Method and apparatus for automatically detecting virtual circuit settings and encapsulation types in a DSL network
View Patent ↗Automatic detection of the virtual circuit setting and encapsulation type of a DSL line. A DSL modem determines the correct virtual path identifier (VPI) and virtual channel identifier (VCI) by sending OAM loopback requests to different VPI/VCI pairs until a valid loopback reply is received. PPPoA encapsulation is detected when a valid reply is received to a PPP LCP configuration request or echo request. PPPoE encapsulation is detected when a valid reply is received to a PPP LCP termination request or a PPPoE discovery offer (a PADO packet) is received in response to a PPPoE discovery initiation request (a PADI packet).
1. A method for determining whether a DSL line (digital subscriber line) is using PPPoA (point-to-point protocol over asynchronous transfer mode) encapsulation comprising:
sending a PPP/LCP (point-to-point protocol/link control protocol) configure-request packet;
if a reply to the sent configure-request packet is received, storing the encapsulation type as PPPoA;
sending a PPP/LCP echo-request packet; and
if a reply to the sent echo-request packet is received, storing the encapsulation type as PPPoA,
wherein the PPP/LCP configure-request and echo-request packets are sent simultaneously.
2. A method as claimed in claim 1 , wherein the reply to the configure-request packet is a PPP/LCP configure-ack packet, configure-nak packet or configure-reject packet.
3. A method as claimed in claim 1 , wherein the reply to the echo-request packet is a PPP/LCP echo-reply packet.
4. A method as claimed in claim 1 , wherein configure-request and echo-request packets are sent rapidly and alternately for a pre-determined time period or until a reply to either a configure-request packet or echo-request packet is received.
5. A method as claimed in claim 1 , wherein the method is carried out by software residing in a DSL modem.
6. A method as claimed in claim 1 , wherein if any reply to the sent configure-request packet is received, determining the encapsulation type as PPPoA.