I Pv6 Nd


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Unit 2 Of ACN

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  • IP Fields: Source Address MUST be the link-local address assigned to the interface from which this message is sent. Destination Address Typically the Source Address of an invoking Router Solicitation or the all-nodes multicast address. Hop Limit 255 Authentication Header If a Security Association for the IP Authentication Header exists between the sender and the destination address, then the sender SHOULD include this header. Narten, et. al. Standards Track [Page 18] RFC 2461 Neighbor Discovery for IPv6 December 1998 ICMP Fields: Type 134 Code 0 Checksum The ICMP checksum. See [ICMPv6]. Cur Hop Limit 8-bit unsigned integer. The default value that should be placed in the Hop Count field of the IP header for outgoing IP packets. A value of zero means unspecified (by this router). M 1-bit "Managed address configuration" flag. When set, hosts use the administered (stateful) protocol for address autoconfiguration in addition to any addresses autoconfigured using stateless address autoconfiguration. The use of this flag is described in [ADDRCONF]. O 1-bit "Other stateful configuration" flag. When set, hosts use the administered (stateful) protocol for autoconfiguration of other (non-address) information. The use of this flag is described in [ADDRCONF]. Reserved A 6-bit unused field. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. Router Lifetime 16-bit unsigned integer. The lifetime associated with the default router in units of seconds. The maximum value corresponds to 18.2 hours. A Lifetime of 0 indicates that the router is not a default router and SHOULD NOT appear on the default router list. The Router Lifetime applies only to the router's usefulness as a default router; it does not apply to information contained in other message fields or options. Options that need time limits for their information include their own lifetime fields. Reachable Time 32-bit unsigned integer. The time, in milliseconds, that a node assumes a neighbor is reachable after having received a reachability confirmation. Used by the Neighbor Unreachability Detection algorithm (see Section 7.3). A value of Narten, et. al. Standards Track [Page 19] RFC 2461 Neighbor Discovery for IPv6 December 1998 zero means unspecified (by this router). Retrans Timer 32-bit unsigned integer. The time, in milliseconds, between retransmitted Neighbor Solicitation messages. Used by address resolution and the Neighbor Unreachability Detection algorithm (see Sections 7.2 and 7.3). A value of zero means unspecified (by this router). Possible options: Source link-layer address The link-layer address of the interface from which the Router Advertisement is sent. Only used on link layers that have addresses. A router MAY omit this option in order to enable inbound load sharing across multiple link-layer addresses. MTU SHOULD be sent on links that have a variable MTU (as specified in the document that describes how to run IP over the particular link type). MAY be sent on other links. Prefix Information These options specify the prefixes that are on-link and/or are used for address autoconfiguration. A router SHOULD include all its on-link prefixes (except the link-local prefix) so that multihomed hosts have complete prefix information about on- link destinations for the links to which they attach. If complete information is lacking, a multihomed host may not be able to choose the correct outgoing interface when sending traffic to its neighbors.
  • I Pv6 Nd

    1. 1. IPv6 Neighbour Discovery by R Radhakrishnan KRISHNA INSTITUTE OF ENGINEERING AND TECHNOLOGY
    2. 2. IPv6 Neighbour Discovery <ul><li>IPv6 Neighbor Discovery (ND) is a set of messages and processes that determine relationships between neighboring nodes. </li></ul><ul><li>ND replaces ARP, ICMP Router Discovery, and ICMP Redirect used in IPv4 and provides additional functionality </li></ul>
    3. 3. Functions of ND
    4. 4. Functions of ND <ul><li>The Neighbor Discovery protocol has nine individual functions, many of which are related to each other. </li></ul><ul><li>They are organized into three functional groups: </li></ul><ul><ul><li>host-router discovery functions </li></ul></ul><ul><ul><li>host-host communication functions </li></ul></ul><ul><ul><li>the redirect function. </li></ul></ul>
    5. 5. Host-Router Discovery Functions <ul><li>Facilitate the discovery of local routers and the exchange of information between them and hosts. This includes four specific functions: </li></ul><ul><ul><li>1. Router Discovery: This is the core function of this group: the method by which hosts locate routers on their local network </li></ul></ul><ul><ul><li>2. Prefix Discovery: Hosts use this function to determine what network they are on, which in turn tells them how to differentiate between local and distant destinations and whether to attempt direct or indirect delivery of datagrams </li></ul></ul>
    6. 6. Host-Router Discovery Functions <ul><ul><li>3. Parameter Discovery: A function by which a host learns important parameters about the local network and/or routers, such as the MTU of the local link. </li></ul></ul><ul><ul><li>4. Address Autoconfiguration: Hosts in IPv6 are designed to be able to automatically configure themselves, but this requires information that is normally provided by a router. </li></ul></ul>
