TCP/IP Packet Information

Spy vs Spy: Operation Silk Road

Packet

A small block of data which is transported from one computer to another.

Header

The part of the packet which contains the sender and destination addresses, the protocol being used and a packet number.

Payload

The part of the packet which contains the actual data which is being sent.

Source Address

The address of the device where the initial message has been sent from.

Destination Address

The address of the device where the message is going to.

Handshake

An agreement which must be made between two devices, before communicating over the internet.

OSI Layer 7: Application

The protocols in this layer determine how the data will be transferred in applications. Web browsers, email clients and file transfer protocols operate here.

OSI Layer 2: Data Link

The layer where the network hardware is located such as the network interface card and cabling. Ethernet and Wi-Fi run here.

OSI Layer 3: Network

This layer routes the packets across the network using the IP protocol

OSI Layer 4: Transport

Sets up the communication between the two devices communicating data and breaks the data in to the agreed packet size. TCP and UDP run here.

IP Address

A numerical address assigned to a device communicating data across the internet. This address changes.

Error Detection

When the receiving device detects that an error has occurred during the transmission of data. The data is then requested again.

Packet Switching

A data network technology. A message is broken in to packets and then sent across a network using the most suitable routes between the source and destination

OSI Layer 1

This layer provides mechanical, electrical and other functional aids available to enable or disable, they maintain and transmit bits about physical connections. This may for example be electrical signals, optical signals (optical fiber, laser), electromagnetic waves (wireless networks) or sound.

OSI Layer 2/Data Link Services

Encapsulation

Frame synchronization

Logical link control (Error & Flow control)

Media access control (MAC, LAN switching, Physical addressing, QaS, VLAN)

MAC address

Media access control

12-character alphanumeric attribute that is used to identify individual electronic devices on a network. An example of a MAC address is: 00-B0-D0-63-C2-26

FCS or Footer

Frame Check Sequence is an error-detecting code added to a frame in a communication protocol. Frames are used to send payload data from a source to a destination.

Ping

The ping command sends an ICMP echo request to a device on the network, and the device immediately responds with an ICMP echo reply.

PDU

Protocol data unit (PDU), otherwise known as a packet, is a single unit of information transmitted among peer entities of a computer network

Routing

Routing is the process of selecting a path for traffic in a network or between or across multiple networks.

In packet switching networks, routing is the higher-level decision making that directs network packets from their source toward their destination through intermediate network nodes by specific packet forwarding mechanisms.

Routing Table

A routing table, or routing information base (RIB), is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes.

ICMP

The Internet Control Message Protocol (ICMP) is a network layer protocol used by network devices to diagnose network communication issues. ICMP is mainly used to determine whether or not data is reaching its intended destination in a timely manner.

ARP

Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever-changing Internet Protocol (IP) address to a fixed physical machine address, also known as a media access control (MAC) address, in a local-area network (LAN)

IGMP

The Internet Group Management Protocol (IGMP) is a protocol that allows several devices to share one IP address so they can all receive the same data. IGMP is a network layer protocol used to set up multicasting on networks that use the Internet Protocol version 4 (IPv4).

RARP

Reverse Address Resolution Protocol (RARP) is a protocol a physical machine in a local area network (LAN) can use to request its IP address. It does this by sending the device's physical address to a specialized RARP server that is on the same LAN and is actively listening for RARP requests.

TCP

Transmission Control Protocol (TCP) is a standard that defines how to establish and maintain a network conversation by which applications can exchange data.

UDP

The User Datagram Protocol, or UDP, is a communication protocol used across the Internet for especially time-sensitive transmissions such as video playback.