Who creates Ethernet standards? What is the difference between Baseband and Broadband transmission? Which physical standard should be used for a web hosting company? Why?
Ethernet is a dominant LAN technology, developed at Xerox Palo Alto Research Center by Metcalfe and Boggs. After the initial development, Ethernet was handed over to IEEE (Institute for Electrical and Electronics Engineers), which created a committee called the 802 committees for developing different standards. This committee was divided into subgroups, namely, 802.1, 802.3, 802.11, 802.16, and the designated standards that they were meant to create were general, Ethernet, wireless LAN, and wi max respectively. Therefore, the subgroup which was responsible for Ethernet standards was 802.3, and this group is now responsible for creating and defining Ethernet standards at the physical and data link layers. The terms 802.3 and Ethernet are interchangeable today and the names of the Ethernet physical layers are clear indicators of their transmission speeds like 10 Mbps will be able to send and receive 10 Mbps across all of its ports and similarly, 100 Mbps will be able to send and receive 100 Mbps across its ports.
Baseband and Broadband transmission
There are two means by which data may be transferred over the Ethernet. these technologies are called baseband and broadband and both of them are different from each other in many different ways. The technology of baseband transmission is one in which the transmitter injects signals into transmission medium like in fiber optics, light pulses are the signal which is injected while the technology of broadband transmission is one where sender transmits signals in radio channels through a radio tuner. Another difference between both the means of transmission is that in a baseband transmission, a single signal consumes the entire bandwidth of the cable whereas, in broadband transmission, signals are sent on multiple frequencies; this allows transmission of multiple signals simultaneously. The signals sent by baseband are digital while those sent by broadband are analog. Another difference is that in broadband, the transmission direction for the signals is unilateral while that in baseband is bi-directional. The distance which the baseband can cover is short while broadband can cover a longer distance. Unlike broadband transmission, the Baseband transmission dominates LAN and the reason is that it is less expensive
Physical standard for web hosting company
A web hosting company is used by its clients for uploading their websites on the internet and making them available online. The physical standard that is most appropriate for a web hosting company, in my opinion, is 100 BASE-TX as it connects stations to switches. This is most suitable for web hosting companies because it has the ability of auto-sensing, which means that detecting slow speed on the other end, too will lower its 100Mbps speed. The 100 Mbps speed is good for page loading and auto-sensing helps to balance both ends and avoid connection from getting blocked. Another option may be of using another standard as an intermediary in between. The standards may differ depending on the requirement based on geographical dispersion
How are switches in an Ethernet LAN organized? What is the difference between a core switch and a workgroup switch? Can a loop help a network designer?
Organization of witches in Ethernet LAN
To determine the arrangement of switches, it is important to know the required speed and the distance to be covered. Knowing the speed is important to determine how much traffic should the switch be capable of carrying and the knowledge of distance is necessary as this helps to determine the number of switches that will be needed and the interval at which they will be placed. The switches are arranged in a hierarchy with one parent switch above each switch and the arrangement is designed through topology and there is only a single path between two switches. The aim of designing the architecture of switches is to pick the shortest distance to minimize costs.
Core switch and workgroup switch
The Ethernet arrangement of switches consists of a core switch and workgroup switch. Both of these switches have their purpose and are different from each other in many ways. The workgroup switches are those which connect a computer to networks via access line whereas core switches are those that carry traffic via trunk lines. This combination of trunk lines and access lines makes the network’s core. Considering the difference in capacities, workgroup switches handle the traffic of only those stations which they serve, therefore, they have limited capacity whereas the core switches can carry the traffic of even a thousand stations and therefore they have more capacity. Stations are connected to the first switch by workgroup switches whereas the core switches connect pairs of switches, pairs of routers, or a switch and a router. If we compare core switches and workgroup switches for their port speeds, then, core switches have much faster port speeds as they handle greater traffic. For workgroup switches, the dominant port speed is 100 Mbps whereas that of core switches is 1 Gbps, in fact, some of the core switches are already using port speeds of 10 Gbps.
while designing a network, care should be taken to not create accidental loops that cause frames to circulate endlessly. Having a single loop path is beneficial as it allows simple operation because, for every switch along the path, the destination address in a frame will appear only once in the switching table. A hierarchal topology is important to avoid loops.
One of the network topologies is called loop (Ring topology). In such topology, a loop can be of great help when designing networks as they use double rings. The transmission lines connect many access units and there are stations attached to thee units. If a break occurs between access units, the two rings are wrapped to become a single long loop, this slows the speed but allows transmission around the points without any disruption in the flow. This makes the network very reliable because otherwise in the case of a single path between two stations, Ethernet is vulnerable to single points of failure meaning that the network is broken into paths when the network connection fails.
