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QUAD Based Secured Multipath Routing Protocol for Mobile Ad hoc Networks
Bellur, R. Ogier, and F. Nikanein, C. Bonnet, and N. Johnson, D. Hu, and J.
Perkins, E. Because Ethernet is scalable, with G Ethernet now many years old while higher data rates are on the standards horizon, the technology can be viewed as presenting a challenge to a traditional Synchronous Optical Network SONET telephony infrastructure. Rationale The advent and expansion of the use of Carrier Ethernet results from a series of inter-related issues. Similar to the VHS versus Beta videotape recorder battle a decade earlier, one technology survived while the other technology was relegated to history.
Although there are still some universities, research laboratories, government agen- cies, and commercial organizations that operate Token-Ring networks, their days are numbered. Due to the increase in Internet access and the use of graphics in e-mails the relatively low data rate of the Mbps Token-Ring network is not suf- ficient for most modern communications networks. Within a few years it is more than likely that the only Token-Ring networks in use will operate in museums. 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 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.
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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.
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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.
Ad Hoc Mobile Wireless Networks: Protocols and Systems
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 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.