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

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Historical Aspects of IPv6

IPv4 address space not big enough• Can’t 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

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Examples of Writing Addresses

3ffe:3700:0200:00ff:0000:0000:0000:0001

can be written

3ffe:3700:200:ff:0:0:0:1

or

3ffe:3700:200:ff::1

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

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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 ::FFFF:a.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)

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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

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Abilene sTLA

Allocated 2001:468::/35

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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

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Other Unicast Addresses

Original provider-based

Original geographic-based

GSE (8+8)

Hain’s Internet Draft for provider-independent (geographically-based) addressing

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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

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Abilene IPv6 Addressing

Two prefixes allocated• 3ffe:3700::/24 on 6bone• 2001:468::/35 sTLA

Planning migration from 6bone addressing

Current addressing plan built on assumption of /35

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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 haven’t received IPv6 addresses

See WG web site for details

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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

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Obtaining Addresses

Drop a note to Abilene NOC (noc@abilene.iu.edu) with request

Will set wheels in motion