    7. 7. Host-Host Communication Functions <ul><li>1. Address Resolution: A device determines the L2 address of another device on the local network from that device's L3 address. Equivalent to ARP in IPv4. </li></ul><ul><li>2. Next-Hop Determination: The method for looking at an IP datagram's destination address and determining where it should next be sent. </li></ul><ul><li>3. Neighbor Unreachability Detection: The process of determining whether or not a neighbor device can be directly contacted. </li></ul><ul><li>4. Duplicate Address Detection: Determining if an address that a device wishes to use already exists on the network. </li></ul>
    8. 8. Redirection <ul><li>1. Redirect Function : A technique whereby a router informs a host of a better next-hop node to use for a particular destination </li></ul>
    9. 9. ICMPv6 Messages Used By the NDP <ul><li>Router Advertisement Messages: Sent regularly by routers to tell hosts that they exist and provide important prefix and parameter information to them. </li></ul><ul><li>Router Solicitation Messages: Sent by hosts to request that any local routers send a Router Advertisement message. </li></ul><ul><li>Neighbor Advertisement Messages: Sent by hosts to indicate the existence of the host and provide information about it. </li></ul><ul><li>Neighbor Solicitation Messages: Sent to verify the existence of another host and to ask it to transmit a Neighbor Advertisement. </li></ul><ul><li>Redirect Messages: Sent by a router to tell a host of a better method to route data to a particular destination. </li></ul>
    10. 10. Router Solicitation Type = 133 Code = 0 Checksum Reserved Possible option: Source Link Layer Address
    11. 11. Router Advertisement Type = 134 Code = 0 Checksum Cur. Hop Limit M O Reserved Router Lifetime Reachable Time Retransmission Timer <ul><li>Possible options: </li></ul><ul><li>-Source Link Layer Address </li></ul><ul><li>MTU </li></ul><ul><li>Prefix Information </li></ul>
    12. 12. Neighbor Solicitation Type = 135 Code = 0 Checksum Reserved Target Address Possible option: Source Link Layer Address
    13. 13. Neighbor Advertisment Type = 136 Code = 0 Checksum R S O Reserved Target Address Possible option: Source Link Layer Address
    14. 14. Prefix Option Type Length Prefix Length L A Reserved Valid Lifetime Preferred Lifetime Reserved Prefix List
    15. 15. What is AR ? <ul><li>Communication On an internetwork is done by sending data at layer three using a N/W layer address. </li></ul><ul><li>The actual transmission of data occurs at layer two using a DLL address. </li></ul><ul><li>It is necessary to define some way of being able to link these two addresses. </li></ul><ul><li>This is done by taking a network layer address and determining what DLL address goes with it, this process is called address resolution. </li></ul>
    16. 16. Why addressing is done at two different layers? <ul><li>As they are very different types of addresses those are used for diff. Purposes. </li></ul><ul><li>Layer two addresses(IEEE 802 MAC addresses)are used for local transmission b/w h/w devices that can communicate directly. </li></ul><ul><li>In contrast layer three addresses(IP addresses) are used in internetworking. </li></ul>
    17. 17. Why AR is necessary? <ul><li>If a client on the local n/w is accessing a server somewhere on the internet. </li></ul><ul><li>Logically this connection can be made directly b/w the client and server. </li></ul><ul><li>But in reality is a sequence of physical links at layer two. </li></ul><ul><li>At each step the decision of where to send the data is made based on a layer three address. </li></ul><ul><li>But the actual transmission must be performed using layer two address. </li></ul>
    18. 18. Dynamic Address Resolution <ul><li>Dynamic address resolution is usually implemented using a special protocol. </li></ul><ul><li>A device that knows only the n/w layer address of another device can use this protocol to request the other device’s h/w address. </li></ul>
    19. 19. LAN Switch Device C IP address: IPC H/W address: #46 Device A IP address: IPA H/W address: #43 Device B IP address: IPB H/W address: #79 Device D IP address: IPD H/W address: #48 Who is IPB? IPB is #79
    20. 20. Dynamic Address Resolution(Contd.) <ul><li>In the previous device A has to send the data to device B but knows only its IP address (“IPB”),and not its H/W address. A broadcast request asking to be send to the H/W address of the device using the IP address “IPB”.B responds back to A directly with the H/W address. </li></ul>
    21. 21. About ARP <ul><li>ARP is a relatively simple request/reply protocol.The source device broadcasts an ARP request looking for a particular device based on it IP address.The device responds with its h/w address in an ARP reply message. </li></ul>
    22. 22. Solicited-Node Address
    23. 23. Solicited-node multicast address from link local address <ul><li>A Node with link-local address of FE80::2AA:FF:FE 28:9C5A </li></ul><ul><li>also listens on the corresponding solicited-node multicast address of FF02::1:FF 28:9C5A </li></ul>
