PDF | Mobile wireless ad hoc networks (MANETs) are a rapidly evolving telecommunications technology. Most of the presented material focuses on different layer protocols for ad hoc networks. . ment systems for ad hoc wireless networks. Ad hoc mobile wireless networks: Principles protocols, and applications | 𝗥𝗲𝗾𝘂𝗲𝘀𝘁 𝗣𝗗𝗙 on ResearchGate | On Jan 1, , S.K. Sakar and others published. Algorithms and Protocols for Wireless and Mobile Ad Hoc Networks (Wiley Series on Parallel and Distributed Computing) · Read more.
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Ad Hoc Mobile Wireless Networks: Principles, Protocols and Applications Wireless Mesh Networking: Networked Systems Architectures, Protocols Lu Yan, . Abstract: Mobile ad hoc networks(MANET) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self. The chapter presents the architectures and protocols of IEEE and A Mobile Ad hoc NETwork (MANET) is a system of wireless mobile nodes that dynamically and L. Blazevic, tingmisscomptarmi.ml~ivan/routing-survey. pdf.
Das, C. Perkins and E. Royer, Performance comparison of two on-demand routing protocols for ad hoc networks, in: Proc. Google Scholar  Z. Hass and M. Google Scholar  M. Jiang, J. Li and Y. Google Scholar  P. Johansson, T. Larsson, N.
Hedman, B. Mielczarek and M. Degermark, Scenario-based performance analysis of routing protocols for mobile ad-hoc networks, in: Proc.
Google Scholar  D. Maltz, Dynamic source routing in ad hoc wireless networks, in: Mobile Computing Kluwer Academic, chapter 5, pp. Google Scholar  G. Lauer, Packet-radio routing, in: Routing in Communications Networks, ed. Steenstrup Prentice Hall, chapter 11, pp. Google Scholar  G. Malkin and M. Steenstrup, Distance-vector routing, in: Routing in Communications Networks, ed. Steenstrup Prentice Hall, chapter 3, pp. Google Scholar  J. Moy, Link-state routing, in: Routing in Communications Networks, ed.
Today over 90 percent of all LANs are based upon Ethernet technology. Frame Compatibility A logical evolution of the use of end-to-end Ethernet technology is to enable data to flow between locations connected via a Metropolitan Area Network MAN as Ethernet frames.
In doing so, this action would eliminate the necessity to convert Ethernet frames into ATM cells or another transport facility and then re-convert them back into their original format. Due to the growth in the transport of real- time data conveying voice and video, the elimination of frame-to-cell-to-frame or other conversions can have a beneficial effect on the reconstruction of voice or video at their destination location.
Simply put, the avoidance of conversion lowers delay time, which is a key metric in determining if a digitized voice stream can be trans- ported and converted back to an analog format without experiencing distortion. Low Cost Most organizations go through a budgetary process where they allocate various funds for different projects into the future.
One of the projects typically budgeted in an IT environment is for network upgrades. In the original LAN wars mentioned earlier in this chapter, Ethernet won over Token-Ring for a variety of reasons, with one of the primary benefits of Ethernet being its low cost; a second key benefit was its ability to scale upward. Concerning the latter, an organization operating a legacy Mbps Ethernet LAN could either upgrade the network to a Mbps Fast Ethernet network or selectively use switches to connect the existing network to a backbone network operating at a much higher data rate.
Similarly, a Fast Ethernet network operat- ing at Mbps could be upgraded to a Gigabit Ethernet network or the end user could selectively use Gigabit LAN switches with some Fast Ethernet ports that could be employed to connect the existing network to a faster high-speed Gigabit Ethernet backbone.
These network scenarios enable data to flow end-to-end as Ethernet frames. This significantly reduces the cost associated with training network personnel as well as the cost of diagnostic equipment. In addition, because the use of LAN switches enables portions of a network to be selectively upgraded, this allows the cost associated with a network upgrade to be spread over more than one budgetary period.
When we discuss the use of Carrier Ethernet to interconnect two or more locations within a metropolitan area, similar cost savings are obtainable due to the ease in connecting existing Ethernet LANs via a Carrier Ethernet service. Thus, the AU Providing the Need for Speed low cost associated with connecting LANs to a Carrier Ethernet service represents another reason for considering the use of this service.
