Developed in 1980s, Layer 2 (L2) switches have been widely applied to high-speed data transmission in the enterprise between end stations. Layer 3 (L3) switch works as routing over IP network, which mainly functions as dealing with network traffic. This article would provide general information about layer 2 and layer 3 switches, their differences as well as guidance on making choices between those two switches.
If you want to figure out the layer things, you must understand what is the OSI model at first. OSI stands for Open Systems Interconnection, which is a model used to standardise the functions of telecommunication and computing systems around the world. It is a controlled hierarchy where information is passed from one layer to the next creating a blueprint for how information is passed from physical electrical impulses all the way to applications.
Basically, there are totally 7 layers in the OSI model, the “layers” refers to how you configure an IT network. Function of each layer is to provide services to the above layer, so L2 props up L3, shown as the below figure.
As per OSI Model, Layer 2 is Data Link Layer (DLL), which is basically divided into two sub-layers: Logic Link Control (LLC) and Media Access Control (MAC). LLC layer provides services to upper layer, and controls frame synchronization, flow control and error checking. MAC layer performs Layer 2 functions like switching, physical addressing etc. Besides, it controls how a computer on the network gains access to the data and permission to transmit it. Traditional switching operates at layer 2 of the OSI model, where packets are sent to a specific switch port based on destination MAC addresses. There are three distinct functions of layer 2 switching. The following figure shows how layer 2 switching working.
- Address learning
- Forward/filter decisions
- Loop avoidance
Layer 3 Switch
With the support of switching and routing technologies, Layer 3 creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing. Compared to Layer 2 switching,Layer 3 switching is a relatively new term. That has been extended by a numerous vendors to describe their products. Here is an example to illustrate it. one school uses this term to describe fast IP routing via hardware, while another school uses it to describe Multi Protocol Over ATM (MPOA). The following figure shows how layer 3 switching working.
Layer 2 Vs. Layer 3 Switching
Layer 2 Data Link: Responsible for physical addressing, error correction, and preparing the information for the media.
Layer 3 Network: Responsible for logical addressing and routing IP, ICMP, ARP, RIP, IGRP, and routers.
Layer 2 networks forward all their traffic, including ARP and DHCP broadcasts. Anything transmitted by one device is forwarded to all devices. This type of broadcast traffic is very fast. When the network gets too large, the broadcast traffic begins to create congestion and decreases network efficiency.
Layer 3 traffic restricts broadcast traffic. Administrators on L3 can segment networks and restrict broadcast traffic to subnetworks, limiting the congestion of broadcast on large networks. This reduce overall traffic levels by allowing administrators to divide networks into smaller parts and restrict broadcasts to only that sub-network.
In a conclusion, there is a limit to the size of a layer 2 network. However, a properly configured layer 3 network with the correct knowledge and hardware can have infinite growth.
Layer 2 switch lacks router hardware, leaving them susceptible to broadcast storm and the additional administrative overhead of IP allocations due to flat subnet across multiple sites. A Layer 3 switch is a high-performance device for network routing. A router works with IP addresses at layer 3 of the model. Layer 3 networks are built to run on on layer 2 networks. But Layer 2 switches only require switching, no routing gear is necessary. Besides, they cost less and offer very low latency.
This is an open question, and the answer actually depends on what is your need. Both layers of the OSI have their role in the architecture of network performance. An L2 network would be more useful broadcasting information between two computers in the same office, close together. Routing controls happen at Layer 3, and that is what most businesses need. If you are looking for some L2/L3 switches, you can take FS a try. We offer L2/L3 network switches with high performance but low costs. For details, please visit www.fs.com.