Derwick Associates and ICMPv6: Difference between pages

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Revision as of 00:09, 6 March 2013 editFergusM1970 (talk \| contribs)4,665 edits This is ridiculous. Yet again Justiciero has tossed out every edit to restore his attack piece. Please STOP IT and discuss your edits before undoing so much work.		Revision as of 23:53, 20 May 2006 edit HannS (talk \| contribs)56 editsNo edit summary
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			The '''ICMPv6''' ('''Internet Control Message Protocol Version 6''') is an integral part of the ] architecture2 and must be completely supported by all IPv6 implementations. ICMPv6 combines functions previously subdivided among different protocols, such as ] (Internet Control Message Protocol version 4), ] (Internet Group Membership Protocol)4, and ] (Address Resolution Protocol), and it introduces some simplifications by eliminating obsolete types of messages no longer in use.
	{{Infobox company
	\| name = Derwick Associates
	\| native_name = Derwick Associates de Venezuela SA
	\| trading_name =
	\| logo = ]
	\| caption =
	\| type =
	\| traded_as =
	\| genre = <!-- Only used with media and publishing companies -->
	\| fate =
	\| predecessor =
	\| successor =
	\| foundation =
	\| founder = Leopoldo Betancourt López<br>Pedro Trebbau López
	\| defunct = <!-- {{End date\|YYYY\|MM\|DD}} -->
	\| location_city =
	\| location_country = ]
	\| locations =
	\| area_served =
	\| key_people =
	\| industry = ]
	\| products = Electrical power<br />Natural gas
	\| production =
	\| services = Engineering<br>Power-plant construction
	\| revenue =
	\| operating_income =
	\| net_income =
	\| aum = <!-- Only used with financial services companies -->
	\| assets =
	\| equity =
	\| owner =
	\| num_employees =
	\| parent =
	\| divisions =
	\| subsid =
	\| homepage = {{URL\|derwickassociates.com/}}
	\| footnotes =
	\| intl =
	}}

			ICMPv6 is a multipurpose protocol; for example, it is used for reporting errors encountered in processing packets, performing diagnostics, performing Neighbor Discovery, and reporting multicast memberships. For this reason, ICMPv6 messages are subdivided into two classes: ''error messages'' and ''information messages''.
	'''Derwick Associates''' is a ] ] company. During an energy crisis in Venezuela in 2009-2010, Derwick won several contracts to construct and provide supplies for a number of ] in that country.<ref name=UltimasNoticias>{{cite web \|url=http://www.ultimasnoticias.com.ve/noticias/actualidad/economia/compras-con-sobreprecio-en-la-emergencia-elect--1-.aspx \|title=Compras con sobreprecio en la emergencia eléctrica \|author=César Batiz \|date=September 26, 2011 \|publisher=Ultimas Noticias \|accessdate=November 25, 2012}}</ref>
			ICMP messages are transported within an ] ] in which extension headers can also be present. An ] message is identified by a value of 58 in the Next Header field of the ] header or of the preceding Header.

			== Packets Format ==
	==Corporate history==
			ICMPv6 packets have the format '''Type, Code & Checksum'''. The 8-bit '''''Type''''' field indicates the type of the message. If the highorder bit has value zero (values in the range from 0 to 127), it is an error message; if the high-order bit has value 1 (values in the range from 128 to 255), it is an information message. The 8-bit '''''Code''''' field content depends on the message type, and it is used to create an additional level of message granularity. The '''''Checksum''''' field is used to detect errors in the ] message and in part of the ] message.
	Derwick is currently registered in ], ], ] and (although presently inactive there) the USA. In Barbados, where it was registered on May 27, 2009, the company is identified as Derwick Associates Corporation.<ref>Corporate Affairs and Intellectual Property Office, , retrieved 4 Mar 2013.</ref> In Venezuela, where it was registered on October 28, 2009, it is called Derwick Associates de Venezuela SA. In Spain, where it was incorporated on 13 January 2011, it is called Derwick Associates International SRL.<ref>Registro Mercantil Central, , retrieved 4 Mar 2013.</ref> In the U.S., it was registered on December 2, 2010, under the name Derwick Associates USA LLC.<ref>Florida Department of State, Division of Corporations, , retrieved 4 Mar 2013.</ref>

