Tektronix SPG8000A User manual

SPG8000A Option PTP operation instructions

This document describes how to conﬁgure the SPG8000A to operate in your PTP network and also provides information about the basics of PTP operation. A list of known bugs

How to conﬁgure Option PTP on the SPG8000A

and operational limitations are included.

General information

The operat addition of PTP functionality, and the menu structure reﬂects this orientation.

Reference mode. The Reference mode selection restricts the possible PTP functions as follows:

Seco

implementingtwomasterswheninInternalmodeorlockedtoGPS,and simultaneous Master and Slave operation.

The primary and secondary PTP systemsmustbeondifferentdomains.

Presets. Most of the PTP functions are saved in the presets. After conﬁguring the instrument, a user can save the Power-on preset so that the desired instrument state is restored when the instrument is powered on.

ion of the instrument is intended to be primarily an SPG with the

If the Reference mode is set to GPS, Genlock or Internal, the primary PTP function is a master.

If the Reference mode is set to PTP, then the primary PTP function is restricted to Slave PTP mode.

Automatically adapting between master and slave functions via the BMCA is not supported.

ndary PTP engine. A secondary PTP engine is also available. This allows

*P061441700*

061-4417-00

Black outputs. The black outputs support a 1pps mode. This is useful for measuring timing between systems.

Firmware update. After a ﬁrmware update, the presets are often not valid and will usually be erased. Therefore, after an update please use the REF button menu to reselect either GPS or PTP as the Reference mode, and then use the PTP button menu to reselect all of the parameters. Next, use the SYSTEM button menu to resave the Power-on preset with your preferred settings.

SPG8000A Option PTP operation i nstructions

Basic setup

recommendations

1. Use the SYSTEM b DHCP or Manual mode. (Press the SYSTEM button, and then press the down arrow twice to access the menu.)

NOTE. Both PTP ports share the same network address. See the PTP network

settings section below for information about how to conﬁgure the two PTP ports.

2. Use the REF button menu to set the Reference mode depending on whether the SPG8000A will be a PTP master, slave or both. (Press the REF button, and then press the left or right arrow to select. Press ENTER to conﬁrm the selectio

3. If Genlock mode is selected as the Reference mode, then also set the time to VITC, LTC, or Internal. In addition, select to use the ST309 data as "input" if ST309 on Drop Frame time code in the limitations section of this document.

n.)

If the SPG8000A is to be the PTP master, select either GPS, Genlock or

Interna

If the SPG8000A is to be a PTP slave, select PTP mode.

If the SPG8000A is to be both a PTP master and slave, select PTP mode

andthenconﬁgure the secondary master.

l mode.

date information is available in the input timecode. Note the limitations

utton menu to set the PTP network IP address using

4. Use t

5. If desired, press the PTP button a second time to access the s econdary PTP

6. Conﬁgure the rest of the SPG8000A as per the online m anual for the SPG8000.

hePTPbuttonmenutoconﬁgure the Primary master or slave PTP proﬁle, message rates, etc. (Press the PTP button once, and then use the arrow keys and the ENTER / BACK keys as necessary to make selections.)

engine. Select parameters as needed.

SPG8000A Option PTP operation instructions

SYSTEM button

additions

PTP network set

to set the Network parameters on the PTP connection. Use this menu to set the DHCP/Manual and other network selections.

This menu also allows setting the DSCP level on the PTP messages. For most situations, the default value of 0 for noncritical General messages and 46 for the Event messages is appropriate. If you are using the AES67 proﬁle, it may help to set both message types to the maximum value of 56. Changing these values resets all of the PTP systems and will disrupt the PTP operation for about 35 seconds.

This menu also allows control of the internal switch. The RJ45 and SFP ports can be conﬁgured as fully cross-linked, isolated or to mirror the RJ45 to the SFP. For most appl ports to both access PTP functions and not allow cross trafﬁc. If you want the ports to work like a normal switch, use the Cross-linked setting. In this setting, all trafﬁc into either port will echo out the other port. In Mirror mode, all the trafﬁc in and out of the RJ45 port will be echoed to the SFP port. This is useful if you need to use Wireshark on a Unicast system. In this case, hook the Wireshark PC to the S

Epoch settings. A second new submenu in the SYSTEM button menu controls the Epoch Selection, which is intended to change the timing on the Black outputs. For PTP systems, set this to the 1970 epoch.

