To make you more familiar with the concepts of network switching and to get acquainted with the reputable vendors of network switches, we have prepared a number of blogs as a series, the different parts of which are as follows:

In this series of blogs you will come across a variety of terms, abbreviations, concepts, and technologies. We have tried to explain the general concepts and terms as much as possible in the first three parts of this series. In the following sections, we assume that you have read these two sections and therefore we will not re-explain these concepts and terms in the following sections. Of course, each vendor also has a number of specific terms and concepts that are explained in blogs related to the same vendor’s products.

Last note, all the content as well as the images used in this series of blogs are taken from the official websites of the reviewed vendors (Cisco, Microtik, HP and Dell).



Part 2 – What is a Network Switch? 


In the previous Part, we discussed a number of terms, technologies, and concepts in the world of computer network switches. We will continue this discussion now.

ISSU: An in-service software upgrade (ISSU) is a method for updating a networking device without the need to stop its ongoing processes and restart, which degrades overall network services.

Line-card slot: A printed circuit board that provides a transmitting/receiving port for a LAN or WAN. Line cards plug into switches and high-end routers, which have a modular chassis that accepts a range of cards. Each line card circuit board is mounted to a metal carrier and is sensitive to electrostatic discharge damage.

MAC Address Table (CAM Table): It is used on Ethernet switches to determine where to forward traffic on a LAN. In fact, the switch learns and stores the MAC addresses of all connected devices. The switch stores the learned MAC addresses in a table that is known as the CAM table.

Metro Ethernet: This service uses physical Ethernet links to establish a connection between the client-side device and the service provider (SP) device. This is a data link layer service in which SP forwards Ethernet frames from one client device (e.g., New York branch) to another client device (New Jersey branch). This service has many similarities to an Ethernet switch. In fact, Cisco describes the service as “a big Ethernet switch.” In other words, Metro Ethernet is like an Ethernet switch to which different routers (routers of different physical sites of the customer company) are connected. The connection is of the fiber Ethernet type, which provides very significant speed. Metro Ethernet receives frames similar to Ethernet switches and forwards them to another site router.

MPLS: One of the most familiar and well-known technologies for implementing WAN networks and communicating between different branches of an organization. Multiprotocol label switching (MPLS) is a technique for speeding up network connections that was first developed in the 1990s. With MPLS, the first time a packet enters the network, it’s assigned to a specific forwarding equivalence class (FEC), indicated by appending a short bit sequence (the label) to the packet.

OLT, ONU or ONT, and ODN: These are the main components in a GEPON system, which have been widely used in the FTTH applications by far. The reduced cabling infrastructure (no active elements) and flexible media transmission contribute to the passive optical networks more ideal for home Internet, voice, and video applications. Additionally, passive optical networks can also be applied in college campuses and business environments, providing cost-effective solutions. As PON technology has continued to improve, the potential applications have expanded as well. (Source: Read more about these components: ABC of PON: Understanding OLT, ONU, ONT and ODN

OpenFlow: it is a communications protocol that gives access to the forwarding plane of a network switch or router over the network. OpenFlow enables network controllers to determine the path of network packets across a network of switches. OpenFlow allows switches from different vendors to be managed remotely using a single, open protocol.

OSPF:  Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS). In other words, the OSPF used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network.

PoE: Power on Ethernet (PoE) switch is a network switch that utilizes Power over Ethernet technology. These switches can support power and data transmission over one network cable at the same time. This greatly simplifies the cabling process. In fact, POE allows you to power a device like an IP phone or wireless access point over the same cable as your data traffic. The IEEE 802.3 PoE standard sets the maximum power that can be sourced by data terminal equipment (DTE) at 15.4W power.

PoE+: It extends the IEEE 802.3 PoE standard to provide the capability to source up to 30W of power over standard Ethernet cabling infrastructure.

PON: Passive Optical Network (PON) is an Internet Service Provider`s (ISP) network that uses point-to-multipoint fiber to the subscriber`s end-points. PON design usually conists of Optical Line Terminal (OLT) deployed at the ISP`s site, number of Optical Network Units (ONU) or Optical Network Treminals (ONT) deployed at the subscriber`s end and fiber optic splitters which split the optical power evenly into all the output ports. PON reduces the amount of fibers compairing to traditional Fiber-to-the-Home network by using fiber optic splitters and sure it almost has no active electrical equipment but only OLT and ONUs/ONTs. PON supports the same services as traditional Ethernet including: High Speed Internet, VoIP, IPTV and analog cable TV broadcasting. (Source:

Port Security: This feature gives us complete control over the devices that connect to the various ports on a switch.

