Stateless Address Autoconfiguration - SLAAC

Giriş
SLAAC RFC 4291, IP Version 6 Addressing Architecture belgesinden tanımlı. SLAAC için EUI64 yöntemi ile IPv6 adresi üretiliyor. Bu yöntem ile ilgili bazı şüphelerin açıklaması şöyle şöyle

Many people had concerns about the original SLAAC method of IPv6 address generation. The primary concern is that a user could be tracked by MAC address, regardless of where the user connected to the public Internet.

SLAAC Algoritması - 48 bit MAC Adresinden Üretme
Açıklaması şöyle

Links or Nodes with IEEE 802 48-bit MACs

[EUI64] defines a method to create an IEEE EUI-64 identifier from an IEEE 48-bit MAC identifier. This is to insert two octets, with hexadecimal values of 0xFF and 0xFE (see the Note at the end of appendix), in the middle of the 48-bit MAC (between the company_id and vendor-supplied id). An example is the 48-bit IEEE MAC with Global scope:

|0              1|1              3|3              4|
|0              5|6              1|2              7|
+----------------+----------------+----------------+
|cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|
+----------------+----------------+----------------+

where "c" is the bits of the assigned company_id, "0" is the value of the universal/local bit to indicate Global scope, "g" is individual/group bit, and "m" is the bits of the manufacturer- selected extension identifier. The interface identifier would be of the form:

|0              1|1              3|3              4|4              6|
|0              5|6              1|2              7|8              3|
+----------------+----------------+----------------+----------------+
|cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm|mmmmmmmmmmmmmmmm|
+----------------+----------------+----------------+----------------+

When IEEE 802 48-bit MAC addresses are available (on an interface or a node), an implementation may use them to create interface identifiers due to their availability and uniqueness properties.

1. Elimizde şöyle bir MAC adresi olsun.
a4:ba:db:fe:b24b

2. Bu adresi ortadan ikiye ayıralım.
a4badb ve feb24b

3. Araya fffe değerini ekleyelim.
a4badbfffefeb24b

4. Her iki byte'tan sonra : karakterini ekleyelim.
a4ba:dbff:fefe:b24b

5. U/L bitini (Universal /Local bit) ters çevirelim (flip) .
a6ba:dbff:fefe:b24b

Privacy Extension
RFC4291 dışında Privacy Extension yöntemi ile IPv6 adresi üretebilmek mümkün.RFC 4941, Privacy Extensions for Stateless Address Autoconfiguration in IPv6 belgesi bu yöntemi anlatıyor. Açıklaması şöyle.

Abstract

Nodes use IPv6 stateless address autoconfiguration to generate addresses using a combination of locally available information and information advertised by routers. Addresses are formed by combining network prefixes with an interface identifier. On an interface that contains an embedded IEEE Identifier, the interface identifier is typically derived from it. On other interface types, the interface identifier is generated through other means, for example, via random number generation. This document describes an extension to IPv6 stateless address autoconfiguration for interfaces whose interface identifier is derived from an IEEE identifier. Use of the extension causes nodes to generate global scope addresses from interface identifiers that change over time, even in cases where the interface contains an embedded IEEE identifier. Changing the interface identifier (and the global scope addresses generated from it) over time makes it more difficult for eavesdroppers and other information collectors to identify when different addresses used in different transactions actually correspond to the same node.

Aslında birçok işletim sistemi SLAAC yerine Privacy Extension veya rastgele adresleme yöntemini kullanıyor.