FP port and use the internal switch to mirror the trafﬁc.

tings. A new submenu in the SYSTEM button menu allows users

ications the Isolated setting is appropriate. This setting allows the two

New PTP button menu

There are two PTP functions: Primary and Secondary. Press the PTP button repeatedly to toggle between the two functions.

The Primary PTP function will be either Master or Slave depending on the Reference selection. Adaptive mode between master and slave is not supported.

The Secondary PTP function is only a master. The primary and secondary PTP functions cannot be on the same domain. The SPG8000A will display an error message if an attempt is made to set them to the same domain.

The entries in the PTP menu vary depending on modes of the instrument. Master and Slave modes need different settings. Multicast, Unicast and Mixed modes have different settings. Different proﬁles allow different ranges for some parameters. The possible PTP menu entries are listed below with a basic description of their function:

Master can be enabled or disabled. Slave is always on.

Proﬁle Type. The following proﬁle types are available: General, ST2059, AVB and AES67. Since each proﬁle retains unique settings, each parameter must be set for each proﬁle type.

Press ENTER to set def aults for the selected proﬁle. The defaults will set a nominal value given the selected proﬁle.

SPG8000A Option PTP operation i nstructions

Domain. Defaul allowed to set both PTP engines to the same domain.

Communicatio must use compatible communication modes. For most proﬁles, this means the master and sla ve communication modes need to match exactly. On the SMPTE proﬁle, the Multicast and Mixed modes are compatible, s o a master in any of these modes will work with a slave in any of those modes.

Unicast is separate and the master and slave must match. Note that the Unicast, and Mixed without negotiation modes require that the IP address of all the masters be entered into the Acceptable Master Table (AMT) of the slave

Announce interval allows setting the rate at which the master will send announc Required. The slave will start by requesting the Desired rate. If the master refuses that rate, the slave will request a slower rate. This continues down to the Required setting. If the master cannot support the Required setting, the communication will not start. The default for the Required setting is the minimum rate / maximum interval allowed in the proﬁle.

Sync interval allows setting the rate at which the master will send sync messages. For Unicast mode there are two settings: Desired and Required. The s rate, the slave will request a slower rate. This continues down to the Required setting. If the master cannot support the Required setting, the communication will not start. The default for the Required setting is the minimum rate / maximum interval allowed in the proﬁle.

e messages. For Unicast mode there are two settings: Desired and

lave will start by requesting the Desired rate. If the master refuses that

ts to a reasonable setting for each proﬁle. Users are not

n mode. All of the master and slave devices on a given domain

Delay Message allows setting the rate at which the master will send delay request messages. For Unicast mode there are two settings: Desired and Required. The slave will start by requesting the Desired rate. If the master

efuses that rate, the slave will request a slower rate. This continues down

r to the Required setting. If the master cannot support the Required setting, the communication will not start. The default for the Required setting is the minimum rate / maximum interval allowed in the proﬁle.

Announce timeout count sets the number of announce messages which can be missed before the device will assume the master is no longer present. After that time, all the devices on the domain will start the process of selecting a new master.

Priority 1 and 2 are used in the BMCA to select the active master. Typically, all the masters should have the Priority 1 parameter set to the same value, and then use the Priority 2 parameter to select the primary master if all have the same clock quality. A lower value is preferred. For example, if you set the Priority 2 parameter of the primary master to 127, then set the Priority 2 parameter of all other masters to 128.

SPG8000A Option PTP operation instructions

One-step and tw for the sync message is sent in the sync (one-step mode) or sent in a follow-up message (two-step mode). Some devices, such as transparent clocks, only work on two-step messages. All slaves are required to work in both one-step and two-step modes.

Delay Mechanism. Two delay modes are available: Peer-to-Peer and End-to-End.

In Peer-to-Peer mode, the Pdelay request and Pdelay response messages

are local to each link in the network. Each device determines the local link and device delays. The sync message from the master then collects the correcti is useful in PTP networks where the routing conﬁguration changes. For Peer-to-Peer mode to work well, all of the devices need to be PTP aware.

