Rate-Varying Multicast Transmission for Clock Distribution in Packet Networks

• US 20110199941A1
• Filed: 02/16/2011
• Published: 08/18/2011
• Est. Priority Date: 02/16/2010
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Ashwood-Smith, Peter, Ouellette, Michel
• Granted Patent: US 8,625,467 B2
• Time in Patent Office: Days
• US Class Current: 370/256
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: H04L 12/1836 with heterogeneous network architecture

Abstract

In at least some embodiments, the disclosure includes an apparatus a root node in a packet based network that multicasts a plurality of packets. The apparatus also includes an intermediary node coupled to the root node and a plurality of leaf nodes coupled to the intermediary node. The root node, the intermediary node, and the plurality of leaf nodes are arranged in a tree topology. The packets are received at the intermediary node from the root node at a data rate equal to the data rate of the leaf node having the maximum data rate. The packets are multicast from the intermediary node to each of the plurality of leaf nodes at a plurality of different data rates such that each particular one of the plurality of leaf nodes receives the packets at a data rate corresponding to the data rate for the particular one of the plurality of leaf nodes.

Claims

1. An apparatus comprising:

a root node in a packet based network that multicasts a plurality of packets;

an intermediary node coupled to the root node; and

a plurality of leaf nodes coupled to the intermediary node,

wherein the root node, the intermediary node, and the plurality of leaf nodes are arranged in a tree topology,

wherein the packets are received at the intermediary node from the root node at a data rate equal to the data rate of the leaf node with the maximum data rate, and

wherein the packets are multicast from the intermediary node to each of the plurality of leaf nodes at a plurality of different data rates such that each particular one of the plurality of leaf nodes receives the packets at a data rate corresponding to the data rate for the particular one of the plurality of leaf nodes.

2. The apparatus of claim 1, wherein the root node is coupled to a master clock associated with the maximum data rate and the leaf nodes are coupled to a plurality of corresponding slave clocks associated with the different data rates of the leaf nodes, and wherein the packets comprise timestamps or frequency/time synchronization information for the master clock and the slave clocks.

3. The apparatus of claim 2, wherein the master clock and the slave clocks are synchronized in a unidirectional or bidirectional manner.

4. The apparatus of claim 2, wherein the same frequency/time synchronization information are provided to the leaf nodes at the different data rates to efficiently use the packet based network bandwidth and reduce the processing and traffic load of a root node while preventing timing loops.

5. The apparatus of claim 1, wherein the tree topology is generated based on various networking technologies utilized within the packet based network.

6. The apparatus of claim 1, wherein the internal node comprises one or more tables that comprise a plurality of downstream data rates associated with a plurality of egress links and an upstream data rate associated with an ingress link, and wherein the upstream data rate corresponds to a maximum of the downstream data rates.

7. The apparatus of claim 1, wherein the same packets are multicast from the root node to the leaf nodes at the different data rates.

8. The apparatus of claim 1, wherein the internal node is part of a plurality of tree topologies that couple a plurality of root nodes to a plurality of leaf nodes, and wherein the internal node is coupled to each tree topology via a corresponding upstream link.

9. The apparatus of claim 1, wherein the different rates of the leaf nodes depend on different performance metrics of the leaf nodes, characteristics of corresponding slave clock designs, various packet network impairments, packet selection and filtering algorithms, oscillators used in the leaf nodes, operational states of the leaf nodes, or combinations thereof.

10. The apparatus of claim 1, wherein the root node is a video content transmitter and the leaf nodes are video content receivers, and wherein a first set of the leaf nodes comprises high capacity receivers and a second set of the leaf nodes comprises lower capacity receivers.

11. A network component comprising:

a packet replication block coupled to an ingress link and configured to replicate a plurality of packets received on the ingress link at an upstream data rate; and

a plurality of packet discard blocks coupled to the packet replication block and to a plurality of egress links and configured to pass through or reduce some of the received packets to match a plurality of downstream data rates associated with the egress links.

12. The network component of claim 11, wherein the packet replication block forwards the same quantity of packets to each of the packet discard blocks.

13. The network component of claim 11, wherein each of the packet discard blocks compares the upstream data rate that is associated with the ingress link in a table of upstream data rates with a downstream data rate that is associated with a corresponding egress link in a table of downstream data rates.

14. The network component of claim 13, wherein each of the packet discard blocks passes through the received packets without further processing if the upstream data rate of the ingress link is about equal to the downstream data rate of the corresponding egress link.

15. The network component of claim 13, wherein each of the packet discard blocks discards a number of packets in a quantity of packets such that the ratio of transmitted packets to discarded packets is about equal to the ratio of the upstream data rate to the downstream data rate of the corresponding egress link if the downstream data rate is less than the upstream data rate.

16. A method comprising:

receiving a plurality of advertised downstream data rates via a plurality of egress links from a plurality of downstream nodes;

assigning an upstream data rate that corresponds to a maximum of the received downstream data rates to an ingress link; and

advertising the upstream data rate via the ingress link to an upstream node.

17. The method of claim 16, wherein the downstream nodes comprise a plurality of internal nodes in a packet based network or a plurality of leaf nodes coupled to the packet based network, and wherein the upstream node corresponds to an upstream internal node in the packet based network or to a root node coupled to the packet based network.

18. The method of claim 17, wherein the downstream data rates and the upstream data rate determine quantities of transmitted messages per second and are stored and maintained by the packets based network.

19. The method of claim 17, wherein the downstream data rates and the upstream data rate are advertized and updated continuously in a dynamic manner as the downstream nodes request higher or lower data rates, are disconnected from the packet based network, and/or join the packet based network.

20. The method of claim 16, wherein the downstream data rates and the upstream data rate are advertized and expressed in powers of two.