1. PTP Update & 1588 Switches

2. Why Adopt IEEE-1588
High accuracy time and frequency transfer via Ethernet
Saves money
Synchronization uses same channel as data (Ethernet)
No additional cable for timing (i.e. no coax or twisted pair)
Common media type
Cat 5 cable or fiber
Ethernet infrastructure
Represents the future of accurate synchronization in an Ethernet centric world

3. Refresher: Packet Delays
Timing
packet
NTP
UDP IP
Ethernet
NTP
UDP IP
Ethernet
NTP Timestamp location
OSI Stack
OSI Stack
PTP Timestamp location
Receive
queue
Transmit
Receive
queue
Transmit
Receive
queue
Transmit
Network

4. 1588 vs NTP vs IRIG Perspective
IEEE-1588
NTP
IRIG
Peak time transfer error
>100 ns
>1 ms
10ms
Network type
LAN
Dedicated coaxial cables
Spatial extent
A few subnets
LAN/WAN
1 mile over coax
Error Source
Switches & port contention with data
Routers & O/S stack delay
Cable delay

5. How Precision is Possible
Message Exchange Technique
Periodic Sync messages broadcast master to slaves (every 2 seconds by default)
Occasional delay measurement slaves to master
Hardware-Assisted Time Stamping
Time stamp leading edge of IEEE-1588 messages at network interface
Time stamp hardware required at master and slaves
Time stamp on send and receive
Removes indeterminate host operating system stack delays
Symmetricom proprietary algorithms use the precise time stamps to steer the oscillator for maximum precision

6. Understanding Slave Sync Accuracy
Sync Accuracy is best defined as “it depends”…
Switches between the Master and Slave reduce synchronization accuracy by way of:
Packet arrival Jitter at switches and the Slave
Network Latency during packet transfer
Each network element contributes delays defined in terms of mean offsets with standard deviations
Switch # Switch # = Combined
Error Error Error

7. Clock Error By Network Element - No Traffic
Boundary Clock and Transparent Clock performance not expected to change with traffic load

8. Switch Characteristics
COTS Switches introduce network timing jitter and diminishes PTP accuracy.
Jitter is induced whenever two packets compete for the same egress port.
1588 enabled switches minimize switch induced network packet jitter.

9. Why Transparent Clocks (Switches)

10. Indeterminate Switch Delay
Master Clock Time
Slave Clock Time
Sync message
Switch t
Sync message 1
Data at
Slave Clock t t 2 2
Follow_Up message
containing value of t 1 t , t
Delay_Req message 1 2 t 3 m t t , t , t 3 1 2 3 t 4
Delay_Resp message
containing value of t 4 t , t , t , t
time 1 2 3 4
Client
Time = (T4 – T3) + (T1 – T2)
Offset

11. Switch Delay & Transparency
Variable packet delay in switch (measured per Sync packet)
Step 1
Delay inside switch varies packet to packet
Transparent Clock (switch) measures the switch delay associated with the Sync Packet using hardware time stamping
Switch modifies the t1 time stamp in the Follow-Up packet by adding the measured switch delay
time sync packet left switch – time sync packet arrived at switch = Sync Packet delay inside switch
Sync Packet
tdepart – tarrive = delay
Step 2
Modify time in Follow-Up
Packet to account for Sync Packet delay
Follow-Up
Packet t1 unmodified
Follow-Up
Packet t1 modified = t1 unmodified + delay

12. COTS & 1588 Enabled Switches with Data Traffic
Synchronization Error vs. Elapsed Time
COTS Switch vs Switch 40
COTS Switch 20
Time Error (microseconds)
-20
No Traffic
5 Mbps TFTP Traffic
-40 5 10 15 20 25 30 35 40 40
1588 Switch 20
Time Error (microseconds)
No Traffic
5 Mbps TFTP Traffic
-20
-40 5 10 15 20 25 30 35 40
Elapsed Time (k*seconds)

