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    IPv6 IPv6 Document Transcript

    • ReferencesDynamic Host Configuration Protocol for IPv6 (DHCPv6) – RFC 3315Neighbor Discovery (ND) for IP Version 6 (IPv6) – RFC 2461Internet Control Message Protocol for IP Version 6 (ICMPv6) – RFC 2463IPv6 Stateless Address Auto-configuration – RFC 2462IPv6 Addressing Architecture – RFC 3513IPv6 Specification – RFC 2460DOCSIS MULPI spec.BSR_64000_IPv6_Phase-1_Requirements_Specification.docIPv6 Essentials, Silvia HagenSpecial Thanks to Rob Faulds and Vasu Jothilingam Copyright © 2008 Motorola Inc. 111 Locke Drive Marlborough, MA 01752 All Rights Reserved 0
    • The IPv6 Datagram Format :Traffic Class: replaces TOS/Difserv byte. Uses all 8 bits (details to follow)Total length of the IPv4 is removed. IP performs fragmentation indicated in IPv6Fragmentation Header.TTL in IPv4 is changed to Hop Limit in IPv6:Protocol field in IPv4 is handled in IPv6 Next Header (extension headers e.g. router header,fragmentation header, etc.)A new capability is added to enable the labeling of packets belonging to particular traffic"flows" for which the sender requests special handling, such as non-default quality of serviceor "real-time" service.Source IP Address: 128 bit address of the sending device.Destination IP Address: 128 bit address of the final destination.No header checksum as in v4 because it was thought to be redundant. Layer 2 does achecksum that includes all of IP. 1
    • To be used by routers to give preferential treatment to IPv6 packets in the sameway as TOS and DIFSERV. Six bits of the DS field are used as a codepoint(DSCP) to select the PHB a packet experiences at each node. A two-bit currentlyunused (CU) field is reservedClassifiers 22/23/60.12.1From RFC3168:The definitions for the IPv4 TOS octet [RFC791] and the IPv6 Traffic Class octethave been superseded by the six-bit DS (Differentiated Services) Field [RFC2474,RFC2780]. Bits 6 and 7 are listed in [RFC2474] as Currently Unused, and arespecified in RFC 2780 as approved for experimental use for ECN. Section 22gives a brief history of the TOS octet. 2
    • Header extensions allow special handling.Next Header: 8-bit selector. Identifies the type of header immediately following theIPv6 header. Uses the same values as the IPv4 Protocol field. In IPv6, optionalinternet-layer information is encoded in separate headers that may be placedbetween the IPv6 header and the upper- layer header in a packet.Extension Headers: Hop-by-Hop Options, Routing (Type 0), Fragment DestinationOptions, Authentication, Encapsulating Security Payload.Flow Label: The 20-bit Flow Label field in the IPv6 header may be used by asource to label sequences of packets for which it requests special handling by theIPv6 routers, such as non-default quality of service or "real-time" service. Similarto an MPLS label. Can be used to identify flows for classification.Next Hop: 8-bit unsigned integer. Decremented by 1 by each node that forwardsthe packet. The packet is discarded if Hop Limit is decremented to zero.Analogous to TTL in v4. 3
    • Interfaces will have more than one address and links can be assigned more thanone prefix.An interface is required to have at least one link-local unicast address that can beautomatically configured and one global address.An interface will have several multicast addresses assigned to it. (no broadcast). 4
    • The IPv6 address is composed of 128 bits divided into 8 sections of 16 bits (onehex word or two bytes), or 16 bytes total. Like IPv4 there are bits that identify thenetwork and bits that identify the interface (more later). There are rules for the useof shorthand notation:Leading zeros can be omitted. Trailing zeroes must remain, of course. Fields ofsuccessive zeros or successive fields of zeros may be represented by a :: . The"::" can only appear once in an address.Be careful when using shorthand notation. It is very useful since this address is solong but can lead to problems if not observed carefully. (see RFC3513 for somegood examples). 5
