The way that telecommunications affects business is that it supports business activity through more effective and efficient ways of physically moving data from point to point. There are several forms of data transfer, which are highly specified to the needs of the user. The business must first evaluate in detail, what their objective is, what the data workload is, and the frequency that data is transferred. Some companies may not need to transfer much data between sites; therefore they may not need to keep a direct connection. Others may be sending data only at peak hours, and need to be able to send it in a timely fashion. This is a very difficult situation, because the time when bandwidth is most closely filled is at peak hours. Therefore, this company will look to high bandwidths so that it does not get filled and slows the transfer speed. All of these scenarios are going to have different interests and needs from telecommunications.
The problem that businesses are facing is the need to move bulkier and more quantities of data more promptly. This brings us to a look at both bandwidth of and throughput of those technologies. James E. Goldman defines bandwidth as a range of frequencies for which data can be transferred (applied data communications, Goldman, pg. 629). Bandwidth is measured in Hz, which is an abbreviation for hertz. One hertz is a cycle per second. Each technology has a specific bandwidth of its physical medium, and therefore, will be either suggested or eliminated for the business need specifications. James E. Goldman, in Applied Data Communications, defines throughput as a PC to PC data rate, where the transmission rate is multiplied by the data compression ratio to give a rate. This is inferring is that bandwidth is the amount of hertz that the physical medium has; throughput is the amount of compression that can be produced to move more data within the specific bandwidth. The business need for faster data transfer hinges on finding technologies that will provide greater amounts of bandwidth, thus allowing for greater throughput rate. So, the question to be asked for this research is how can SMDS provide a beneficial solution to corporations that are looking for greater bandwidth and throughput for LAN to LAN interconnection, or how can a growing business implement SMDS to connect information systems at satellite locations?
The segments that will be covered are a comprehensive review of what is known about SMDS, a statement of what method was used for gathering information, coverage of the findings and analysis of those findings, and a conclusion of this subject. The next section will start with the review.
Applied Data Communications describes SMDS as a connectionless high-speed data service (applied data communications, Goldman, pg. 648). A connectionless technology is a technology that does not set up a direct connection between the sending and receiving points. A direct connection line is one, which physically runs from one point to another. This means that SMDS does not use a point to point format for send and receiving data. It is not ‘turned on’ at all times.
Created in 1991, SMDS is a connectionless end-to-end data transfer technology. Bellcore devised it for LAN to LAN interconnection. The technology uses a cell format that is 53 bytes long. This format is the basic format used in Asynchronous Transmission Mode. Each cell is then sent to a SMDS switch. The SMDS switch reads the address on each cell and sends them out over common telephone lines. This is what is meant by connectionless. Each cell can be sent over a different physical path but arrive in the correct order, in the same way they left. Since there is a destination, a source, and a specific cell address, the technology does not bother with setting up a direct connection between the two. Also within the address is the cell’s correct order. The switch reads this and makes sure that the cell is put in the correct order. This is a very basic overview of how the technology works.
The main concept SMDS was conceived for was the high-speed transfer of data from LAN to LAN. The nature of this technology is better suited for the data transfer of several LANs in a WAN. The data is usually sent in bursts from LAN to LAN, therefore a constant connection is wasted when there is no data to be transferred. By using SMDS, a WAN will not necessitate a direct connection between LANs, and can be more efficient in transferring data. I have talked about why SMDS is a good fit for connections between LANs. Now I would like to talk about the actual transfer of data in the SMDS service.
SMDS uses a protocol that is called SMDS Interface Protocol (SIP). This protocol is compliant with the IEEE 802.6 DQDB standards. There are three layers of protocol used in SIP. The highest layer is the SIP layer 3, which intermediates between user’s data and the next layer. The third layer uses SMDS packets. These packets consist of a 9188 byte data field. The size of this data field allows for ease of use by LANs to move data. The next layer is the SIP layer 2. This layer uses 53 byte cells, which are broken up from the SIP layer 3 packets to be sent on the telephone network. The final layer is the SIP layer 1, which is divided into two parts. One part is the Physical Layer Convergence Protocol. This portion is responsible for deciding the map of the physical layer (i.e. what route the cell should take to the destination). The second portion is the Physical Medium Dependent Protocol, which decides what medium will be used to transfer the cells created in layer 2. The next segment will go over the bandwidth and throughput of the technology.
When looking into SMDS and it capabilities for bandwidth and throughput, you will have to look at other technology. The reason for this, is the fact that SMDS is a connectionless data transfer technology. The actual technology of the service ends at the router. You then must look at the physical medium that is used between routers. SMDS has it’s own capabilities and is functional with several technologies. In the Findings portion, I will be defining use of several technologies, including the different categories of bandwidth that SMDS is compatible with.
