Q#01: what is routing, what are its types can you differentiate between the types of routing used in communication networks?Answer:Routing:Routing is the act of moving information across an internetwork from a source to a destination. Along the way, at least one intermediate node typically is encountered. Routing is often contrasted with bridging, which might seem to accomplish precisely the same thing to the casual observer. The primary difference between the two is that bridging occurs at Layer 2 (the link layer) of the OSI reference model, whereas routing occurs at Layer 3 (the network layer). This distinction provides routing and bridging with different information to use in the process of moving information from source to destination, so the two functions accomplish their tasks in different ways. There are three types of routing Static Dynamic Combined static and dynamicStatic routing:Small networks, hosts that get their routes from a default router, and default routers that only need to know about one or two routers on the next few hops.Dynamic routing:Larger internetworks, routers on local networks with many hosts, and hosts on large autonomous systems. Dynamic routing is the best choice for systems on most networks.Combined static and dynamic:Routers that connect a statically routed network and a dynamically routed network, and border routers that connect an interior autonomous system with external networks. Combining both static and dynamic routing on a system is a common practice.Q#02 what is a routing table and what information does it depict and how it affects the performance of a router?Answer:Routing table:In computer networking a routing table, or routing information base (RIB), is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. Both routers and hosts maintain a routing table. The routing daemon on each system updates the table with all known routes. The system's kernel reads the routing table before forwarding packets to the local network. The routing table lists the IP addresses of networks that the system knows about, including the system's local, default network. The table also lists the IP address of a gateway system for each known network. The gateway is a system that can receive outgoing packets and forward them one hop beyond the local network. The following is a simple routing table for a system on an IPv4-only network

Fig 01 : Routing Table

Q: what is a difference between a router a hub and a switch?Answer:The functions of the three devices the hub , switch and router are all quite different from one another, even if at times they are all integrated into a single device. Which one do you use when? Let's take a look...Hub:A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Switch:In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.Router:A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP.s network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.Q#04 what is a protocol and what are the main types of routing protocols, characterize them also?Answer:Routing Protocol:A routing protocol specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network. Routing algorithms determine the specific choice of route. Each router has a priori knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network.There are following main types of routing protocols Interior gateway protocols type 1, link-state routing protocols, such as OSPF and IS-IS Interior gateway protocols type 2, distance-vector routing protocols, such as Routing Information Protocol, RIPv2, IGRP. Exterior gateway protocols are routing protocols used on the Internet for exchanging routing information between Autonomous Systems, such as Border Gateway Protocol (BGP), Path Vector Routing Protocol.Q#05 what is an IP address, classify IP addresses also explain the sub net masks and net masks?Answer:Internet Protocol Address (IP address):An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.[1] An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there. The IP address can be classified in to following main types Class A Class B Class C Class D Class EOf the five classes, D and E are dedicated to special purposes, so I will leave those alone for now. Classes A, B and C are the ones actually assigned for normal (unicast) addressing purposes on IP internetworks, and therefore the primary focus of our continued attention.

Fig 02: IP address classes

Sub nettingSub netting enables the network administrator to further divide the host part of the address into two or more subnets. In this case, a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format.Subnet mask:A subnet mask separates the IP address into the network and host addresses (). Sub netting further divides the host part of an IP address into a subnet and host address () if additional sub network is needed. It is called a subnet mask because it is used to identify network address of an IP address by performing a bitwise AND operation on the net mask.Net mask:A net mask is a 32-bit mask used to divide an IP address into subnets and specify the networks available hosts. In a net mask, two bits are always automatically assigned. For example, in 255.255.225.0, "0" is the assigned network address; and in 255.255.255.255, "255" is the assigned broadcast address. The 0 and 255 are always assigned and cannot be used.