    • The following are NOT legal representations of the above prefix (be careful, themask is /60 in these examples. Examples are from the v6 Architecture spec.):12AB:0:0:CD3/60 (may drop leading zeros, but not trailing zeros, within any 16-bitchunk of the address)12AB::CD30/60 (address to left of "/" expands to12AB:0000:0000:0000:0000:000:0000:CD30)12AB::CD3/60 address to left of "/" expands to12AB:0000:0000:0000:0000:000:0000:0CD3Usually when referring to the Prefix it can be called subnet. Prefix Length is themask. Prefix length is always denoted using slash notation /64 for 64 consecutiveones bits.Addresses are thought to be given to companies in the range of /48 to /58 withcompanies using the remaining bits, up to 64, for subnets. Address allocation isstill to be decided.Blocks of /12, /16, /18, /20, /21, /22, /23 addresses have be allocated to worldwideregistries. See IPv6 Unicast Address Assignments, IANA.org 6
    • The address 0:0:0:0:0:0:0:0 is called the unspecified address. It must never beassigned to any node. It indicates the absence of an address. One example of itsuse is in the Source Address field of any IPv6 packets sent by an initializing hostbefore it has learned its own address.The unicast address 0:0:0:0:0:0:0:1 is called the loopback address. It may beused by a node to send an IPv6 packet to itself. It may never be assigned to anyphysical interface. It is treated as having link-local scope, and may be thought ofas the link-local unicast address of a virtual interface (typically called "theloopback interface") to an imaginary link that goes nowhere.Site local was in early specs. but is now deprecated. 7
    • Global addresses are formed by appending an interface identifier to a prefix ofappropriate length. Prefixes are obtained from Prefix Information options contained inRouter Advertisements.Router Advertisements are sent periodically to the all-nodes multicast address(if usingAuto-address configuration). To obtain an advertisement quickly, a host sends outRouter SolicitationsAll Global Unicast addresses other than those that start with binary 000 have a 64-bitinterface ID field (i.e., n + m = 64) (from RFC 4291)Currently Global Unicast addresses are assigned address beginning with 2000::/3.www.iana.org/assignments/ipv6-address-space(last updated 2008-05-13)Random generated Interface IDs are desired by Cablelabs as a security precaution bynot allowing the MAC address (part of EUI) to be visible on the internet.IPv6 Prefix Allocation Reference Note [RFC4291]----------- ---------- --------- ----0000::/8, 0100::/8, 0200::/7, 0400::/6, 0800::/5, 1000::/4 Reserved by IETF2000::/3 Global Unicast4000::/3, 6000::/3, 8000::/3, A000::/3, C000::/3, E000::/4, F000::/5, F800::/6 Reserved by IETFFC00::/7 Unique Local UnicastFE00::/9 Reserved by IETFFE80::/10 Link Local UnicastFEC0::/10 Reserved by IETFFF00::/8 Multicast 8
    • Link Local Prefix FE80::/10FEC0::/10 was previously defined as a Site-Local scoped address prefix. Thisdefinition has been deprecated as of September 2004 [RFC3879]. 9
    • Interface-local scope spans only a single interface on a node, and is useful onlyfor loopback transmission of multicast.Link-local and site-local multicast scopes span the same topological regions asthe corresponding unicast scopes.Admin-local scope is the smallest scope that must be administratively configured,i.e., not automatically derived from physical connectivity or other, non- multicast-related configuration.Organization-local scope is intended to span multiple sites belonging to a singleorganization.FF01:0:0:0:0:0:0:101 means all NTP servers on the same interface (i.e., the samenode) as the sender.FF02:0:0:0:0:0:0:101 means all NTP servers on the same link as the sender.FF05:0:0:0:0:0:0:101 means all NTP servers in the same site as the sender.FF0E:0:0:0:0:0:0:101 means all NTP servers in the internet. 10
