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IPv6 over xDSL: The DIODOS Proposal
Athanassios [email protected]
Greek Research & Technology Network
International IPv6 Workshop, Kopaonik, March 6th,2005
International IPv6 Workshop - Kopaonik, March '05 2
Outline
Introduction to DSL technology IPv6 services over DSL The DIODOS project IPv6 services in DIODOS
International IPv6 Workshop - Kopaonik, March '05 3
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.
International IPv6 Workshop - Kopaonik, March '05 4
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 (?)
Subscriber
CPE
ModemDSLAM BBRAS
Network Access Provider (NAP)
Network Service Provider (NSP)
Radius server
RouterEdge router
International IPv6 Workshop - Kopaonik, March '05 5
Implementation details
xDSL modem Encapsulates Subscribers’ traffic to ATM cells, signal (de)modulation
DSL Access Multiplexer (DSLAM) Signal (de)modulation, aggregates traffic over ATM links
Broad Band Remote Access Concentrator BBRAS Terminates the Subscribers’ ATM connections, forwards traffic to the
NSP edge router.
Radius Server Contains configuration templates
NSP edge router
International IPv6 Workshop - Kopaonik, March '05 6
Subscriber
CPE
ModemDSLAM
xDSL
ATM
PHY
IPv6
802.3
PHY
802.3RFC1483
ATM
xDSL
Ethernet bridging
PHY
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!
International IPv6 Workshop - Kopaonik, March '05 7
PPP over AAL5 (PPPoA)
Subscriber
CPE
Modem DSLAM BBRAS
Network Access Provider (NAP) / Network Service
Provider
Radius server
Router
xDSL
ATM
PHY
IPv6
802.3
PHY
802.3RFC1483
ATM
xDSLPHY
PPPoA
IPv6
RFC1483
ATM
PHY
PPPoA
IPv6
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.
International IPv6 Workshop - Kopaonik, March '05 8
PPP over AAL5 (PPPoA)
Subscriber
CPE
Modem DSLAM LAC(BBRAS)
Router
PPPoA
Network Access Provider (NAP)
Network Service Provider (NSP)
Radius server
LNS(Edge router)
L2TP
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.
International IPv6 Workshop - Kopaonik, March '05 9
PPP over Ethernet (PPPoE)
Subscriber
CPE
Modem DSLAM BBRAS
Network Access Provider (NAP) / Network Service
Provider
Radius server
Router
xDSL
ATM
PHY
IPv6
802.3
PHY
802.3RFC1483
ATM
xDSLPHY
PPPoE
IPv6
RFC1483
ATM
PHY
PPPoE
IPv6
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.
International IPv6 Workshop - Kopaonik, March '05 10
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)
International IPv6 Workshop - Kopaonik, March '05 11
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
International IPv6 Workshop - Kopaonik, March '05 12
DIODOS Entities
Network Access Provider (NAP) Network Service Provider
GRNETProvide the Internet interconnection services
Accounting – Management ISPsMaintaining the radius serversAccounting and billing of Subscribers
International IPv6 Workshop - Kopaonik, March '05 13
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
International IPv6 Workshop - Kopaonik, March '05 14
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!
International IPv6 Workshop - Kopaonik, March '05 15
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.
International IPv6 Workshop - Kopaonik, March '05 16
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.
International IPv6 Workshop - Kopaonik, March '05 17
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.
International IPv6 Workshop - Kopaonik, March '05 18
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