Generic Computer Networking Switches
The Generic Computer Networking Switches are devices used in computer networks. These switches have many useful features, such as high-speed buffer memory, Spanning tree, and Cell header protection. This article covers some of the most common features of these switches and their applications. You will learn about the advantages of these switches, as well as how to select one that meets your needs. Also, learn about some of the important features that will ensure your network stays running smoothly.
Cut-through switching reduces the time required to forward a packet through the switch
In order to increase the speed of a network, it is essential that a packet is forwarded as quickly as possible. General-purpose CPUs are often too slow for forwarding traffic through a switch. While they may be very fast at running random access applications, they are too slow for manipulating network traffic. This is because traffic handling requires frequent lookups in large memory tables, such as the Layer 2 MAC addresses, Layer 3 IP routes, and Layer 4 ACLs (access control lists).
Catalyst 9300 Series switches implement StackWise-480 technology, a technology that enables a fabric of six counter-rotating rings to increase a switch's total stack capacity to 480 Gbps. This technology also enables spatial reuse, which doubles the system throughput by enabling multiple flows to co-exist.
High-speed buffer memory
Generic computer networking switches have a pool of high-speed buffer memory, which is dynamically allocated to each port. Historically, the memory capacity of switches has been limited, which has created problems for network applications. But recent developments in programmable switch ASICs have provided more options for offloading functionality. One example is the ability to set the buffer size of individual ports. The following diagram demonstrates how the buffer memory is accessed and used by each port of a generic computer networking switch.
Today, high-speed switches use as much as 50 percent of the chip area for memory management. However, the performance of such switches is not yet comparable with the performance of their high-speed counterparts. The gap between switching and memory speed is widening. This is why some manufacturers are implementing deep buffers and wrap the switch fabric with small, fast buffers. Then, they can use the off-chip memory to increase performance.
High-speed buffer memory on generic computer networking switch hardware can be overloaded by data traffic. In such a case, the network may have to wait for an inflow of data. Fortunately, the Internet makes this unnecessary. But the question is, what is the optimal buffer size? And is it worth it? In the end, it all boils down to the size of the network's buffer. The Internet, for example, adds an entirely new dimension to the problem.
Non-blocking switch hardware can distinguish between queued and unqueued packets. When a port is busy, it can discard a packet. Therefore, it is important to configure non-blocking switches with VC tables to avoid congestion. By configuring these switches properly, you can ensure that your network is able to handle more traffic than you expect. Further, they can also distinguish between packets with different source-destination pairs.
In the end, the simplest solution to the problem is to configure the switch's high-speed buffer memory to be large. Large network buffers can 'eat up' slop in timing and allow for more precise and coarser rate control algorithms. Smaller network buffers provide little tolerance for approximate approaches, which is why they are not preferred. But, despite the fact that the network buffer size can be changed easily, the research community still has a long way to go before it is adopted widely.
When using a Spanning Tree, each switch has a root port (with one exception, the Root Bridge). A Root Port is the switch's direct path to the Root Bridge. If there are more than one root port, switching loops will occur. Root Ports receive and forward data packets for the local switch. This allows a spanning tree to work with multiple switches. This feature has several disadvantages, however.
RSTP maintains backup details for discarding ports and does not cause timeouts. However, STP does not segregate ports by VLAN, and multiple spanning trees can be desirable. While RSTP does not require a port type configuration, enabling it will prevent any problems from arising with user computers. For example, setting the port type to edge will prevent BPDU packets from being sent when the link state changes. This can reduce spanning tree traffic.
Ports are classified into two types: active and disabled. The active device connected to a port goes through different states during the spanning tree process. When a port is in a learning or listening state, the spanning tree algorithm detects its status. If the port is in this state, it will listen for BPDUs and learn the source address from frames. When a port enters this state, packet forwarding is blocked or disabled.
Another advantage of Spanning Tree is that it helps avoid routing loops in a network. It constantly defines available paths through a network and prevents redundant links from occurring. Furthermore, the Spanning Tree algorithm has the ability to detect disabled nodes and route traffic around them. This makes it possible for networks to function even when the network is suffering from problems. These issues can be caused by hardware failures, network configuration changes, or temporary bandwidth problems.
While simple ring networks work fine with a small number of computers, when hundreds of devices are added, this approach becomes unwieldy. Computers need to send packets through hundreds of nodes, which causes the network to experience congestion and decreased bandwidth. As a result, the Spanning Tree protocol was developed in the mid-90s, and eventually won the LAN topology wars over Token Ring. With Ethernet becoming significantly cheaper and faster, the spanning tree emerged as the standard for computer network switches.
Cell header protection
A switch with cell header protection will not forward frames that are not destined for a specific port. This way, traffic that is destined for a specific port will only be forwarded to that port. A switch with this feature also keeps traffic isolated by maintaining the switching logic. If a frame is destined for a specific port, it will not be forwarded to another port. This means that a frame that is destined for a different port will never reach that device.