| 摘要 |
A propagation delay in the transmission of a frame from an initiator node to a peer node is determined by initially identifying a frame number and byte offset of a first incoming frame from the peer node at a time when the initiator node outputs a portion of a transmitted frame. The portion of the transmitted frame may be the first byte of a sub-frame within the transmitted frame. At the peer node, the frame number and byte offset of a second frame to be supplied to the initiator node is identified at a later time when the frame portion transmitted by the initiator node is received by the peer node, and such information is transmitted to the initiator node. Thus, since the frames output and received by the initiator node are typically of fixed duration, the frame number and byte offset of the incoming frame represent the time when the initiator node outputs the frame portion (a transmit time). In addition, the frame number and byte offset of the second frame represents the time at which the frame portion is received by the peer node (a receive time). Accordingly, by comparing the frame numbers and byte offsets of the first and second frames received from the peer node, a difference between transmit and receive times or propagation delay can be obtained. |
| 主权项 |
1. A method, comprising:
transmitting a first plurality of frames from a first node provided at a first location; receiving, at the first node, a second plurality of frames from a second node provided at a second location spaced from the first location; storing in a memory a first value of a first temporal location in a first one of the second plurality of frames, the first temporal location corresponding to a first time when a portion of said one of the first plurality of frames is transmitted from the first node to the second node; storing in the memory a first frame number identifying the first one of the second plurality of frames; receiving, at the first node, a second value of a second temporal location in a second one of the second plurality of frames, the second temporal location corresponding to a second time, after the first time, when the portion of said one of the first plurality of frames is received at the second node; receiving, at the first node, a second frame number identifying the second one of the second plurality of frames; and determining a length of time associated with a transmission of the portion of said one of the first plurality of frames based on the first value, the second value, the first frame number, and the second frame number, wherein each of the first plurality of frames includes an overhead section and a payload section, wherein the first plurality of frames includes a first bytes, and the second plurality of frames includes a second bytes, such that a number of said first bytes (L) in each of the first plurality of frames is equal to a number of said second bytes in each of the second plurality of frames, each of the first bytes being output from the first node during a byte period (Byte_Period), and each of the second bytes is output from the second during the byte period, the first value is indicative of the first temporal location being a first position in said first one of the second plurality of frames that is temporally spaced from a beginning of said first one of the second plurality of frames by a first plurality of said byte periods (Byte_Offset—1), and the second value is indicative of the second temporal location being a second position in said second one of the second plurality of frames that is temporally spaced from a beginning of said second one of the second plurality of frames by a second plurality of said byte periods (Byte_Offset—2), said determining the length of time (PD) associated with the transmission of the portion of the said one of the first plurality of frames from the first node to the second node is in accordance with:
PD=[(FN—1*L+Byte_Offset—1)−(FN—2*L+Byte_Offset—2)]*Byte_Period, where: FN—1=the first frame number,
FN—2=the second frame number. |