High Network Access Speeds The ability to connect locations via Carrier Ethernet implies the transport of data at high speeds. Thus, the use of Carrier Ethernet enables locations within a met- ropolitan area to be connected to one another via access lines that operate at high data rates. When transporting delay-sensitive data such as real-time voice and video minimizing network ingress and egress times can be quite beneficial.
A second area that deserves mention is the use of Carrier Ethernet as a replace- ment for lower-speed T1 and T3 transmission systems. A T1 line was originally developed to transport 24 digitized voice conversations, and by the early s was primarily used as a 1. Similarly, the T3 transmission system was originally developed to trans- port 28 T1 lines, each transporting 24 digitized calls.
Today, a majority of local loop T3 lines are used to provide large organizations with Internet access at a data rate approaching 45 Mbps. Through the use of Carrier Ethernet it becomes possible to obtain an access line operating at a gigabit data rate. Mass Market for Technology A fifth driving factor behind the acceleration in the use of Carrier Ethernet is the mass market for Ethernet technology. Having won the LAN wars many years ago, Ethernet in a variety of flavors represents the dominant technology for moving data over local area networks.
This results in Ethernet providing an economy of scale for developing such products as LAN switches, router ports, and network adapters. Because Carrier Ethernet is based on Ethernet, the mechanism required to connect Ethernet LANs to a carrier Ethernet service does not represent a quantum leap in technology.
Instead, the connection can occur using off-the-shelf products, which enables a mass market of equipment to be usable.
This in turn drives down the cost of interconnecting Ethernet LANs via a Carrier Ethernet service, resulting in the use of the service becoming more appealing. Through the use of Carrier Ethernet it becomes relatively easy for one office to back up its data onto the data storage residing at another office. Thus, one of the AU In addition, organizations can use Carrier Ethernet to transmit backup data to off-site storage repositories, providing another option for business recovery that can be tailored to changing data patterns and either supplement or complement conventional backup strategies where tapes or disks are transported to an off-site storage facility.
Now that we have an appreciation for a few of the driving forces contributing to the growth in the use of Carrier Ethernet, we will turn our attention to some of the technology issues that enable the relatively high data rate of this new version of Ethernet to be used effectively. Enabling Technologies In this section we will examine a core series of relatively new technologies that enable organizations to effectively use Carrier Ethernet.
Copper and Fiber Infrastructure Over the past decade significant improvements in the data transmission rate obtain- able via copper wires occurred while many communications carriers strung fiber into buildings or to the curb where copper was used to deliver high-speed data for relatively short distances into the home.
Concerning the use of copper, although conventional modems are only capable of reaching a data rate of approximately 56 Kbps, such modems only use approximately 4 KHz of the bandwidth of copper- based wiring. In actuality, the available bandwidth of twisted-pair copper wiring is over 1 MHz. However, because the telephone network was originally developed to transport voice, low and high pass filters are used to form a passband of approxi- mately 4 KHz, limiting the ability of modems to transmit data at high speed.
In doing so, they used their current copper-based local loop, which runs from a telephone exchange to the customer presence, to become capable of transporting both voice and data. Through the use of Frequency Division Multiplexing FDM the ADSL modem created two frequency bands above the voice band, enabling both voice calls and data transmission to occur simultaneously over a common copper-wire connection.
Note that the lower 4 KHz is used for voice. In comparison, the larger bandwidth devoted to data transmission supports downstream central office to subscriber transmission while the lower amount of bandwidth devoted to data transmission is used to support upstream subscriber to central office communications. This partition of upper frequency into two differ- ent sized bands results in an asymmetric data rate and is designed to support typical Internet access where short amounts of upstream transmissions in the form of URLs are followed by lengthy downstream transmissions in the form of Web pages.
For both FTTC and FTTN the communications carrier installs fiber to a central location in a residential area and then uses existing copper wire to provide a high-speed connection via a version of ADSL into a residence. Because this eliminates digging and installing fiber directly into a residence, the communi- cations carrier can significantly reduce the cost of service.
However, new services such as IPTV require a data rate at or above 20 Mbps to support both standard and high-definition television, limiting the distance over which ADSL can be used to avoid routing fiber directly into a residence. Although different versions of ADSL are normally sufficient for residential and some business users, other business users who need to interconnect locations require AU Providing the Need for Speed a balance between upstream and downstream data rates.
This standard defines symmetrical data rates from to Kbps in increments of 64 Kbps for transmission over a single copper-wire pair. When two copper pairs are used, the data rate ranges from to Kbps in Kbps increments. VDSL can achieve data rates up to 52 Mbps in the downstream channel and up to 16 Mbps in the upstream channel, which is considerably faster than data rates obtain- able via the use of any version of ADSL.
