IPv6 Addressing

1
IPv6 Addressing

• Internet2 IPv6 Workshop
• Research Triangle Park, NC
• 5-7 March 2002

2
Overview of Addressing

• Historical aspects
• Types of IPv6 addresses
• Work-in-progress
• Abilene IPv6 addressing

3
Historical Aspects of IPv6

• IPv4 address space not big enough
• Cant get needed addresses (particularly outside
  Americas)
• Resort to private (RFC1918) addresses
• Competing plans to address problem
• Some 64-bit, some 128-bit
• Current scheme unveiled at Toronto IETF (July
  1994)

4
Types of IPv6 Addresses

• Like IPv4
• Unicast
• Multicast
• Anycast
• but designed into specifications from the
  beginning

5
Representation of Addresses

• All addresses are 128 bits
• Write as sequence of eight sets of four hex
  digits (16 bits each) separated by colons
• Leading zeros in group may be omitted
• Contiguous all-zero groups may be replaced by
  
• Only one such group can be replaced

6
Examples of Writing Addresses

• 3ffe3700020000ff0000000000000001
• can be written
• 3ffe3700200ff0001
• or
• 3ffe3700200ff1

7
Interface Identifiers

• Sixty-four bit field
• Guaranteed unique on subnet
• Essentially same as EUI-64
• Formula for mapping IEEE 802 MAC address into
  interface identifier
• Used in many forms of unicast address

8
Types of Unicast Addresses

• Unspecified address
• All zeros ()
• Used as source address during initialization
• Also used in representing default
• Loopback address
• Low-order one bit (1)
• Same as 127.0.0.1 in IPv4

9
Types of Unicast Addresses

• Link-local address
• Unique on a subnet
• Result of router discovery or neighbor discovery
• High-order FE80/64
• Low-order interface identifier
• Site-local address
• Unique to a site
• High-order FEC0/48
• Low-order interface identifier
• What is a site?

10
Types of Unicast Addresses

• Mapped IPv4 addresses
• Of form FFFFa.b.c.d
• Used by dual-stack machines to communicate over
  IPv4 using IPv6 addressing
• Compatible IPv4 addresses
• Of form a.b.c.d
• Used by IPv6 hosts to communicate over automatic
  tunnels

11
Types of Unicast Addresses

• Aggregatable global unicast address
• Used in production IPv6 networks
• Goal minimize global routing table size
• From range 2000/3
• Three fields in /64 prefix
• 16-bit Top Level Aggregator (TLA)
• 8-bit reserved
• 24-bit Next Level Aggregator (NLA)
• 16-bit Site Level Aggregator (SLA)

12
Types of Unicast Addresses

• Aggregatable global unicast address

13
Top-Level Aggregators

• Allocated by RIRs to transit providers
• In practice, RIRs have adopted slow-start
  strategy
• Start by allocating /35s
• Expand to /29s when sufficient use in /35
• Eventually move to /16s

14
Abilene sTLA

• Allocated 2001468/35

15
NLAs and SLAs

• NLAs used by providers for subnetting
• Allocate blocks to customers
• Can be multiple levels of hierarchy
• SLAs used by customers for subnetting
• Analogous to campus subnets
• Also can be hierarchical

16
Other Unicast Addresses

• Original provider-based
• Original geographic-based
• GSE (88)
• Hains Internet Draft for provider-independent
  (geographically-based) addressing

17
Multicast Address

• From FF00/8
• Address contains four-bit scope field
• Unlike IPv4 multicast, scope is explicitly
  defined in address
• Low-order 112 bits are group identifier, not
  interface identifier

18
Anycast Address

• Used to send packets to all interfaces on a
  network (like IPv4 anycast, not all will
  necessarily respond)
• Low-order bits (typically 64 or more) are zero

19
Abilene IPv6 Addressing

• Two prefixes allocated
• 3ffe3700/24 on 6bone
• 2001468/35 sTLA
• Planning migration from 6bone addressing
• Current addressing plan built on assumption of /35

20
Allocation Procedures

• GigaPoPs allocated /40s
• Expected to delegate to participants
• No BCP (yet) for GigaPoP allocation procedures
• Direct connectors allocated /48s
• Will (for now) provide addresses to participants
  behind GigaPoPs which havent received IPv6
  addresses
• See WG web site for details

21
Registration Procedures

• Providers allocated TLAs (or sTLAs) must register
  suballocations
• ARIN allows rwhois or SWIP
• For now, Abilene will use SWIP
• Will eventually adopt rwhois
• GigaPoPs must also maintain registries
• Will probably have central Abilene registry

22
Obtaining Addresses

• Drop a note to Abilene NOC (noc_at_abilene.iu.edu)
  with request
• Will set wheels in motion