2.3 TCP/IP reference Model

TCP/IP Reference Model is a four-layered suite of communication protocols. It was developed by the DoD (Department of Defence) in the 1960s. It is named after the two main protocols that are used in the model, namely, TCP and IP. TCP stands for Transmission Control Protocol and IP stands for Internet Protocol.

The four layers in the TCP/IP protocol suite are −

• Host-to- Network Layer −It is the lowest layer that is concerned with the physical transmission of data. TCP/IP does not specifically define any protocol here but supports all the standard protocols.
• Internet Layer −It defines the protocols for logical transmission of data over the network. The main protocol in this layer is Internet Protocol (IP) and it is supported by the protocols ICMP, IGMP, RARP, and ARP.
• Transport Layer − It is responsible for error-free end-to-end delivery of data. The protocols defined here are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
• Application Layer − This is the topmost layer and defines the interface of host programs with the transport layer services. This layer includes all high-level protocols like Telnet, DNS, HTTP, FTP, SMTP, etc.

The following diagram shows the layers and the protocols in each of the layers −

2.4 Ethernet Technology – Types of Ethernet, properties of Ethernet, Collision detection and Recovery, Ethernet hardware address, Ethernet Frame Format

What is Ethernet?

1. Ethernet is a type of communication protocol that was created at Xerox PARC in 1973 by Robert Metcalfe and others, which connects computers on a network over a wired connection. 
2. It is a widely used LAN protocol, which is also known as Alto Aloha Network. It connects computers within the local area network and wide area network.
3. Numerous devices like printers and laptops can be connected by LAN and WAN within buildings, homes, and even small neighbourhoods.
4. It offers a simple user interface that helps to connect various devices easily, such as switches, routers, and computers. 
5. A local area network (LAN) can be created with the help of a single router and a few Ethernet cables, which enable communication between all linked devices. 

Different Types of Ethernet Networks

There are some kinds of Ethernet networks, which are discussed below:

• Fast Ethernet: This type of Ethernet is usually supported by a twisted pair or CAT5 cable, which has the potential to transfer or receive data at around100 Mbps. They function at 100Base and 10/100Base Ethernet on the fiber side of the link if any device such as a camera, laptop, or other is connected to a network. The fiber optic cable and twisted pair cable are used by fast Ethernet to create communication. 
• Gigabit Ethernet: This type of Ethernet network is an upgrade from Fast Ethernet, which uses fiber optic cable and twisted pair cable to create communication. It can transfer data at a rate of 1000 Mbps or 1Gbps. In modern times, gigabit Ethernet is more common. This network type also uses CAT5e or other advanced cables, which can transfer data at a rate of 10 Gbps.
• 10-Gigabit Ethernet: This type of network can transmit data at a rate of 10 Gigabit/second, considered a more advanced and high-speed network. It makes use of CAT6a or CAT7 twisted-pair cables and fiber optic cables as well. This network can be expanded up to nearly 10,000 meters with the help of using a fiber optic cable.
• Switch Ethernet: This type of network involves adding switches or hubs, which helps to improve network throughput as each workstation in this network can have its own dedicated 10 Mbps connection instead of sharing the medium. Instead of using a crossover cable, a regular network cable is used when a switch is used in a network. For the latest Ethernet, it supports 1000Mbps to 10 Gbps and 10Mbps to 100Mbps for fast Ethernet.

2.5 Wireless LAN

Wireless LANs (WLANs) are wireless computer networks that use high-frequency radio waves instead of cables for connecting the devices within a limited area forming LAN (Local Area Network). Users connected by wireless LANs can move around within this limited area such as home, school, campus, office building, railway platform, etc. Most WLANs are based upon the standard IEEE 802.11 standard or WiFi.

Components of WLANs

The components of WLAN architecture as laid down in IEEE 802.11 are −

• Stations (STA) − Stations comprises of all devices and equipment that are connected to the wireless LAN. Each station has a wireless network interface controller. A station can be of two types −
  • Wireless Access Point (WAP or AP)
  • Client
• Basic Service Set (BSS) − A basic service set is a group of stations communicating at the physical layer level. BSS can be of two categories −
  • Infrastructure BSS
  • Independent BSS
• Extended Service Set (ESS) − It is a set of all connected BSS.
• Distribution System (DS) − It connects access points in ESS.

