to the appropriate device.
Layer 3 of the OSI model: The Network Layer
Operations at the network layer
Functions at the network layer organize the addressing and delivery of data packets across the network and internet from the host device to the destination device. This includes directing the packets from one router to another router across the internet, based on the internet protocol (IP) address of the destination network. The destination IP address is contained within the header of each data packet. This address will be stored for future routing purposes in routing tables along the packet’s path to its destination.
All data packets include an IP address; this is referred to as an IP packet or datagram. A router uses the IP address to route packets from network to network based on information contained in the IP header of a data packet. Header information communicates more than just the address of the destination. It also includes information such as the source IP address, the size of the packet, and which protocol will be used for the data portion of the packet.
Layer 3 of the OSI model: The Network Layer
Format of an IPv4 packet
IPv4 packet is made up of two sections, the header and the data:
The size of the IP header ranges from 20 to 60 bytes. The header includes the IP routing information that devices use to direct the packet. The format of an IP packet header is determined by the IPv4 protocol.
The length of the data section of an IPv4 packet can vary greatly in size. However, the maximum possible size of an IP packet is 65,536 bytes. It contains the message being transferred to the transmission, like website information or email text.
There are 13 fields within the header of an IPv4 packet:
- Version
Version: The first 4-bit header tells receiving devices what protocol the packet is using. The packet used in the illustration above is an IPv4 packet.
There are 13 fields within the header of an IPv4 packet:
- IP Header Length (HLEN)
HLEN is the packet’s header length. This value indicates where the packet header ends and the data segment begins.
There are 13 fields within the header of an IPv4 packet:
Type of Service (ToS)
Type of Service (ToS): Routers prioritize packets for delivery to maintain quality of service on the network. The ToS field provides the router with this information.
There are 13 fields within the header of an IPv4 packet:
Total Length
Total Length: This field communicates the total length of the entire IP packet, including the header and data. The maximum size of an IPv4 packet is 65,535 bytes.
There are 13 fields within the header of an IPv4 packet:
Identification
Identification: For IPv4 packets that are larger than 65, 535 bytes, the packets are divided, or fragmented, into smaller IP packets. The identification field provides a unique identifier for all the fragments of the original IP packet so that they can be reassembled once they reach their destination.
There are 13 fields within the header of an IPv4 packet:
Flags
Flags: This field provides the routing device with more information about whether the original packet has been fragmented and if there are more fragments in transit.
There are 13 fields within the header of an IPv4 packet:
Fragmentation Offset
Fragmentation Offset: The fragment offset field tells routing devices where in the original packet the fragment belongs.