However, this additional data rate is only applicable for relatively short distances of approximately feet or meters. Because many communications carriers are replacing copper-based main feeds routed from neighborhoods to central offices with fiber optic, this action allows them either to install an FTTC or FTTN infrastructure. Thus, VDSL represents a mechanism for businesses to access a nearby fiber-optic transmission facility at a relatively high speed without having to wait for a communications carrier to extend the fiber into their facility.
One version, which is supported by a part- nership between Alcatel, Texas Instruments, and other vendors, uses a carrier system AU DMT divides signals into separate chan- nels, each 4-KHz wide, and modulates data on each channel. VPNs are used to enable the creation of a private network across a shared public network infrastruc- ture such as the Internet or even a metropolitan area network formed by the use of communications carrier facilities to interconnect two or more locations within a city or general metropolitan area.
A site-to-site VPN allows secure connectivity to occur between fixed locations such as many branch offices and a regional office. From the internal network the remote user may be able to access various computational facilities depending upon the availability of access to different com- puters connected to the internal network.
For both types of VPNs secure tunnels are created between sites by encapsulating user traffic within other packets. Encap- sulation results in an additional header or headers, tags, or labels that correspond to the tunneling protocol being prefixed to the tunneled packets.
Although tun- neled data does not have to be encrypted to be transported via a VPN, in reality encryption is almost always used to hide the contents of the tunneled data from persons who could monitor network traffic as such traffic flows over a public packet network. In addition to encryption, it is also important to verify the originator of a data transmission session. Thus, most tunneled data transported via a VPN is both authenticated and encrypted.
Both hardware- and software-based VPNs are available. Some VPNs are provisioned by the service provider; others can be provisioned by the customer. Layer 2 VPNs that provide site-to-site connectivity can be provisioned between computers, switches, or rout- ers. In an Ethernet environment, this action results in dual conversions because Ethernet must be converted into IP packets to flow at the network layer and then reconverted to the destination MAC address for delivery as an Ethernet frame.
If the addresses were previously resolved, the router can immediately discover the correct IP address without broadcasting an ARP message and waiting for a response.
Otherwise the router will broadcast an ARP and wait for a response. Summary The use of a variety of well-proven site-to-site VPNs enables Carrier Ethernet to be used to interconnect geographically dispersed locations within a metropolitan area in a secure manner.
This means that the engineers and the accountants have two separate broadcast domains, with the exception of port 3 which allows both engineers and accountants to access a router that is in turn connected to the Internet. Also note that the engineers have one port in their VLAN that is connected to a server port 2 and the accountants have two ports in their VLAN port 0 and port 1 connected to a server.
In addition, because AU Broadcast Domain Reduction Through the use of VLANs the sizes of broadcast domains can be reduced, in effect reducing the overhead resulting from the transmission of ARP and other messages. At the same time, users can configure the VLAN to structure broadcast domains to their particular working environment.
Instead of having to move cables physically, the use of a VLAN enables the con- figuration of different VLANs to occur electronically to represent required subnets.
Thus, the use of a VLAN reduces the effort required to create subnets. Because AU Thus, the use of VLANs may be able both to simplify the effort of technicians as well as minimize the time required to make a change, resulting in a more efficient use of personnel. Reduce Hardware Requirements As indicated in our discussion of subnet creation, the use of a VLAN eliminates the need for configuring subnets through cabling.
Thus, we can say that the use of VLANs can reduce hardware requirements. However, one port was in turn connected to a router to provide access to the Internet and was assigned to each VLAN as a mechanism to enable both engineers and accountants to access the Internet.
Thus, we can note that the use of VLANs provides a mechanism for traffic control. Thus, VLANs could be formed at Layer 7 based upon application or at a lower layer based upon information contained in the Layer 2 through Layer 6 headers. MPLS represents a standards-based technology used to speed up network traffic by prefixing a label to each packet AU Providing the Need for Speed that provides routing information concerning the path a packet should traverse through a network.
Because MPLS results in the use of labels prefixed to packets that specify a specific path through a network, the time required to route each packet is minimized, enhancing the transit of packets through the network. As packets are routed through an MPLS network for the most part they can be forwarded at Layer 2 switching level instead of at Layer 3 routing level, making traffic move faster. In addition, MPLS enables users to manage different data streams based on priority and the service plan they subscribe to.