In End-to-End mode, the sync, follow up, delay request and delay

response messages go through the network all the way between the master and slave. End-to-End mode is useful in PTP networks where some or all devices are not PTP aware.

Acceptable Master Table is required in Unicast and Mixed without Negotiation modes. Enter the IP address of all masters into the AMT of the slaves. The AMT can support up to eight IP addresses.

o-step communication mode controls whether the timestamp

ons as it propagates from the master to slave. Peer-to-Peer mode

Asymmetric delay allows correcting the slave timing for any asymmetric delay in the network. Use the 1 pps or other timing signal to determine the

uired delay. This should not be necessary if the network is PTP aware.

req

ST2059 proﬁle menu selections. When ST2059 is the selected proﬁle and the SPG8000A is conﬁgured as a PTP master, these additional menu selections appear. These settings only drive the Synchronization Metadata message content and have no effect on the operation of the master. Each of these menu selections

an be set to “Auto” to ensure that the metadata bits are sent in a valid state.

ST2059 SM Default Frame. Sets the metadata message ﬁelds to indicate the selected frame rate: 23.98, 24, 25, 29.97, 30, 47.95, 48, 50, 59.94, 60, 71.92, 72, 100, 119.9, or 120.

ST2059 SM Drop Frame Flag. Sets the metadata message bit for the Drop Frame Flag to enabled or disabled.

ST2059 SM CFID. Sets the metadata message bit for the Color Frame ID to enabled or disabled.

SPG8000A Option PTP operation i nstructions

Status menu

Web UI and SNMP

Known bugs and

limitations

Press the STATU status. The PTP master and PTP slave status sections have multiple pages that can be displayed using the left and right arrow.

The master status reports the clock quality and some of the ST2059-2 metadata parameters it is sending.

The slave status reports the clock quality and some of the ST2059-2 metadata parameters it is receiving.

The Web UI a that are available from the front panel. See the SPG8000A User Manual for more information on the SNMP command set.

The foll

owing is a list of known bugs and operational limitations:

Genlock to PAL with VITC or 25 Hz LTC is fully functional. Genlock to NTSC wi accounting for the drop frame compensation. Therefore, there may be a few frames of error until the scheduled jam sync had occurred.

The Peer-to-Peer delay mode has had limited testing. The basic messages are present but a full system has not been demonstrated.

S button then use the down arrow to select different types of

nd SNMP allow users to control of most of the instrument functions

th VITC or 30 Hz Drop Frame LTC basically works but is not fully

ST2059-2 SM leap seconds are not fully implemented. The other messages should be working.

Slave Lock takes about 2.5 minutes.

AVB and AES67 proﬁles have had limited testing.

The

PTP operational overview

SPG8000A Option PTP operation instructions

PTP introduction

Option PTP for the SPG8000A adds two Precision Time Protocol (PTP) engines to the SPG system. The primary PTP engine has the capability to be a master PTP source or lock the SPG to the PTP as a slave. The secondary PTP engine canonlybeamaster.

PTP operating modes. The basic operating mode of the SPG is set in the Reference Select menu. The reference selection drives the allowed function of the primary PTP engine as follows:

If the SPG reference selection is set to internal,ortolocktoanexternalGPS, NTSC, PAL, Tri-level or CW signal, then the primary PTP engine can only beamaster.

If the SPG reference selection is set to lock to an external PTP signal, then the primary PTP engine can only be a slave.

PTP master selection. In a PTP network, all the masters on the network are evaluated by the Best Master Clock Algorithm (BMCA). The BMCA runs on all devices, and chooses a master based on several parameters. Some of the parameters relate to clock quality; conversely the Priority 1 and Priority 2 parameters are set by the user to inﬂuence the choice of a master:

Priority 1. This parameter deﬁnes which clocks are allowed to be considered as masters. To be considered as a master, the value should be set to 128 or less. Priority 1 is the ﬁrst criteria in the BMCA, so if Priority 1 is set to a lower value than other devices on the system, then it will be chosen even if the clock quality is poor. Typically, all the masters in a domain should have the same value for the Priority 1 parameter.

iority 2. This parameter is used to break the tie between masters that have

Pr the same clock quality. Several values may be used to deﬁne a hierarchy of devices. Most proﬁles use 128 as a default, so a value of 127 or lower would indicate a preferred master.

