Scheme for Estimating ADSL Link Capacity Based on Delay Measurements of Different Length Packets

Streaming services such as voice and video based on IP technologies have been deployed widely throughout the world. The Asymmetric Digital Subscriber Line (ADSL) is one of broadband access technologies used to offer these services. Network operators and/or integrators must estimate ADSL link rates from the Network Operation Centers (NOC) which are far away from the customer's site. They must also use a simple measuring scheme so that existing network node facilities are not unduly burdened. Unfortunately, there is no practical scheme that can satisfy these requirements. This letter proposes a practical scheme that can estimate ADSL link rates. The proposed scheme allows us to estimate ADSL link rates from measurements made at the NOC using existing communications protocols and network node facilities; it imposes no heavy traffic overhead. The proposed scheme consists of two major steps. The first step is to collect measured data of round trip times (RTT) for both long and short packets to find their minimum values of RTTs, i.e. those do not include queuing delays. The RTT measurements are simply conducted by sending Internet Control Message Protocol (ICMP) echo request messages. The second step is to estimate the ADSL down- and up-link rates by using the difference in RTT between long and short packets and the experimentally-obtained correlated relationships between ADSL down- and up-link rates. RTTs are experimentally measured for an IP network, and it is shown that the down- and up-link rates can be obtained in a simple manner.