    • Link Local is autoconfigured with the link-local prefix and the EUI of the interface.The Global address is sent to the interface by DHCPv6 or it is manuallyconfigured. In the BSR the Global addresses will be manually configured, and thatgenerally applies to all router interfaces . Whereas host address will come fromDHCPv6.The following multicast addresses are automatically generated by the BSR forrouter interfaces:The All-Nodes multicast addressThe All-Routers multicast addressThe Solicited-Node multicast address (note: there is a solicited node multicastaddress for each and every unicast address on the interface)The last three bytes of the Solicited-Node multicast address will be the last threebytes of the unicast Intrerface ID.For Example: the CM will send a DHCP Solicit message on the HFC network tothe FF02::1:2 multicast address, which is a link-scoped address. The BSR willreceive that message and forward it to the DHCP server specified in the cableipv6 helper address configured in the Loopback (Cable Bundle) interface.The site-scoped all dhcp servers multicast address is used by the relay agent tosend messages to all dhcp servers within the site or because it does not know theunicast address of the dhcp servers. Usually the BSR knows the unicast addressof the dhcp server. 11
    • The IEEE defined 64-bit extended unique identifier (EUI-64) is a concatenation ofthe 24-bit /_or 36-bit_ /company_id value by the IEEE Registration Authority and a_/the/_ extension identifier assigned by the organization with that company_idassignment _/resulting in a 64 bit unique identifier/_. /_The extension identifiersshall be 40 bits for the 24-bit company_id (OUI-24) and 28 bit for the 36 bitcompany_id (OUI-36).The first byte of the 64 bit EUI has a bit that identifies whether the EUI address isunique globally or not. The bit is automatically set by the interface driver when itautoconfigures the link-local address. In the example above the bit is set so thefirst byte of the EUI shows 0x02. 12
    • 0000::/96 was previously defined as the "IPv4-compatible IPv6 address" prefix.This definition has been deprecated by [RFC4291].Global Address are reserved by:IANA: Internet Assigned Numbers AuthorityThe Réseaux IP Européens Network Coordination Centre (RIPE NCC) is theRegional Internet Registry (RIR) for Europe, the Middle East and parts of Central...APNIC: Regional Internet Registry that allocates IP and AS numbers in the AsiaPacific regionAfrNIC: Regional Internet Registry that will allocates IP and AS numbers in theAfrican regionLACNIC: Latin American and Caribbean Internet Addresses Registry 13
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    • ND is sort of a combination of IPv4 ARP and Router Discovery. ND is a protocol that uses ICMP messages for Duplicate Address Detection, Router Discovery, address Resolution, Neighbor Unreachability Detection CM uses Neighbor Solicitation (NS) message from Neighbor Discovery (ND) protocol [RFC2461], for Router Discovery and DAD. The CMTS will not do Router Discovery but will do Router Advertisements. A Neighbor Solicitation is used for link-layer address resolution (like ARP in IPv4) or Neighbor Unreachability Detection. When doing a packet capture you would see many NS. The way to determine what kind they are is by looking at the destination address: If the destination address in the NS is a multicast address (usually the solicited node multicast address), the source is resolving a link-layer address. If the destination address is unicast address the source is verifying neighbor reachability.Source Address Destination Address ND Message Tpyeall-zero (::0) all-routers multicast Stateless autoconfigall-zero (::0) Solicited node multicast DADUnicast Solicited node multicast Link Layer Addr ResolutionUnicast Unicast Unreachability Detection 15
    • A single request-response pair of packets is sufficient for both the initiator and the target toresolve each others link-layer addresses. the initiator sends a NS with its IPv6 addresswith the target address (IPv6) to be resolved. The initiator includes its link-layer address inthe Neighbor Solicitation. The device owning that IP address returns a NeighborAdvertisement with its MAC address and unicast IP address to the initiator. Now bothdevices have the IPv6 address and associated MAC address.Node needs to send packet to gateway. Looks in its IPv6 Neighbor Table (similar to ARPtable) for the MAC address. If it is not there, the node will send a neighbor solicitationusing multicast address of the target node i.e. solicit nodes multicast ipv6 source addr ipv6 source addr ipv6 destination addr ipv6 destination addr ICMP Header Type ICMPHeader Type Responders IPv6 Addr target addr Responders MAC Addr MAC addr 16