After choosing the topic SMDS, I did 7-10 hours of research on search engines and books to first get a grasp of what SMDS was and what sort of research question I should formulate for this paper. I then found a very insightful point that James E. Goldman makes in his book, Applied Data Communications, is that telecommunications should be evaluated on four properties to recognize if it is a benefit to business (applied data communications, Goldman, 64). The first of these properties related to the question is asking does the technology allow for faster data transfer? The second property asks does the technology move data more efficiently? The third property asks if the technology makes data transfer more reliable? The fourth and final property question is does the technology make data transfer more secure? I will be using this evaluation method in the analysis of SMDS.
I used this form of evaluation to procure and glean my research. The methods used in acquiring information for the research were aided by using Internet sources, a primary source that has been and is currently using the technology, and various magazine articles about the subject. I did approximately 15 hours of search engine queries for perusing and gleaning data from the Internet. I used both Excite and Lycos search engines to find the information I am using. Several of the sources found on the Internet were highly technical in nature; therefore, I had to start at a basic knowledge of the technology. I looked through articles on reviews of this new technology. I chose to look in PC World and PC Magazine for a technical review of the technology, Business Week for any possible cases of a businesses implementing this technology. After contacting a primary source that uses SMDS, they directed me to a case study that was done over the use of the technology and how it was a benefit to them. The next section will be the findings and analysis of those findings.
SMDS has been found to have several advantages for specified areas of data transfer. The first of these advantages is packet network reliability. Packet network reliability is important because, when you look at Ethernet and its collision rate at higher data transfer periods. In an Ethernet environment, packets have a higher rate of collision, and the ability to be lost. When using SMDS as a source of data transfer, it is found that the reliability of packets making it from point to point without error or collision is much higher.
The strong suit for SMDS is security. This is because each destination is assigned one of several address numbers. When the packet is sent out, it is given a destination address. This packet is then sent out over a nonspecific physical path. Each packet will take a different path to get to the destination. This means that there is much less chance for someone to catch all the packets being sent. The reason that this makes SMDS more secure is that, the technology would keep a person guessing on which packet is sent where and what information is in that packet. Therefore, each packet may not be as secure, but the data being sent is more secure.
Another way that SMDS is a security enabling technology is by having specific addresses for a destination. These give users more security by allowing them and only them to know the destination addresses. This way nothing can be sent or received without a destination address.
The performance that SMDS gives is LAN-like. This means that there are several nodes on the service, which can send and receive data. SMDS can be used on DS0, T1, T3, and SONET to give the speed and performance that is asked of it. SMDS had data transfer rates that are from 1.544 mbps to 44.736 mbps, when using a T1 or T3 connection, respectively (alpeda.com, pg. 1). The next step for SMDS is to use Synchronous Optical Network, (SONET), as a form of data transfer. This will allow a data transfer rate of 155 mbps (alpeda.com, pg. 1). This kind of data transfer rate allows SMDS to be a viable type of data transfer service. It allows the technology to have bandwidth on demand.
The final advantage to SMDS is that it has logical fully meshed connectivity. Logical fully meshed connectivity means that with this service a node can be lost and performance of data transfer between other points is not hindered by it (qes-inc.com, glossary of terms, pg. 2).
As with anything, if there is advantages to a technology, there is also disadvantages that accompany that technology. There are certain disadvantages that are related to connectionless technologies, and disadvantages related to SMDS only.
The disadvantages found with connectionless technologies is there is no error correction, flow control, or ability to assure each packet arrives. Connectionless data transfer uses a variety of physical paths to transfer data from point to point. Therefore, when a packet is sent, it may be sent out of sequence, may not be properly sent, or connection on that path stops transfer completely. A packet could take a pathway that has a bad connection or damage to it, leaving it unable to arrive in correct order or possible not at all. This leaves these duties up to the end user to take care of. By having the end user left with these responsibilities, data can be corrupted much easier (applied data communications, Goldman, pg. 305).
SMDS is a connectionless technology; therefore it will incur the same downfalls. Some other SMDS specific disadvantages are that the expense of using SMDS is much higher than using other forms of data transfer. The service is usually billed by the hour or by the byte (oreilly.com, pg. 2). SMDS has an overhead of 5 bytes. This is lower than many connected-oriented technologies, but is still a hindrance to SMDS ability to transfer more data efficiently. There are several concerns with SMDS, such as unknown latency, suitability for digitized and video services, difficulty of trouble-shooting, and fair allocation of bandwidth (oreilly.com, pg. 2). There is also a lot of rebuttal that says that ATM is a better technology to use for the majority of WAN data transfer. This is the subject of the next section.
SMDS is said to be the precursor to the data transfer technology ATM. Both technologies use cell relay as a sub-layer. An advantage that SMDS has over ATM is that it is specified commercial implementation; whereas, ATM is just for data switching or a formatting scheme. SMDS is also interoperable with SONET, which allows it to project speeds up to 155 mbps. Overall, SMDS has more features defined for it than ATM does (oreilly.com, pg. 1). As for right now, ATM has become the choice for faster speed data transfer, and frame-relay is being used for slower transfers. In a SMDS advertising article, Pacific Bell used the idea that SMDS is a good starter kit for setting a business up for transfer to ATM (pacbell.com, pg. 2). Another article by CERFNet, sited that the similarities between ATM and SMDS will allow users to migrate from SMDS to ATM more easily (cerf.net, pg. 3). The only contention to this is that SMDS will be able to use SONET.
