ISDN vs. Frame Relay for Small LAN Internet Access May 1, 1997 Introduction: Say you are the owner of "The Kirkland Microbrewery", and you wish to establish a presence on the Internet. Being a former Microsoft employee, you are quite computer literate, and plan to set things up in house, using your own LAN. You see no need to pay an Internet presence provider a lot of money for services and bandwidth which you don't really need. You plan to have a web site on which to advertise your brews and special events; the site will gets hits, but the traffic will be relatively low. Also, you plan to run a few mailing lists, to announce events and discuss your brewing processes with interested customers. You feel that it is important for all of your brewers to also have email, news, and web access as well; it's important for them to be able to communicate with your customers. Looking at your requirements for incoming and outgoing bandwidth, you estimate that you will need a connection in the 56 to 128 kbps (kilobits per second) range. There are two technologies that you would consider for this connection: ISDN and Frame Relay. Background - The requirements: The scenario in the Introduction is typical of the situation which we are considering in this paper; there are many cases which fit into the sort of bandwidth needs we are discussing. One characteristic is that we wish to connect a small LAN, consisting of from 1 to a small number of nodes (certainly not more than 100), to a larger network. One very popular larger network to connect to is certainly the Internet, but it is worth noting that there are other choices, such as connecting a regional office to a corporate network. In this paper, we will refer to our link as being a link to the Internet, but for almost all considerations, it could just as easily be a link to such a corporate or campus network. We must also characterize the network traffic that we expect to go across our link. We can certainly expect email to go across our link; this traffic will likely be fairly balanced, both incoming and outgoing. We plan to run some sort of server on our network, serving data across the link; this would be something like an ftp or http server. Note that our needs here will be relatively light; if we expect more than a few concurrent users to be accessing our server, we will almost certainly need more bandwidth than our planned 56 to 128 kbps. We also expect the users of our LAN to have data access requirements; they will need web access, news access, etc. Again, we can't expect to have to many users accessing the link at the same time or our bandwidth requirements may grow. Note that there are some other technologies that might be better suited if we alter the requirements a bit. If we are looking for a scenario where we only need to give web/news access to our LAN users and don't care so much about running a server, we might consider the new 56 kbps modems that are coming available, which give us 56 kbps access (in theory anyway) for data coming into our LAN, but send data out over the link at a slower rate. Other technologies such as ADSL, which should be available "Real Soon Now", have similar properties, and higher bandwidths. Also, if our server requirements outweigh our desire to provide our users with Internet access, it makes more sense to run our server on the other end of the link, either having our provider host our server, or co-locate our server on their network. This is a good way to ensure very high bandwidth availability, and avoiding the link costs that we would normally need to get that bandwidth. The Contenders - ISDN and Frame Relay: >From Dan Kegel's ISDN Page (Reference 1): "ISDN cards and TA's are like modems, but 5 times faster. They require special telephone lines, which cost a little (or a lot, depending on your phone company) more than normal phone lines." ISDN, at least from our perspective, works a lot like a modem connection, except we order a special line from the phone company. In particular, we buy an ISDN "modem", ISDN card, or ISDN router, and run the Point to Point Protocol (PPP) or something similar, which many people also use to connect standard modems to the Internet. The ISDN line will cost a bit more from the phone company than a normal phone line, but it shouldn't require any new wiring to be put in. Then, we use this to establish a dedicated connection to our Internet provider. Note that dial-on-demand connections are also available, and are somewhat cheaper (if traffic levels are low), but these are not ideal for our scenario. When you get an ISDN line, you get 2 B-channels, each of which have a bandwidth of 64 kbps. For a 56 kbps connection, you use one B-channel for data (your network connection), and the other is free; with the right equipment, you can connect a phone and use that channel for normal voice communication, even while your data link is running. For a 128 kbps connection, you use both B-channels for data. Some ISDN connections and Internet providers will allow you to have a 56 kbps connection, and automatically connect the other channel on-demand, to give you a 128 kbps connection when needed. This is somewhat less common, but bears mentioning. This 2 B-channel configuration is referred to as a Basic Rate Interface (BRI). Note that another configuration is also available; the Primary Rate Interface (PRI), which consists of 23 B-channels. >From "Frame Relay: Networks for Today and Tomorrow" (Reference 2): "Frame relay is a packet based interface standard that has been optimized for the transport of protocol-oriented data." Frame Relay implements a packet switched network (as opposed to the circuit switched ISDN), which works over the traditional phone companies network. So, similarly to ISDN, we purchase a Frame Relay router, and a Frame Relay circuit from the phone company. Frame Relay circuits should not require any special wiring from the phone company, though they