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CREATING AN INTERNET PROTOCOL VERSION 6 UNICAST ADDRESS FROM A BIT INDEXED EXPLICIT REPLICATION EXTENSION HEADER

IP.com Disclosure Number: IPCOM000250571D
Publication Date: 2017-Aug-03
Document File: 4 page(s) / 61K

Publishing Venue

The IP.com Prior Art Database

Related People

Ijsbrand Wijnands: AUTHOR [+2]

Abstract

The BitPositions numeric value of the bits in a BitString is used to create a valid unicast address by combining the BitPosition numeric value with the Internet Protocol version 6 (IPv6) unicast destination address. The unicast prefix is used as the sub-domain/set identifier.

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Copyright 2017 Cisco Systems, Inc. 1

CREATING AN INTERNET PROTOCOL VERSION 6 UNICAST ADDRESS FROM A BIT INDEXED EXPLICIT REPLICATION EXTENSION HEADER

AUTHORS: Ijsbrand Wijnands

Pierre Pfister

CISCO SYSTEMS, INC.

ABSTRACT

The BitPositions numeric value of the bits in a BitString is used to create a valid

unicast address by combining the BitPosition numeric value with the Internet Protocol

version 6 (IPv6) unicast destination address. The unicast prefix is used as the sub-

domain/set identifier.

DETAILED DESCRIPTION

Internet Engineering Task Force (IETF) Internet-Draft “An IPv6 based BIER

Encapsulation and Encoding” (available at https://tools.ietf.org/html/draft-pfister-bier-

over-ipv6-01) details a proposal to use an IPv6 destination address to encode a Bit Indexed

Explicit Replications (BIER) BitString. One advantage of that proposal is that due to the

BIER forwarding logic, an Internet Protocol version 6 (IPv6) unicast address is produced

at the egress router. In other words, a unicast IPv6 address is a BIER BitString with a single

bit set. As a result, it is possible to convert the BIER encoded destination address into a set

of unicast addresses. This model is very beneficial as the router can send the packet unicast

to the host/server. The downside of this approach is that the number of bits that can be

encoded in the IPv6 destination address is limited, with a theoretical maximum of 100, and

a more likely realistic maximum of 64.

If the BIER BitString is encoded as an IPv6 extension header a much larger space

may be allocated to enable encoding 256 or more bits. A solution is presented herein to use

an extension header to encode the BIER BitString, while allowing the unicast destination

addresses to be easily generated such that the egress router may forward the packets unicast

to the host/server.

An extension header is used to encode the BIER BitString. For the IPv6 destination

address, an IPv6 unicast prefix, and not a multicast address, is used. For example, if

Copyright 2017 Cisco Systems, Inc. 2

CAFE::0/64 is the address prefix, the actual forwarding of the packet is not based on this

prefix, but rather is based on the BIER BitString encoded in the IPv6 header.

When the egress BIER router is reached, the router may generate IPv6 unicast

packets by taking each remaining BitPosition in the extension header and using the

BitPosition(s) to generate the unicast destination address. For example:

BIER BitString Hex: 0x7, Binary: 0111

The unicast prefix is CAFE::0/64

Three unicast packets are generated:

CAFE::1

CAFE::2

CAFE::3

Using this logic provides the best of both worlds: more bits in the BitString may be

encoded due to using an extension header, and a convenient mechanism to generate unicast

IPv6 packets is enabled. It is beneficial for the egress router to generate unicast packets

because this avoids multicast processing on the egress router, thereby eliminating the need

for multicast listener discovery (MLD) and designated router (D...