630   SNTP source port 123

Created: 28 Jan 2009

Status: In Force (green)

Part: Part 8-1 (2004)

Links:

Page: 89

Clause: 21

Paragraph:

Category: Issue for edition 2 of this part

Issue

SNTP (RFC 2030) requires use of a fixed UDP source port number ("The UDP port number assigned to NTP is 123, which should be used in both the Source Port and Destination Port fields in the UDP header."). This is needlessly incompatible with implementors of either NTP (RFC 1305) or new SNTP (RFC 4330) which allows (the more usual) ephemeral source port number. A fixed source port number is also incompatible with NAT protocols which makes WAN-based more difficult.

Note that a change to RFC 4330 is not needed at this time.

Proposal

Change clause 21 from "...through the use of SNTP ..." to "through the use of SNTP with the exception that ephemeral UDP source port numbers may be used instead of the SNTP-specified fixed port number ..."

Discussion Created Status
16 Jun 10 In Force (green)
I suggest to call these parameters MMS-Port and SNTP-Port, as there may be several protocols with different ports running on UDP or TCP.
It will be introduced into part 6 schema, however the formal semantic definition must be in 8-1. 		18 Mar 09 Ballot Period
SNTP [RFC2030] does not REQUIRE that a specific UDP/IP port be used for communication. This can be made explicit in 61850-6 using a new P-Type specified in Table 111(Part 6 imports tPTypeEnum from part 8-1). As a side benefit, IP-based protocols which may run over either UDP or TCP can be explicitely specified.
I suggest two new entries be added to Table 111:
IP-UDP-PORT : (UDP) Port number : o : Shall be limited to no more than 5 characters. Characters shall be limited to 0 to 9.
IP-TCP-PORT : (TCP) Port number : o : Shall be limited to no more than 5 characters. Characters shall be limited to 0 to 9.
For the SNTP case example, <P type="IP-UDP-PORT">123</P> could be used to specify the most common usage of SNTP.
27 Feb 09 Not Applicable
RFC 2030 states the following:

"NTP Message Format

Both NTP and SNTP are clients of the User Datagram Protocol (UDP)
[POS80], which itself is a client of the Internet Protocol (IP)
[DAR81]. The structure of the IP and UDP headers is described in the
cited specification documents and will not be detailed further here.
The UDP port number assigned to NTP is 123, which should be used in
both the Source Port and Destination Port fields in the UDP header.
The remaining UDP header fields should be set as described in the
specification."

Note that the use of port 123 is "should" and therefore allows the flexibility that was suggested and is compatible with current implementations. Additionally, SCL currently allows the configuration of the port.

Therefore, no change is required.
09 Feb 09 Not Applicable

 

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