A network designer should then keep both these things in mind, first is not to let the creation of accidental loops occur as they can make a simple operation very complex and the other thing is to focus on the topology. Forming a ring topology helps in having a reliable established network which may help in the smooth flow of data and not bring up any hindrances
Can Bluetooth be used to replace a WLAN? Describe how a wireless network can be used as a secured mesh network.
LLAN uses radio or infrared lights for the physical layer of transmission. These wireless LANs supplement the wired LANs and are not meant to replace them as their access points are linked to the wired LANs to access the resources.
Blue tooth is a wireless technology that is designed for Personal Area Networks. This technology covers a distance of only 10 m and has a speed of only 3 Mbps and is used as a means of connecting to and exchanging information between PDAs, laptops, printers, and other such devices. Bluetooth technology can’t replace WLAN because both have vital differences, even though they are based on the same standard. Bluetooth doesn’t work the same way as WLANs, it is dependant on configured units whereas WLANs are as same as wired networks with the difference that they are modulated on carrier waves. The speed of Bluetooth in-between frequencies is very fast and this prohibits the transfer of long data blocks, this is a major disadvantage that is not present in WLANs as they can easily carry these huge data blocks. Another major difference is that Bluetooth transfers over a short distance range whereas the distance range of WLAN is much larger (“Consulting”, 2001).
Mesh networks are those in which wireless devices route frames among themselves without using the wired LAN. A mesh network can also be created using individual clients and servers. Wireless mesh networks (WMNs) consist of routers and clients. WMNs can be integrated with other networks such as the Internet functions of the router like gateway and bridging. The mesh clients may form a network among themselves and can be either stationary or mobile; they may normally also form the network with mesh routers. WMNs are expected to resolve the limitations and improve the performance of ad hoc networks and different forms of wireless networks like wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WANs) (Wang, Wang, and Akyildiz, 2005).
WLAN transmits its signals through frequencies from the host/ sender to wireless routers (frames) for frame formation. From one router, the signal is transferred to another one, this is called frame forwarding. After going through a designated or required number of frames, the message finally reaches the other host (receiver).
While securing a WMN, it is not safe to rely only on the WHS (wi-Fi Hot Spots) for security as communications are multi-hop. If we centralize all security operations at the WHS, this would delay attack detection and treatment, thus, giving the adversary an undeniable advantage. Multi-hopping also makes routing a very important and necessary functionality of the WMN; and like all critical operations, may be attempted an attack by an adversary. Wireless Mesh Networks (WMNs) pose three critical security challenges: (i) to detect corruption of TAPs (Transit Access Points) (ii) to secure the routing mechanism, and (iii) to define a proper fairness metric to ensure a certain level of fairness. To secure the WMN, one may use secure routing protocols or identify a node attack by realizing that the original network topology is not in place, thus disabling the routing device or installing new ones. Thus, the keys to a secure WMN lie in typically mutual authentication of the different devices and data integrity and confidentiality (Salem and Hubaux, n.d.)
Explain either CSMA/CA or RTS/CTS. What is the difference between 802.11g and 802.11b?
One of the main issues in communication is the effective transmission of messages. If two 802.11 devices whether they are stations or access points, transmit their signals at the same time, they will merge, get jumbled, and become unreadable. For this reason, it is important to have some sort of standard for media access control. 802.11 has two standards for this media access control, namely, CSMA/CA + ACK and RTS/ CTS and because of these standards stations and access points do no transmit the signals simultaneously. The more common mechanism which is also compulsory is CSMA/CA + ACK. CSMA/CA+ ACK stands for carrier sense multiple access with collision avoidance plus acknowledgment. In this mechanism, the sender listens for traffic, when it doesn’t see any traffic it waits till the critical value of time and when there is still no traffic past that critical value, it sends without waiting. The receiver on the other hand immediately sends acknowledgment on receipt but if the acknowledgment is not received by the sender, it again resends the message using CSMA/CA.