Fig 03: example of a net mask and an example of its binary conversion.Counting out the bits in the binary conversion allows you to determine the net mask length. In the above example, you have an example of a 32-bit address. However, this address is a broadcast address and does not allow any hosts (computers or other network devices) to be connected to it.Q#06 Remember the OSI model can you identify the various protocols working on the layer wise structure of OSI model?Answer:OSI protocols:The Open Systems Interconnection (OSI) protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T starting in 1977.While the seven-layer OSI model is still often referenced, of the protocols themselves only X.400, X.500, and IS-IS have had much lasting impact. The goal of a series of open, non-proprietary network protocols is now met by the competing TCP/IP stack.Layer 1: physical layer:This layer deals with the physical plugs and sockets and electrical specification of signals only.This is the medium over which the digital signals are transmitted. It can be twisted pair, coaxial cable, optical fiber, wireless, or other transmission media.Layer 2: data link layer:The data link layer packages raw bits from the physical layer into frames (logical, structured packets for data). It is specified in ITU-T Rec. X.212 [ISO/IEC 8886], ITU-T Rec. X.222 and others. This layer is responsible for transferring frames from one host to another. It might perform error checking. This layer further consists of two sub layers: MAC and LLC.Layer 3: network layer:The layer 3 (network layer) has following important protocols Q: How does MPLS helps in improving data rate and routing?Answer: Multiprotocol Label Switching, MPLS is the process of data packets labels. When data packets are transmitted over a network connection, their labels are examined instead of having to examine the contents, thus determining the network destination in a more efficient manner. This method can improve data transmission speeds because there is no need to use a routing table to do a lookup on where the data packet is being sent.Due to the virtual paths between network nodes, MPLS is not dependent on an OSI model data link layer. It also virtually eliminates the necessity to use layer-2 networks for different types of network traffic. By including the MPLS header, containing one or more labels, to each data packet, networks gain a much needed improvement in data transmission efficiency, helping to decrease costs in the end.Limitations of Optical Media: these are the following main disadvantages or limitations of the optical mediaPrice: Even though the raw material for making optical fibers, sand, is abundant and cheap, optical fibers are still more expensive per meter than copper. Although, one fiber can carry many more signals than a single copper cable and the large transmission distances mean that fewer expensive repeaters are required.

Fragility: Optical fiber is more fragile than electrical wires.Affected by chemicals: The glass can be affected by various chemicals including hydrogen gas (a problem in underwater cables.)Opaqueness: Despite extensive military use it is known that most fiber become opaque when exposed to radiation.Requires special skills: Optical fiber cannot be joined together as a easily as copper cable and requires additional training of personnel and expensive precision splicing and measurement equipment

BDMA (Beam division multiple Access)When a base station communicates with mobile stations, an orthogonal beam is allocated to each mobile station. The BDMA technique of the present invention divides an antenna beam according to locations of the mobile stations to allow the mobile stations to give multiple accesses, thereby significantly increasing the capacity of the system. Mobile stations and a base station are in an LOS (Line of Sight) state, when they exactly know each others positions; they can transmit beams which direct to each others position to communicate without interfering with mobile stations at cell edge.It is an object of the present invention to provide a beam division multiple access system and a method thereof for a mobile communication system as a new space division method using a phase array antenna. Which use beam forming technology and uses multiple beam forming pattern simultaneously in a cell, allowing giving multiple access. Fig 01: BDMAADSL (Asymmetrical Digital Subscriber Line):ADSL is a type of DSL broadband communications technology used for connecting to the Internet. ADSL allows more data to be sent over existing copper telephone lines (POTS), when compared to traditional modem lines. A special filter, called a micro filter, is installed on a subscriber's telephone line to allow both ADSL and regular voice (telephone) services to be used at the same time. ADSL requires a special ADSL modem and subscribers must be in close geographical locations to the provider's central office to receive ADSL service. Typically this distance is within a radius of 2 to 2.5 miles. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). Fig 02: DSL infrastructure building blocks

ADSL have basically two building blocks which are given below DSLAM B-RAS devicesWhen digital data is sent from a DSL subscribers premises, it travels from subscribers computer or network through a DSL modem and on to the other end of the line at the phone companys Central Office (CO). At the CO end of the line (local loop) the data is received by the DigitalSubscriber Line Access Multiplexer (DSLAM). The DSLAM aggregates the digital data streams coming from a number of subscribers onto a single high-capacity uplink (ATM or Gigabit Ethernet backhaul) to the Internet Service Provider. A broadband remote access server routes traffic to and from broadband remote access devices, including DSL access multiplexers and the ISP's network. The key benefits of using broadband remote access servers are:They provide a single point for change controlB-RAS is a common, access-agnostic operational model It is multiservice access node (MSAN) independent If network changes are required, its better to make changes at a single B-RAS server than at dozens of devices. HDSL (High Bit rate Digital Subscriber Line)HDSL (High bit-rate Digital Subscriber Line), one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in both directions. HDSL can carry as much on a single wire of twisted-pair cable as can be carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection Fig: HDSL