			== Types of ICMP messages ==
	==Directors==
			Type - Meaning <br>
	The following individuals are listed as directors of the firm: Pedro Trebbau López, Leopoldo Alejandro Betancourt López, Gonzalo X. Guzman López, Edgar Romero Lazo, and Iker Candida.<ref name=UltimasNoticias/>
			1 - Destination Unreachable <br>
			2 - Packet Too Big<br>
			3 - Time Exceeded<br>
			4 - Parameter Problem<br>
			128 - Echo Request<br>
			129 - Echo Reply<br>
			130 - Group Membership Query<br>
			131 - Group Membership Report<br>
			132 - Group Membership Reduction<br>
			133 - Router Solicitation<br>
			134 - Router Advertisement<br>
			135 - Neighbor Solicitation<br>
			136 - Neighbor Advertisement<br>
			137 - Redirect<br>

			== ICMP Message Transmission ==
	==Venezuelan power station contract==
			A node that forwards an ICMP message has to determine both the source and the destination ] addresses for the ] message. Particular care must be put into the choice of the source address. If a node has more than one unicast address, it must choose the source address of the message as follows:<br>
	The firm was awarded 12 contracts for such installations in Venezuela during a 2009-2010 energy crisis in that country. Four contracts were awarded by ] (which in December 2011 became part of ]), five by ] SA (PDVSA, with the contract negotiated by Bariven, a division of PDVSA), and one by the ] (CVG).
			* If the message is a response to a message sent to one of the node unicast addresses, the Source Address of the reply must be that same address.
			* If the message is a response to a message sent to a multicast or anycast group to which the node belongs, the Source Address of the reply must be a unicast address belonging to the interface on which the multicast or anycast packet was received.
			* If the message is a response to a message sent to an address that does not belong to the node, the Source Address should be the unichecking the error (for example, the unicast address belonging to the interface on which the packet forwarding failed).
			* In other cases, the node routing tables must be examined to determine which interface will be used to transmit the message to its destination, and the unicast address belonging to that interface must be used as the Source Address of the message.
			<br>
			When an ICMP node receives a packet, it must undertake actions that depend on the type of message. The ICMP protocol must limit the number of error messages sent to the same destination to avoid network overloading. For example, if a node continues to forward erroneous packets, ICMP will signal the error to the first packet and then do so periodically, with a fixed minimum period or with a fixed network maximum load. An ICMP error message must never be sent in response to another ICMP error message.

			== Error Messages ==
	Bariven awarded contracts in 2010 amounting to more than $760 million for power plants to Derwick and two other intermediaries. Of that sum, the contracts awarded to Derwick amounted to $209 million. The $760 million sum included surcharges of over $403 million, of which just under $87 million were surcharges paid to Derwick. There were allegations by a journalist of double billing by Derwick for the same parts,<ref name=UltimasNoticias/> although none of these allegations were backed up by evidence.<ref name=UltimasNoticias/>
			ICMPv6 error messages are similar to ] error messages. They belong to four categories: ''Destination Unreachable, Packet Too Big, Time Exceeded'', and ''Parameter Problems''.

			== Informational Messages ==
	In February 2013 it was reported that Derwick had been largely responsible for the recent increase in generating capacity in the ] metropolitan area.<ref>''El Nacional'', 04 Feb 2013, Retrieved 13 Feb 2013.</ref>
			A second type of ICMP message is the informational message. These messages are subdivided into three groups: ''diagnostic messages, messages for the management of multicast groups'', and ''Neighbor Discovery messages''.

