What does STP message do which send from switch to PC

What does STP message do which send from switch to PC

Switches do not send STP (Spanning Tree Protocol) messages to PCs or end devices. STP is a protocol used by switches to prevent loops in a network by ensuring that there is only one active path between any two network devices. STP operates at the layer 2 (data link) level of the OSI model and is used to identify and disable redundant paths in a network.

When STP is enabled on a switch, it sends BPDU (Bridge Protocol Data Unit) messages to other switches in the network to exchange information about network topology and identify the root bridge. The root bridge is the switch with the lowest bridge ID and serves as the central point of control for the network.

PCs and end devices do not participate in STP or receive BPDU messages. They are simply connected to the switch ports and communicate with other devices on the network through the switch. The switch uses STP to manage its own internal network topology and ensure that traffic is forwarded on the most efficient path, but it does not send STP messages to end devices.

So the STP message is a broadcast from one switch to another switch, and the PCs or end devices will not respond it?

Yes, that's correct. STP messages are sent as broadcasts by switches to communicate with other switches in the network. The STP messages contain information about the switches and the network topology, and are used by switches to elect a root bridge and determine the best path for forwarding traffic.

PCs and end devices do not participate in the STP process and do not receive or respond to STP messages. They simply send and receive data packets through the switch, which uses STP to manage its internal network topology and ensure that traffic is forwarded on the most efficient path. The STP messages are only relevant to switches and are not part of the normal communication process between PCs and other network devices.

What does DTP message do which send from switch to PC

DTP (Dynamic Trunking Protocol) is a Cisco proprietary protocol that is used to negotiate the trunking mode between two switches or between a switch and another network device. DTP messages are sent between switches to dynamically enable or disable trunking on a particular port.

When a switch is connected to another switch or to a network device such as a router, it sends a DTP message to negotiate the trunking mode on the port. The DTP message includes information about the switch's capabilities and requests information about the other device's capabilities. The negotiation process determines whether the port should be configured as a trunk port or an access port.

If both devices support trunking, the port is configured as a trunk port and can carry traffic from multiple VLANs. If one or both devices do not support trunking, the port is configured as an access port and can carry traffic from only one VLAN.

It's important to note that DTP messages are only sent between switches and not between switches and PCs or other end devices. PCs and end devices are typically connected to access ports on a switch, and do not participate in the DTP negotiation process.

The ping process creates an ICMP echo request message and sends it to the lower process.

Yes, that's correct. When a user issues a ping command to test connectivity to another device on the network, the operating system creates an ICMP (Internet Control Message Protocol) echo request message and sends it to the destination device.

The ICMP echo request message contains information such as the source and destination IP addresses, a sequence number, and a timestamp. When the destination device receives the ICMP echo request, it sends back an ICMP echo reply message to the source device, which indicates that the destination device is reachable and responsive.

The ping process relies on the lower layers of the OSI model to transmit the ICMP messages. The ICMP echo request message is encapsulated in an IP (Internet Protocol) packet, which is then encapsulated in a data-link layer frame for transmission over the network. The lower layers of the OSI model, such as the network layer and data-link layer, are responsible for transmitting the ICMP message to the destination device and returning the response to the source device.

What's the PDU info?

PDU stands for Protocol Data Unit, which is a generic term used to describe the data structure or packet used by a particular network protocol. A PDU contains information about the protocol, the data being transmitted, and the addressing information needed to deliver the data to its intended recipient.

In the context of the OSI (Open Systems Interconnection) model, each layer uses a specific PDU format to encapsulate data for transmission across the network. The PDU at each layer is typically referred to by a specific name, such as a segment, packet, or frame.

For example, in the TCP/IP protocol suite, the PDU at the application layer is typically referred to as a message or data, while the PDU at the transport layer is called a segment. The PDU at the network layer is referred to as a packet, while the PDU at the data-link layer is called a frame.

Understanding the PDU for each layer of the OSI model is important for troubleshooting network issues and identifying the source of problems. By examining the PDU at each layer, network engineers can identify which layer is responsible for a particular problem and take appropriate action to resolve it.

osi 7 layers, layer1 is physical, and layer 7 is application

Yes, that's correct. The OSI (Open Systems Interconnection) model is a conceptual framework that describes the communication functions of a telecommunication or computing system. It defines seven layers that describe the different functions involved in transmitting data over a network:

Physical Layer: This layer is responsible for transmitting raw data over a physical medium, such as copper or fiber optic cables. It defines the physical characteristics of the medium, such as voltage levels, signal timing, and bit synchronization.

Data Link Layer: This layer is responsible for organizing raw data into frames, which can be transmitted over the physical medium. It also handles error detection and correction, flow control, and media access control.

Network Layer: This layer is responsible for routing data between different networks. It uses logical addressing to identify the source and destination of data packets, and it selects the best path for transmitting data across the network.

Transport Layer: This layer is responsible for providing reliable data transfer between end systems. It establishes a connection-oriented or connectionless transport service, and it handles segmentation and reassembly of data packets.

Session Layer: This layer is responsible for establishing, maintaining, and terminating sessions between end systems. It allows multiple applications to share a single network connection, and it handles session synchronization and recovery.

Presentation Layer: This layer is responsible for translating data between different formats and character sets. It also handles data compression, encryption, and decryption.

Application Layer: This layer is responsible for providing network services to end users. It includes protocols such as HTTP (HyperText Transfer Protocol), FTP (File Transfer Protocol), and SMTP (Simple Mail Transfer Protocol).

Remembering the seven layers of the OSI model can be helpful for understanding how network communication works and for troubleshooting network issues.

When I send a message out, does the message start from physical to application layer, or start from application layer to physical layer?

In the OSI model, the message flow starts from the Application layer and moves down to the Physical layer. This process is known as encapsulation.

When a message is sent out from an application, it is first processed by the Application layer, which prepares the data for transmission. The data is then passed down to the Presentation layer, which converts the data into a format that can be understood by the receiving application. The Session layer then manages the connection between the two applications.

After the Session layer, the Transport layer takes over and provides end-to-end communication by establishing a reliable data transfer between the two hosts. The Network layer then adds the necessary addressing and routing information to the data packet, which enables it to be transmitted across the network.

The Data Link layer is responsible for framing the data into frames, adding addressing information, and detecting errors. Finally, the Physical layer converts the digital signal into a format that can be transmitted over the physical medium, such as electrical signals or light.

In summary, the message flow starts from the Application layer and moves down to the Physical layer in the OSI model. Each layer adds its own header and/or trailer to the data, resulting in encapsulation of the data as it moves down the layers.

How about the message flow when received a message?

When a message is received, the message flow follows the opposite direction of the OSI model layers. This process is known as decapsulation.

When a message is received, it first goes through the Physical layer, where it is converted from a physical signal to a digital signal. The Data Link layer then examines the received bits and extracts the frame, which contains addressing and control information.

The Network layer then examines the destination address in the packet header and determines the next hop to forward the packet. The Transport layer reassembles any segments or packets that were fragmented during transmission and delivers the entire message to the appropriate application.

The Session layer manages the connection between the two applications and ensures that the message is delivered in the correct order. The Presentation layer converts the data into a format that can be understood by the receiving application, and the Application layer delivers the message to the intended recipient.

In summary, when a message is received, the message flow follows the opposite direction of the OSI model layers, starting from the Physical layer and moving up to the Application layer. Each layer removes its header and/or trailer from the data, resulting in decapsulation of the data as it moves up the layers.

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