13. Previewing the…

14. SyncSwitch TC100 IEEE-1588 Transparent Clock

15. SyncSwitch TC100
It’s an Ethernet switch with IEEE-1588 transparency a.k.a IEEE-1588 v1 Compliant Transparent Clock
Three (3) Models:
8x 10/100BaseT ports
6x 10/100BaseT ports 2x Multi mode fiber
6x 10/100BaseT ports 2x Single mode fiber

16. Key SyncSwitch TC100 Features
Industry firsts..
1U Rack mounted TC
AC powered TC
IEEE-1588 v1 Transparency
IEEE-1588 v2 support comes later
Copper or copper/fiber mix of ports
GUI interface for custom configuration
Basic configuration operates as a regular switch (plug & play!) 
Prototype SyncSwitch

17. Advanced Features Simple Network Management Protocol (SNMP)
Custom MIB
IGMP Snooping
Forward multicast traffic only to the hosts interested in that traffic.
VLAN
A VLAN has the same attributes as a physical LAN, but it allows for end stations to be grouped together even if they are not located on the same LAN segment.
Supports network ring topology
Rapid Spanning Tree Protocol (RSTP)
OSI layer-2 protocol which ensures a loop free topology for any bridged LAN.

18. Range Ring Topology Idea
outputs
outputs
Fiber
Copper
outputs
outputs

19. How well does it work? Grandmaster, 7x 1588 SyncSwitches, 1x slave
Packet arrival jitter at slave < 400 ns
<58 ns error per switch

20. When to use the SyncSwitch
Probably need a SyncSwitch…
If data & timing packets travel the same network
If measured error at slave is *not* acceptable
If there are traffic bottlenecks at switches
If Sub millisecond timing is required
Absolutely if <1 ms timing required
Probably don’t need a SyncSwitch…
If measured error at slave is acceptable
If desired timing accuracy at slave is in the milliseconds
If using a network of Hubs

21. Deployment            Timing Grandmaster Data /Root
Bottleneck
(port contention,
5 in, 1 out)
Bottleneck
(port contention,
2 in, 1 out)
Distribution
/Network
/Application
Slave          

22. Transparent Clock vs Boundary Clock
Switch
Measures switch induced Sync packet delay
Modifies Follow-Up packet time stamp (adds the delay)
Flattens time distribution topology
Increases packet load on Grandmaster
Boundary Clock
Switch & Clock
Slave on one port
Master on all other ports
Built-in internal clock synchronized to the upstream master
Cascaded Boundary Clocks can accumulate error
Hierarchal time distribution topology
Decreases packet load on Grandmaster
Sync Packet
tdepart – tarrive = delay
Follow-Up
Packet t1 unmodified
Follow-Up
Packet t1 modified = t1 unmodified + delay   S M M
Slaves

23. XLi IEEE-1588 Grandmaster

24. XLi IEEE 1588 Grandmaster 1x Port
Master or Slave
Base XLi
GPS Module
1x IEEE 1588 module
IEEE compliant, v1
Operates as grandmaster or ordinary clock (master/slave)
Supports Best Master Clock Algorithm
TIET (Time Interval/Event Timing on J1)
1/sec measurement output from RS-232 and/or Telnet/NIC

25. TIET (Time Interval/Event Timing)
Measure the time interval difference between XLi Grandmaster 1PPS and an external 1PPS
Application: Measure time transfer accuracy Master to Slave
XLi TIET Output: 1/sec measurement output from RS-232 and/or Telnet/NIC
Time Interval
Master 1PPS
Slave 1PPS

26. XLi 1588 Grandmaster 2 Port
Master
Master/Slave
Same base features as 1x Port XLi Grandmaster
Includes 2x IEEE 1588 cards
Configurations
Master/Master
Master/Slave

