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Murali B.V.S

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 Agenda History 

 What is the Diff b/w NTP and SNTP

How NTP works?

Internals of NTP

 About Brocade SNTP

Limitations

Configurations

Display Commands

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Introduction…  Normally PC maintains two types of clocks internally 

Software Clock

Hardware clock

The software clock runs when the computer is turned on andstops when the computer is turned off.

 The hardware clock uses a battery and runs even while thecomputer is turned off.

Both clock times are not unique.

 What is the need for standard and Accurate time ?  What are the protocols are supported for this ?

Three major timing protocols are supported.

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Timing protocols… 

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NTP - Introduction• NTP is a protocol for synchronizing the clocks on computers

over packet-switched data networks

• NTP delivers accurate and reliable time in spite of faults inthe network

• Provides a connectionless service (UDP in the TransportLayer)

• NTP is used on Internet

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NTP - Clock Strata

NTP uses a hierarchical organization of clocks• Stratum 0.- Composed by: Atomic Clocks, GPS Clocks.

• Stratum 1 - Primary • Time Servers.- Computers attached to stratus 0 devices

• They act as servers for requests from Stratus 2

• Stratum 2• Computers sending NTP requests to Time Servers in Stratum 1

•

Computers in this level will reference to several time servers tosynchronize their clocks

• S2 Computers will peer with another S2 computers to providemore reliable and robust time for all devices in the peer group

• They act as servers for requests from Stratus 3

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NTP - Clock Strata•

Stratum 3, 4, … • Computers employ the same NTP function as in Stratum 2

• Potentially up to 16 levels

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NTP - Determining Time

Timestamps exchanged between the server and clients(subnet peers)

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NTP Data packet  LI = leap indicator VN = version numberStrat = Stratum (0-15)Poll = poll intervallPrec = Precision

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Diff b/w NTP and SNTP

NTP : Network Time Protocol (RFC 1305) SNTP : Simple Network Time Protocol (RFC 4330)

Imp Points: NTP protocol packets are entirely interchangeable with SNTP protocol

packets. a NTP server cannot differentiate a request for time originating from a

NTP client or SNTP client.

The difference between the NTP and SNTP protocols lie in thealgorithms used to implement the protocols.

NTP uses complex algorithms to calculate accurate time.

SNTP is a simplified sub-set of the algorithms used by the NTPprotocol.

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Contd.. SNTP is ideal for synchronising computers at the leaves of a

network.

It is ideally suited to less powerful processors, such as micro-controllers and embedded systems, which do not require the

accuracy of NTP.

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Limitations… 

The Brocade device can be configured both as an SNTP serverand as an SNTP client.

Brocade device to consult up to three SNTP servers for thecurrent system time and date.

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Config and Display

SNTP as a client :

Command : sntp server 208.99.8.95

Syntax: [no] sntp server { <ip-address> | <hostname> | ipv6 <ipv6-address> } [<sntp-version>] [ authentication-key <key-ID> <key-

string>] SNTP as a Server :

Command : sntp server-mode use-local-clock authentication-key abc123

Syntax: [no] sntp server-mode [ use-local-clock [ stratum <stratum-number> ] ] [ authentication-key <key-string> ] 

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Contd

Display Commands

show sntp associations

show sntp status

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Contd..

SNTP Server Information… 

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