The ﬁnal tie-breaker in the BMCA is the clock ID. This is usually the MAC address so it provides a unique value by which the BMCA can choose.

Network topology. In a typical IEEE1588 PTP network, many devices may be either masters or slaves. If the c urrent master stops working, all the devices that are capably of being a master broadcast their clock quality and a new master is selected.

For video networks it may make sense to depart from the telecom-style PTP topology and dedicate devices to be only masters or slaves. This is the approach supported by the SPG8000A, which allows for a more traditional primary and backup master structure controlling a range of slave devices. The BMCA is still used to select the active master and the network still takes the place of the ECO in the legacy Black-burst/Tri-level network. See the SPG8000A User Manual for suggestions on possible network topologies.

SPG8000A Option PTP operation i nstructions

The ﬁve basic PTP timing

messages

There are ﬁve ba Follow-up, Delay request, and Delay re sponse. Other messages are present in some instances. For example, grant requests and responses appear in unicast systems, and Type Length Value (TLV) management messages appear in SMPTE ST2059 proﬁle systems.

Announce me

capability. This message contains the clock quality and priority settings needed for the BMCA to evaluate which device is the best master.

Sync message. The Sync message is sent by the master and is used to measure the propagation delay from the master to slave. The sync message may contain the times message. The receiver must timestamp the sync message upon receipt. These two timestamps are usually called “t1” and “t2” and provide the ﬁrst delay measurement.

Follow-up message. The Follow-up message is sent only in cases where the PTP ne message.(Seepage10,One-step and two-step operation.)

Delay request message. The Delay request is sent by the slave. The time at which it is sent is noted by the slave, but is not included in the message. This time is usually called “t3.” When the delay request is received by the master, the master tim

tamp indicating when it was sent, or that time may be in the Follow-up

twork hardware is not capable of inserting the timestamp into the Sync

estamps the receive time. This timestamp is usually called “t4.”

sic timing messages in a PTP system: Announce, Sync,

ssage. The Announce message is sent by the master to advertise its

Delay response message. The delay response is sent from the master to the

slave. The response contains the t4 time stamp from when the master received the delay request. Once the slave receives the delay response, it has the second pair of timestamps needed to calculate the second delay measurement of the

lave to master delay.

SPG8000A Option PTP operation instructions

Message timing

PTP timing messages.

. The following ﬁgure show the relationships between the ﬁve

Proﬁles

The IE and Announce messages, and optional functions such as grandmaster clusters. Speciﬁc industries wanting to use PTP are encouraged to deﬁne their own “proﬁle,” which allows the PTP standard to be tuned for speciﬁc applications. The proﬁle deﬁnes the default and range of each parameter, and deﬁnes with options are required, allowed or prohibited.

In the SPG8000A, the proﬁle can be initialized to the default value for a given proﬁle and mode. After setting the reference mode, the user should go to the PTP me parameters to the default value for both the selected proﬁle and operating mode (Master, Slave or Adaptive). After initialization, the user can modify the proﬁle parameters and save a s part of an instrument preset. The allowed range of the parameters is restricted to that which is allowed for the given proﬁle type.

EE1588 standard deﬁnes multiple parameters, such as the rates for Sync

nu and select the proﬁle. The user then has the options to initialize the proﬁle

SPG8000A Option PTP operation i nstructions

Domains

One-step and two-step

operation

The IEEE1588 st to coexist simultaneously on one physical Ethernet connection. For example, on a given network one master and several slaves can be using domain 0 while a second master and other slaves are using domain 1. These two PTP services are independent. One use for this is to have masters on different domains provide PTP on different proﬁles. For example, domain 0 might be an AES67 proﬁle, domain 1 could be a ma master on the SMPTE ST2059 proﬁle.

Since the SPG8000A has two PTP engines, the instrument ca mastering on two domains and two proﬁles simultaneously. With multiple SPGs, more domains and proﬁles can coexist on the same network.