Because the best way to explain the operation of MPLS is by example, we will do that next. Architecture In an MPLS network, packets need to be labeled so they can flow via predefined paths through the network.
The prefix of labels provides an identifier that can include information based on the routing table entry to include destination, bandwidth delay, and other metrics such as data that reference the source IP address, Layer 4 port number, differentiated service value, and similar data.
Once this classification is completed and mapped, different packets are assigned to Label Switch Paths LSPs which provide the routing through the network as labels are then swapped as packets flow through routers in the network. Using a database, each LER matches the destination of the packet to an entry in the database to determine if a packet should be labeled. If so, an MPLS shim header is inserted into the packet. As such, the shim header is not a part of either layer, but is used as a mechanism to provide Layer 2 and Layer 3 information to the MPLS network.
The shim header consists of 32 bits that are divided into four fields. Twenty bits are used to define the label. The next 3 bits are reserved for experimental functions, followed by a 1-bit slack function and 8 bits for a Time To Live TTL value. Through the insertion of a shim header both Layer 2 and Layer 3 protocols are considered. The resulting shim header is then used by LSRs in the network to forward packets through the network. The actual label varies based upon the type of network.
In addition, the LER forwards the frame out of its serial 1 s1 port towards the first LSR it is directly connected to. At that location router R2 examines the label in the packet and forwards the packet on port s2 towards router R4.
At router R4 the label in the packet is again examined and the frame is routed onto port s1 towards router R5.
At router R5 another examina- tion of the label results in the packet being forwarded out port s1 to router R6, where the label informs that router to deliver the packet onto port eO where the destination station resides. To do so, the router will first check its cache memory to determine if a MAC address was previously learned for the IP address. If so, it will use that MAC address. Note that once a label is inserted into a packet at the edge of an MPLS network, routing is expedited through the network.
This is because routers in the network use the labels inserted into packets and label forwarding informa- tion maintained by LSRs simply to forward packets out onto an appropriate interface. To do so, an LSR uses the label as an index into its label information base. Each entry in the label information base consists of an incoming label and one or more subentries.
Those subentries include the outgoing label, out- bound interface, and outbound link-level data. When the router matches the inbound label to an entry in its label information, the inbound label is replaced or swapped with the outbound label, link-level data is used to replace other link-level data in the packet, such as the MAC address, and the packet is then forwarded via the outbound interface. Thus, MPLS forwarding is based upon label swapping.
Because a simple label-swapping process is employed, the time between a packet arriving at an MPLS router and being forwarded onto an outbound interface is minimized. In addition, because MPLS provides an easy method to mark pack- ets as belonging to a particular class after they are initially classified, this enables MPLS to be used to define a level of QoS through the network.
Such applications can include the transport of most any type of digital data, ranging in scope from digitized voice to videoconferencing. Interconnecting Distributed Offices Because Carrier Ethernet represents a metropolitan area transport facility, it is ide- ally suited for interconnecting offices located within a metropolitan area.
Because it is possible to use bridges or switches to connect Ethernet LANs residing in different locations, it becomes possible to interconnect offices directly at Layer 2.
In addi- tion, if offices require the ability to transport data that requires a QoS capability to be recognized, most Carrier Ethernet services provide this capability. Due to the high data rate provided by Carrier Ethernet it becomes possible to use this transport facility to back up data in real time or stagger backups to pre- defined periods during the day.
For either situation, the high data rate provided by Carrier Ethernet eliminates the need to transfer data physically via tape or disk to off-site storage and the transportation and personnel costs associated with the physical movement of data. This means that different data streams with different QoS requirements can then be supported, enabling voice, data, and AU Now that we have a general appreciation for the applications that can be supported via Carrier Ethernet, we conclude this introductory chapter by turning our attention to some of the chal- lenges facing this transport service.
Challenges to Carrier Ethernet Earlier in this chapter it was mentioned that the author would be remiss if he did not mention a series of challenges facing end users who wish to consider the use of Carrier Ethernet. In this concluding section of this introductory chapter, we will turn our attention to a series of technical and economic issues that serve to inhibit the use of Carrier Ethernet.
In addition, as we discuss each issue we will also dis- cuss, when relevant, how such issues could be migrated to enable an organization to make better use of a Carrier Ethernet service.
