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Issue Definition*:6RD and IPv6 allocation policy

Jan Žorž (Go6 Institute Slo)

Mark Townsley (Cisco)

*Or, Why we had to wake up on Friday to be here?

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Aspects of IPv6 Transition Mechanisms

Tunnel or Translate

Stateless or Stateful

SP-Managed or not SP-Managed

6rd is a Stateless, SP-Managed, Tunneling Protocol

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IPv6 Prefix from an IPv4 Address

The following construction is what allows 6rd to be SP-managed and Stateless

Subnet-ID

642001:db8

0 /n

ISP 6rd IPv6 Prefix

Interface ID198.51.100.1

/m

Subscriber IPv4 address

Subscriber Delegated IPv6 Prefix

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6rd – Encapsulation and Packet Flow

IPv4-only Access Network

CE

6rd

6rd Border Relays

Dual StackDual StackDual Stack

Dual Stack

6rd

IPv4

IPv6 in IPv4 (protocol 41) encapsulation Within a domain, IPv6 traffic follows IPv4 routing CEs reach BRs via IPv4 anycast

“…externally 6rd looks, feels and smells like native IPv6 ” – RIPE Labs

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CE

6rd

6rd Border Relays

Dual StackDual StackDual Stack

Dual Stack

6rd

6rd – CE Provisioning

6rdPrefix6rdPrefixLenIPv4MaskLen6rdBRIPv4Address

Each 6rd CE within a 6rd Domain requires a single DHCP option* carrying 4 values

These 4 values are the same for all CEs within the domain

*May also be configured with TR-69 or otherwise

IPv4

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6rd – Deployments

CE

6rd

6rd Border Relays

Dual StackDual StackDual Stack

Dual Stack

6rd

IPv4

Defined in RFC 5969 Commercially available products from a number of vendors First deployment in 2007, multiple deployments today

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Q: What should /n and /m be?

Subnet-ID

642001:db8

0 /n

ISP 6rd Prefix

Interface ID198.51.100.1

/m

IPv4 (0-32 bits)

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Starting simple: /n = 28, /m = 60

Subnet-ID

642001:db8

0 /28

ISP 6rd IPv6 Prefix

Interface ID198.51.100.1

/60

32 bits

One 6rd domain 6rd provisioning is identical for all CEs Convenient conversion between subscriber IPv6 and IPv4

address Allows 16 IPv6 subnets in the home ISP needs a /27 or shorter

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But what if you cannot get a /27?/n = 32, /m = 64

2001:db8

0 /32

ISP 6rd IPv6 Prefix

Interface ID198.51.100.1

/64

32 bits

Still a single domain, but /64 does not allow multiple subnets for the subscriber

• No subnets, no routing• Common features such as Guest + Home SSIDs become

very difficult• Support for 802.15.4 for Sensors, Zigbee, etc. • Ultimately leads to IPv6 NAT

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Using less than 32 bits of IPv4

Subnet-ID

642001:db8

0 /32Interface ID.51.100.1

/56

If the IPv4 space is an aggregate, 6rd need not carry the common bits

For example, in a CGN world of 10/8, we just don’t carry around the 10

64

2001:db80:0

0 /36Interface ID.51.100.1

/60

24 bits

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Multiple 6rd Domains

8 bits32 bits

ISP 6rd IPv6 Prefix

Interface ID (64 bits)20 bits

Distinct IPv4 Aggregates

8 bits32 bits Interface ID (64 bits)16 bits

8 bits32 bits Interface ID (64 bits)18 bits

8 bits32 bits Interface ID (64 bits)19 bits

More efficient in terms of IPv6 space usage However, CEs in different domains require different configuration Operations begin to get more complicated, traffic patterns not as

efficient, etc.

3 bits

4 bits

8 bits

4 bitsIPv4 /12

IPv4 /16

IPv4 /14

IPv4 /11

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How do I get my /27?"2^(48-(P+1))" "2^(48-(P+1)) + Growth"

Growth -> 20% 10% 5% 0%

Prefix Size Years -> 3 3 3 0

22 33,554,432 19,418,074 25,209,941 28,985,580 33,554,432

23 16,777,216 9,709,037 12,604,971 14,492,790 16,777,216

24 8,388,608 4,854,519 6,302,485 7,246,395 8,388,608

25 4,194,304 2,427,259 3,151,243 3,623,197 4,194,304

26 2,097,152 1,213,630 1,575,621 1,811,599 2,097,152

27 1,048,576 606,815 787,811 905,799 1,048,576

28 524,288 303,407 393,905 452,900 524,288

29 262,144 151,704 196,953 226,450 262,144

30 131,072 75,852 98,476 113,225 131,072

31 65,536 37,926 49,238 56,612 65,536

/27 yields /60 for the home /29 yields /62 for the home

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Possible solutions

1. Declare this is a non-problem

2. Special 6rd policy. e.g., /27 granted based on ability and intention to deploy more rapidly with 6rd

3. Allow /29 to anyone

4. Others?