On Wed, 17 Oct 2007 11:14:32 +0800 Shaochun Wang <[EMAIL PROTECTED]> wrote: > Danny Mayer wrote: > > Shaochun Wang wrote: > But why the following entry exists in /etc/services file? > ntp 123/tcp # Network Time Protocol
NTP is "defined" to be using UDP/123. See the RFC for the protocol
specification:
RFC 958 NTP http://www.faqs.org/rfcs/rfc958.html
RFC 1305 NTPv3 http://www.faqs.org/rfcs/rfc1305.html
RFC 1769 SNTP http://www.faqs.org/rfcs/rfc1769.html
The /etc/services file comes from the IANA port assignment:
http://www.iana.org/assignments/port-numbers
When IANA officially assigns a port, it always assigns both TCP and
UDP for easier maintainance and fewer confusion. When you see "ntp
123/tcp" it doesn't necessarily mean that NTP is using TCP/123. Just to
reserve it in order to prevent future confusion.
(Am I correct on this? ^^;)
From the IANA you can see
telnet 23/udp
http 80/udp
https 443/udp
pop3 110/udp
Telnet/HTTP/HTTPS/POP3 doesn't go UDP, right? (Oh, you don't know?
^^; Never mind...)
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