Linux Learning Switch

Switch Summary:

The similarities between the switch and the bridge are as follows:

1. Bridges and switches are linked to LAN segments.

2. Bridges and switches use the MAC Address table to identify the network segment to which the data frame is destined.

3. Bridges and switches help reduce network traffic.

Switch-to-bridge is a great advantage to eliminate network congestion:

1. Dedicated inter-device communication: Increases frame throughput. Each port on the switch corresponds to one user and a differential segment of the network. In such a configuration, each user can access the full bandwidth without competing for the available bandwidth with other users. Therefore, no conflict occurs.

2. Multiple simultaneous sessions: forwarding or exchanging multiple packets simultaneously can enable multiple simultaneous sessions, so you can increase the network's ability by increasing the number of supported sessions. Because IO buffering and fast internal transmission exist between ports. Switches that can support all combinations of possible frame transfers across all ports can provide both wire-speed and nonblocking performance.

3. Full-duplex communication: When a link is differentiated, the two hosts can simultaneously maneuver the data, called full-duplex communication.

For example, a point-to-point 100mb/s Link has a 100Mbs transmission capacity and an acceptable capacity of 100mb/s. Therefore, there is an effective capacity of 200mb/s on a single connection. When you create a link connection, the switch automatically negotiates the configuration between half-duplex and full-duplex.

Media Rate Adjustment:

LAN switches with different port media rates can be adjusted between 10 and 100 or 100 to 1000mb/s to match bandwidth as needed. If you do not have this capability, ports with different media rates cannot be run at the same time.

Features of the switch:

Learning: For each received data frame, the switch saves the source MAC address and the switch port number that accepts the data frame to its internal MAC address table;

1. If the source MAC address in the received data frame does not appear in the MAC Address table, add the entry directly to the MAC address table

2. If the source MAC address in the received data frame already appears in the MAC Address table, update the timestamp of the entry

3. Dynamic Learning MAC address entries are cached in the MAC address table for 30 seconds

Attention:

1. Multiple MAC addresses can be bound per port

2. Only one port can be bound per MAC address

Forward:

Purposeful forwarding:

After receiving the data frame, the switch reads the destination MAC address in the data frame, finds its MAC address table, finds the destination address in the MAC Address table, and sends the data frame out of the MAC address table to the corresponding port;

No destination forwarding:

Flooding

After the switch receives the data frame, reads the destination MAC address in the data frame, if the destination MAC address is a multicast address, a broadcast address, or a MAC address that does not exist on its own Mac surface, the switch will want to forward the data frame in addition to the port that accepts all active states except the data frame;

Filter:

If the switch receives a data frame, finds that the destination MAC address of the data frame corresponds to the port and the port that receives the data is the same port, then such data, filtering does not accept

Switch Features:

1. High port density. The most common are 24-port and 48-port switches with speeds of 10mb/s and 100mb/s, respectively. A large enterprise switch can support hundreds of ports.

2. Greater frame buffer: It is useful to store more frames before you have to discard the received frames, especially if there are congestion ports on the server or other parts of the network.

3. Port speed: Depending on the cost of the switch, the switch may support the mixed media rate. The ports of the 10mb/s and 100mb/s have been met, but the ports of 1gb/s or 10gb/s have greater flexibility.

4. Fast Internal switching: Fast Internal switching can support multiple rates of 10mb/s ... The port. The method used may be a fast internal bus or shared memory. However, this can affect the overall performance of the switch.

Two forwarding methods for exchanging data between network interfaces by switches:

Passthrough switching: The switch responds to data immediately after it receives data, even if the transfer is not complete. The switch determines which port the data goes to, based on the first frame it receives, and does not need to buffer the data to begin processing. This is the faster of the two methods, but the method does not have error checking to ensure the accuracy of the data.

Store-and-forward switching: When the switch accepts data, the data is stored in the buffer only after the full frame is received. In the stored procedure, the switch analyzes the frame to obtain information about its destination. The switch also checks for errors during the second process.

Fragment loss swap: The fragment discard swap key ensures that enough bytes are read from the source to detect the conflict before forwarding.

The switch processes the unicast frames in the LAN:

1. When the port receives a unicast frame, the switch compares the destination MAC address to the MAC address in the Address table

2. If the switch determines that the destination MAC address of the frame is in the same network segment as the source address, the frame is not forwarded. This process is called filtering, and by performing this procedure, the switch can significantly reduce the traffic passing between network segments because unnecessary frames have been filtered out.

3. If the switch determines that the destination MAC address of the frame is no longer unified with the source address, it forwards the frame to the appropriate network segment.

4. If the switch does not have an entry for the destination address, it sends the frame to all ports except the port that received the frame. This process is known as flooding.

To swap frames: a-->lan-->b

1. The switch accepts a broadcast frame sent by PC A from Port 1

2. The switch enters the source MAC address and the switch port that received the frame into the Mac table.

3. Because the destination address is broadcast, the switch will pan the frame floodway all the ports except the one that received the frame.

4. The destination device uses a unicast frame that has been sent to PC A to answer the broadcast.

5. The switch enters the source MAC address of PC B and the port number of the switch that receives the frame into the Mac table, locates the destination address of the frame and its associated port on the Mac frame.

6. The switch now does not need flooding to forward frames between the source device and the destination device because its Mac table can identify the entry for the relevant port.

Linux Learning switches