Some PTP messages have a time stamp associated with them. This time stamp indicates the time of the local clock when the mess age was sent or received. In some cases, the hardware is capable of embedding the time stamp in the message as it is sent. This is known as “one-step” mode since the message and its associated time are sent together.

In other cases, the hardware is not capable of inserting the time into the message, so inste since there are two messages.

It is interesting to note that in End-to-End mode, o effected by the one-step and two-step setting since it is the only message that needs the transmit time stamp inserted. This means that other than masters, all devices should be able to process either one-step or two-step message types. In a similar fashion, Peer-to-Peer mode has some messages that may require follow-up support.

ad it is sent in a second follow-up message. This is called “two-step” mode

andard deﬁnes “domains,” which allow multiple PTP services

ster using the AVB (802.1AS) proﬁle, and domain 127 could be a

n provide PTP

nly the Sync message is

Multicast, Unicast, and

Mixed Communication

modes

Therearethreebasicmessagemodesfor PTP: Multicast, Unicast, and mixed Multicast and Unicast. For full Multicast or Unicast modes, all of the PTP messages are sent in the selected mode type.

ome proﬁles, such as some telecom proﬁles and the SMPTE ST2059 proﬁle,

For s a mixture of Multicast and Unicast are allowed. On the SMPTE proﬁle unique mixed mode, the Announce and Sync messages are sent as multicast. However, the Delay request and Delay Response messages are sent as Unicast.

Some points to understand about communication modes:

Whatever mode is chosen, t he master and slave must match or be compatible

Multicast and Mixed mode may need IGMP joins and leaves

Full Unicast must have the master address in all slave AMTs

Unicast without negotiation does not allow master to regulate load

Two masters can be used on different domains to serve slaves on different communication modes

SPG8000A Option PTP operation instructions

Multicast syst

received without knowing the address of the sender. This allows a slave to hook up to the network, receive the announce messages and discover the identity of the master. Multicast in some networks requires the devices to use IGMP to join and leave the multicast group.

In Multicast PTP systems, the master sets the rate of the announce and sync messages. The master also sends the maximum allowed delay request rate in the delay response message. Ideally, the slave will use that value to set the delay request ra rate is typically the same as the sync rate, but may be higher or lower.

Unicast system messages. Unicast messages require the address of the master be entered into the Acceptable Master Table (AMT) in each slave. If there are multiple masters, the IP address for each master must be entered in the AMTs of all th

In Unicast PTP systems, the slave must have the address of the master in its

able master table. The slave sends several grant request s to the master

accept requesting speciﬁc rates for each message type. If the master accepts the grant requests, it w ill send grant acknowledges. If the master denies the grant, the slave may send a new grant request at a lower rate. This process may continue for several iterations until the master and slave agree on a rate. The maste r and slave will then start exchanging the PTP messages. If the master ca nnot support a ny of

ates requested by the slave, then the slave will not be able to lock to the master.

the r

em messages. Multicast messages are broadcast and so they can be

te although some slave set this rate independently. The delay request

e slaves.

Mixed mode system messages. In Mixed Mode systems, some messages are Multicast and some are Unicast. For the SMPTE ST2059 proﬁle, the Announce and Sync messages are sent as Multicast. This allows devices to discover the active master. The Delay Request rate is conﬁgured for Unicast, so the slave and

aster must exchange grant messages before the system will start the full range

m of messages.

n Mixed mode without negotiation, the delay request rate set by the slave must

I be equal to or less than the Sync rate set by the master. Otherwise, the slave will not be able to connect to the master.

SMPTE proﬁle system messages. For SMPTE proﬁle systems, a given domain must use one type of message for all Announce, Sync and Follow up messages. Therefore, all masters and slaves on that domain must be conﬁgured for either Multicast or they all must be conﬁgured for Unicast.

For SMPTE mixed mode, the Announce, Sync, and Follow up m essages are conﬁgured as Multicast so that the delay requests can be Multicast, Unicast, or Unicast without negotiation. To use this combination, set the master and slave to any of the modes: Multicast, Mixed, or Mixed without negotiation. The masters will support all of the slave modes simultaneously.