    • A router sends periodic Router Advertisements containing list of IPv6 prefixesassigned to a link (to be used for stateless autoconfiguration), availability of therouter as default router.CM can send a Router Solicitation to trigger a transmission of RA.The BSR will send RAs on the cable side to advertise itself as the default routeri.e. the Lifetime byte will be non-zero.In Release 5.1 the BSR will send the Router Advertisement with the M bit flag setto 1. This indicates to the CMs that it is to use Stateful address configuration i.e.go to the DHCPv6 server for its address. (if the M bit is set to 0, the host wouldperform Stateless autoconfiguration).Unsolicited Router Advertisements are not strictly periodic: the interval betweensubsequent transmissions is randomized to reduce the probability ofsynchronization with the advertisements from other routers on the same link. Eachadvertising interface has its own timer. 17
    • Duplicate Address Detection (DAD): CM sends a NS message with query aboutCMs link-local address, if no response, address is ok, otherwise a responsemeans that there is another device on the local link with the same Link Localaddress. Will do the same for its global IP address. 18
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    • To facilitate the transition, DOCSIS 3.0 and to support legacy product, DOCSIS3.0 allows for both IPv4 and IPv6."In Dual-stack Provisioning Mode (DPM), the CM attempts to acquire both IPv6and IPv4 addresses and parameters through DHCPv6 and DHCPv4 almostsimultaneously.” from MULPI spec.When provisioning in Alternate Provisioning Mode, the CM tries to provision usingIPv6 first. If IPv6 provisioning is unsuccessful, either because IPv6 Addressacquisition or the TFTP configuration file download fails, the CM abandons IPv6provisioning and attempts provisioning using IPv4.CM acts as a bridge linking CPEs to IPv6 services through the CMTS. To begin itis anticipated that the CPE traffic will use IPv4 and that DHCP servers will supportboth (or there will be two servers, one for each.)DHCP extended to support IPv6 scopes and new IPv6 options are defined. 20
    • IP provisioning mode for the cable modems is configured in each cable interface using the "cable ipprov-mode" command. The options are IPv4(default), IPv6 only, Alternate Provisioning Mode, andDual Stack provisioning mode.The MDD communicates to the CMs:DS Ambiguity Resolution List and DS Channel Info for DS Channel Bonding (rel 5.0)IP initialization parameters (IPv4/v6) (rel 5.1).Note: the TI modem must see a DS Channel list in the MDD (i.e. a fiber node must be configured in the BSR) tocome up in v6.Other TLVs for DOCSIS 3.0 that are not support yet, that are in the MDD:Early Authentication and Encryption (EAE) TLVUpstream Active Channel List TLVUpstream Ambiguity Resolution Channel ListUpstream Frequency Range (standard 5-42 or extended 5-85)Symbol Clock Locking IndicatorCM-Status Event Control TLVUpstream Transmit Power Reporting TLVDSG DA-DSIS Association EntryRegistration Response Timeout OverrideNo Dynamic Bonding-group Change in this release. All CMs will de-register when the bonding group ischanged. 21
    • After CM power on, the CM will auto-configure its own Link Local addresss, usingEUI-64, which will be the embedded HFC MAC address for the cable-side(Management Interface) and verify that the address is unique using DAD (seebelow).CM uses Router Solicitation (RS) message from Neighbor Discovery (ND)protocol [RFC2461] to seek a default router.ND is a collection of ICMP messages used for duplication address resolution,router discovery, link-layer address resolution, neighbor unreachability detection.The BSR sends RAs (Router Advertisements) on the cable interface with the M bitset to 1 and O bit set to 0 directing the CM to use DHCPv6 for IP addressesacquisition.The BSR will be an IPv6 DHCP Relay Agent and will support both four-wayexchange (Solicit - Advertise - Request - Reply) and the two-way, Rapid Commitoption (Solicit - Reply).On the cable-side interface we will only accept RS, will not send RS. On otherinterfaces will not send RS (we are a router).A CM will not do DHCPv6 if it does not receive a RA. So in the case of the CMreceiving an MDD with the prov-mode set to IPv6 only, the modem will continue tosend RS and look to receive RA. If the BSR is not sending RA and the CM prov-mode (from the MDD) is set to APM or Dual Stack the CM will come up (register)using IPv4 DHCP. 22
