Server Options
 from Pogo,
Walt Kelly
from Pogo,
Walt Kelly
The chicken is getting configuration advice.
Last update:
	24-Sep-2009  16:12
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Table of Contents
Following is a description of the configuration commands in NTPv4. There are
	two classes of commands, configuration commands that configure an association
	with a remote server, peer or reference clock, and auxilliary commands that
	specify environmental variables that control various related operations. 
The various modes described on the Association Management page
	are determined by the command keyword and the DNS name or IP address. Addresses
	are classed by type as (s) a remote server or peer (IPv4 class A, B and C),
	(b) the IP broadcast address of a local interface, (m) a multicast address (IPv4
	class D), or (r) a reference clock address (127.127.x.x). For type m addresses
	the IANA has assigned the multicast group address IPv4 224.0.1.1 and IPv6 ff05::101
	(site local) exclusively to NTP, but other nonconflicting addresses can be used. 
If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected,
	support for the IPv6 address family is generated in addition to the default
	IPv4 address family. IPv6 addresses can be identified by the presence of colons ":" in
	the address field. IPv6 addresses can be used almost everywhere where IPv4 addresses
	can be used, with the exception of reference clock addresses, which are always
	IPv4. Note that in contexts where a host name is expected, a -4 qualifier
	preceding the host name forces DNS resolution to the IPv4 namespace, while a -6 qualifier
	forces DNS resolution to the IPv6 namespace.
Configuration Commands
	- server address [options ...]
 peer address [options ...]
 broadcast address [options ...]
 manycastclient address [options ...]
 pool address [options ...]
 unpeer [address | associd]
- These commands specify the time server name or address to be used and the
		mode in which to operate. The address can be either a DNS name or a
		IPv4 or IPv6 address in standard notation. In general, multiple commands of
		each type can be used for different server and peer addresses or multicast
		groups.
		
			- server
			
- For type s and r addresses (only), this command mobilizes a persistent
				client mode association with the specified remote server or local reference
				clock. If the preempt flag is specified, a preemptable client mode
				association is mobilized instead.
			
- peer
			
- For type s addresses (only), this command mobilizes a persistent symmetric-active
				mode association with the specified remote peer.
			
- broadcast
			
- For type b and m addressees (only), this command mobilizes a persistent
				broadcast or multicast server mode association. Note that type
				b messages go only to the interface specified, but type m messages go to
				all interfaces.
			
- manycastclient
			
- For type m addresses (only), this command mobilizes a manycast client
				mode association for the multicast group address specified. In this mode
				the address must match the address specified on the manycastserver command
				of one or more designated manycast servers.
			
- pool
			
- For type s messages (only) this command mobilizes a client mode association
				for servers implementing the pool automatic server discovery scheme described
				on the Association Management page. The address
				is a DNS name in the form area.pool.ntp.org, where area is
				a qualifier designating the server geographic area such as us or europe.
			
- unpeer
			
- This command removes a previously configured association. An address or association ID can
				be used to identify the association.  Either an IP address or DNS name can be used.  This
				command is most useful when supplied via ntpq runtime
				configuration commands :config and config-from-file.
		
 
Command Options
	- autokey
	
- Send and receive packets authenticated by the Autokey scheme described
		in the Authentication Options page. This option
		is mutually exclusive with the key option.
	
- burst
	
- When the server is reachable, send a burst of eight packets instead of the
		usual one. The packet spacing is normally 2 s; however, the spacing between
		the first and second packets can be changed with the calldelay command
		to allow additional time for a modem or ISDN call to complete. This option
		is valid only with  the server command and type s addressesa.
		It is a recommended option when the maxpoll option is greater than
		10 (1024 s).
	
- dynamic
	
- Allows a server/peer to be configured even if it is not reachable at configuration
		time. It is assumed that at some point in the future the network environment
		changes so that this server/peer can be reached. This option is useful
		to configure servers/peers on mobile systems with intermittent network
		access (e.g. WLAN clients). Note: the current implementation does not
		support this option.
	