Total Cost of Operation It is important to recognize that Carrier Ethernet represents a packet transmission service. As such, users may have either to download or lease network access devices at the edge of the network as well as pay a fee for service. The fee can vary from a per-packet charge to a fixed monthly rate, depending upon the manner by which the communications carrier bills for the use of its service. Thus, end users must estimate carefully the total cost to use a Carrier Ethernet service.
Packet Overhead A second item that warrants consideration is the potential overhead associated with transporting packets through a Carrier Ethernet network. Then, if MPLS is used, a shim header will also be added to the packet. Note that the overhead is 26 bytes.
In the lower portion of the figure, the Ethernet frame is shown encapsulated within an IP packet consisting of a byte IPv4 header and either a byte TCP header or 8-byte UDP header, with a 4-byte shim header inserted between the Layer 2 and Layer 3 headers. When the Ethernet payload is relatively small, this results in a high overhead.
Conversely, as the Ethernet payload approaches or reaches its maximum length of bytes, the overhead decreases. One way to expedite response is through defining manage- ment changes and troubleshooting responsiveness within a Service Level Agree- ment SLA.
Reliability Because Carrier Ethernet represents a service the reliability of network operations is beyond the control of the end user. Although end users normally cannot control the reliability of Carrier Ethernet, they can and should check the mesh structure of the network for redundancy as well as ensuring that SLAs provide a penalty for an unacceptable level of reliability. In addition, the last-mile connection to the end user can be enhanced through the use of a SONET ring or the use of fiber to two different carrier offices.
Providing the Need for Speed Security As data flows through a Carrier Ethernet network, it has the potential for viewing through the use of diagnostic testing equipment.
In addition, it is possible that data can be mirrored to another site, inadvertently viewed by carrier personnel, and misrouted to another organization although a low probability. Due to the preceding as well as other security issues, it is important to recognize that Carrier Ethernet represents a public transport system that can be shared by many users.
If authentication or encryption is required, users should consider establishing a secure site-to-site VPN over the Carrier Ethernet network. QoS Another challenge that warrants discussion is for the service provider to maintain a desired QoS level. As the use of Carrier Ethernet expands, users having the require- ment to transport real-time data between sites can also be expected to increase.
At some point in time, this could result in the inability of the network to provide a desired QoS level.
Although an end user has no direct control over a Carrier Ethernet network, you do have an indirect control mechanism in the form of a Service Level Agree- ment, which defines different network parameters to include a desired QoS level and penalties if the carrier does not provide that level of service. If the author assumes each reader is well versed in the fundamentals of the subject, some readers new to the field may be literally left at the starting gate.
If the author assumes that readers are not well versed in the fundamentals of the subject and they are, a large number of readers may be bored by a review of what they consider to represent trivial material. To strike a balance this author decided to include a chapter covering networking concepts in this book.
This chapter can be skimmed by advanced readers or they can focus their attention upon sections that are of interest. However, for readers new to the field of communications technology this chapter will provide a foundation for better understanding the concepts presented in subsequent chapters.
Thus, this chapter represents a trade-off to provide readers who require a background in net- working concepts with such information. In this chapter we will discuss transport technologies that provide the mecha- nism for moving data through networks. In doing so we will also discuss popu- lar Layer 2 and Layer 3 data protocols, network interfaces, network equipment, and network facilities.
Thus, as the title implies, we will focus our attention upon acquiring a solid foundation concerning networking concepts. Transport Technologies There are three basic transport technologies associated with different versions of Ethernet: In actuality, as we discuss transport technologies we will note that the use of optical fiber Gigabit and 10 Gigabit Ethernet LANs permits such networks to 21 AU LANs A Local Area Network, as its name implies, represents a network that transports data over relatively short distances.
Prior to the turn of the century we could define a short distance in terms of hundreds of meters for a single LAN or several thou- sand meters when LANs were bridged to extend their transmission distance. Since the turn of the century Ethernet LANs in the form of Gigabit and 10 Gigabit Ethernet that primarily use fiber-optic cable provide transmission distances up to 70 km.
In actuality, a WAN can span the globe, and there are several global networks in operation that consist of leased lines and routers and multiplexers that allow data to be routed literally around the globe.
Although the transmission distance of WANs is capable of being significantly longer than that of LANs, the trade-off is typically in the data rate obtainable on each type of network.
Thus, unless a fiber cable can be run directly into a building the high- est data rate obtainable is limited to approximately 50 Mbps when VDSL Very- high-data-rate DSL is used on the copper access line. In comparison, when a fiber connection is available for the access line, it is possible to use a switch or router port to maintain the LAN operating rate on the WAN.