27. TimeMonitor/TimeAnalyzer Software (Option)
Chart
View Functions
Collect and analyze time interval data from the XLi Grandmaster
Extensive graphing and charting functions
Perform extensive analysis on collected data
Collect data via RS-232 or TCP/IP interfaces
Runs on Windows® NT, 2000, XP

28. Testing with a Single Port Grandmaster
Third party IEEE 1588 slave characterization and network element delay measurements.
Baseline the slave (via crossover or hub)
Substitute network elements or topologies for study and characterization

29. Testing with a Dual Port Grandmaster
The XLi Grandmaster hosts a second IEEE 1588 module that acts as a slave
Baseline the XLi card slave (via crossover or hub)
Substitute network elements or topologies for study and characterization

30. One Way Path Latency Testing
Network separates the Grandmaster from the slave by an inconvenient distance.
One XLi Grandmaster operates as a master
Remote Grandmaster is configured with the IEEE 1588 module operating as a slave
Slave module 1 PPS compared to GPS referenced XLi clock.
GPS time is the common time reference

31. IEEE-1588 v2 in the XLi GM What When How Price
Support IEEE-1588 v2 Default Profile
When
Fall 2008
How
ECO in new models
TBD regarding update to fielded models
Price
No price change to existing XLi GM
Upgrades to fielded XLi GM units
Details and price TBD

32. Looking ahead….. …at IEEE-1588 v2 (PTPv2) …at the big picture

33. Approved IEEE-1588 v2 Status From the source… 3/14/2008
Please note that this is still a draft standard. . . that has been submitted to the IEEE for final approval. . . The approval is on the RevCom agenda for their 26 March 2008 meeting. . . If the draft is approved the IEEE editorial staff typically takes several months before the final version of the standard is available. This editorial process does not permit any technical changes.
Regards,
John C. Eidson
Chair P1588
Approved

34. IEEE 1588 v2 Main Elements New message types and formats
More message rate choices
Unicast
Fault Tolerance
Alternative timescales
Transparent clocks
On the fly timestamps
Profiles
Security
More here than any one vendor will implement in a single solution

35. Message Update Intervals
PTPv1
1,2,4,16, 64 seconds Default
PTPv2
More than 18 hexillion choices
As small as 30 fs
As large as 3 days
No profile will support all of these choices

36. Unicast Messages PTPv1 All messages multicast
Every node in the same subnet hears every message
PTPv2
Optional unicast mode
Slaves request unicast stream
Sync update interval
Master can grant none, all or part of request
Broadcast
(1:all)
Multicast
(1:group)
Unicast
(1:1)

37. Alternate Time Scales PTPv1 TAI is only allowed time scale
TAI has no leap seconds
UTC offset field
Flag indicate unknown accuracy
PTPv2
Alternative time scales allowed
Feature pushed into standard by Symmetricom
Allows for time scales with leap seconds or DST jumps

38. Profiles PTPv1 v1 tailor made for industrial automation PTPv2
Many optional features
Profiles limit choices
Profiles created by industry specific standards body

39. Looking ahead….. …at IEEE-1588 v2 (PTPv2) …at the big picture

40. 1588 marketplace snapshot…
XLi GM
NI PCI 1588 (GPS)
Meinberg M600/PTP ?
Grandmaster
/Root
Westermo
Ruggedcom PTP Router
TimeProvider 5000
Rockwell +
Cisco
SyncSwitch
Hirschman BC ?
Westermo TC
Distribution
/Network
Techron
Meinberg Syncbox
NI PCI 1588
ZHW ?
/Application
Slave
XLi GM

41. Symmetricom Directions
Symmetricom Corporate
Committed to packet based timing solutions
Timing Test & Measurement Division (TTM)
SyncSwitch TC100 Transparent Clock
IEEE-1588 v2 support coming soon
XLi Grandmaster
IEEE-1588 v2 support by year end
IEEE-1588 v2 will eventually be in most clock form factors
1U clocks
Bus cards
Custom modules