Method of determining passive round trip time, RTT, delay in a telecommunications system

1. A method of determining a passive Round Trip Time (RTT) delay in a telecommunications system for exchanging data packets in accordance with a data transmission protocol between a first device and a second device operatively connected to the telecommunications system, wherein the first device is identified by a first device identification, wherein the second device is identified by a second device identification, wherein the data packets comprise an address part including a source address and a destination address, the method comprising:

receiving, by a node in the telecommunications system, a data packet originating from the first device and directed to the second device, the address part of the data packet comprising the first device identification as source address and the second device identification as destination address; and

when the data transmission protocol refers to a Quick User Datagram Protocol (UDP) Internet Connections (QUIC) protocol;

modifying, by the node, the first device identification of the source address of the received data packet;

modifying, by the node, the received data packet having an address part comprising the modified first device identification as source address and the second device identification as destination address to provide a modified data packet;

linking, by the node and in an address translation table, the address part of the received data packet with the address part of the modified data packet;

transmitting, by the node and at a first point in time, the modified data packet to the second device;

receiving, by the node and at a second point in time and from the second device, a further data packet, the further data packet having an address part comprising the modified first device identification as destination address and the second device identification as source address;

modifying, by the node, the received further data packet having an address part comprising the first device identification as destination address and the second device identification as source address, using the address translation table, to provide a modified further data packet;

transmitting, by the node, the modified further data packet to the first device; and

determining, by the node, the RTT delay from the first and second points in time.

2. The method of claim 1 :

wherein the first device is a User Equipment (UE) connecting to an access network of the telecommunications system;

wherein the second device is a server of the telecommunications system;

wherein the RTT is measured for Round Trip Time client (RTTc) delay in uplink communication direction.

3. The method of claim 1 :

wherein the first device is a server of the telecommunications system;

wherein the second device is a User Equipment (UE) connecting to an access network of the telecommunications system;

wherein the RTT is measured for Round Trip Time server (RTTs) delay in downlink communication direction.

4. The method of claim 1 :

wherein the data transmission protocol is an Internet Protocol OP) type data transmission protocol;

wherein the address part of a data packet comprises 5-tuple information including IP address and port number of the first device, IP address and port number of the second device, and a protocol identification identifying the data transmission protocol; and wherein the node, prior to modifying the address part of the received data packet, checks the protocol identification included in the address part.

5. The method of claim 1 , wherein the modifying the first device identification comprises modifying one or both of the source IP address and port number.

6. The method of claim 5 , wherein the modifying the source port number comprises one of:

incrementing the source port number by 1; decrementing the source port number by 1;

incrementing the source port number by an arbitrary integer value; and decrementing the source port number by an arbitrary integer value.

7. The method of claim 1 :

wherein the source IP address comprises a host part and a network part; wherein the modifying the source IP address comprises modifying the host part by one of: incrementing the source IP address by 1; decrementing the source IP address by 1;

incrementing the source IP address by an arbitrary integer value; and decrementing the source IP address by an arbitrary integer value.

8. The method of claim 1 , wherein the receiving the further data packet comprises inspecting, by the node, the address part of data packets received from the second device until receiving a first further data packet having an address part comprising the modified first device identification as destination address and the second device identification as source address.

9. The method of claim 1 , wherein the modifying the data packet received from the first device is applied, by the node, to all subsequent data packets for a same data stream received from the first device.

10. The method of claim 1 , wherein the modifying the further data packet received from the second device is applied, by the node, to all subsequent further data packets for a same data stream received from the second device.

11. The method of claim 1 , wherein the first point in time and the second point in time are stored as a first time stamp and a second time stamp, respectively, in the address translation table stored in the node.

12. The method of claim 1 , wherein the node is one of a Packet Data Network (PDN) Gateway (P-GW) and a Policy Control and Enforcement Point (PCEP) in an access network of the telecommunications system.

13. A node, configured to operate in a telecommunications system, for determining a passive Round Trip Time (RTT) delay for exchanging data packets in accordance with a data transmission protocol between a first device and a second device operatively connected to the telecommunications system, wherein the first device is identified by a first device identification, wherein the second device is identified by a second device identification, wherein the data packets comprise an address part including a source address and a destination address, the node comprising:

a transceiver for exchanging the data packets; a storage device for storing an address translation table; and

a computer controlled RTT measuring device, wherein the RTT measuring device is configured to control the transceiver device and the storage device so that the node is operative to:

receive a data packet originating from the first device and directed to the second device, the address part of the data packet comprising the first device identification as source address and the second device identification as destination address; and

when the data transmission protocol refers to a Quick User Datagram Protocol (UDP) Internet Connections (QUIC) protocol:

modify the first device identification of the source address of the received data packet;

modify the received data packet having an address part comprising the modified first device identification as source address and the second device identification as destination address to provide a modified data packet;

link, in the address translation table, the address part of the received data packet with the address part of the modified data packet;

transmit, at a first point in time, the modified data packet to the second device;

receive, at a second point in time and from the second device, a further data packet, the further data packet having an address part comprising the modified first device identification as destination address and the second device identification as source address;

modify the received further data packet having an address part comprising the first device identification as destination address and the second device identification as source address, using the address translation table, to provide a modified further data packet;

transmit the modified further data packet to the first device; and determine the RTT delay from the first and second points in time.

14. A non-transitory computer readable recording medium storing a computer program product for controlling a node in in a telecommunications system for determining a passive Round Trip Time (RTT) delay for exchanging data packets in accordance with a data transmission protocol between a first device and a second device operatively connected to the telecommunications system, wherein the first device is identified by a first device identification, wherein the second device is identified by a second device identification, wherein the data packets comprise an address part including a source address and a destination address, the computer program product comprising software instructions which, when run on processing circuitry of the node, causes the node to:

receive a data packet originating from the first device and directed to the second device, the address part of the data packet comprising the first device identification as source address and the second device identification as destination address; and

when the data transmission protocol refers to a Quick User Datagram Protocol (UDP) Internet Connections (QUIC) protocol:

modify the first device identification of the source address of the received data packet; modify the received data packet having an address part comprising the modified first device identification as source address and the second device identification as destination address to provide a modified data packet;

link, in the address translation table, the address part of the received data packet with the address part of the modified data packet; transmit, at a first point in time, the modified data packet to the second device; receive, at a second point in time and from the second device, a further data packet, the further data packet having an address part comprising the modified first device identification as destination address and the second device identification as source address;

modify the received further data packet having an address part comprising the first device identification as destination address and the second device identification as source address, using the address translation table, to provide a modified further data packet; transmit the modified further data packet to the first device; and determine the RTT delay from the first and second points in time.