	==~~Donations~~==		==See also==
			* RFC 1885
	In January 2012, Derwick donated funds for the construction of a football field in Sucre.<ref>{{cite web \|url=http://globovision.com/articulo/ocariz-entrega-quinta-cancha-de-futbol-de-grama-artificial-en-sucre \|title=Ocariz entrega quinta cancha de futbol de grama artificial en sucre \|author= \|date= \|publisher= \|accessdate=November 25, 2012}}</ref>

			]
	==References==
			]
	{{Reflist}}

			Contribution of the students of the class ('']'') : Protocolos3 - of (])
	]
	]
	]

Revision as of 23:53, 20 May 2006

The ICMPv6 (Internet Control Message Protocol Version 6) is an integral part of the IPv6 architecture2 and must be completely supported by all IPv6 implementations. ICMPv6 combines functions previously subdivided among different protocols, such as ICMP (Internet Control Message Protocol version 4), IGMP (Internet Group Membership Protocol)4, and ARP (Address Resolution Protocol), and it introduces some simplifications by eliminating obsolete types of messages no longer in use.

ICMPv6 is a multipurpose protocol; for example, it is used for reporting errors encountered in processing packets, performing diagnostics, performing Neighbor Discovery, and reporting multicast memberships. For this reason, ICMPv6 messages are subdivided into two classes: error messages and information messages. ICMP messages are transported within an IPv6 packet in which extension headers can also be present. An ICMP message is identified by a value of 58 in the Next Header field of the IPv6 header or of the preceding Header.

Packets Format

ICMPv6 packets have the format Type, Code & Checksum. The 8-bit Type field indicates the type of the message. If the highorder bit has value zero (values in the range from 0 to 127), it is an error message; if the high-order bit has value 1 (values in the range from 128 to 255), it is an information message. The 8-bit Code field content depends on the message type, and it is used to create an additional level of message granularity. The Checksum field is used to detect errors in the ICMP message and in part of the IPv6 message.

Types of ICMP messages

Type - Meaning
1 - Destination Unreachable
2 - Packet Too Big
3 - Time Exceeded
4 - Parameter Problem
128 - Echo Request
129 - Echo Reply
130 - Group Membership Query
131 - Group Membership Report
132 - Group Membership Reduction
133 - Router Solicitation
134 - Router Advertisement
135 - Neighbor Solicitation
136 - Neighbor Advertisement
137 - Redirect

ICMP Message Transmission

A node that forwards an ICMP message has to determine both the source and the destination IPv6 addresses for the ICMP message. Particular care must be put into the choice of the source address. If a node has more than one unicast address, it must choose the source address of the message as follows:

If the message is a response to a message sent to one of the node unicast addresses, the Source Address of the reply must be that same address.
If the message is a response to a message sent to a multicast or anycast group to which the node belongs, the Source Address of the reply must be a unicast address belonging to the interface on which the multicast or anycast packet was received.
If the message is a response to a message sent to an address that does not belong to the node, the Source Address should be the unichecking the error (for example, the unicast address belonging to the interface on which the packet forwarding failed).
In other cases, the node routing tables must be examined to determine which interface will be used to transmit the message to its destination, and the unicast address belonging to that interface must be used as the Source Address of the message.

When an ICMP node receives a packet, it must undertake actions that depend on the type of message. The ICMP protocol must limit the number of error messages sent to the same destination to avoid network overloading. For example, if a node continues to forward erroneous packets, ICMP will signal the error to the first packet and then do so periodically, with a fixed minimum period or with a fixed network maximum load. An ICMP error message must never be sent in response to another ICMP error message.

Error Messages

ICMPv6 error messages are similar to ICMPv4 error messages. They belong to four categories: Destination Unreachable, Packet Too Big, Time Exceeded, and Parameter Problems.

Informational Messages

A second type of ICMP message is the informational message. These messages are subdivided into three groups: diagnostic messages, messages for the management of multicast groups, and Neighbor Discovery messages.