PTP

Implementation Challenges and

Best Practices

28 MAY 2018

Karl J. KuhnSr. Applications Engineer

karl.j.kuhn@tektronix.com

SDI Video Plant

2

IP Video Plant

3

IP packets

carrying

video

TimePerfect Stream

Low-Jitter on Video over IP

Point to Point Jitter is low

4

TimeEveryone Sharing the

Same Pipe

Higher-Jitter on Video over IP

5

Synchronization Accuracy• Accuracy traditionally is based the smallest element of the video

• Analog Video (NTSC)

◦ approx. 800 picoseconds

◦ one degree of Subcarrier

• Digital Video (SDI)

◦ Within a pixel

◦ 13.5 nanosecond for HD Rates

• PTP

◦ time accuracy between two slave devices to master within 1μs

◦ Accuracy enough to align the datagramsIP

SRC

IP

DST

RTP Header w/

TimeStamp

Video Payload

ST2110

ST 2110 Timing

7

PTP

Reference

Clock

2110 Enabled Device

Internal

Clock

1 6 3 4 2 2 5 60 6 7 2 2 8 3 2

Zero Offset Zero Offset

Video Datagram Audio Datagram

0 6 7 2 2 8 3 2 RTP Timestamp 1 6 3 4 2 2 5 6

0 6 7 2 2 8 3 2 1 6 3 4 2 2 5 6

28 MAY 2018

PTP Network

Transparent

Switches

Boundary

Switches

Backup

Network

Primary

Network

Redundant System, Air-Gapped

9

Spine

Leaf

Spine

Leaf Leaf

Spine

Leaf

Spine

Leaf Leaf

Client Client Client Client Client Client

Network 1 Network 2

Redundant System, Cross Connected

10

Spine

Leaf

Spine

Leaf Leaf

Spine

Leaf

Spine

Leaf Leaf

Client Client Client Client Client Client

Network 1 Network 2

PTP Spine – Leaf Network

11

Spine

Leaf, BC

Spine Spine Spine

Client Client Client Client Client Client

Network 1 Network 2

PTP BCLeaf

PTP BCLeaf

PrimaryPTP Master

BackupPTP Master

PTP only

Leaf, BC Leaf, BC Leaf, BC Leaf, BC Leaf, BC

First Step to Troubleshooting PTPVERIFY THE SETTING OF THE GRANDMASTER (GM)

• Setting of all the slave clocks need to match the setting of the GM• Domain

• Domain is defined a number from 0 to 127• Profile

• General Profile send Sync commands .5perSec• AES Profile send Sync commands 1per Sec• SMPTE Profile send Sync commands 8 per Sec

• Communication Mode• Multicast,• Unicast• SMPTE Mixed Mode

28 MAY 2018 12

Verify PTP DomainYOU NEED TO KNOW THE DOMAIN YOU ARE TROUBLESHOOTING

• Domain is defined by a number from 0 to 127• Verify all devices are in the correct PTP Domain (0 to 127)

• In order for Devices to share PTP commands they need to be in the same Domain• Each Domain will have a Grandmaster Clock

Note:

If you do not know what the Domain

Check your GM settings or

Capture a Pcap File of the Stream

with the Prism or WireShark.

Each PTP IP packet will have the

Domain value.

PTP Status

WireShark28 MAY 2018 13

Verify PTP ProfilePROFILES HAVE DIFFERENT ANNOUNCE AND SYNC INTERVAL

PTP Status

• The three Profiles use in Broadcasting are:

General Profile send Sync commands 1perSec

AES Profile sends Sync commands 4 per Sec

SMPTE Profile sends Sync commands 8 per Sec

• There are other differences between the Profiles

• SMPTE has a mixed communication mode

• Mixed Mode uses both Multicast and Unicast

28 MAY 2018 14

Verify Sync Messages Rates(THIS CAN SHOW NETWORK ISSUES

DROPPING THESE MESSAGES COULD CAUSE LOCKUP PROBLEMS)

Active FieldsCounts number of

messages per Sec.Active Fields

Prism’s IP Session Display / PTP Tab28 MAY 2018

Verify Switches Support MulticastPTP USES A DEFAULT MULTICAST ADDRESS (224.0.1.129)

• PTP aware device should automatically join the PTP Multicast▪ Announce, Delay-Respone,& Follow-UP messages uses port 320

▪ Sync & Delay-Request messages uses port 319

• Port 319 carries the time sensitive messages

SPG8000a PTP Status

Prism IP Status Display show

the two ports used by PTP

28 MAY 2018 16

Verify the PTP Grand Master(GM)BEST MASTER CLOCK ALGORITHM (BMCA) DETERMINES THE GM

• Master based on several parameters that are carried by the Announce

• Priority 1 (Default Value 128)

• Lowest value wins (Range 0-255)

• Use to exclude devices from being

able to be the GM

• Clock Class

• Clock Accuracy

• Clock Variance

• Priority 2 (Default Value 128)

• Lowest value wins (Range 0-255)

• Use to designate user default GM

• Final tie breaker

• Clock ID usually MAC address

Verify Master ID Matches desired GM

BMCA Values from the GM

IP Session Display / PTP Tab

Denotes quality

of GM Lock

28 MAY 2018 17

Verifying Video Lock in the IP worldJUST LIKE BASEBAND VIDEO YOU NEED THE SIGNALS TO SYNCHRONIZED TO A

COMMON REFERENCE

PTP Timing Display

28 MAY 2018 18

PTP Graphing

1928 MAY 2018

RTP Sequence error / CRC error

• “Isolate the root cause of CRC error ”

◦ An error in IP layer causes RTP Sequence

Error and CRC Error

◦ An error in SDI layer causes CRC Error Only

20

“NEED MULTILAYER TROUBLESHOOTING METHODOLOGY”

28 MAY 2018

28 MAY 2018 21

ST 2110-21 Traffic Shaping and Delivery Timing

28 MAY 2018 22

ST 2110-21 Traffic Shaping and Delivery Timing

28 MAY 2018 23

ST 2110-10 Stream Timing

28 MAY 2018 24

ST 2110-10 Stream Timing

28 MAY 2018 25

ST 2110-10 Stream Timing

28 MAY 2018 26

ST 2110-20

PIT Histogram ST2110

28 MAY 2018 27

28 MAY 2018 28

ST 2110-20

PTP

Implementation Challenges and

Best Practices

28 MAY 2018

Karl J. KuhnSr. Applications Engineer

karl.j.kuhn@tektronix.com