    • BSR inserts the following DHCPv6 options in upstream DHCPv6 messages (SOLICIT, REQUEST etc.) while relaying the CM’s DHCPv6 messages in a Relay-Forward message to DHCP server. DHCPv6 Interface-ID option (Option Code-18) : containing the IP address of cable interface on which DHCPv6 message is received DOCSIS Relay Agent CM MAC Address Option (Option Code-39): containing the MAC address of cable modem from which DHCPv6 message is received. CMTS DOCSIS Version Number (encoded in DHCPv6 Relay Agent CMTS Capabilities Option-Option Code-38): containing the major ad Minor DOCSIS version of CMTS.BSR relays the DHCPv6 messages to the CM including:Vendor Specific Options (Option Type – 17) Enterprise Number: 4491 (CableLabs) TFTP Server Addresses option (Option code - 32) Configuration File Name option (Option code - 33) Syslog Server Addresses option (Option code - 34) TLV5 encoding (Option code - 35) DOCSIS Device Identifier option (Option code - 36) CableLabs client configuration (Option code - 37) Option Request option (Option Code - 1) 23
    • The DHCP server supplies the CM with a globally unique address in IPv6 format.The CM management interface MUST join the all-nodes multicast address andthe solicited-node multicast address of the IPv6 address acquired throughDHCPv6.The CM will perform DAD on the new addresses.If the CM gets an the IPv6 addresses it must use it for communication with theTODv6 and TFTPv6 servers.The TFTPv6 server responds with a CM configuration file with some IPv6parameters (see classifiers below).If any step in the process fails the CM will reset its MAC and try again. 24
    • In Dual-stack Provisioning Mode (DPM), the CM attempts to acquire both IPv6and IPv4 addresses and parameters through DHCPv6 and DHCPv4 almostsimultaneously. For the acquisition of time-of-day and the download of aconfiguration file the CM prioritizes the use of the IPv6 address over the IPv4address. If the CM cannot obtain an IPv6 address, or if it cannot download aconfiguration file using IPv6, it tries downloading it using IPv4. In this mode, theCM makes both the IPv4 and the IPv6 addresses, if successfully acquired,available for management. (from DOCIS MULPI Spec). 25
    • When provisioning in Alternate Provisioning Mode, the CM tries to provision usingIPv6 first. If IPv6 provisioning is unsuccessful, either because IPv6 Addressacquisition or the TFTPv6 configuration file download fails, the CM abandons IPv6provisioning and attempts provisioning using IPv4. (from DOCIS MULPI Spec) 26
    • Configuration file parameters new to DOCSIS 3.0 that deal with IPv6 (excludingmulticast).See Table G–1 - Summary of Configuration File Parameters for a completelisting of all TFTP file parameters for DOCSIS 3.0. 27
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    • BSR supports IPv4 to IPv6 Address/Header translation in downstream directionusing configured IPv4/IPv6 address ranges, for supporting management of IPv6CMs from IPv4 management server. BSR will do the reverse mapping inupstream direction.BSR also supports the IPv6/IPv4 address/header translation for IPv6 manageraddressing an IPv4 cable modem.BSR will perform Address/Header translation only for management trafficto/from CMs. BSR will not perform Address/Header translation for CM’sregistration traffic (like DHCP, TFTP etc.)The address range can be a single device to a single device (one-to-onemapping) or a range of addresses, for example toFC00:0:0:45:221:1EFF:FED8:FC00 where the last byte of the IPv6 address willrepresent the last byte of the IPv4 addresses.It is important, if the BSR has a default route, to remove the route from the routetable both IPv4 and IPv6, otherwise the incoming packet will turn right around andgo back out the default route. This is why: When a packet from the IPv4 SNMPserver comes into the BSR, the BSR looks in its route table to determine where tosend it. If there is no route for the packet then the BSR will look to see if there isan Address Translation configured for it. It there is an entry in the AddressTranslation table it will translate and send the packet to the CM. Otherwise it willdrop the packet. So if a default route is in the route table the BSR will forward thepacket to the default route before it even checks the Address Translation table.Same in the upstream direction.The other thing to be careful with is determining a range of IPv4 addresses whichare in decimal to IPv6 addresses which are in hex. 29