RTS/ RTC is a control mechanism for communication between the access point and device and stands for Request to Send/Request to Clear. This mechanism is by the wireless protocol standard 802.11 to reduce frame collisions. The process initiates by the node that wishes to transfer data, sending an RTS message to the destination node asking it for permission to send messages. The access point may respond by sending CTS (Clear to Send) which means that the station that issued RTS may send the message. The CTS also restrains other stations in the meanwhile from sending data as it contains a time value that alerts other stations to hold off from accessing the medium while data is being transmitted. Because of the inclusion of this time value, collisions are prevented (Geier, 2002). RTS/CTS is only an option, not mandatory for communication except when 802.11 b stations operating at 11 Mbps and 802.11 g stations operating at 54 Mbps share 802.11 wireless access points.
802.11g and 802.11b there are different rated speeds for 802.11 transmission standards and lie between 11 Mbps and 54 Mbps there are three standards of 802.11 and these are 802.11 a, 802.11b, and 802.11g. 802.11b is the most widely accepted standard and has a rated speed of only 11 Mbps. The price of its equipment is also cheaper because of the increasing demand of 802.11g. this standard is used for internet connectivity only and not for large file transfers because of the comparatively slower speed (“standards”, 2007).
802.11g is a new standard that is starting to dominate and is now replacing the standard of 802.11b. the operating frequency range is the same i.e. 2.4 GHz but the product prices are relatively more because of the added benefits. This is different from the 802.11b standard as it can be used for both internet access and file sharing. The main advantage of 802.11g lies in its faster speed of file transfer which may go up to 108mbps as compared to only 11 Mbps of the former standard (“standards”, 2007). 802.11g is compatible with 802.11 b as they use the same frequency range. This means that the 802.11g access point can serve both 802.11g and 802.11b clients and it is compatible with older equipment that has 802.11b, therefore it is an advantageous upgrade. The high speed of 802.11g has resulted in increased spending on WLAN equipment for many companies thus becoming the most widely installed 802.11 technology.
What is a PSTN? What is carried on a PSTN? How does the local loop relate to the transport core? What is signaling?
Telecommunication is the transmission of voice and video through different mediums and PSTN is a technology related to it. PSTN is the worldwide telecommunications network and stands for Public Switched Telephone Network. Every time a call is made to any part of the world; it is first sent directly to the PSTN. It establishes a dedicated circuit (also referred to as a channel) for the duration of transmission like a telephone call. It is now almost digital and covers mobile phones, besides fixed-line phones. All the telephones are not connected through the PSTN for example phone calls are typically for military use. Besides, there are many corporate networks linked to the PSTN only through limited gateways (LINFO, 2005). PSTN carries video as well as voice traffic and consists of four elements: customer premises equipment, transport, access, and signaling.
Customer premises equipment is that equipment that is owned by customers and encompasses three elements telephone handsets, wiring, and PBX (Public branch exchange). PBX is like an internal switch and workers as a router between different types of equipment and wiring is the most expensive component. An access line is needed by the customer to reach the central transport core and an access system represents a huge amount of investment. The element transmission represents the process of taking voice signals from one subscriber’s access line and delivering them to another customer’s access line. The transport core is based on trunk lines and switches, internally. Signaling is related to activities linked to controlling a call.
The PSTN is almost entirely digital but only internally because residential customers send and receive signals that are analogous and consequently rise and fall smoothly in their intensity over time.
The PSTN is not a single whole system but is a linked connection of smaller telephone networks owned by different carriers like local, long-distance domestic, or international.
Signaling refers to all the activities related to controlling a call like setting up a path for conversation through the transport core, monitoring and end of the path, and other supervisory functions. In a telephone network, the signaling method that is used to provide control and management functions is called Common Channel Signaling (CCS) which includes addressing, call information, and supervisory functions this also determines the status of the network and control the amount of traffic (“Tips”, n.d.)
Customers need an access line to reach the central transport core, these access lines are collectively called the local loop. The whole access system consists of both local loop and termination equipment which is present in end, office at the end of the transportation core. The local loop relates to the transport core as the transport core requires the local loop for the transmission of traffic. It is through the access lines that the voice is transferred across to different locations and it is the access lines that are a major constituent of access systems. The end office switch is a member of both the access line and the transportation core and is the transition point between them.
Akyildiz , I.F., Wang, X. and Wang, W. (2005). Wireless mesh networks: a survey, Web.
Consulting. Bluetooth – An Overview, (2004). Web.
Geier, J. (2002). Improving WLAN Performance with RTS/CTS, Web.
LINFO. PSTN Definition, (2005). Web.
Salem, N.B. and Hubaux, J.P. (n.d.). Securing Wireless Mesh Networks, Web.
Standards. 802.11a vs. 802.11b vs. 802.11g, Web.
Tips. What is Signaling System No.7 (SS7), Web.