Internet Engineering Task Force Jun-ichiro itojun Hagino
INTERNET-DRAFT IIJ Research Laboratory
Expires: January 13, 2001 Kazu YAMAMOTO
IIJ Research Laboratory
July 13, 2000
Requirements for IPv6 dialup PPP operation
draft-itojun-ipv6-dialup-requirement-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
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Distribution of this memo is unlimited.
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be January 13, 2001.
Abstract
The memo tries to identify design choices in IPv6 dialup PPP services by
ISPs.
1. Problem domain
With the deployment of IPv6 [Deering, 1998] , it becomes more apparent
that we have different operational requirements in IPv6 dialup PPP
operation, from IPv4 dialup PPP operation. For example, it would be
desirable to see static address allocation, rather than dynamic address
allocation, whenever possible. With IPv4 this has been impossible due
to address space shortage, and IPCP [McGregor, 1992] dynamic address
allocation has been used. With IPv6 it is possible to perform static
address allocation from ISPs to downstream customers, as there's enough
address to spare.
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DRAFT Requirements for IPv6 dialup PPP operation July 2000
The document tries to summarize possible design choices in IPv6 dialup
PPP operation. Actual operational practices should be documented
separately.
2. Design choices
2.1. The usage pattern
o Static clients. Computers located in home and offices do not usually
change its configurations, nor upstream ISPs. It would be desirable
to make a static address allocation in this case.
o Roaming clients. Roaming clients, like travelling users with notebook
PC, have different requirement from static clients. It is not usually
possible to make a static address allocation, as travelling users may
connet to multiple ISPs from different countries.
2.2. Address space
It is desired to assign /48 address space, regardless from usage pattern
or size of the downstream site. It is to make future renumbering in
downstream site easier on ISP change. /128 assignment MUST NOT be made,
as it will advocate IPv6-to-IPv6 NAT.
2.3. Address allocation
o Static address allocation. ISPs will allocate a static address space
(/48) to a downstream customer, on contract time. There will be no
protocol involved in address allocation - allocation will be informed
by paper.
o Static address allocation, with some automation. It may be possible
to define a common protocol for configuring customer-side router(s)
from the upstream ISP, eliminating necessity of paper-based allocation
and configuration labor in the customer site. Note that router
renumbering protocol is not always suitable for this. Router
renumbering protocol assumes that the routers and control node to be
in the same administrative domain.
o Dynamic address allocation.
2.4. Where to assign address
o Assign address to ppp interface. The form assigns /128 to the
customer computer, or /64 onto the PPP link. The form of address
assignment should not be used, as it advocates IPv6-to-IPv6 NAT. In
the following diagram, "Lx" denotes link-local address, and "Gx"
denotes global address.
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DRAFT Requirements for IPv6 dialup PPP operation July 2000
ISP router
|La, Ga
| ppp link
|Lb, Gb
Customer computer
o Assign address to the interface behind the customer router. The form
assigns /64 to the network segment behind customer router.
ISP router
|La
| ppp link
|Lb
Customer router
|Gb
==+=== Gx/64
In the cases where the customer has only a single computer, it is
possible to have virtual network segment behind the customer computer.
ISP router
|La
| ppp link
|Lb
Customer computer
|Gb
==+=== Gx/64 (VIRTUAL)
Note that, however, /64 assignment will make it harder for customer
site to evolve in the future. /64 assignment is not recommended.
o Assign address to the cloud behind the customer router (/48). In this
case, the upstream ISP has no idea about the topology in the customer
site. Actually, it is not necessary for the upstream ISP to know
about the address usage in the customer site. Static address
assignment is highly recommended in this case, as it is painful to
renumber the whole /48 cloud every time we reconnect the dialup PPP
link between the ISP and the customer site.
ISP router
|La
| ppp link
|Lb
Customer router
|Gb
(((Gx/48 cloud)))
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2.5. Routing
o Static routing. ISPs will configure static route, pointing to the
customer site, for the address space assigned to the customer site.
Customer router (or customer computer) will install default route,
pointing to the ISP router via PPP link.
o Simple dynamic routing. ISPs can exchange routes by using simple
dynamic routing protocols like RIPng. This allows the customer site
to adapt to PPP link status better. This also makes it easier to
detect PPP link disconnection. If the ISP announces non-default
routes to the downstream customer, it may help downstream to configure
multihomed connectivity (connection to multiple upstream ISPs)
[Hagino, 2000] ISPs may want to filter out bogus routing announcements
from the downstream.
3. Security considerations
The document talks about no security issues.
References
Deering, 1998.
S. Deering and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification" in RFC2460 (December 1998). ftp://ftp.isi.edu/in-
notes/rfc2460.txt.
McGregor, 1992.
G. McGregor, "The PPP Internet Protocol Control Protocol (IPCP)" in
RFC1332 (May 1992). ftp://ftp.isi.edu/in-notes/rfc1332.txt.
Hagino, 2000.
Jun-ichiro Hagino, "IPv6 multihoming support at site exit routers" in
draft-ietf-ipngwg-ipv6-2260-00.txt (June 2000). work in progress
material.
Change history
None.
Acknowledgements
(not yet)
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DRAFT Requirements for IPv6 dialup PPP operation July 2000
Author's address
Jun-ichiro itojun HAGINO
Research Laboratory, Internet Initiative Japan Inc.
Takebashi Yasuda Bldg.,
3-13 Kanda Nishiki-cho,
Chiyoda-ku,Tokyo 101-0054, JAPAN
Tel: +81-3-5259-6350
Fax: +81-3-5259-6351
Email: itojun@iijlab.net
Kazu YAMAMOTO
Research Laboratory, Internet Initiative Japan Inc.
(for postal address, see above)
Email: kazu@iijlab.net
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