Passive Optical Network (PON):Passive Optical Network (PON) is a high bandwidth Point-to-Multipoint (P2MP) optical fiber network based on the Asynchronous Transfer Mode protocol (ATM), Ethernet or TDM.Components used in Passive Optical NetworkPONs generally consist of an OLT (Optical Line Termination), which is connected to ONUs (Optical Network Units). Optical Line Terminal (OLT):An OLT resides in the local exchange (central office), connecting the optical access network to the metro back-boneOptical Network Units (ONUs)The ONU provides the interface between the customers data, video, and telephony networks and the PON. Its function is to receive traffic in a optical format and convert it into customers desired format (Ethernet, IP multicast, T1, etc.)

Fig 01: Passive Optical Network

Properties of PONs PONs relies on light waves for data transfer. Only passive optical components are used such as optical fiber, splices and splitters. PONs minimizes the fiber deployment in both the local exchange office and the local loop. PONs provides higher bandwidth due to deeper fiber penetration, offering gigabit per second solutions.Ethernet PONs (EPONs)Ethernet passive optical networks (EPON) are an emerging access network technology that provides a low-cost method of deploying optical access lines between a carrier office (CO) and customer site. We can say that, Ethernet Passive Optical Networks (EPONs) represents the convergence of low-cost Ethernet equipment and low-cost fiber infrastructure, to be the best candidate for the Next-Generation access network. There are following main features of EPONs EPONs deliver data, video and voice over a single platform EPONs offer higher bandwidth EPONS are less expensive than APONs EPONs provide broader service capabilities

Working:In a EPON the process of transmitting data downstream from the OLT to multiple ONUs is fundamentally different from transmitting data upstream multiple ONUs to the OLT.

GPON:GPON is a point-to-multipoint access mechanism. Its main characteristic is the use of passive splitters in the fiber distribution network, enabling one single feeding fiber from the provider's central office to serve multiple homes and small businesses. GPON has a downstream capacity of 2.488 Gb/s and an upstream capacity of 1.244 Gbp/s that is shared among users. Encryption is used to keep each user's data secured and private from other users. Although there are other technologies that could provide fiber to the home, passive optical networks (PONs) like GPON are generally considered the strongest candidate for widespread deploymentsGPON Mechanism: GPON adopts Wavelength Division Multiplexing (WDM) technology, facilitating bi-direction communication over a single fiber. Fig Multiplexing in GPON To separate upstream/downstream signals of multiple users over a single fiber, GPON adoptsTwo multiplexing mechanism: In downstream direction, data packets are transmitted in a broadcast manner. In upstream direction, data packets are transmitted in a TDMA manner.Downstream Data:The downstream data in the GPON is follows the following mechanism. It is also called the broadcast mode.

Upstream Data:The Upstream data is transferred in the following manner. it is also called the TDMA mode.

ORTHOGONAL FREQUENCY DIVISION MULTIPLEXINGOrthogonal frequency division multiplexing (OFDM) is a multi-carrier digital modulation technique that has been recognized as an excellent method for high speed bi-directional wireless data communication. OFDM effectively squeezes multiple modulated carriers tightly together, reducing the required bandwidth but keeping the modulated signals orthogonal so they do not interfere with each other.To see how OFDM works, it is necessary to look at the receiver. This acts as a bank of demodulators, translating each carrier down to DC. The resulting signal is integrated over the symbol period to regenerate the data from that carrier. The same demodulator also demodulates the other carriers. As the carrier spacing equal to the reciprocal of the symbol period means that they will have a whole number of cycles in the symbol period and their contribution will sum to zero - in other words there is no narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth.Broadband :In telecommunications, broadband is wide bandwidth data transmission with an ability to simultaneously transport multiple signals and traffic types. The medium can be coaxial cable, optical fiber, twisted pair, DSL local telephone networks or wireless broadband. In contrast, baseband describes a communication system in which information is transported across a single channel.[1]