are more expensive than a normal phone line. Through the router, we then establish a dedicated connection to our Internet provider. Something to observe here is that this is not the same as a phone connection; there is no dialing, and there are no long distance charges, regardless of where your Internet provider is located. Issues for comparison: There are 5 main issues that we will use to compare the two technologies, ISDN and Frame Relay: 1) Cost: How much does our link cost? Note that there are two distinct costs that we must consider. There is the deployment cost (the equipment and setup cost), and the monthly costs associated with our network link. 2) Scalability: If we get a 56 kbps connection, how easily can we upgrade our connection to 128 kbps? How easy is it for us to go above our current high bandwidth of 128 kbps? 3) Reliability: Our connection does not do much good if it is down all the time, and even if it can be kept up, we don't want to spend all of our time maintaining it. 4) Performance: If we compare an ISDN connection and a Frame Relay connection rated at the same bandwidth, are the bandwidths really the same, or does one do better than the other? Other performance factors that might be important are latency, and how many network errors we see on our connection. 5) Future: This is a bit related to issue #2, Scalability. How well will our technology serve us in the future, as bandwidth requirements and expectations increase? How will our technology be supported in the future, both by the phone company and by Internet providers? A couple of notes on our comparison; I live in the Seattle area, so I am using local phone companies and Internet providers for price comparisons. I believe prices will be fairly similar in most major cities, but I really haven't looked. In particular, if you cannot find an Internet provider that provides a local ISDN call for you, Frame Relay is clearly the technology of choice for you. Also, while I am focusing on the technologies as they appear to us the end user, it is important to keep in mind how the technologies affect our Internet provider as well, as that will affect the price and performance of our Internet connection as well. Cost: This table compares ISDN and Frame Relay costs at 56 kbps. We compare two different Internet providers; Alternate Access (Reference 3) is a fairly established Seattle area access provider, whereas 2alpha (Reference 4) is a smaller, newer provider (and appears to be willing to cut their profit margins a bit closer). 2alpha's rates are quite a bit lower, but they charge for additional traffic beyond 750 megabytes per month. Also, there are two major phone companies in the area; US West, and GTE. ISDN Frame Relay Phone company charges GTE Setup charges $120 $317 GTE Monthly charges $95 $75 US West Setup charges $300 $500 US West Monthly charges $70 $87 Internet provider charges Alternate Access Setup charges $250 $250 Alternate Access Monthly charges $150 $150 2alpha Setup charges $125 $75 2alpha Monthly charges $125 $75 Here is the same table at 128 kbps. ISDN Frame Relay Phone company charges GTE Setup charges $120 $317 GTE Monthly charges $95 $235 US West Setup charges $300 $700 US West Monthly charges $70 $246 Internet provider charges Alternate Access Setup charges $500 $500 Alternate Access Monthly charges $300 $300 2alpha Setup charges $225 $130 2alpha Monthly charges $225 $130 Also, we must consider equipment costs (prices come from CDW as of April 27, 1997) (Reference 5). For routers, we will consider the Ascend product line; there are certainly other choices, but Ascend is one of the most popular (and easiest to find retail costs on) (Reference 6). The Ascend Pipeline 50 router, ISDN version, is listed at $578; the Frame Relay (56 kbps only) version lists at $1099. To get Frame Relay at rates above 56 kbps, we must look at the Ascend Pipeline 130, which supports rates from 56 kbps to T1 (1500 kbps) rates, and lists for $1279. For ISDN only, we can get even cheaper rates by getting an ISDN "modem" or card; the US Robotics Courier I-Modem (internal version) is available for $289. Looking at these numbers, the first thing that springs out is that Frame Relay is much more expensive at 128 kbps, due to the phone company charges; with either phone company, the per month charges are about $150 more for 128 kbps Frame Relay than for ISDN. Another thing to notice is that, due to more expensive equipment, and more expensive setup charges from the phone company, setup costs for Frame Relay are much higher than for ISDN. The phone companies charge at least $200 more to set up Frame Relay than ISDN, and the equipment charges could be as much as $1000 more for Frame Relay. Lastly, at 56 kbps, if we use 2alpha as our Internet provider, and GTE as our phone company, our monthly charges are in fact $70 cheaper for Frame Relay. However, it will take us between 6 months and a year for Frame Relay to actually be cheaper, due to the greater start up costs. In general, ISDN has the advantage on price, but Frame Relay at 56 kbps has some advantages as well. Scalability: There are two issues with regards to scalability. First, when we talks about expanding a connection from 56 kbps to 128 kbps, ISDN has a great advantage. Every ISDN modem or router supports both 56 kbps and 128 kbps connections; it is just a matter of using one or two of your B-channels. Also, your ISDN line automatically supports both 56 kbps and 128 kbps as installed; you get 2 B-channels whether you want them or not. For Frame Relay, cheaper routers do not support 128 kbps, but only 56 kbps connections, so unless you plan ahead, you will have to buy a new router to go from a 56 kbps connection to a 128 kbps connection. Also, Frame Relay circuits from the phone company come in 2 varieties; one is usable at 56 kbps only, the other at 128 kbps and up (up to T-1 rates, around 1500 kbps). So, to upgrade your phone circuit, you need