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16-454: ICMPv6 has a framework for extensions to implement new features. Several extensions have been published, defining new ICMPv6 message types as well as new options for existing ICMPv6 message types. For example, Neighbor Discovery Protocol (NDP) is a node discovery protocol based on ICMPv6 which replaces and enhances functions of ARP . Secure Neighbor Discovery (SEND) is an extension of NDP with extra security. Multicast Listener Discovery (MLD)

32-539: A pseudo-header of IPv6 header fields according to the IPv6 standard, which consists of the source and destination addresses, the packet length and the next header field, the latter of which is set to the value 58 . Following this pseudo header, the checksum is continued with the ICMPv6 message. The checksum computation is performed according to Internet protocol standards using 16-bit ones' complement summation, followed by

48-473: A cryptographic method that is independent of IPsec . Neighbor Discovery Proxy (ND Proxy) provides a service similar to IPv4 Proxy ARP and allows bridging multiple network segments within a single subnet prefix when bridging cannot be done at the link layer. NDP defines five ICMPv6 packet types for the purpose of router solicitation, router advertisement, neighbor solicitation, neighbor advertisement, and network redirects. These messages are used to provide

64-533: A final ones' complement of the checksum itself and inserting it into the checksum field. Note that this differs from the way it is calculated for IPv4 in ICMP , but is similar to the calculation done in TCP . The payload of an ICMPv6 message varies according the type of message being sent. It begins at bit 32 immediately after the header described above. For some messages such as destination unreachable or time exceeded there

80-454: A fixed network maximum load. An ICMP error message must never be sent in response to another ICMP error message. Neighbor Discovery Protocol The Neighbor Discovery Protocol ( NDP ), or simply Neighbor Discovery ( ND ), is a protocol of the Internet protocol suite used with Internet Protocol Version 6 (IPv6). It operates at the internet layer of the Internet model , and

96-453: Is no defined message body. Others define a use only for the first four bytes of the body with no other defined content: In the case of NDP messages the first four bytes are either reserved or used for flags/hoplimit. While the reset of body has unspecified structured data: For a redirect the first bytes of the message body are reserved but not used. This is followed by a Target and destination address. Unspecified options can be attached to

112-670: Is responsible for gathering various information required for network communication, including the configuration of local connections and the domain name servers and gateways. The protocol defines five ICMPv6 packet types to perform functions for IPv6 similar to the Address Resolution Protocol (ARP) and Internet Control Message Protocol (ICMP) Router Discovery and Router Redirect protocols for IPv4 . It provides many improvements over its IPv4 counterparts. For example, it includes Neighbor Unreachability Detection (NUD), thus improving robustness of packet delivery in

128-524: Is set to the value 58 . The ICMPv6 message consists of a header and the protocol payload. The header contains only three fields: Type (8 bits), Code (8 bits), and Checksum (16 bits). Control messages are identified by the value in the type field. The code field gives additional context information for the message. Some messages serve the same purpose as the correspondingly named ICMP message types. There are two subtypes of Multicast Listener Query messages: These two subtypes are differentiated by

144-538: Is used by IPv6 routers for discovering multicast listeners on a directly attached link, much like Internet Group Management Protocol (IGMP) is used in IPv4 . Multicast Router Discovery (MRD) allows the discovery of multicast routers. ICMPv6 messages may be classified as error messages and information messages . ICMPv6 messages are transported by IPv6 packets in which the IPv6 Next Header value for ICMPv6

160-507: The IP address 2001:db8::55 . To send the message, it also requires Computer 2's MAC address . First, Computer 1 uses a cached NDP table to look up 2001:db8::55 for any existing records of Computer 2's MAC address ( 00:EB:24:B2:05:AC ). If the MAC address is found, it sends an Ethernet frame containing the IP packet onto the link with the destination address 00:EB:24:B2:05:AC . If

176-445: The cache did not produce a result for 2001:db8::55 , Computer 1 has to create a solicited-node multicast address by taking the least-significant 24 bits of Computer 2's address and appending them to the prefix ff02::1:ff00:0 / 104 , which is ff02::1:ff00:55 , and create a solicited-node multicast MAC address by taking the least-significant 24 bits of Computer 2's solicited-node multicast address and appending them to

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192-471: The contents of the Multicast Address field, as described in section 3.6 of RFC 2710 Note that the table above is not comprehensive. The current complete list of assigned ICMPv6 types can be found at this link: IANA: ICMPv6 Parameters . ICMPv6 provides a minimal level of message integrity verification by the inclusion of a 16-bit checksum in its header. The checksum is calculated starting with

208-405: The end: When an ICMPv6 node receives a packet, it must undertake actions that depend on the type of message. The ICMPv6 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

224-410: The following functionality: IANA maintains a list of all current NDP options as they are published. Two computers in an office ( Computer 1 and Computer 2 ) are connected to each other in a local area network by Ethernet cables and network switches , with no intervening gateways or routers . Computer 1 has a packet to send to Computer 2 . Through DNS, it determines that Computer 2 has

240-485: The prefix 33:33:FF:xx:xx:xx , which is 33:33:FF:00:00:55 , and send a neighbor solicitation message requesting an answer for 2001:db8::55 (destination ff02::1:ff00:55 IP address and destination 33:33:FF:00:00:55 MAC address), which is accepted by Computer 2 which is listening on its own solicited-node multicast address on the local network. Computer 2 responds with a neighbor advertisement message containing its MAC and IP addresses. As part of fielding

256-588: The presence of failing routers or links, or mobile nodes. The Inverse Neighbor Discovery ( IND ) protocol extension allows nodes to determine and advertise an IPv6 address corresponding to a given link-layer address, similar to Inverse ARP for IPv4. The Secure Neighbor Discovery Protocol (SEND), a security extension of NDP, uses Cryptographically Generated Addresses (CGA) and the Resource Public Key Infrastructure (RPKI) to provide an alternative mechanism for securing NDP with

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