To access the Internet, a residential user should be connected to ISP which routes their traffic to the Internet. Several technologies are used for this purpose -- Frame Relay, ISDN, LL, ADSL WiMax, etc. I will describe the two most actually used technologies -- the Leased Line and ADSL services.
- Leased Line provides guaranteed traffic bandwidth. When LL is used to connect to the internet, a given traffic bandwidth is reserved to the user end to end. This mean if a user chooses LL 2MB, he can send/receive traffic at any time at 2MB bandwidth value. When the line is not used, the available bandwidth is still reserved and not used by other users, even if the physical line and equipment are shared. The logical line still reserved.
- ADSL connection is shared traffic bandwidth. ADSL is different when dealing with bandwidth reservation. The bandwidth value for a user is reserved between the user’s home and first access equipment (DSLAM), but on DSLAM uplink to Internet network, no reservation is performed – the goal is to deliver traffic with best effort. So a user with ADSL 2MB can receive traffic at 2MB as a maximum value, but not all the time; if the network is full, there is no guarantee that the user’s traffic will be delivered. Another key point of ADSL is that sending and receiving traffic bandwidth is not equal – this is the meaning of the ASYMETRIC name; the uplink traffic (traffic sent from user to the Internet) is lower than downlink traffic.
- Comparing ADSL to LL. How can users make the best choice to connect their systems to the internet? Each technology is more efficient for certain internet usages.
- For example suppose that you need install a web server at your home/company. Most traffic is considered as uplink traffic, and since the ADSL uplink bandwidth is very low, ADSL is not the recommended solution for this case. Another reason that LL would make the best solution is that up-time for LL is higher than ADSL; LL is supposed to never come down, whereas ADSL is not so stable of a service. So using ADSL for web servers can affect the users satisfaction and connectivity. The same choice is better any time you need to provide some real-time service without having to stop troubles, ex: remote connectivity between different company sites.
- Suppose now that one user needs to connect his home or company to the Internet just for browsing websites and other services. No quality of non-stop service is required for this case, so ADSL is a good choice. Using LL will result in higher cost because LL is always more expensive than ADSL. There is no need to pay more in this case because the user’s needs can be satisfied simply by using ADSL.