A computer-implemented method of using a client-side probing device, the method comprising: monitoring by the client-side probing device, one or more encrypted communications sessions between a client computing device and a server computing device, wherein each encrypted communications session includes transmitting a plurality of encrypted data objects between the client and server computing devices; deriving, by the client-side probing device, timing information regarding an encrypted communications session; and transmitting, from the client-side probing device to a server-side probing device, the derived timing information, wherein deriving the timing information includes: receiving an indication, from the server-side probing device, of a location within an encrypted communication session for which timing information is to be derived wherein the location within the encrypted communications session is indicated via a byte offset from the start of a portion of the encrypted communications session; determining when the indicated location within an encrypted communication session has been received by the client computing device; and storing a timestamp associated with the received indicated location within an encrypted communication session; and wherein determining when the indicated location within an encrypted communication session has been received includes: for each received encrypted data object, determining if the received encrypted data object is included with the indicated encrypted communications session, determining the byte range within the indicated encrypted communications session associated with the received encrypted data object, and comparing the byte range associated with the received encrypted data object to the indicated byte offset. monitoring by the client-side probing device, one or more encrypted communications sessions between a client computing device and a server computing device, wherein each encrypted communications session includes transmitting a plurality of encrypted data objects between the client and server computing devices; deriving, by the client-side probing device, timing information regarding an encrypted communications session; and transmitting, from the client-side probing device to a server-side probing device, the derived timing information, wherein deriving the timing information includes: receiving an indication, from the server-side probing device, of a location within an encrypted communication session for which timing information is to be derived wherein the location within the encrypted communications session is indicated via a byte offset from the start of a portion of the encrypted communications session; determining when the indicated location within an encrypted communication session has been received by the client computing device; and storing a timestamp associated with the received indicated location within an encrypted communication session; and wherein determining when the indicated location within an encrypted communication session has been received includes: for each received encrypted data object, determining if the received encrypted data object is included with the indicated encrypted communications session, determining the byte range within the indicated encrypted communications session associated with the received encrypted data object, and comparing the byte range associated with the received encrypted data object to the indicated byte offset. receiving an indication, from the server-side probing device, of a location within an encrypted communication session for which timing information is to be derived wherein the location within the encrypted communications session is indicated via a byte offset from the start of a portion of the encrypted communications session; determining when the indicated location within an encrypted communication session has been received by the client computing device; and storing a timestamp associated with the received indicated location within an encrypted communication session; and wherein determining when the indicated location within an encrypted communication session has been received includes: for each received encrypted data object, determining if the received encrypted data object is included with the indicated encrypted communications session, determining the byte range within the indicated encrypted communications session associated with the received encrypted data object, and comparing the byte range associated with the received encrypted data object to the indicated byte offset. for each received encrypted data object, determining if the received encrypted data object is included with the indicated encrypted communications session, determining the byte range within the indicated encrypted communications session associated with the received encrypted data object, and comparing the byte range associated with the received encrypted data object to the indicated byte offset.