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DXD8/PTP User Manual (rev 2.15)
13. PTP v1 (IEEE Std 1588-2002) Implementation - Firmware Option
The translation between PTPv1 and PTPv2 is implemented as specified in section “18. Compatibility Requirements” of IEEE Std
1588-2008 (PTPv2). It is available on the DXD-8 with the PTP option (DXD8/PTP).
13.1 SELECTING PTP V1
PTPv1 mode is selected in the PTP menu PORT CONTROLS. Select “PTP Version 1” in the line
“PTP VERSION”.
13.2 DIFFERENCES IN SETTINGS FOR PTP MENU ‘5.2 GRANDMASTER’
• Domain:
The range of Domain numbers in PTPv1 is just 0~3, as opposed to 0~127 for PTPv2.
If a Domain number greater than 3 is set for a port running in PTPv1 mode, then:
-
The DXD will issue the warning "PTP: Domain Number exceeds PTP-V1 limit"; and
-
The actual number used on the bus will be converted to lie in the range 1~3
(4
→
1, 5
→
2, 6
→
3, 7
→
1, 8
→
2, etc.).
• Priority 1:
PTPv1 does not have PRIORITY settings, but it does have the concept of “Preferred Master Clock”.
Translation between the two is as follows:
PRIORITY 1 = 127 ....... Preferred Master Clock = TRUE
PRIORITY 1 = 128 ....... Preferred Master Clock = FALSE
Other values may be used for PRIORITY 1, with all values less than 127 resulting in Preferred Master Clock being TRUE,
and all values greater than 128 making Preferred Master Clock FALSE.
• Priority 2:
Translation of this value is more obscure. PTPv1 keeps track of whether or not a device is a Boundary Clock, and PTPv2
PRIORITY 2 is mapped to that setting as follows:
PRIORITY 2 = 127 (or less) ....... Boundary Clock = TRUE
PRIORITY 2 = 128 (or more) ....... Boundary Clock = FALSE
Changing PRIORITY 2 will not necessarily result in observable operational differences.
13.3 DIFFERENCES IN SETTINGS FOR PTP MENUS ‘PORT TIMING’
• Announce Interval:
PTPv1 does not use Announce messages, but the DXD-8 continues to use this timing value internally while operating in
PTPv1 mode. The value is not critical, but it is used in the calculation of the SYNC message timeout (see below).
• Announce Receipt Timeout:
Although PTPv1 does not use Announce messages, the DXD-8 port in PTPv1 mode will use this value to determine
whether or not PTPv1 SYNC messages have timed out (i.e. stopped arriving). Note that the timeout is measured in
ANNOUNCE INTERVAL’s (above), whereas PTPv1 measures its SYNC message timeout in SYNC INTERVAL’s. The math
is not difficult, but it may be simpler if the ANNOUNCE INTERVAL is set the same as the SYNC INTERVAL.
The PTPv1 default for this setting is 10 SYNC INTERVAL’s.
ERROR
PTP Domain Number
exceeds PTP-V1 limit
Press Any Key to Clear
CAUTION
: Using values _other_ than 127 and 128 in a system where both V2 and V1 devices are present is
_not recommended_ as the V2 devices will recognize the differences between priorities beyond 127 and 128,
and their Best Master Clock algorithms will respond accordingly, whereas the V1 devices will not.
