Method for measuring network delay using gap time
View Patent ↗Methods, apparatuses and systems directed to measuring delay attributable to a network. The network delay is computed, in one implementation by determining a round-trip time for a network connection based on the arrival times of selected packets transmitted by first and second endpoints to establish the network connection, measuring the time gaps between consecutively increasing data packets in an ordered packet stream associated with a transaction, comparing the measured time gaps to the round-trip time, and computing a network delay for the transaction by adding the round-trip time to the measured time gaps that exceed the round trip time.
1. In a network, a method for computing the delay attributable to a network, the method comprising
determining a round-trip time for a network connection based on the arrival times of selected packets transmitted between first and second endpoints;
measuring the time gaps between consecutively increasing data packets in an ordered packet stream associated with a transaction over the network connection between the first and second endpoints;
comparing the measured time gaps to the round-trip time; and
computing a network delay for the transaction by adding the round-trip time to the measured time gaps that exceed the round trip time.
2. The method of claim 1 wherein the round-trip time for the network connection is based on the arrival times of handshake packets transmitted by first and second endpoints to establish the network connection.
3. The method of claim 2 wherein the determining step comprises
receiving, at a network device, a first handshake packet transmitted from a first host to a second host;
recording the arrival time of the first handshake packet;
receiving, at the network device, a second handshake packet, responsive to the first handshake packet, transmitted from the second host to the first host;
recording the arrival time of the second handshake packet;
receiving, at the network device, a third handshake packet, responsive to the second handshake packet, transmitted from the first host to the second host;
recording the arrival time of the third handshake packet;
computing the round trip time based on the difference between the arrival time of the first handshake packet and the third handshake packet.
4. The method of claim 2 wherein the determining step comprises
receiving, at a network device, a first handshake packet transmitted from a first host to a second host;
recording the arrival time of the first handshake packet;
receiving, at the network device, a second handshake packet, responsive to the first handshake packet, transmitted from the second host to the first host;
recording the arrival time of the second handshake packet;
receiving, at the network device, a third handshake packet, responsive to the second handshake packet, transmitted from the first host to the second host;
recording the arrival time of the third handshake packet;
computing a first component round trip time based on the difference between arrival time of the first handshake packet and the second handshake packet;
computing a second component round trip time based on the different between the arrival time of the second handshake packet and the third handshake packet; and
adding the first and second component round trip times to yield the round-trip time for the network connection.
5. The method of claim 1 wherein the determining step comprises
receiving, at a network device, a TCP SYN packet transmitted from a first host to a second host;
recording the arrival time (T 2 ) of the TCP SYN packet;
receiving, at the network device, a TCP SYN/ACK packet transmitted from the second host to the first host;
recording the arrival time (T 4 ) of the TCP SYN/ACK packet;
receiving, at the network device, a TCP ACK packet transmitted from the first host to the second host;
recording the arrival time (T 6 ) of the TCP ACK packet;
computing a first component round trip time based on the difference between the arrival time (T 4 ) of the TCP SYN/ACK packet and the arrival time (T 2 ) of the TCP SYN packet;
computing a second component round trip time based on the different between the arrival time (T 4 ) of the TCP SYN/ACK packet and the arrival time (T 6 ) of the TCP ACK packet;
adding the first and second component round trip times to yield the round-trip time for the network connection.
6. The method of claim 1 wherein the time gaps are measured only with respect to consecutively increasing data packets flowing in one direction.
7. The method of claim 1 wherein the time gaps are measured with respect to consecutively increasing data packets in both directions.
8. The method of claim 1 wherein the measuring step comprises
recording packet arrival times for data packets corresponding to the transaction, wherein duplicate packets corresponding to the transaction are ignored; and
comparing the packet arrival times between the consecutively increasing data packets.
9. The method of claim 1 further comprising
computing a server delay for the transaction;
computing a total delay for the transaction.
10. The method of claim 9 further comprising computing a normal transmission time for the network connection based on the total delay minus the server delay and the network delay.
11. The method of claim 1 further comprising storing the network delay in a database.