Cabling and Testing In a LAN environment the end user is responsible for installing required equipment to include cabling.
In addition, the end user also becomes responsible for any test- ing and troubleshooting that may become necessary. This means that while the communications carrier is responsible for testing and troubleshooting from the access line through the network, when a problem materializes the cause may not be obvious and finger-pointing between the communications carrier and end user can occur.
Wireless A third transport technology that warrants attention is wireless. Wireless LANs were first developed approximately a decade ago, but have only recently gained acceptance by government agencies and corporations due to their enhanced secu- rity and higher operational speed.
A peer-to- peer wireless LAN network results in each station having the ability to com- municate directly with every other station within its range. In comparison, a centralized wireless LAN results in all communications flowing through an access point. One port provides a connection to the wireless interface in the form of an antenna, and a second port provides a connection to a wired LAN infrastructure.
Because all com- munications flow through the access point, it can be thought of as a relay. Thus, in a AU Providing the Need for Speed wireless infrastructure network the transmission distance between two stations can be further apart than in a peer-to-peer network that does not use an access point.
Two or more BSSs are connected together through the use of an extended service set. Thus, we will briefly discuss the role of the ESS. Through the use of an ESS, roaming becomes possible. Thus, in allowing roaming as well as in extending access of wireless stations onto a wired infrastructure, the AP performs frame conversion.
Now that we have an appreciation for the basic networking transport technolo- gies, we will turn our attention to several data protocols.
Although we will go into considerable additional detail when we discuss the Ethernet frame in Chapter 4, the purpose of this section is simply to become acquainted with each protocol. Ethernet Ethernet represents a now near-ubiquitous LAN protocol that operates at the data link layer.
Although the frame composition of Ethernet is near-uniform from its operation at 10 Mbps through 10 Gigabit, its physical layer varies to define the use of a different type and number of copper wiring and signaling as well as the use of different types of fiber-optic cable and the signaling mechanisms used to transport data over fiber.
Thus, in actuality Ethernet can be considered to represent a family of similar frame-based networking technologies for local and metropolitan area networks. In addition to Ethernet the graphic user interface, the computer mouse, and the laptop can all trace their initial develop- mental concepts to work performed at PARC. Later, the source and destination address fields were expanded to 48 bits to enable global addressing. In the United States Patent Office granted Xerox, Metcalfe, and his team patent number for their Ethernet network technology.
Through his efforts the first formal Ethernet AU Providing the Need for Speed standard, referred to as the DIX standard in recognition of the three companies, was published in The DIX standard resulted in a Mbps operating rate on a coaxial bus and defined the use of bit destination and source addresses.
Access Method The access method developed for Ethernet can be traced to the Aloha packet net- work operating in the Hawaiian Islands during the s and s. If so, it can begin transmission; if not, the computer waits until it is idle plus an interframe gap period of 9. If circuitry detects the occurrence of a collision the computer will continue transmission until a minimum packet time, referred to as a jam signal, is reached.
Here the jam signal ensures that all receivers detect the collision. Next, the computer updates its transmission-attempt counter and compares it to the maximum number of transmission attempts allowed. If that number is reached, the computer aborts further transmission. If that number has not been reached, a random backoff period is computed and, when reached, the computer begins anew by checking the medium.
Of course, if no collision occurs the computer has a successful transmission and the frame reaches its destination. Perhaps recognizing a good standard as well as not wishing to literally reinvent the wheel, the IEEE used the DIX Ethernet standard as the basis for an evolving family of Ethernet standards defined by its This series of standards initially followed the following format: Also during the IEEE published its During the IEEE published its Also during the IEEE defined media access control layer bridging in its Although the frame format remained unchanged, the signal- ing used by each version of Fast Ethernet differed.
Shortly after the release of the This standard also supports single-mode fiber at a distance of up to 10 km. That standard was built upon over the past five years via annexes that lifted the oper- ating speed of wireless transmission from a maximum of 2 to 54 Mbps with the The 10 GbE standard defines five physical layer stan- dards for transmission over copper.
Due to the relatively young age of this standard, it is difficult to predict which of the nine physical layer standards will eventually have the most usage. The IEEE Those objectives included supporting a Gbps operating rate of at least m on multi-mode fiber and at least 10 km on single-mode fiber for full-duplex opera- tions while preserving the Ethernet frame format and frame size standards.