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    • No support for IPv6 from the CPE such traffic will be dropped by the BSR (inRelease 5.1)Dynamic IPv6 Routing Protocols (some examples): RIPng (next gen.), OSPFv3,IS-IS6, BGPv6. (none are currently supported in the BSR) 31
    • In Release 5.1 IPv6 processing will be done on the SRM.In Release 6.x the IPv6 will be processed forwarded by the HSIM.(Ethertype for IPv4 is 0x0800) 32
    • Note:1. The link local address for the interface is automatically configured when firstIPv6 prefix is configured on that interface.2. Cannot configure both ‘secondary’ and ‘link-local’ option for the same IPv6address/prefix.3. The user specified link-local address can be configured before any primary orsecondary IPv6 address is configured for the interface.4. BSR will not allow IPv6 address to be configured on an interface if TRI isenabled on that interface (via encapsulation dot1q CLI command). Similarly BSRwill not allow TRI to be enabled on an interface if IPv6 subnets are alreadyconfigured on that interface. 33
    • When configuring the interface IPv6 address you have the option to configure theInterface ID manually and show in the second option or to use the EUI-64 addresswhich has the interface MAC address automatically embedded in the IPv6address, shown as the first example. 34
    • This command shows the Link-Local and Global IPv6 addresses for eachinterface and the state of the interface. 35
    • Primary IPv4 address for the CMs because the provisioning mode is APM or DualStack but also because of the legacy 1.x/2.0 IPv4 Cable Modems i.e. the non-DOCSIS 3.0 modems. 36
    • For multicast addresses see earlier slide.1 and 2 Not used. 0 setting means this parameter not used3 BSR will send a Neighbor Solicit on the cable interface once every 1 second, ifwe get no response from a previous NS.4 BSR will send a router advertisement every 200 seconds. Remember that ahost, in this case a cable modem, will send a Router Solicit when it initializes itsinterface. We respond to the RS immediately with an RA.5 BSR will send a parameter, this lifetime, in its router advertisement. 37
    • In the DHCP debug shown above we see the two message Rapid Commit DHCPoption. 38
    • Used to add static routes to the IPv6 route table.Where optional parameter “distance” specifies the cost of the route; range <1-255>; If not specified cost of zero is assumed. 39
    • Dynamic protocols that support IPv6 (not currently supported by the BSR)OSPFv3IS-IS v6 ExtendedRIPnG (next generation)Connected networks are added to the route table when the interface is configuredfor IPv6Local Networks signify host routes to the BSR. Currently these addresses are notdisplayed in the v6 route table.Static networks are added to the route table when an ipv6 static route isconfigured. 40
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    • INCOMPLETE Address resolution is in progress and the link-layeraddress of the neighbor has not yet been determined.REACHABLE Roughly speaking, the neighbor is known to have beenreachable recently (within tens of seconds ago).STALE The neighbor is no longer known to be reachable but until traffic issent to the neighbor, no attempt should be made to verify its reachability.DELAY The neighbor is no longer known to be reachable, andtraffic has recently been sent to the neighbor.Rather than probe the neighborimmediately, however, delay sending probes for a short while in order togive upper layer protocols a chance to provide reachability confirmation.PROBE The neighbor is no longer known to be reachable, andunicast Neighbor Solicitation probes are being sent to verify reachability.(from the ND rfc) 42
    • IPv6 Traffic statisticsIPv6 DHCP statisticsShow cable modem will now display the IPv6 address. 43
    • There is also a Traceroute6 command. 44
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