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IPv6 over xDSL: The
DIODOS Proposal
Athanassios Liakopoulos
[email protected]
Greek Research & Technology Network
International IPv6 Workshop,
Kopaonik, March 6th,2005
Outline
Introduction to DSL technology
 IPv6 services over DSL
 The DIODOS project
 IPv6 services in DIODOS

International IPv6 Workshop - Kopaonik, March '05
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Entities involved in an xDSL
environment


Subscriber (xDSL User)
Network Access Provider (NAP)
 Responsible
for the management of the copper local
loop.

Network Service Provider
 Responsible
for providing interconnection with the
Internet.
 May offer other added-value services.
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Basic Network Elements

Subscriber (DSL User)
 PC,

modem, CPE router
Network Access Provider (NAP)
 DSLAM,

BBRAS, radius server (?)
Network Service Provider
 Edge
router, radius server (?)
CPE
Network Access
Provider (NAP)
Router
Subscriber
Modem
DSLAM
BBRAS
Network Service
Provider (NSP)
Edge router
Radius
server
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Implementation details

xDSL modem


DSL Access Multiplexer (DSLAM)


Terminates the Subscribers’ ATM connections, forwards traffic to
the NSP edge router.
Radius Server


Signal (de)modulation, aggregates traffic over ATM links
Broad Band Remote Access Concentrator BBRAS


Encapsulates Subscribers’ traffic to ATM cells, signal
(de)modulation
Contains configuration templates
NSP edge router
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Ethernet bridging over ATM





The CPE forwards IP packets using multi-protocol encapsulation over ATM
adaptation layer 5 (AAL5).
Minimum functionality is required for CPE, aka xDSL modem (L3 unaware
device).
A single ATM PVC is used for IPv4/6 interconnection
Subscriber’s PCs are configured with static IPv6 address, or via DHCPv6 or
via auto-configuration
This method does not support authentication and authorization functionality!
CPE
Modem
Subscriber
DSLAM
Ethernet bridging
IPv6
802.3
PHY
802.3
PHY
RFC1483
ATM
ATM
xDSL
PHY
xDSL
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PPP over AAL5 (PPPoA)




The CPE supports IPv6/4 packet forwarding and interconnects multiple
systems in the Subscriber’s local network.
A single PPPoA session is established over a ATM PVC allowing the CPE
router to establish two PPP sessions; an IPv6 (IPCPv6) and an IPv4 (IPv4)
IPv6 addresses are assigned automatically over the PPP sessions using
attributes stored in a centralised radius server or a local database.
The CPE can be authenticated using one of the multiple protocols, such as
PAP, CHAP, MS-CHAP, EAP, etc.
PPPoA
CPE
Router
Modem
Network Access
Provider (NAP) /
Network Service
Provider
DSLAM
BBRAS
Subscriber
IPv6
802.3
802.3
PHY
IPv6
IPv6
PPPoA
PPPoA
RFC1483
ATM
PHY
xDSL
ATM
xDSL
Radius
server
RFC1483
PHY
ATM
PHY
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PPP over AAL5 (PPPoA)

In case the NAP and the NSP are different, the PPP sessions do not
terminate at the BBRAS but at the edge router.

BBRAS = L2TP Access Concentrator (LAC)
 Edge router = L2TP Network Server (LNS)


Two PPP sessions are established from the CPE router, which terminate at
the LNS.
Address assignment and authentications methods are performed in the
same was as previously but now the radius server is managed by the NSP.
PPPoA
L2TP
CPE
Network Service
Provider (NSP)
Network Access
Provider (NAP)
Router
Subscriber
Modem
DSLAM
LAC
(BBRAS)
LNS
(Edge router)
Radius
server
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PPP over Ethernet (PPPoE)

Separate PPP sessions are established between the CPE and the
BBRAS for IPv6 and IPv4 traffic.

Sessions terminate in the LNS in the NSP network (not shown).
 PPP sessions may terminate in the Subscriber’s system. This allows the
CPE to be L3 unaware and, thus, cheap(!) but requires specific software
to be installed in the Subscribers’ systems.
PPPoE
Network Access
Provider (NAP) /
Network Service
Provider
CPE
Router
Modem
DSLAM
BBRAS
Subscriber
IPv6
802.3
802.3
PHY
IPv6
IPv6
PPPoE
PPPoE
RFC1483
ATM
PHY
xDSL
ATM
xDSL
Radius
server
RFC1483
PHY
ATM
PHY
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The DIODOS project


In Greek, the word “diodos” means “passage”.
Established under the authority of the Ministry of
Development, the Ministry of National Education
& Religious Affairs and the Ministry of Transport
and Communications
 Realised
by the General Secretariat for Research and
Technology with the support of Greek Research &
Technology Network.

http://www.diodos.net.gr/ (in greek)
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DIODOS objectives (?)

Improve the quality of training in Greece
 Enabling
tele-teaching, collaboration,
videoconferencing, etc
 Easy access to available content, such as digital
libraries, multimedia content, virtual labs, etc.



Increase the penetration of broadband technology
in Greece
Give motives to ISPs to improve their
infrastructure
Create future potential Users
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DIODOS Entities
Network Access Provider (NAP)
 Network Service Provider

 GRNET
 Provide

the Internet interconnection services
Accounting – Management
 ISPs
 Maintaining
the radius servers
 Accounting and billing of Subscribers
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Obstacles

Greece-wide service
 Centralised


architecture, high availability
Limited amount of time for implementation and
deployment
Management complexity
 Three
different entities involved
 Information System had to be implemented
 Lack of management tools

Open to all competitive ISPs
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Why IPv6 support is important?

“Always-on” xDSL connections require a
routable IP address per subscriber
 Thousands
of new IPv4 addresses have to be
allocated for DIODOS connections.


In the hypothetical case that all the students on Aristotle
University of Thessaloniki take advantage of DIODOS
programme, more than 150 class C networks has to be
allocated!
A /9 IPv4 address has to be allocated to all Greek
Universities!
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Why IPv6 support is important? (2)

Take advantage of the experience gained from
other IPv6 deployments in Greece.
 GRNET
provides IPv6 interconnection services since
the end of 2003.
 The Greek School Network (GSN) introduced IPv6
interconnection services over xDSL on a pilot basis.
If DIODOS will support only IPv4 services, it may affect
the impact of the other IPv6-enalbed networks.
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Why IPv6 support is important? (3)

Exposing students to new technologies is
one of the major objectives of any
educational system.
 New
advanced services and applications may
take advantage of the unique IPv6 features,
 Large portion of Greek student still has not
access to IPv6 technology
DIODOS could become a “vehicle” to improve the
educational process and further stimulate innovation.
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Possible IPv6-enabled
implementations

Use Global Unicast IPv6 and Private IPv4
addresses
 Overcome
the IPv4 depletion problem
 Static NAT is used for IPv4 connectivity

Possible scalability problems.
 Problems
with application protocols caring IP
addresses in their payload



Application-Level Gateways (ALG) are needed
Affected protocols: ICMP, FTP, H.323, SNMP, DNS, NetBIOS
over TCP/IP (NBT) etc.
Difficulties with IPSec.
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Possible IPv6-enabled
implementations

Use open replay 6to4 servers
 No
solution to IPv4 depletion problem
 Security configuration

Tunnel Broker
 More
complex solution than 6to4 tunneling
 No solution to IPv4 depletion problem

Open VPN solutions
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Thank you!
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