DistOS-2011W NTP - Revision history

Wahmed2: /* References */

2011-03-03T15:44:48Z

References

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	*Wikipedia for Marzullo’s algorithm: http://en.wikipedia.org/wiki/Marzullo's_algorithm Accessed on 13th Feb 2011		*Wikipedia for Marzullo’s algorithm: http://en.wikipedia.org/wiki/Marzullo's_algorithm Accessed on 13th Feb 2011

			*Linux Home Networking : "How To : NTP Server" : http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch24_:_The_NTP_Server Accessed on 15 Feb 2011

Wahmed2: /* Conclusion */

2011-03-01T05:19:07Z

Conclusion

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	They main problem of NTP is under heavy load, constantly changing offsets may cause frequent clock re-adjustments by NTP. Each time it re-adjust, packets transmitted at later time may have smaller time stamps than packets transmitted earlier resulting in interfere with path monitoring. Future plan is to Global Positioning System receivers for clock synchronization among edge routers.		They main problem of NTP is under heavy load, constantly changing offsets may cause frequent clock re-adjustments by NTP. Each time it re-adjust, packets transmitted at later time may have smaller time stamps than packets transmitted earlier resulting in interfere with path monitoring. Future plan is to Global Positioning System receivers for clock synchronization among edge routers.

			Whether its traffic in air or ground or buying selling things carefully coordinated , reliable and accurate time is vital. In some cases ill-gotten time might cause DNS caches to to expire and entire internet to implode on the root servers , which was one of the threat on the eve of millennium in 1999. Critical data files might expire before they are created, and an electronic message might arrive before it was sent. Reliable and accurate computer time is necessary for any real-time distributed computer application, which is what much of our public infrastructure has become.

	=References=		=References=

Wahmed2: /* Conclusion */

2011-02-28T19:45:25Z

Conclusion

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	=Conclusion=		=Conclusion=

	Overall, there has been lots of work going on NTP , due to high demand of distributed clinet-server architect based application. This was carried on a very small linux based lab , in future i guess there will be need to test on large industry based scale , where many systems can be connected and than test to see how the delay from clients to server causes disturbance in algorithm. There will be issues for sure since as the information travels it takes time and that delayed time will need to be adjusted more and will be focus of future work.		Overall, there has been lots of work going on NTP , due to high demand of distributed clinet-server architect based application. This was carried on a very small linux based lab , in future I guess there will be need to test on large industry based scale , where many systems can be connected and than test to see how the delay from clients to server causes disturbance in algorithm. There will be issues for sure since as the information travels it takes time and that delayed time will need to be adjusted more and will be focus of future work. The most important feature of NTP relevant to this paper is its scalability: its phase lock loop clock discipline is designed for small scale networks so that NTP can maintain low offsets among clocks, even if propagation delays increase significantly.

			They main problem of NTP is under heavy load, constantly changing offsets may cause frequent clock re-adjustments by NTP. Each time it re-adjust, packets transmitted at later time may have smaller time stamps than packets transmitted earlier resulting in interfere with path monitoring. Future plan is to Global Positioning System receivers for clock synchronization among edge routers.

	=References=		=References=

Wahmed2: /* 3.2 Client */

2011-02-22T18:38:30Z

3.2 Client

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	==~~3.2~~ Client==		== Client==

	There are also two clients for our LLTP, level2 client and level3 client. Level3 client is very straight forward where the level3 is a bit more complicated.		There are also two clients for our LLTP, level2 client and level3 client. Level3 client is very straight forward where the level3 is a bit more complicated.