    24. 24. AR in IPv6 <ul><li>Address resolution in IPv6 uses the new Neighbor Discovery (ND) protocol instead of the Address Resolution Protocol. </li></ul><ul><li>A device trying to send an IPv6 datagram sends a Neighbor Solicitation message to get the address of another device </li></ul><ul><li>The device responds with a Neighbor Advertisement . </li></ul><ul><li>The request is sent using a solicited-node multicast address rather than broadcast, to improve efficiency. </li></ul>
    25. 25. AR in IPv6 <ul><li>Host A MAC address: 00-AA-00-11-11-11 </li></ul><ul><li>Link-local address of FE80::2AA:FF:FE11:1111. </li></ul><ul><li>Host B MAC address: 00-AA-00-22-22-22 </li></ul><ul><li>Link-local address: FE80::2AA:FF:FE22:2222. </li></ul><ul><li>To send a packet to Host B, Host A must use address resolution to resolve Host B’s link-layer address. </li></ul><ul><li>Based on Host B’s IP address, Host A sends a solicited-node multicast Neighbor Solicitation to the IP address :-FF02::1:FF22:2222 and MAC address 33-33-FF-22-22-22 </li></ul>
    26. 27. Processing by Node B Host B, having registered the solicited-node multicast address of 33-33-FF-22-22-22 with its Ethernet adapter, receives and processes the Neighbor Solicitation. Host B responds with a unicast Neighbor Advertisement message
    27. 29. lifetimes for an autoconfigured address
    28. 30. Auto configuration process <ul><li>A tentative link-local address is derived based on the link-local prefix of FE80::/64 and the 64-bit interface identifier. </li></ul><ul><li>Using duplicate address detection </li></ul><ul><ul><li>to verify the uniqueness of the tentative link-local address </li></ul></ul><ul><ul><li>Neighbor Solicitation message is sent with the Target Address field that is set to the tentative link-local address </li></ul></ul>
    29. 31. Auto configuration process <ul><li>If a Neighbor Advertisement message sent in response to the Neighbor Solicitation message is received, this indicates that another node on the local link is using the tentative link-local address and address autoconfiguration stops. At this point, manual configuration must be performed on the node </li></ul>
    30. 32. Auto configuration process <ul><li>If no Neighbor Advertisement message is received, the tentative link-local address is assumed to be unique and valid. </li></ul><ul><li>The link-local address is initialized for the interface. </li></ul><ul><li>The corresponding solicited-node multicast link-layer address is registered with the network adapter. </li></ul>
    31. 33. Auto address continues <ul><li>The host sends up to 3 Router Solicitation messages (by default). </li></ul><ul><li>If no Router Advertisement messages are received, then the host uses a stateful address configuration protocol to obtain addresses and other configuration parameters. </li></ul><ul><li>If a Router Advertisement message is received, the Hop Limit, Reachable Time, Retrans Timer, and the MTU (if the MTU option is present) are set. </li></ul><ul><li>Uniqueness determined for each prefix </li></ul>
    32. 34. Address auto-configuration <ul><li>Avoids Manual configuration of individual machines before connecting them to the network. </li></ul><ul><ul><li>Address auto-configuration assumes that each interface has an unique ID </li></ul></ul><ul><li>Plug-and-play communication is achieved through the use of link-local addresses </li></ul><ul><ul><li>Small sites should not need stateful servers </li></ul></ul><ul><li>A large site with multiple networks and routers should not require the presence of a stateful address configuration server. </li></ul><ul><li>Address configuration should facilitate the graceful renumbering of a site's machines </li></ul>
    33. 35. Stateless Autoconfiguration Generate a link local address Verify this tentative address is OK. Use a neighbor solicitation with the tentative address as the target. ICMP type 135 If the address is in use a neighbor advertisement message will be returned. ICMP type 136 If no response, assign the address to the interface. At this point the node can communicate on-link. Fail and go to manual configuration or choose a different interface token.
    34. 36. Stateless Autoconfiguration Assign address to interface. Node joins the All Routers multicast group. FF02::1 Sends out a router solicitation message to that group. ICMP type 133 Router responds with a router advertisement. ICMP type 134
    35. 37. Stateless Autoconfiguration Look at the “managed address configuration&quot; flag If M = 0 proceed with stateless configuration If M = 1 stop and do stateful config Look at &quot;other stateful configuration&quot; flag If O = 0 finish If O = 1 use stateful configuration for other information
    36. 38. Stateless Autoconfig <ul><li>Routers are to send out router advertisements at regular intervals to the all-hosts address. </li></ul><ul><ul><li>This should update lifetimes. </li></ul></ul><ul><li>Note that stateless autoconfig will only configure addresses. </li></ul><ul><ul><li>It will not do all the host configuration you may well want to do. </li></ul></ul><ul><li>RFC 2462 defines IPv6 Stateless Autoconfig </li></ul>