SPG8000A Option PTP operation i nstructions

BMCA

The Best Master the domain. This is partially explained in the introduction to this document. The BMCA operation varies somewhat as function of communication mode.

Multicast mode. In Multicast mode, the active master sends announce messages that all o ther masters and slaves can receive. So all devices can evaluate the BMCA and decide on the best master. If any device detects that its BMCA rating is better than the current master, it will send an an the active master.

Unicast mode. In Unicast mode, slaves only get Announce messages if they establish a grant from the master. Therefore, each slave must set up a grant with every device in its AMT. Since the masters do not set up grants from other masters, they do not have the information to evaluate the BMCA and know if they are the active master. It is up to the slaves to evaluate the BMCA based on the announce message they get from each master in their AMT. Each slave then decides which master is the best and then set up grants for the other message types. If slaves on a given network have a different list of masters in their AMT, then they may choose a different master.

Mixed mode. In a SMPTE ST2059 mixed environment, the announce message is Multicast. Therefore, the BMCA can follow the Multicast conventions.

Clock Algorithm (BMCA) is used to choose the active master on

nounce and take over as

Compensating for causes

of asymmetric delay

Several factors can cause the PTP message delay to be different for the messages sent from the master to slave as opposed to the messages the other direction from the slave to master. Unless corrected, this propagation delay asymmetry will cause an o ffset in the clock phase equal to ½ the difference in the two path delays. There are 4 main causes of asymmetric delay: Rate mismatch in the ports on a switch, Trafﬁc mismatch on the two paths, message type mismatch, and c able delay variation. The paragraphs below contain hints on how to design the system to minimize the delay asymmetry. Alternatively, the SPG8000A provides a way to manually enter a correction value to cancel the delay error.

Rate mismatch. Rate mismatch in a switch causes a delay asymmetry due to the fact that the switch does a “store and forward” on messages. This means the entire message must be stored in the buffer before it starts to be “forwarded” or sent out. For example, for a 100 Mb input and 1 Gb output, the switch must wait for the entire message to clock in at the slow rate before it can start outputting the message at the high rate. Conversely for a 1 Gb/s input and 100 Mb/s output, the entire packet is quickly read in at the faster rate, so then the output can start sooner, albeit at a lower rate.

While the total time is the same for both directions, the delay on the fast-in, slow-out direction is shorter on the packets which contain the This effect is signiﬁcant on a 100 Mb/1 Gb rate mismatch, but much less signiﬁcant on a 1 G/10 G switch since the message time at 1 Gb/s is quite short. If the switch supports Transparent Clock (TC) mode, then this rate mismatch delay effect is corrected by the TC delay correction.

PTP timestamps.

SPG8000A Option PTP operation instructions

Trafﬁcmismatc

two paths. If there is a high percentage of trafﬁc utilization on the master to slave path, then most of the PTP messages may be delayed s i gni ﬁcantly. If the trafﬁc on the other direction is signiﬁcantly different, then the messages on the path may not suffer the same delay.

This effect can be quite large depending on the trafﬁc, the quality of the switch, and the number of switches in the network. To reduce this effect, a user should avoid large loading on the PTP network, use high-quality switches that avoid this delay vari time information to allow the slave to correct for this delay.

Message type mismatch. Another cause of delay asymmetry is message type mismatch. For example, if the sync message is Multicast and the delay request is Unicast, then some switches may process the messages differently and cause a

ntial delay. Since the SMPTE proﬁle allows a mixed mode operation,

differe switches should be evaluated to ensure they do not have this effect. If transparent mode switches are used, then this effect should be corrected by the slave.

Cable delay variation. The actual propagation delay through Cat 5 cable can be signiﬁcantly different in one direction versus the other direction. This can be due to etc. The PTP system is incapable of removing this effect, so the best way to prevent this is to use high-quality cable with a minimum variation in the physical propagation delay.

the twist rate on the pairs, routing inside the sheath, material differences,

h. Another cause of asymmetric delay is trafﬁc mismatch on the

ance, or use PTP Transparent mode switches which will insert residence

Tektronix SPG8000A User manual

Specifications and Main Features

Frequently Asked Questions

User Manual