to order a whole new service from the phone company, with the stiff setup charges that that entails. However, if we consider the fact that we may need to expand our connection beyond 128 kbps, Frame Relay has the advantage. Your 128 kbps connection with work just as well at rates up to T-1 speeds (around 1500 kbps), with only a slight increase in connection charges for each additional 128 kbps that you wish to add. Also, Frame Relay routers which work at rates of 128 kbps also work up to T-1 speeds. For ISDN, to get more than 128 kbps, you will need to get a PRI connection instead, which means getting a new connection from the phone company, at greatly increased rates. Also, to use more than 128 kbps, you will need to get a much more expensive router to handle your ISDN needs. Reliability: Frame Relay has the reputation of being more reliable. When asked why Wolfe Internet Access was willing to discount their listed Frame Relay charges, but not their ISDN charges, Robert Hyry (Reference 7) says: "ISDN is more expensive for us to provide and it is also less hassle- free so we have not offered discounts on ISDN." (Note: Wolfe Internet Access initially quoted me a price of $200 per month on both services; they do not quote prices on their web page) (Reference 8). However, I believe that much of this reputation may be due to the existence of ISDN modems and PC cards. These present a more unstable environment than a router since there are hardware integration issues dealing with the much-feared PC serial port. If, on the other hand, you have a quality ISDN router, I would expect the stability and reliability of your link to comparable to that you would achieve with a Frame Relay router. Performance: >From DigiLink Network Services: ISDN vs. Frame Relay Cost Comparison (Reference 9): "Important Note: ISDN service provides up to 4:1 link compression at no extra cost, which can provide up to 512Kbps throughput. Compression over Frame Relay service is not available." This compression is due to ISDN being a point to point link, as opposed to the packet switching technique of Frame Relay. However, as anyone who has used a modem which supports compression (any of your standard v.34 modems) realizes, the effective compression is generally far less than the optimum compression. Considering that most high volume Internet traffic involves sending already-compressed data over the link, such as images and file transfers, which will not compress any further, you would do well to even get 25% out of your compression. We will consider ISDN to have a slight advantage over Frame Relay in this area, but do not be fooled by gaudy 4:1 maximum compression numbers. Future: While I raised the issue of the future for evaluating the two technologies, I don't believe there is a significant advantage for either. Both ISDN and Frame Relay are extensively deployed right now; many of the Internet providers in the Seattle area offer one or both. Because of this, I believe that both the phone companies and providers will continue to support both technologies for some time. There are certainly some technologies that will threaten to offer cheaper high speed access in the next few years, such as ADSL and cable modems. However, given that are already a number of users of both ISDN and Frame Relay, support isn't going to go away until new technologies are not only available, but are extensively deployed. As for which technology is going to be more successful in the future, I don't think that weighs on our decision at all. If either ISDN or Frame Relay evolves to offer cheaper, faster access, it will almost certainly require us to purchase new equipment in any case, so our choice of ISDN or Frame Relay now isn't likely to have any effect when that day comes. We could just as easily purchase new equipment of a different technology as upgrade the equipment of our current technology. Conclusions: As the owner of "The Kirkland Microbrewery", (and having read this paper), you carefully consider your options. Frame Relay might be a bit cheaper in the long run at 56 kbps, but ISDN is cheaper to set up, and much cheaper at 128 kbps; ISDN has the advantage here. In terms of scalability, ISDN goes easily from 56 kbps to 128 kbps, while Frame Relay does not, so unless we expect our bandwidth needs to go beyond 128 kbps, ISDN works better for us. In terms of performance and reliability, ISDN and Frame Relay are fairly similar, and the future prospects for either technology look fairly even. For you, the clear choice is ISDN; there is just no reason to spend the extra money on Frame Relay. We will leave just one small caveat; Frame Relay does scale above 128 kbps much better, so if you believe that your bandwidth needs might grow quickly, that may be a better choice. References: 1) Dan Kegel. (1996). Dan Kegel's ISDN Page [Online]. Available at: http://www.alumni.caltech.edu/~dank/isdn/isdn_ai.html [April 1997]. 2) Frame Relay Forum. (1994). Frame Relay: Networks for Today and Tomorrow [Online]. Available at: http://www.frforum.com/4000/4001.html [April 1997]. 3) Alternate Access Inc. (1997). Welcome to Alternate Access Inc. [Online]. Available at: http://www.aa.net [April 1997]. 4) 2alpha (1997). 2alpha - An Innovative Internet Service Provider [Online]. Available at: http://www.2alpha.com [April 1997]. 5) Computer Discount Warehouse (1997). CDW - Computer Discount Warehouse [Online]. Available at: http://www.cdw.com [April 1997]. 6) Ascend Communications (1997). Ascend Communications Home Page [Online]. Available at: http://www.ascend.com [April 1997]. 7) Robert Hyry (Robert_Hyry@wolfe.net). (April 25, 1997). Re: Dedicated ISDN. Email to the author. 8) Wolfe Internet Access (1997). Welcome to Wolfe Internet [Online]. Available at: http://www.wolfe.net [April 1997]. 9) DigiLink Network Services (1997). ISDN vs. Frame Relay Cost Savings [Online]. Available at: http://www.digilink.net/frisdn-savings.html [April 1997].