Wahmed2: /* Development Details */

2011-02-22T18:38:05Z

Development Details

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	= Development Details=		= Development Details=

	*3.1 Server		== Server==

	As it is mentioned in section-2, there are two servers in our LLTP model. One is level 1 and the other is level 2. Both servers wait for a client with time requests and upon receiving one send the time string. Code structure for both the servers is almost similar with minor technical differences which are explained later in this section. Both servers use a infinite for loop for waiting for the		As it is mentioned in section-2, there are two servers in our LLTP model. One is level 1 and the other is level 2. Both servers wait for a client with time requests and upon receiving one send the time string. Code structure for both the servers is almost similar with minor technical differences which are explained later in this section. Both servers use a infinite for loop for waiting for the
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	*3.2 Client		==3.2 Client==

	There are also two clients for our LLTP, level2 client and level3 client. Level3 client is very straight forward where the level3 is a bit more complicated.		There are also two clients for our LLTP, level2 client and level3 client. Level3 client is very straight forward where the level3 is a bit more complicated.
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	[[File:level2clientcode2.jpg]]		[[File:level2clientcode2.jpg]]

	*3.3 Daemon client and server		== Daemon client and server==

	The level2 client and server runs as a daemon process to give them the privilege to run continuously in the background. As both the client and server in level2 does not need any user interference and need to run all the time to update the system clock of the running computer from the level1 server.		The level2 client and server runs as a daemon process to give them the privilege to run continuously in the background. As both the client and server in level2 does not need any user interference and need to run all the time to update the system clock of the running computer from the level1 server.
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	[[File:codefordaemon.jpg]]		[[File:codefordaemon.jpg]]

	*3.4 Marzullo’s algorithm and function marzullo(long [])		== Marzullo’s algorithm and function marzullo(long []) ==

	Marzullo’s algorithm, invented by Keith Marzullo, is an agreement algorithm used to select sources for estimating accurate time from a number of noisy time sources. A modified version of his algorithm, intersection algorithm, is use in NTP. We used the simplified version of this algorithm to choose the best possible time from our time sources (level1 servers).		Marzullo’s algorithm, invented by Keith Marzullo, is an agreement algorithm used to select sources for estimating accurate time from a number of noisy time sources. A modified version of his algorithm, intersection algorithm, is use in NTP. We used the simplified version of this algorithm to choose the best possible time from our time sources (level1 servers).

Wahmed2: /* 2.5 Level 3 client */

2011-02-22T18:35:25Z

2.5 Level 3 client

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	Each level2 server is connected to 4 level1 servers. It polls time from each level1 server and chooses the best time and synchronizes its system clock. How the best time is achieved is described in the section 3 below with code explanation. There are maximum 5 level2 servers with our LLTP model. Each level2 server is connected to 4 different level1 servers. None of the level2 server has the same level1 server set.		Each level2 server is connected to 4 level1 servers. It polls time from each level1 server and chooses the best time and synchronizes its system clock. How the best time is achieved is described in the section 3 below with code explanation. There are maximum 5 level2 servers with our LLTP model. Each level2 server is connected to 4 different level1 servers. None of the level2 server has the same level1 server set.

	==~~2.5~~ Level 3 client==		== Level 3 client==

	Bottom of the LLTP hierarchy is level3 client. It only runs a client program that polls time from the level2 servers. It can only connect/request time from one of our level2 servers at a time. It also requires the knowledge of the IP address of the level2 server. For the load management purpose level 3 clients are not able to connect to a Level1 servers.		Bottom of the LLTP hierarchy is level3 client. It only runs a client program that polls time from the level2 servers. It can only connect/request time from one of our level2 servers at a time. It also requires the knowledge of the IP address of the level2 server. For the load management purpose level 3 clients are not able to connect to a Level1 servers.

Wahmed2: /* 2.4 Level 2 server and client */

2011-02-22T18:35:17Z

2.4 Level 2 server and client

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	[[File:LTTPHireachy.jpg]]		[[File:LTTPHireachy.jpg]]

	==~~2.4~~ Level 2 server and client==		== Level 2 server and client==

	Level 2 servers run two different programs. A client program to synchronize its system clock with the level1 servers and a server program that waits for any level 3 client for time request. Upon the request it sends its synchronized system time to the client. Level 2 servers also synchronize its system clock with the other level2 servers.		Level 2 servers run two different programs. A client program to synchronize its system clock with the level1 servers and a server program that waits for any level 3 client for time request. Upon the request it sends its synchronized system time to the client. Level 2 servers also synchronize its system clock with the other level2 servers.

