多选题Which three statements are true regarding the Network Time Protocol (NTP) in JUNOS platforms?（）AMD5 authentication is supported.BA client always synchronizes to a server even when the difference between the server clock and the local clock differs by a

An SPFILE is a binary file.

An SPFILE cannot reside on a client.

An SPFILE cannot contain static parameters.

An SPFILE can store changes persistently across instance restarts.

An SPFILE can be read by the database server， but it is not written to by the server.

An SPFILE must be created manually， before creating a database， even if you use the DatabaseConfiguration Assistant （DBCA） to create the database.

Global buffers such as the InnoDB buffer pool are allocated after the server starts, and are never freed

Thread buffers are allocated when a client connects, and are freed when the client disconnects

Buffers that are needed for certain operation are allocated when the operation starts, and freed when it ends

User buffers are allocated at server startup and freed when the user is dropped

All dynamic buffers that are set with a SET GLOBAL statement immediately get allocated globally, and are never freed

MD5 authentication is supported.

A client always synchronizes to a server even when the difference between the server clock and the local clock differs by a large amount.

JUNOS software can provide a primary time reference.

The boot-server configuration allows a router to synchronize its clock when it boots up, regardless of the offset between the NTP clock source and its internal clock.

It is useful to correlate timestamps on log files and other events for troubleshooting and forensics.

Utilizing Syslog improves network performance.

The Syslog server automatically notifies the network administrator of network problems.

A Syslog server provides the storage space necessary to store log files without using router disk space.

There are more Syslog messages available within Cisco IOS than there are comparable SNMP trap messages.

Enabling Syslog on a router automatically enables NTP for accurate time stamping。

A Syslog server helps in aggregation of logs and alerts.

MD5 authentication is supported by the Junos OS

Server mode is not supported by the Junos OS

The Junos OS can provide a primary time reference

The Junos OS does not support the use of a boot server

Multicast addresses 224.0.1.0 through 238.255.255.255 are called globally scoped addresses. They are used to multicast data between organizations and across the Internet

The multicast address 224.0.0.1 is a globally scoped address that has been reserved for the Network  Time Protocol （NTP） by the IANA

Multicast addresses 239.0.0.0 through 239.255.255.255 are called limited scope addresses. They are  constrained to a local group or organization

Multicast addresses 224.0.0.5 and 224.0.0.6 are limited scoped addresses that have been reserved for  OSPF

Multicast addresses 224.0.0.0 through 224.0.0.255 are used for network protocols on local LAN segments. Because they are always transmitted with a Time to Live （TTL） of 1， they are never forwarded  by a router

Up to three external authentication server types can be used simultaneously.

Only one external authentication server type can be used simultaneously.

If the local password database is not configured in the authentication order， and the configured authentication server is unreachable， authentication is not performed.

If the local password database is not configured in the authentication order， and the configured authentication server rejects the authentication request， authentication is not performed

Up to three external authentication server types can be used simultaneously.

Only one external authentication server type can be used simultaneously.

If the local password database is not configured in the authentication order, and the configured authentication server  bypassed.

If the local password database is not configured in the authentication order, and the configured authentication server authentication is rejected.

MD5 authenticaton is supported by the Junos OS

Server mode is not supported by the Junos OS

The Junos OS can provide a primarytime reference

The Junos OS does not support the use of a boot server

NTP updates are sent in the timezone they are collected in，and the syslog server will adjust based  on the input time.

NTP authentication verifies the source，not the recipient.

NTP authentication requires that the recipient has multiple strata clocks to ensure accuracy.

Secure NTP can be configured to use SHA-1 hashing，since NTP is very insecure.

A stratum 0 clock should be configured at the core of every network，so it can connect to an accuratetime source.

The Junos OS supports client, server, and symmetric modes of NTP operation.

Synchronized time on all network devices makes log messages more useful for troubleshooting.

Authentication methods are not supported.

The Junos OS must be used as the primary time reference.