US 6,487,689 B1 · Receiver initiated recovery algorithm (RIRA) for the layer 2 tunneling protocol (L2TP)

Abstract

A Layer 2 Tunneling Protocol (L2TP) receiver performs a receiver initiated recovery algorithm (RIRA) when the number of lost or out-of-order payload packets exceed a predetermined value. In particular, the receiver maintains a number of variables: the “next sequence number expected to be received” (Sr) value, and Snl, which stores the value of the currently received “next sent” (Ns) sequence number from the latest received packet. When the value of Snl>Sr+adjustment, the receiver portion resets the value of Sr to the value of Snl and passes all packets to the upper layer of the protocol stack. The value of the adjustment variable represents the number of packets that may be dropped or out-of-order at the receiver before the receiver initiates recovery. The receiver also sends (either via piggybacking or a zero-length message) an ACK packet to inform the sender of the new Sr value at the receiver.

Claims10

Dependent claims

A method for use in a layer 2 tunneling protocol (L2TP) receiver, the method comprising the steps of:

receiving packets from an L2TP sender;
causing the receiver to store an index value related to sent packets;
incrementing the stored index value for each received packet;
comparing a current stored index value with an L2TP expected-value parameter;
and
initiating a recovery process when the current stored index value exceeds the L2TP expected-value parameter by a predetermined threshold amount.

3 more elements

Dependencies are inferred from the claim text.

Receiver initiated recovery algorithm (RIRA) for the layer 2 tunneling protocol (L2TP)

Life of this patent

Receiver initiated recovery algorithm (RIRA) for the layer 2 tunneling protocol (L2TP)

Life of this patent

Abstract

Claims10