- iburst
	
- When the server is unreachable, send a burst of eight packets instead of
		the usual one. The packet spacing is normally 2 s; however, the spacing between
		the first and second packets can be changed with the calldelay command
		to allow additional time for a modem or ISDN call to complete. This option
		is valid only with the server command and type s addresses. It is
		a recommended option with this command.
	
- key key
	
- Send and receive packets authenticated by the symmetric key scheme described
		in the Authentication Options page. 
		The key specifies the key identifier with values from 1 to
		65534, inclusive. This option is mutually exclusive with the autokey option.
	
- minpoll minpoll
 maxpoll maxpoll
- These options specify the minimum and maximum poll intervals for NTP messages,
		in seconds as a power of two. The maximum poll interval defaults to 10
		(1024 s), but can be increased by the maxpoll option to an upper limit
		of 17 (36 h). The minimum poll interval defaults to 6 (64 s), but can
		be decreased by the minpoll option to a lower limit of 3 (8 s).
	
- mode option
	
- Pass the option to a reference clock driver, where option is
		an integer in the range from 0 to 255, inclusive. This option is valid
		only with type r addresses.
	
- noselect
	
- Marks the server or peer to be ignored by the selection algorithm but visible
		to the monitoring program. This option is ignored with the broadcast command.
	
- preempt
	
- Specifies the association as preemptable rather than the default persistent.
		This option is ignored with the broadcast command and is most useful
		with the manycastclient and pool commands.
	
- prefer
	
- Mark the server as preferred. All other things being equal, this host will
		be chosen for synchronization among a set of correctly operating hosts. See
		the Mitigation Rules and the prefer Keyword page
		for further information. This option is valid only with the server and peer commands.
	
- true
	
- Mark the association to assume truechimer status; that is, always survive
		the selection and clustering algorithms. This option can be used with any association,
		but is most useful for reference clocks with large jitter on the serial port
		and precision pulse-per-second (PPS) signals. Caution: this option defeats
		the algorithms designed to cast out falsetickers and can allow these sources
		to set the system clock. This option is valid only with the server and peer commands.
	
- ttl ttl
	
- This option specifies the time-to-live ttl for the broadcast command
		and the maximum ttl for the expanding ring search used by the manycastclient command.
		Selection of the proper value, which defaults to 127, is something of
		a black art and should be coordinated with the network administrator.
	This option is invalid with type r addresses.
- version version
	
- Specifies the version number to be used for outgoing NTP packets. Versions
		1-4 are the choices, with version 4 the default.
	
- xleave
	
- Operate in interleaved mode (symmetric and broadcast modes only). (see NTP
			Interleaved Modes)
Auxilliary Commands
	- broadcastclient
	
- Enable reception of broadcast server messages to any local interface (type
		b address). Ordinarily, upon receiving a broadcast message for the first
		time, the broadcast client measures the nominal server propagation delay using
		a brief client/server exchange, after which it continues in listen-only mode.
		If a nonzero value is specified in the broadcastdelay command, the
		value becomes the delay and the volley is not executed. Note: the novolley option
		has been deprecated for future enhancements. Note that, in order to avoid
		accidental or malicious disruption in this mode, both the server and client
		should operate using symmetric key or public key authentication as described
		in the Authentication
		Options page. Note that the novolley keyword is incompatible with
		public key authentication.
	
- manycastserver address [...]
	
- Enable reception of manycast client messages (type m)to the multicast group
		address(es) (type m) specified. At least one address is required. Note that,
		in order to avoid accidental or malicious disruption, both the server and client
		should operate using symmetric key or public key authentication as described
		in the Authentication Options page.
	
- multicastclient address [...]
	
- Enable reception of multicast server messages to the multicast group address(es)
		(type m) specified. Upon receiving a message for the first time, the multicast
		client measures the nominal server propagation delay using a brief client/server
		exchange with the server, then enters the broadcast client mode, in which it
		synchronizes to succeeding multicast messages. Note that, in order to avoid
		accidental or malicious disruption in this mode, both the server and client
		should operate using symmetric key or public key authentication as described
		in the Authentication Options page.
Bugs
The syntax checking is not picky; some combinations of ridiculous and even
	hilarious options and modes may not be detected.