Types of WLANS

WLANs, as standardised by IEEE 802.11, operate in two basic modes, infrastructure, and ad hoc mode.

• Infrastructure Mode − Mobile devices or clients connect to an access point (AP) that in turn connects via a bridge to the LAN or Internet. The client transmits frames to other clients via the AP.
• Ad Hoc Mode − Clients transmit frames directly to each other in a peer-to-peer fashion.

Advantages of WLANs

• They provide clutter-free homes, offices and other networked places.
• The LANs are scalable in nature, i.e. devices may be added or removed from the network at greater ease than wired LANs.
• The system is portable within the network coverage. Access to the network is not bounded by the length of the cables.
• Installation and setup are much easier than wired counterparts.
• The equipment and setup costs are reduced.

Disadvantages of WLANs

• Since radio waves are used for communications, the signals are noisier with more interference from nearby systems.
• Greater care is needed for encrypting information. Also, they are more prone to errors. So, they require greater bandwidth than the wired LANs.
• WLANs are slower than wired LANs.

2.6 Bluetooth

Bluetooth wireless technology is a short range communications technology intended to replace the cables connecting portable units and maintaining high levels of security. Bluetooth technology is based on Ad-hoc technology also known as Ad-hoc Pico nets, which is a local area network with a very limited coverage.

History of Bluetooth

WLAN technology enables device connectivity to infrastructure based services through a wireless carrier provider. The need for personal devices to communicate wirelessly with one another without an established infrastructure has led to the emergence of Personal Area Networks (PANs).

• Ericsson’s Bluetooth project in 1994 defined the standard for PANs to enable communication between mobile phones using low power and low cost radio interfaces.
• In May 1988, Companies such as IBM, Intel, Nokia and Toshiba joined Ericsson to form the Bluetooth Special Interest Group (SIG) whose aim was to develop a de facto standard for PANs.
• IEEE has approved a Bluetooth based standard named IEEE 802.15.1 for Wireless Personal Area Networks (WPANs). IEEE standard covers MAC and Physical layer applications.

The usage of Bluetooth has widely increased for its special features.

• Bluetooth offers a uniform structure for a wide range of devices to connect and communicate with each other.
• Bluetooth technology has achieved global acceptance such that any Bluetooth enabled device, almost everywhere in the world, can be connected with Bluetooth enabled devices.
• Low power consumption of Bluetooth technology and an offered range of up to ten metres has paved the way for several usage models.
• Bluetooth offers interactive conferences by establishing an adhoc network of laptops.
• Bluetooth usage model includes cordless computer, intercom, cordless phone and mobile phones.

Piconets and Scatternets

1. Bluetooth enabled electronic devices connect and communicate wirelessly through short range devices known as Piconets. 
2. Bluetooth devices exist in small ad-hoc configurations with the ability to act either as master or slave the specification allows a mechanism for master and slave to switch their roles. 
3. Point to point configuration with one master and one slave is the simplest configuration.
4. When more than two Bluetooth devices communicate with one another, this is called a PICONET. 
5. A Piconet can contain up to seven slaves clustered around a single master. The device that initialises the establishment of the Piconet becomes the master.

Spectrum

Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHZ, using a spread spectrum hopping, full-duplex signal at a nominal rate of 1600 hops/sec. the 2.4 GHZ ISM band is available and unlicensed in most countries.

Range

Bluetooth operating range depends on the device Class 3 radios have a range of up to 1 metre or 3 feet Class 2 radios are most commonly found in mobile devices have a range of 10 meters or 30 feet Class 1 radios are used primarily in industrial use cases have a range of 100 metres or 300 feet.

Data rate

Bluetooth supports 1 Mbps data rate for version 1.2 and 3Mbps data rate for Version 2.0 combined with Error Data Rate.