As mentioned before, the PDU is the final structure of the data that is sent and received between systems. The PDU consists of multiple layers that are parsed together to create the final output.
The first layer that is received is the information about the network medium via which bits are received from the host. This information is in the form of a protocol, and there are many different protocols depending on what kind of network you are receiving data on.
A common protocol is Ethernet, which specifies how to organize and transfer information via electrical signals. When you receive data from another computer via Ethernet, your computer automatically recognizes this and organizes the data accordingly.
Another common protocol is Wireless Access Protocol (WAP), which specifies how to organize and transfer information via wireless signals. When you receive data from another computer via WAP, your computer must have a special component installed to recognize this protocol and organize the data accordingly.
What is a PDU?
A Protocol Data Unit (PDU) is the term used for a message sent between two devices in a network. A PDU is made up of a header and a payload.
The header includes information about the message, such as source and destination addresses, and how to process the payload. The payload contains the actual information being transmitted.
The way a PDU is constructed determines which layers of the OSI model it uses. For example, a TCP segment is a PDU at the transport layer, with its header containing source and destination ports. An IP packet is a PDU at the network layer, with its header containing source and destination IP addresses.
A PDU can be either an upper-layer protocol data unit (such as a TCP segment or an IP packet) or an lower-layer protocol data unit (such as an Ethernet frame).
What is the format of the PDU?
A PDU, or protocol data unit, is a term used to describe the format in which bits are received from the network medium by the NIC of a host. A PDU is comprised of two parts: the header and the payload.
The header contains information about the bit stream being transmitted, such as its source and destination addresses and whether or not encryption was used.
The payload contains the actual data being transmitted, such as email messages or files. The length of this part depends on how many bytes were being transmitted when the bit stream was received by the NIC.
When bits are received from the network medium by the NIC of a host, there are three possible PDUs: binary, Octet-mapped, and VA-list formats. Each one has its own specific header and payload format.
What is the difference between synchronous and asynchronous transmission?
Synchronous transmission is a method of data transfer in which the sending device and receiving device both have to be present at the same time in order to exchange information.
This is accomplished through what is known as a baud rate. A baud rate is the number of signals per second that transmit information.
The sending device has to send all of its bits before the receiving device can receive them. Then, the receiving device has to process all of the bits before the sending device can send more bits. This creates a bottleneck and synchronization problem.
Asynchronous transmission does not have this issue. The sending device can send all of its bits at one time and then stop transmitting for a brief period before sending more bits. The same goes for the receiving device – it can process all of the incoming data at one time and then wait before processing more data.
What is the difference between single-ended and double-ended signals?
There is a very important difference between single-ended and double-ended signals. In single-ended signals, the bit value is represented by a change in the signal voltage level (from 0 to 1 or from 1 to 0). In double-ended signals, the bit value is represented by a change in the signal voltage level and pulse duration (from short to long or from long to short).
In other words, in single-ended signals, the information carried by the signal is either 0 V or some other voltage level that represents a 0 or 1. In double-ended signals, the information carried by the signal is either 0 V or some other voltage level that represents a short time period or a long time period.
This distinction is very important because it determines which of these formats can receive and transmit single-ended and double-ended signals. For example, if you have an SD card reader that only accepts single-ended signals but your device sends you a double-anded signal, then your device will not be able to transfer any data to/from the SD card. Likewise, if you have an SD card reader that only accepts double-anded signals but your device sends you a single-anded signal, then your device will not be able to transfer any data to/from the SD card.
Can you explain the 8-bit, 16-bit, and 32-bit formats in detail?
When a host sends a packet to the router, the router receives the packet from the network medium. The header of this packet contains information about where the packet came from (source IP address and source port) and where it is going (destination IP address and destination port).
If there is enough room in the destination IP address field, then the destination IP address will be set to 0.0.0.0. If there isn’t enough room in the destination IP address field, then it will be set to 255.255.255.255 instead.
The router then looks at its ARP cache to find out what interface belongs to 0.0.0.0 or 255.255.255.255 (if there are multiple on that network). Then, it sends the packet to that interface on that host so that it can be received by 0/8.
Why do we need different formats?
Since the Internet is a global network, it requires a lot of effort to ensure information is sent to the correct destination. This is done through various protocols, or sets of rules.
A protocol for transmitting data across the internet is called IPv6. It has its own format for presenting information, which requires different PDUs to be able to read it.
IPv6 uses 128-bit addresses instead of 32-bit like IPv4 does. This means that there are twice as many numbers available, which can be used to identify each device. This also makes it more difficult for devices to incorrectly identify each other.
Because of this difference in format, devices need to be able to adapt and interpret the information being received in order to process it correctly. Having different PDUs that can handle different formats ensures that all devices on the internet can process information correctly.
What are some of the commonly used PDU formats?
There are several common formats that the data is stored in once it has been processed. These formats include binary, ASCII, and hexadecimal.
Binary format represents the data as 1s and 0s, ASCII represents the data as characters, and hexadecimal represents the data as numbers.
Which of these you use depends on what you are doing with the data. If you are writing a program that needs to process the data, then you would use binary format. If you are printing out the data in plain text, then ASCII is appropriate. And if you are working with graphs or diagrams, then hexadecimal is needed.
Binary format is also known as byte format due to the way data is organized in bytes. By using this format, all of the information is clear and accessible for computer processing.
Which pdu format is used when bits are received from the network medium by the nic of a host?
When the nic receives bits from the network medium, it interprets them as either a frame or a packet. If it is a frame, then it checks to see if it is an addressed frame or an unaddressed frame.
If the frame is addressed, the nic extracts the data from the received frame and passes it onto the device driver of the corresponding device. If the frame is unaddressed, then the device driver extracts any data contained within and forwards it onto its corresponding device for processing.
If it is a packet, then both cases are handled in similar ways. The packet is passed onto its corresponding protocol for further processing. Some of these protocols include TCP, IP, and L2 Protocols. After this happens, some of these protocols send a confirmation back to the nic stating whether or not they received their data.