Domains
A domain is an interacting set of clocks that synchronize to one another using PTP. Clocks are assigned to a domain by virtue of the contents of the Subdomain name (IEEE 1588-2002) or the domainNumber (IEEE 1588-2008) fields in PTP messages they receive or generate. Subdomains allow multiple clock distribution systems to share the same communications medium.
| Subdomain name field contents (IEEE1588-2002) | IPv4 multicast address (IEEE1588-2002) |
domainNumber (IEEE1588-2008) |
Notes |
|---|---|---|---|
| _DFLT | 224.0.1.129 | 0 | Default domain |
| _ALT1 | 224.0.1.130 | 1 | Alternate domain 1 |
| _ALT2 | 224.0.1.131 | 2 | Alternate domain 2 |
| _ALT3 | 224.0.1.132 | 3 | Alternate domain 3 |
| Application specific up to 15 octets | 224.0.1.130, 131 or 132 as per hash function on Subdomain name | 4 through 127 | User-defined domains |
Read more about this topic: Precision Time Protocol, Protocol Details
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