1. Clocking & Sync
SyncE , NTP , PTP etc.
Oded Rotter
oded1233@gmail.com
Based On:
http://en.wikipedia.org/wiki/Synchronous_Ethernet
http://www.metroethernetforum.org/Assets/White_Papers/Packet_Synchronization_over_Carrier_Ethernet_Net
works_for_MBH_2012021.pdf
http://www.ipinfusion.com/products/zebos/protocols/carrier-ethernet/timing-and-synchronization
http://www.cisco.com/c/en/us/products/collateral/routers/asr-9000-series-aggregation-services-
routers/white_paper_c11-500360.html
http://en.wikipedia.org/wiki/Network_Time_Protocol
http://en.wikipedia.org/wiki/Precision_Time_Protocol
http://en.wikipedia.org/wiki/Synchronization_in_telecommunications
http://tagus.inesc-id.pt/~pestrela/timip/Challenges_deploying_PTPv2_in_a_Global_Financial_company.pdf
www.ietf.org/proceedings/68/slides/tictoc-3/tictoc-3.ppt
http://www.nist.gov/el/isd/ieee/upload/tutorial-basic.pdf
www.eecis.udel.edu/~mills/database/brief/distlec/distlec.ppt
2. מושגים
• Synchronous Ethernet (SyncE)
• Precision Time Protocol (PTP)
• Network Time Protocol (NTP)
• Simple Network Time Protocol (SNTP)
• Adaptive Clock Recovery (ACR)
• Primary Reference Clock (PRC)
• Primary reference source (PRS)
• Cesium oscillator
• Global Positioning System (GPS)
• Building Integrated Timing Supply (BITS)
• Synchronization Supply Unit (SSU)
• Two-Way Time Transfer (TWTT)
3. Stratum
Stratum 0
These are high-precision timekeeping devices such as atomic (cesium, rubidium)
clocks, GPS clocks or other radio clocks. They generate a very accurate pulse per
second signal that triggers an interrupt and timestamp on a connected computer.
Stratum 0 devices are also known as reference clocks.
Stratum 1
These are computers whose system clocks are synchronized to within a few
microseconds of their attached stratum 0 devices. Stratum 1 servers may peer with
other stratum 1 servers for sanity checking and backup.[8] They are also referred to as
primary time servers.[2][3]
Stratum 2
These are computers that are synchronized over a
network to stratum 1 servers. Often a stratum 2 computer will query several stratum 1
servers. Stratum 2 computers may also peer with other stratum 2 computers to
provide more stable and robust time for all devices in the peer group.
Stratum 3
These are computers that are synchronized to stratum 2 servers. They employ exactly
the same algorithms for peering and data sampling as stratum 2, and can themselves
act as servers for stratum 4 computers, and so on.
14. NTP
1985
NTPv0
(RFC 958)
NTP Packet
Header, offset &
delay calculation
1988
NTPv1
(RFC 1059)
Comprehensive
specification
of protocol
and algorithms
Client and server,
symmetric
operational
modes
1989
NTPv2
(RFC 1119)
NTP Control
Message
Protocol
(Management
of clients)
Support for
cryptographic
authentication
based on
64-bit data
encryption
Standard (DES)
keys
1992
NTPv3
(RFC1305)
Improve
stability and
accuracy (new
algorithm)
Broadcast
operational
mode
2010
NTPv4
RFC5905
Support of security
features
Support of
automatic
configuration
Algorithm
improvements
(Performance)
Backward
compatible with
NTPv3
Significant revision
of NTPv3