• Hub vs Switch vs Routers

Hub L2 Switch L3 Switch Router
Forwards packets it receives through one port to every other port on the device. Any packets addressed to those machines will only get sent to that port.

Separate collision domain.

Perform L2 and some or all functions normally performed by a router. A router can also define subnets and will filter traffic as needed
Total network bandwidth is limited to the speed of the hub, i.e. a 10Base-T hub provides 10Mb bandwidth max, no matter how many ports it has. Total network bandwidth is determined by the number of ports on the switch. i.e. an 8 port 100Mb switch can support up to 800Mb/s bandwidth. Increase efficiency by delivering the traffic of a multicast group Determine which port it needs to forward a packet through, and also will translate packets between different protocols if needed.
Half duplex Full duplex. Allows both transmit and receive data at the same time Full duplex. Allows both transmit and receive data at the same time Traffic forwarded based and Broadcasts are generally not forwarded
Limits  of interconnection No limits  of interconnection No limits  of interconnection Used to interconnect LANs


  • Protocols

A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behavior of a hardware connection.

Common protocols

IP (Internet Protocol)

UDP (User Datagram Protocol)

TCP (Transmission Control Protocol)

DHCP (Dynamic Host Configuration Protocol)

HTTP (Hypertext Transfer Protocol)

FTP (File Transfer Protocol)

Telnet (Telnet Remote Protocol)

SSH (Secure Shell Remote Protocol)

POP3 (Post Office Protocol 3)

SMTP (Simple Mail Transfer Protocol)

IMAP (Internet Message Access Protocol)


  • Throughput or Network Throughput

The average rate of successful message delivery over a communication channel. These data may be delivered over a physical or logical link, or pass through a certain network node. The throughput is usually measured in bits per second (bit/s or bps), and sometimes in data packets per second or data packets per time slot.

The system throughput or aggregate throughput is the sum of the data rates that are delivered to all terminals in a network


  • What is Latency?

Latency is a measure of amount of time between the start of an action and its completion, whereas throughput is the total number of such actions in a given amount of time.


  • MDI-X

The Cross Over Function is implemented in each port at the switch and is denoted by MDI-X


  • Trunking

Bundling of several lines in parallel to form one common connection.
Benefits of this are the higher achievable data rate (as a sum of all data rates of the respective lines) and the better robustness: if one line fails, the throughput will decrease by the data rate of the failed line, but the connection as a whole will still remain stable.


  • Spanning Tree Protocol (STP)

The purpose of Spanning Tree is to prevent loops in the LAN and to select the fastest network links, if there are redundant links in the network.  In the event that a link in the network goes down, Spanning Tree will failover to the alternate link, if one exists.


  • Virtual Local Area Network (VLAN)

A network of computers that behave as if they are connected to the same wire even though they may actually be physically located on different segments of a LAN. One of the biggest advantages of VLANs is that when a computer is physically moved to another location, it can stay on the same VLAN without any hardware reconfiguration.

Allows having several VLANs over a single switch in such a manner that all the LANs will operate in parallel and may not be even aware of each other.

There are several types of VLANs:

Port Based VLANs (Layer 1)

MAC Based VLANs (Layer 2)

Protocol Based VLANs (Layer 2)

IP Subnet Based VLANs (Layer 3)


  • Broadcast Domain

A broadcast domain is a specific address that sends signals to all devices in the same group. For example, all tenants in an apartment complex receiving a letter, or a group email, all people in that list should receive this message. Usually a broadcast address will hit all devices attached to a switch.


  • Collision Domain

A collision domain is a networking segment where two signals can have a collision. A switch or network bridge will forward frames with addresses that are not in its domain, and will duplicate and broadcast frames to the devices inside its network.


  • Unicast

A piece of information is sent from one point to another point. In this case there is just one sender, and one receiver.


  • Broadcast

A piece of information is sent from one point to all other points. In this case there is just one sender, but the information is sent to all connected receivers.


  • Multicast

a piece of information is sent from one or more points to a set of other points. In this case there is may be one or more senders, and the information is distributed to a set of receivers (there may be no receivers, or any other number of receivers).


  • SNMP

Simple Network Management Protocol (SNMP) is used in network management systems to monitor network-attached devices for conditions that warrant administrative attention. It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects.

SNMP exposes management data in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications.


  • RMON

The Remote Network MONitoring (RMON) MIB was developed by the IETF to support monitoring and protocol analysis of LANs. The original version (sometimes referred to as RMON1) focused on OSI Layer 1 and Layer 2 information in Ethernet and Token Ring networks. It has been extended by RMON2 which adds support for Network- and Application-layer monitoring and by SMON which adds support for switched networks. It is an industry standard specification that provides much of the functionality offered by proprietary network analyzers. RMON agents are built into many high-end switches and routers.


  • Small Form Factor Pluggable (SFP):

A standard for optical transceiver modules. The SFP standard allows a flexible choice of fiber optic transceivers (Single & Multi-Mode) for devices with a SFP slot. Depending on the application, an individually selected SFP module containing the required technology and wavelength can be inserted. FPs are hot-swappable input/output devices.