Methods and apparatus for providing timing analysis for packet streams over packet carriers
View Patent ↗A network device such as a router or switch, in one embodiment, includes a timing analyzer which is capable of providing timing analysis over one or more network circuits. The timing analyzer, in one aspect, receives a data packet traveling across a circuit emulation service (“CES”) circuit such as T1 or E1 circuit. Upon obtaining an arrival timestamp associated with the data packet, the arrival timestamp is stored in a timestamp buffer in accordance with a first-in first-out (“FIFO”) storage sequence. After identifying the oldest arrival timestamp in the timestamp buffer, an offset is generated based on the result of comparison between the arrival timestamp and the oldest timestamp. The timing analyzer can also be configured to generate timing reports on-demand based on generated offset(s).
1. A network system to adjust timing for packet transmission, comprising:
an ingress component coupled to a first circuit emulation service (“CES”) circuit and configured to generate a first timestamp indicating arrival time of a first data packet traveling across the first CES circuit;
a timing analyzer coupled to the ingress component and configured to calculate a timing offset in accordance with the first timestamp, wherein the timing analyzer includes a timestamp buffer configured to store a plurality of arrival timestamps based on a first-in first-out (“FIFO”) storage sequence, a rate calculator coupled to the timestamp buffer and configured to compare an oldest timestamp in the timestamp buffer with a newly arrived timestamp to identify an offset, and a log coupled to an ingress rate manager and configured to record rate lock status when the first offset falls within a predefined range; and
an egress element coupled to the timing analyzer and configured to adjust egress clock rate for outgoing packet streams in response to the timing offset.
2. The system of claim 1 , wherein the ingress component includes an ingress rate manager configured to generate a timing report in response to the offset.
3. The system of claim 2 , wherein the ingress component is coupled to a second CES circuit and configured to generate a second timestamp indicating arrival time of a second data packet traveling across the second CES circuit.
4. The system of claim 3 , further comprising a second timestamp buffer coupled to the ingress component and configured to store the second timestamp based on a circular storage sequence.
5. The system of claim 1 , further comprising a jitter buffer coupled to the ingress component and configured to queue a plurality of packets according to sequence numbers of packets before the packets are being routed.
6. The system of claim 1 , further comprising a block of adaptive rate control mechanism coupled to the ingress component and configured to generate an outbound rate for sending data streams.
7. The system of claim 1 , wherein the timing analyzer is configured to generate a warning signal if the timing offset is greater than a range of predefined limits.
8. A network device, configured to generate timing offsets associated with a network transmission, comprising:
an egress element configured to send data streams based on an adjusted egress rate;
a jitter buffer coupled to the egress element and configured to temporarily store packets; and
an ingress component coupled to the jitter buffer and coupled to a circuit emulation service (“CES”) circuit for receiving data packets, wherein the ingress component includes,
a monitor component configured to monitor incoming packets from a packet switching network (“PSN”);
a stamp generator coupled to the monitor component and configured to generate a timestamp each time a packet arrives;
an offset calculator coupled to the stamp generator and configured to calculate time difference between the arrival time of the most recent packet and arrival time of oldest packet stored in a timestamp buffer, wherein the offset calculator includes a timestamp buffer for storing arrival timestamps based on a first-in first-out (“FIFO”) storage sequence, a rate calculator for comparing an oldest timestamp in the timestamp buffer with a newly arrived timestamp to identify an offset, and a log coupled to an ingress rate manager and configured to record rate lock status when the offset falls within a predefined range.
9. The network device of claim 8 , wherein the ingress component further includes a timing comparator coupled to the offset calculator and configured to provide a deviation or divergence value.
10. The network device of claim 9 , wherein the timing comparator compares the offset against a range of acceptable limits.
11. A network device, configured to generate timing offsets associated with a network transmission, comprising:
an egress element configured to send data streams based on an adjusted egress rate;
a jitter buffer coupled to the egress element and configured to temporarily store packets; and
an ingress component coupled to the jitter buffer and coupled to a circuit emulation service (“CES”) circuit for receiving data packets, wherein the ingress component includes,
a monitor component configured to monitor incoming packets from a packet switching network (“PSN”);
a stamp generator coupled to the monitor component and configured to generate a timestamp each time a packet arrives;
a timing analyzer coupled to the ingress component and configured to calculate a timing offset in accordance with the first timestamp, wherein the offset calculator includes a timestamp buffer for storing arrival timestamps based on a first-in first-out (“FIFO”) storage sequence, a rate calculator for comparing an oldest timestamp in the timestamp buffer with a newly arrived timestamp to identify an offset, and a log coupled to an ingress rate manager and configured to record rate lock status when the offset falls within a predefined range.
12. The network device of claim 11 , further comprising an offset calculator coupled to the stamp generator and configured to calculate time difference between the arrival time of the most recent packet and arrival time of oldest packet stored in a timestamp buffer.
13. The network device of claim 11 , wherein the ingress component further includes a timing comparator coupled to the offset calculator and configured to provide a deviation or divergence value.
14. The network device of claim 13 , wherein the timing comparator compares the offset against a range of acceptable limits.