Thus, in the near future versions of Ethernet will operate from 10 Mbps to Gbps using the same frame format and frame size standards. Network Interfaces No discussion of Carrier Ethernet would be complete without a discussion of the two types of network interfaces: In a Carrier Ethernet environment where transmission is focused upon a met- ropolitan area there will more than likely be a single network operator.
Thus, the primary area of concern for most end users will be the UNI. In addition, even if a Carrier Ethernet service provides a gateway to a long-distance carrier the NNI issues will occur between each network operator, enabling the end user to focus attention upon becoming compatible from an access perspective with the Carrier Ethernet operator. Network Equipment The ability to transport data depends upon both the use of equipment and a trans- port media.
In this section we will focus our attention upon a range of communica- tions equipment that represents the foundation of modern networking. During the s most PC manufacturers began to include the NIC as a chipset built into the motherboard. This chipset performed the same functions as a stand-alone adapter-based NIC. That is, when receiving serial data bit by bit the chipset stores the frame in a buffer and examines its destination address. If the destination address matches the address of the chipset, further processing occurs; otherwise the frame is discarded.
If the two match, the frame is considered to have been received correctly; otherwise, an error of one or more bits is considered to have occurred and the originator of the frame is then informed of this situation. Assuming the frame was correctly received, the chipset will pass the data field as a series of parallel bytes to the computer.
Similarly, when data is to be transmitted onto the LAN the chipset receives parallel data from the computer, computes and adds a CRC to form a frame and when the media is free transmits the frame as a series of serial bits. Con- cerning GbE, Intel and other manufacturers now offer a variety of Gigabit Ethernet controller chips that are being incorporated onto computer, switches, and router motherboards. Thus, in a few years we can expect a majority of Ethernet NICs will actually be fabricated as chips installed on the motherboard of different com- munications devices.
Hubs The initial version of Ethernet used a coaxial cable bus-based structure that defined the minimum and maximum distances where stations could be attached to the media. Later another version of Ethernet that used a thin version of coaxial cable was standardized as 10BASE Because coaxial cable is both more expensive and less flexible than twisted pair, developers looked for a method whereby they could use twisted-pair wire. In doing so they needed a method that would make stations on the network aware of the fact that another station was using the hub as a mechanism to minimize colli- sions.
The result was the development of a hub-based version of Ethernet that was AU Operation A hub contains multiple ports that function similar to a bus. That is, when data from one station connected to the hub is transmitted to another station the data is repeated to all stations connected to the hub.
Thus, by repeating transmission input on one port onto all other ports the hub functions as a bus. In addition to introducing the use of less expensive and more flexible wiring, 10BASE-T enabled full-duplex transmission. Because two wire pairs were used, transmission could occur on one wire pair while the other allowed the simultane- ous reception of data.
Although this capability had limited use for workstations, throughput would increase when servers were connected to a hub. Passive versus Intelligent Hubs The previously described hub is commonly referred to as a passive hub as it simply repeats data entering one port onto all other ports. The next evolution of Ethernet resulted in the development of the intelligent hub, which included the ability of an administrator to monitor traffic flowing through the device as well as to configure each port in the hub.
Because an intelligent hub enabled an administrator to manage certain hub features, this type of hub was also referred to as a managed hub. Providing the Need for Speed Switches Both passive and intelligent hubs have a key limitation in that they only allow one data flow through the device at any point in time.
Manufacturers recognized that this limitation could be overcome by incorporating buffer memory and a micro- processor into a hub, resulting in a new type of communications device known as a switch or switching hub. A switch originally was a Layer 2 device, examining the destination address of each Ethernet frame.
This type of switch was capable of operating at Layer 2 or Layer 3. Today some switches are capable of operating through the application layer Layer 7. Operation The Layer 2 switching hub device operates based upon the three Fs, flood- ing, forwarding, and filtering, using a reverse learning process. That is, as a frame enters the switch, the device examines its MAC source address and the port number it entered the switch.
If this is the first occurrence of the source address, it is then entered into the switching table along with the port number that the frame entered the switch. The Handbook of Ad hoc Wireless Networks.
Security for Wireless Ad Hoc Networks. Mobile Ad Hoc Networking. Wireless Ad Hoc and Sensor Networks: Theory and Applications. Mobile Ad-Hoc and Sensor Networks, 3 conf. Wireless Ad Hoc Networking: Mobile and Wireless Networks Security.
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