Wahmed2: /* 2.3 Level 1 server */

2011-02-22T18:35:04Z

2.3 Level 1 server

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	My target is to develop a time synchronizing software for a small office or lab with a large number of computer where a very few computer has internet connectivity but all the computers are connected together in a local network. As a result not all the computer is able to connect to internet for time accuracy. LLTP uses similar hierarchical, semi-layered sources as NTP. Each layer of this hierarchy is termed as level and assigned a layer number starting with 1.		My target is to develop a time synchronizing software for a small office or lab with a large number of computer where a very few computer has internet connectivity but all the computers are connected together in a local network. As a result not all the computer is able to connect to internet for time accuracy. LLTP uses similar hierarchical, semi-layered sources as NTP. Each layer of this hierarchy is termed as level and assigned a layer number starting with 1.

	==~~2.3~~ Level 1 server==		== Level 1 server==

Wahmed2: /* 2.2 Structure */

2011-02-22T18:34:55Z

2.2 Structure

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	The 64-bit timestamps used by NTP consist of a 32-bit second part and a 32-bit fractional second part. I followed the same time structure for our LLTP which gives us a time scale of 232 seconds (136 years) and a theoretical resolution of 2-32 seconds (233 picoseconds).		The 64-bit timestamps used by NTP consist of a 32-bit second part and a 32-bit fractional second part. I followed the same time structure for our LLTP which gives us a time scale of 232 seconds (136 years) and a theoretical resolution of 2-32 seconds (233 picoseconds).

	==~~2.2~~ Structure==		== Structure==

	NTP uses a hierarchical, semi-layered system of levels of clock sources; each level of this hierarchy is termed a stratum and assigned a layer number starting with 0 at the top. The stratum level defines its distance from the reference clock and exists to prevent cyclical dependencies in hierarchy.		NTP uses a hierarchical, semi-layered system of levels of clock sources; each level of this hierarchy is termed a stratum and assigned a layer number starting with 0 at the top. The stratum level defines its distance from the reference clock and exists to prevent cyclical dependencies in hierarchy.

	My target is to develop a time synchronizing software for a small office or lab with a large number of computer where a very few computer has internet connectivity but all the computers are connected together in a local network. As a result not all the computer is able to connect to internet for time accuracy. LLTP uses similar hierarchical, semi-layered sources as NTP. Each layer of this hierarchy is termed as level and assigned a layer number starting with 1.		My target is to develop a time synchronizing software for a small office or lab with a large number of computer where a very few computer has internet connectivity but all the computers are connected together in a local network. As a result not all the computer is able to connect to internet for time accuracy. LLTP uses similar hierarchical, semi-layered sources as NTP. Each layer of this hierarchy is termed as level and assigned a layer number starting with 1.

	==2.3 Level 1 server==		==2.3 Level 1 server==

Wahmed2: /* 2.1 NTP timestamps */

2011-02-22T18:34:45Z

2.1 NTP timestamps

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	In this section the background information of Network Time protocol and the hierarchical model and the comparison with the original NTP designed by Dave Mills is reviewed. For unambiguity I will call the protocol as Linux lab time protocol (LLTP) and the original Network time protocol as NTP.		In this section the background information of Network Time protocol and the hierarchical model and the comparison with the original NTP designed by Dave Mills is reviewed. For unambiguity I will call the protocol as Linux lab time protocol (LLTP) and the original Network time protocol as NTP.

	==~~2.1~~ NTP timestamps==		== NTP timestamps==

	The 64-bit timestamps used by NTP consist of a 32-bit second part and a 32-bit fractional second part. I followed the same time structure for our LLTP which gives us a time scale of 232 seconds (136 years) and a theoretical resolution of 2-32 seconds (233 picoseconds).		The 64-bit timestamps used by NTP consist of a 32-bit second part and a 32-bit fractional second part. I followed the same time structure for our LLTP which gives us a time scale of 232 seconds (136 years) and a theoretical resolution of 2-32 seconds (233 picoseconds).