Solved

When UDP is used for NTP service and when TCP is used for NTP service?

Posted on 2008-10-15
4
7,997 Views
Last Modified: 2013-12-16
I check from /etc/services and I find that there are 2 lines for ntp services:
ntp             123/tcp
ntp             123/udp

I got an answer from EE expert that I cannot telnet to NTP server using port 123 as it is UDP. I wonder when TCP is used for NTP service.
0
Comment
Question by:tballah
  • 3
4 Comments
 
LVL 10

Expert Comment

by:PeturIngiEgilsson
Comment Utility
ntp/tcp is listed as a reserved port for ntp.
Does not mean anything is listening on it.

It would confuse people if you would have different reserved ports for both the TCP and UDP protocols.
0
 
LVL 10

Expert Comment

by:PeturIngiEgilsson
Comment Utility
example:
port 80 TCP is reserved for HTTPd
It would be confusing if you had port 80 TCP for HTTPd and port 80 UDP running something completely diffrent.
0
 
LVL 1

Author Comment

by:tballah
Comment Utility
I know a bit from DNS service that it uses port 53/UDP for query and 53/TCP for zone transfer between primary and secondary DNS server. I was thinking the same way for NTP service as defined in /etc/services. By the way who could I know the nature of the service whether it is pure UDP or TCP?
0
 
LVL 10

Accepted Solution

by:
PeturIngiEgilsson earned 250 total points
Comment Utility
use `netstat -na|grep LISTEN` to see if anything is listening on the 123/TCP

As i stated.. 123/TCP is only listed in /etc/services as a reservation...
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

Network Interface Card (NIC) bonding, also known as link aggregation, NIC teaming and trunking, is an important concept to understand and implement in any environment where high availability is of concern. Using this feature, a server administrator …
SSH (Secure Shell) - Tips and Tricks As you all know SSH(Secure Shell) is a network protocol, which we use to access/transfer files securely between two networked devices. SSH was actually designed as a replacement for insecure protocols that sen…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

8 Experts available now in Live!

Get 1:1 Help Now