Patent ID: 9736118
Date: 2017-08-15
CPC Classifications: H04L

Claim:
1. A method comprising: receiving, at a gateway device of a computer network, a session initiation protocol (SIP) request destined for a SIP device of the computer network; forwarding, by the gateway device, the SIP request to the SIP device; starting, by the gateway device, a first timer for the SIP request; after a first period of the first timer, designating, by the gateway device, the SIP request as a new half open session and moving, from a first queue, the SIP request as the new half open session into a half open session queue when a response to the SIP request is not received from the SIP device within the first period of the first timer; monitoring, by the gateway device after the first period, for responses to the half open sessions, including the response to the new half open session, in the half open session queue; comparing, by the gateway device, a number of half open sessions in the half open session queue, including the new half open session, for the SIP device to a threshold; removing, by the gateway device during a denial of service attack, an oldest half open session from the half open sessions when the number is greater than or greater than or equal to the threshold, and otherwise maintaining the half open sessions; re-designating, by the gateway device, the new half open session as a full SIP session when the response to the SIP request is received after the first period; and rejecting subsequent SIP requests during the denial of service attack; wherein existing SIP sessions are maintained during the denial of service attack.