SONET is a fiber-optic transport system that allows for data to be transferred for long distances, and is a popular medium for connectivity for Metropolitan Area Networks. SONET transfers data in increments that are based on multiples of 51.84 Mbps (cerf.net, pg 4). The top end of data transfer is set at 155 Mbps. This allows users to send mulitgigabits over single-mode fiber-optic and still receive high operational, administrational, and management capabilities (cerf.net, pg 4). It’s the incorporation of these two technologies will allow users to get very high performance for setting up connectivity between LANs. An article about the incorporation of SMDS and SONET talked about how compatible these two technologies are. It specified that SONET is rated at 155 Mbps, and that SMDS can operate at that rate and will be able to continue to be compatible as that rate increased (cerf.net, pg 4). The point that they tried to emphasize was that the only thing that was going to change to stay compatible, was small hardware purchases.
SMDS is a service, but to run the service, users will have to purchase certain equipment. The main components that were suggested to have were:
SMDS is a relatively new technology and is implemented by only a handful of businesses. One particular business that is using SMDS for internet access is CERFNet, a subsidiary of General Atomics. A case study was done over the company and their use of SMDS. The focus of the article was to emphasize that SMDS gives full access to Internet and mail services, support of large usage and broadband requirements, multiple host connectivity, security, high-speed access, privacy, and functionality. CERFNet’s customer base includes universities, schools, libraries, and portions of the commercial sector. Before implementing SMDS, CERFNet had been bogged down by countless physical connections. By using SMDS, a business can have one easy-to-manage interface. This allowed CERFNet to provide a value-added performance, and in turn provide it at a low cost. As the article stated, companies providing services like this are more interested in low-cost than maintaining large backbones (cerf.net, pg. 1). The direction that CERFNet took was to provide secure LAN-like performance that could use the already implemented telephone lines. This would also relieve the responsibility of having to maintain those lines for CERFNet. CERFNet explained in the article that because SMDS is technology independent, it is a good way to provide service to customers that use frame relay, FDDI, ATM, and dedicated private lines (cerfnet.com, pg. 2). The company also felt that because SMDS is a broadband technology that can be compatible with whatever new speed rate is invented, that it would be a technology to stick with.
After reading over all the information, SMDS gives the impression that it is a technology that is important and viable to businesses. The problem with this is which businesses and what needs are being met by this technology?
The first property that should be analyzed is the speed that SMDS provides as a technology. There are several levels that SMDS works on, when concerned with speed. SMDS can be compatible with DS0 that is below 1.544 Mbps, up to being compatible with SONET that can run at speed of 155 Mbps. Therefore if a business is looking for a technology that is broadband and can perform at very high rates of data transfer, SMDS can provide those needs.
The second property that needs to be analyzed in deciding the viability of SMDS for a business is the efficiency of the technology. If a business is looking for technical efficiency, SMDS performs that task. As stated above, SMDS provides service with less physical ware than any connected-oriented technology. This means that a business will spend less time maintaining physical connections, and setting up new ones. If a business is looking to the efficiency of data transfer, this technology will fit the needs. SMDS is a technology designed for broadband data transfer. Therefore, SMDS will be able to provide the efficiency of transferring data at rates up to 155 Mbps.
The third property of analysis to be used to determine the use of SMDS as a viable business tool is reliability. SMDS is defined as a connectionless technology, and therefore is by nature an unreliable data transferring technology. The reason that connectionless technologies are unreliable is due to the fact that packets can be lost or hindered by damaged or broken connection. Connectionless technologies use several pathways, and cannot ensure that all pathways used are of the best condition, as a connection-oriented technology would have one line that was maintained. Therefore reliability can be a possible setback, but is as probable as a connection-oriented technology.
The final property that SMDS should be analyzed on is the characteristic of security. As aforementioned in the technological review, SMDS is a technology known for it’s great ability to secure data that is being transferred. The service is specifically set up with direct addresses and several pathways used to secure packets being transferred. With all of these functions set up in this technology, a business looking for a broadband service that is highly secure, then SMDS is the selection they should choose.
After having done the research on Swithched multimegabit data service, it has become paramount that this service is a service that should be looked into as a feasible technology in the business world in the future. As more businesses look to expand and become multi-site, there will be a need to keep from physically stringing wires from point to point, but to find a way to better utilize what is in place already. SMDS can be used to be beneficial to that problem. It is a broadband technology that will be useful in the future as businesses will be less and less willing to make and maintain the burden of a hefty backbone. This will shift the responsibility to the SMDS provider, and will allow the business to incur much less expense. So, if a business is looking for a technology to push high amounts of data from point to point, and does not want to handle the inconvenience of making and maintaining a backbone; it should look to SMDS for a connectionless broadband solution to take care of its needs.
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