# US 2014/0153591 A1 · Packet Delay Distribution Rate Filtering

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- Number: US 2014/0153591 A1
- Document ID: US20140153591A1
- Status: Published application
- Kind: A1
- Application number: 13/796,015
- Filed: 2013-03-12
- Published: 2014-06-05
- Earliest claimed: 2012-12-03
- Assignees: LSI Corporation
- Applicants: Lsi Corporation
- Inventors: P. Stephan Bedrosian
- Web page: https://patentgrep.com/patent/US20140153591A1

## CPC

- H04J 3/0658: {Clock or time synchronisation among packet nodes}
- H04J 3/0661: {using timestamps}
- H04L 41/142: using statistical or mathematical methods
- H04L 43/0852: Delays
- H04L 43/0858: {One way delays}
- H04L 43/0864: Round trip delays
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

To test the timing-recovery process of a receiving (i.e., slave) node in a packet-based network, a packet filter is configured in a test configuration that already contributes a natural delay distribution to the packet flow arriving at the slave node. The resulting delay distribution of the arriving packet flow is the combination of that natural delay distribution and the effects of the packet filter, which deterministically or statistically reduces the number of packets with delays within the anchor value window arriving at the slave node (i.e., received packets having packet delays within the slave node's anchor value window). The packet filter can be adjusted to test the slave node's timing-recovery process for a wide variety of packet-flow conditions (e.g., different rates of packets with delays within the anchor value window).

## Claims

### Claim 1

A machine-implemented method comprising:
(a) a packet filter determining, for a packet in a forward packet flow in a packet-based network, whether or not to shift the packet outside of an anchor value window of a timing-recovery process;
(b) if the packet filter determines to shift the packet outside of the anchor value window, then the packet filter adding a specified non-zero delay offset value to an incoming packet delay value for the packet to generate an outgoing packet delay value for the packet, such that the outgoing packet delay value for the packet will be outside of the anchor value window when the packet arrives at a slave node of the packet-based network, wherein the slave node is configured to perform the timing-recovery process; and
(c) the packet filter transmitting the packet towards the slave node with the outgoing packet delay value.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
(d) the packet filter receiving a reverse measurement packet from the slave node;
(e) the packet filter determining whether or not to add additional delay to the reverse measurement packet;
(f) if the packet filter determines to add the additional delay to the reverse measurement packet, then the packet filter adding the additional delay to the reverse measurement packet;
(g) the packet filter transmitting the reverse measurement packet to a master node of the packet-based network, wherein the master node responds by transmitting a forward measurement packet to the slave node;
(h) the packet filter receiving the forward measurement packet from the master node; and
(i) the packet filter transmitting the forward measurement packet to the slave node,

### Claim 3 (depends on 1)

The method of claim 1, wherein, if the packet filter determines not to shift the packet outside of the anchor value window, then the packet filter does not add the specified non-zero delay offset value to the incoming packet delay value for the packet in generating the outgoing packet delay value.

### Claim 4 (depends on 1)

The method of claim 1, wherein, independent of the determination of step (a), the packet filter adds a fixed delay to the incoming packet delay value for the packet to account for processing delay of the packet filter in generating the outgoing packet delay value.

### Claim 5 (depends on 1)

The method of claim 1, wherein step (a) further comprises:
(a1) the packet filter receiving the packet from a master node in the packet-based network;
(a2) the packet filter determining the incoming packet delay value for the packet; and
(a3) the packet filter determining whether or not the packet is inside the anchor value window, wherein the packet filter determines whether or not to shift the packet outside the anchor value window only after the packet filter determines that the packet is inside the anchor value window.

### Claim 6 (depends on 1)

The method of claim 1, wherein step (a) further comprises:
(a1) the packet filter receiving the packet from a master node in the packet-based network; and
(a2) the packet filter determining the incoming packet delay value for the packet, wherein the packet filter determines whether or not to shift the packet outside the anchor value window independent of any determination of whether or not the packet is inside the anchor value window.

### Claim 7 (depends on 1)

The method of claim 1, wherein the packet filter is part of a network emulator that generates the forward packet flow.

### Claim 8 (depends on 1)

The method of claim 1, wherein the packet-based network comprises at least one of:
an upstream link connecting the packet filter to a master node of the packet-based network; and
a downstream link connecting the packet filter to the slave node, wherein at least one of the upstream link and the downstream link contributes at least a portion of a natural delay distribution to the forward packet flow.

### Claim 9 (depends on 1)

The method of claim 1, wherein step (a) comprises:
(a1) the packet filter assigning a modulo count value to the packet;
(a2) the packet filter comparing the assigned modulo count value to a specified threshold value; and
(a3) the packet filter determining whether or not to shift the packet outside of the anchor value window based on the comparison of step (a2).

### Claim 10 (depends on 1)

The method of claim 1, wherein step (a) comprises:
(a1) the packet filter assigning a random value to the packet;
(a2) the packet filter comparing the assigned random value to a specified threshold value; and
(a3) the packet filter determining whether or not to shift the packet outside of the anchor value window based on the comparison of step (a2).

### Claim 11 (depends on 1)

The packet filter of claim 1.

### Claim 12 (depends on 5)

The packet filter of claim 5.

### Claim 13 (depends on 7)

The network emulator of claim 7.

### Claim 14 (depends on 9)

The packet filter of claim 9.

### Claim 15 (depends on 10)

The packet filter of claim 10.

### Claim 16 (depends on 1)

The packet-based network of claim 1.

### Claim 17 (depends on 5)

The packet-based network of claim 5.

### Claim 18 (depends on 7)

The packet-based network of claim 7.

### Claim 19 (depends on 8)

The packet-based network of claim 8.

### Claim 20 (depends on 1)

The slave node of claim 1, wherein the slave node is configured to transmit a current anchor value to the packet filter.