In fact, we can prevent devices other than our approved devices from operating on the network. Obviously we can set that port 17 of the switch only works when a printer with a specific MAC is connected to this port. Otherwise, the port will be disabled or even shutdown at all, and even when the approved device is reconnected, it will not turn on automatically.

QoS: Quality of service (QoS) is the use of mechanisms or technologies to manage traffic and ensure the performance of critical applications.  Common services for which it is required include internet protocol television (IPTV), online gaming, streaming media, videoconferencing, video on demand (VOD), and Voice over IP (VoIP). Using QoS, organizations can optimize the performance of various applications on their network and gain visibility into the bit rate, delay, jitter, and packet rate of their network. The key goal of QoS is to enable networks and organizations to prioritize traffic, which includes offering dedicated bandwidth, controlled jitter, and lower latency. The technologies used to ensure this are vital to enhancing the performance of business applications, wide-area networks (WANs), and service provider networks. (Source:

SDN: Software-defined networking (SDN) technology is an approach to network management that enables dynamic, programmatically efficient network configuration in order to improve network performance.

SFP, SFP+, and QSFP: We suggest you read these two articles. (1) Fiber Optic Cabling Solutions, and (2) SFP vs SFP+ vs QSFP: What’s the difference?

SOHO: It is the abbreviation for Small Office/Home Office network. SOHO network is meant for use in small businesses. SOHO is the smallest of the small businesses.  The self-employed people and sometimes by a small group people up to 1-5 people are privately own and operate it. These networks are small LANs, and they consists of less than 10 computers. In fact, a SOHO network can be a small wired Ethernet LAN or made of both wired and wireless computers.

STP: The STP (Spanning Tree Protocol) is responsible for preventing loops on the internet layer, and the IEEE Institute has named and introduced this protocol with the IEEE 802.1d standard.

In order for the STP protocol to be able to prevent loops from forming in layer 2, it must have a proper understanding of all its topology and connections. This information is obtained by messages called BPDUs, through Layer 2 equipment on which the STP protocol is implemented. In the event of a loop, the STP blocker blocks the ports involved in creating the loop, leaving only the best Layer 2 path between the equipment open for use and ensuring that no loop is created.

Switching Capacity: This term of a switch refers to the maximum amount of data that can be transmitted between a switch interface processor or interface card and a data bus. The switching capacity indicates the total data exchange capability of the switch, in bps.

Throughput capacity: This term (it also called forwarding capacity) refers to the capability of the switch to forwarding packets, in PPS (Packet per second), that is, the number of packets that can be forwarded by the switch per second.

Uplink Port: This port on a switch is used to connect a device or a smaller local network to a larger network. In other words, an uplink port is a specially designed port found on some pieces of networking devices to allow these devices to communicate with each other. The two switches are connected directly to each other through uplink port.

UPoE: or Universal POE. It is a Cisco proprietary technology that extends the IEEE 802.3 PoE standard to provide the capability to source up to 60W of power over standard Ethernet cabling infrastructure.

UPoE+: It is a Cisco proprietary technology that extends the IEEE 802.3 PoE standard to provide the capability to source up to 90W of power.

VLAN: By default, broadcast packets forward on all ports. As a result, network traffic increases and efficiency decreases.

Now suppose that the computers in the IT department and finance department are all connected to the same switch. Here we can divide this switch into two areas for financial clients and IT clients. For example, allocate the first 14 ports to the financial department and the next ten ports to the IT department.

VLAN stands for Virtual LAN. We have now virtually divided our LAN into two LANs for the financial department and the IT department. Broadcast packets of a VLAN are no longer routed into other VLANs. Basically, VLAN switching is also used to reduce collision.

The scope of a VLAN is actually the broadcast domain of the VLAN. That is, each broadcast packet sent by a port moves only within the VLAN range of which the port is a member. If, for example, ports 6 to 16 of a switch are members of a VLAN, each broadcast packet of each of these ports is sent only to VLAN members, ports 6 to 16. The most important reason to use a VLAN is to increase the number of broadcast domains, resulting in better bandwidth utilization, lower CPU and RAM usage, and increased network infrastructure performance.

An interface can be considered for each VLAN and assigned an IP address to it.

xPON: This article provides a fairly complete description of this technology: An Analysis of xPON Technology Development

XVLAN: Virtual Extensible LAN (VXLAN) is a proposed encapsulation protocol for running an overlay network on existing Layer 3 infrastructure. VXLAN endpoints, which terminate VXLAN tunnels and may be either virtual or physical switch ports, are known as VXLAN tunnel endpoints (VTEPs).

The VXLAN protocol supports the virtualization of the data center network while addressing the needs of multi-tenant data centers by providing the necessary segmentation on a large scale. VXLAN will make it easier for network engineers to scale out a cloud computing environment while logically isolating cloud apps and tenants.







Read other blogs related to this series: