Take the Next Step with the Next Generation Protocol

1998 Naoto Shimazaki  <shimaz-n@pg.highway.ne.jp>

Sat Aug 15 23:37:54 JST 1998

This document describes an idea for use of IPv6 over the amateur radio. IPv6 has huge address space and it supports real-time traffic. IPv6 realize new applications. For example, managing IPv4 address is not easy. It is possible to encode our "call sign" into IPv6 address. It enables us to managing IP address much easier.

Table of Contents:

1. What' IPv6

1.1.  What the IPv6 Has Advantages of
1.2.  Simplified Header Format
1.3.  Extension Header
1.4.  Extended Address Space
1.5.  Real-time Support
1.6.  What Isn't IPv6

2. Why IPv6?

2.1.  IPv6 Targets Exciting Applications
2.2.  IPv6 Supports Real-time Traffic
2.3.  IPv6 Can Automate the Address Management

3. Address Mapping

4. IPv6 Implementations and Ported Application Programs

5. Conclusion

1. What's IPv6

IPv6 is a next generation of IP. IP is a inter networking protocol used in all over the world. Since the IP we are using today is version four, the current version of IP often called IPv4.

1.1.  What the IPv6 Has Advantages of

The most important advantage in IPv6 is its design concept. That is,

Keep Concept

IPv6 keeps good concept in IPv4. This policy is based on the fact that IPv4 has been a major player on the Internet for more than two decades. IPv6 specification is fixed by deleting groundless spec, not used spec in IPv4, keeping good spec and bringing in new idea. And, IPv6 header format was simplified and became easy to implement.

Extended address space based on statistical estimation

The new address space is set to be large enough to connect 1000 trillion computers through one trillion networks.

The huge address space of IPv6 gives much deeply hierarchical address structure instead of only three layers on IPv4. And the huge space gives quite new address usages.

Careful Planning of address assignment

The meaning of any part of the address space will be discussed and agreed before practical use. Many address regions are reserved for future use. These reserved addresses are used not only when it faces the address shortage but also when new idea of address use is introduced.

1.2.  Simplified Header Format

The header format of IPv6 is simplified. Here is the list of interesting changes in header fields.

version field

The very first 4bits are version field as same as IPv4. Their contents are no longer important because IP version is identified by link layer protocol instead of this field.

priority value 

The next 4bits indicate priority. This field is used to support real-time traffic.

flow label

Newly added field. This field is used to support real-time traffic.

payload length

The total length field in IPv4 is replaced by pay load length field. The pay load length holds the length of "payload data" in the packet. The pay load length isn't including header's length. In other words, subtracting header's length from total length gives payload length.

next header

One or more extension headers may follow the first header. Next header is identifier of nearest trailing extensional header.

hop limit

Same as time to live (TTL) in IPv4 but the details of specifications are simplified.

The fields for header length, type of service, identification, flag, flagment offset, header checksum are omitted. Considering experience in IPv4, these fields are redundant and waste in routers and rarely used efficiency.

1.3.  Extension Header

IPv6 can handle various optional information on consistent system. Several kind of extension headers are already defined for routing, authentication and security. The option field in IPv4 is absolutely redesigned. Today, option field in IPv4 is rarely used.

1.4.  Extended Address Space

The systematic use of huge address space is main concept of IPv6.

IPv6 has 128bit address space. The first 10bits are defined to categorize the address regions. They are categorized on meaning of address region. Other hand, IPv4 address is divided only by size of address region.

1.5.  Real-time Support

IPv6 supports the real-time traffic by effective use of flow label and priority. The supporting real-time of IPv6 is based on "fair queuing" mechanism.

Normally, router has only one queue par interface. The packets arrived at the router are always put into the last of queue. The packet arrived first reaves the router first.  The order of packets is never changed. In fair queuing, router has two or more queue par interface. Each queue has own priority. The packets arrived at the router are put into certain queue matching priority of each packet. The router processes the queues to satisfy priority of each queue. This means that the higher priority packets reave the router more quickly.

IPv6 router defines queue the packet to be put in by priority and flow label in packet header.

Some routers partly supports real-time traffic on IPv4. However, IPv6 router gives much better support.

1.6.  What Isn't IPv6

IPv6 is:

- Not a "rich" IP

- Not a "light weight" IP

Unfortunately, you would not get any interesting effects if you replace IPv4 by IPv6 on the intranet in your office. Because IPv4 has enough ability to handle usual intranet requirements. So, why IPv6?

2. Why IPv6?

2.1. IPv6 Targets Exciting Applications

The difference between IPv4 and IPv6 is their target application. IPv4 has been used to connect computer-based applications. Compared to this, IPv6 will connect "everything," like phones, sensors, handy tools, and others.

The real-time applications will change their network platform from IPv4 to IPv6.  Because the applications target commonplace person, not computer mania, who like to use more stylish tools to access their applications. Much more number of tiny goods are likely to be IPv6 node because IPv6 has huge address space.

IPv6 realizes the mobile networking using IP handover. The IP handover is new technique to change IP address of specific node without disconnecting TCP session.  It is like handover among mobile phone base stations. This hand-over feature is not provided in IPv4.

IPv6 is expected to be common inter connection technology used in every field includes home automation, industrial monitoring, mobile phone, education and much more.

2.2.  IPv6 Supports Real-time Traffic

The world wide web is a "classical" application today. More attractive voice and moving picture real-time application is drawing people.

Some important technical elements to make high-speed and flexible radio data link have been developed in amateur radio.

2.3.  IPv6 Can Automate the Address Management

Most important problem for us in IPv4 is the address management. The IPv4 address is managed by human. It is difficult to manage the address automatically on IPv4.  IPv6 can solves this problem. Their address of network protocol must be unique each other. Getting unique address without centralized administration is difficult.

It is pretty nice idea to map specific identifier which is already managed and not to conflict each other into IP address by one-to-one translation. It enable us getting unique IP address without new address administration.

We have "call signs" of radio stations and they are unique each other among all over the world. IPv6 has enough address space to hold our call sign after mapping.  Compared to this, no enough bits are left for optimize routing if the call sign is put into IPv4 address space. Because the name space of call sign is about as large as IPv4 address space.

Also IPv6 provides something other plug and play feature. For example, IPv6 node can completely initialize itself with getting temporally IPv6 address automatically using Ethernet physical address.

IPv6 is easy to use. IPv6 has great possibility of various new applications. IPv6 will give you absolutely new world. So why not IPv6?

3.  Address Mapping

This section describes an idea of mapping call sign to IPv6 address one-to-one.

Our call sign consists of number digit and alphabet. Single letter of the call sign is to be encoded into one six bit binary integer.  

Here is the translation table between letters of call sign and integer.

call sign letter  integer
" " 0
"0" 1
"1" 2
... ...
"9" 10
"A" 11
"B" 12
... ...
"Y" 35
"Z" 36
reserved 37
... ...
reserved 63

The call sign is translated into an array of six bit binaries, reversed, and put in IPv6 address. The reason of reversing alignment of the encoded call sign letter will be discussed later.

Here is an example figure of IPv6 address. The encoded call sign is "7L4FEP", which is my  call sign.

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
reserved for network prefix
reserved for network prefix
reserved (1)             "P" "E"                          
        "E" "F" "4" "L" "7" (2)                        

(1) reserved for network prefix or call sign extension. (2) host address space

The last 4 bits are used for host address. Each radio station is able to have at most 14 hosts directly connected to foreign world.

The first 64 bits are reserved for network prefix. For the present, some fixed bit pattern is assigned.

The bits from 64th to 87th are reserved for future use. It should be zero. If the length of call sign is extended from six letters to seven letters, the bits from 82th to 87th are used for extended letter. If the network prefix has to be longer, the bits from 64th to 81th are used. If it has to be much longer, the bits from 82th to 87th are used. Then, these bits became unusable for call sign extension.

On other words, the encodes call sign grows tail to head and the network prefix grows head to tail. That is the reason of reversing alignment of the encoded call sign letter.

4.  IPv6 Implementations and Ported Application Programs

Many of software platforms like Linux and BSD are going to support IPv6 today. Major internet application programs are already compatible with IPv6. Refer to this URL to get useful information about IPv6:


Recent version of Linux kernel already supports IPv6 and fair queuing. I confirmed it by linux-2.1.115. See this page:



There is the project to implement IPv6 stack to FreeBSD. See this page:


WIDE IPv6 working group:


5.  Conclusion

It gives us much merit making amateur radio network on IPv6 with address mapping method described here.

Specific application to use IPv6 in amateur radio is under development.

We need some skills to use IPv6 now because software platform like Linux is no stable when used with IPv6 today. But soon it will be easier on amateur radio to use IPv6. Net work newcomer will enjoy data communication on amateur radio

Naoto Shimazaki, 7L4FEP


(Original PDF)