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PANA in DSL networks
draft-morand-pana-panaoverdsl-01.txt
Lionel Morand France Telecom
Alper Yegin
Samsung
Yoshihiro Ohba
Toshiba
John Kaippallimalil
Huawei
IETF-71, Philadelphia
Draft History
• IETF 66:
– PANA use case for DSL removed from PANA
Framework
• IETF 67:
– First presentation of the "PANA over DSL" draft (v00)
• IETF 67 and IETF 71:
– Draft frozen during finalization of PANA protocol
– DSL Liaison on access authentication requirements
• IETF 71:
– Update version of the "PANA over DSL" draft (v01)
• Based on final version of the PANA base protocol and
comments received and outputs of DSLF liaison discussions
IETF-71, Philadelphia
Context
• Evolution of DSL architecture in two steps:
– Moving from ATM-based aggregation to Gigabit Ethernet
– Moving from PPP-based environment to IP-based model
• "IP Sessions" model ongoing work in DSL Forum
– Basically, an IP session represents the subscriber IP traffic
associated with an IP address
• Need for a subscriber access authentication mechanism
– DSL Forum working around DHCP evolution for supporting EAP
• DSL Liaison discussion during IETF70 in the Internet Area meeting
session
– PANA should also be considered a natural candidate
• Fulfill DSL Forum security requirements provided in the Liaison
IETF-71, Philadelphia
Summary
• Provides guidelines for PANA deployment over
DSL access networks
• Focus on DSL networks migrating from:
– a traditional PPP access model
• Where PPP is used to carry authentication parameters
(PAP/CHAP or EAP methods)
– to a pure IP-based access environment
• No built-in explicit per-subscriber access authentication
– Use of DHCP option 82 for implicit line-based authentication
• PANA provides such a mechanism in this environment
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From v00 to v01
• Alignment with PANA final specification
• Clarification on the possible PAA-EP interface
– Removal of reference to SNMP or ANCP
– Description of DHCP snooping/triggering mechanism
• Reorganization of the draft
– New section on the use of the MAC address as
authorized device ID
– Added section on specific implementation example
• With the use of Link-local IPv4 address
• More details in message flow descriptions
IETF-71, Philadelphia
PAA/EP Location
PAA/EP
DSL Modem/RG
ISP
DSLAM
BRAS
API or
DHCP Snooping
PAA
EP
DSL Modem/RG
ISP
DSLAM
BRAS
IETF-71, Philadelphia
PaC
PaC Location
PAA/EP
DSL Modem/RG
PaC
ISP
DSLAM
Bridge
1/ Bridged Mode in IPv4/IPv6
BRAS
PAA/EP
PaC
DSL Modem/RG
ISP
DSLAM
NAT/Router
2a/ Routed Mode in IPv4
BRAS
PaC
PAA/EP
PaC
DSL Modem/RG
PaC
DSLAM
Router
2b/ Routed Mode in IPv6
ISP
BRAS
IETF-71, Philadelphia
Use of PRPA/POPA
• Mainly useful in IPv4 context
– to prevent waste of scarce IP resources
• In IPv4 context, PRPA may be:
– Link-local IP address
– Private IP address
– Temporary allocated IP address
• with short-lease and/or limited use
• After a successful authentication, POPA is
configured using DHCP
IETF-71, Philadelphia
Generic Message Flows
DSL Model/RG
or host
DSLAM
BRAS
(PaC)
(EP)
(PAA)
AAA Server
1. PRPA Configuration
2. PAA Discovery
3. PANA Authentication
RADIUS/Diameter Authentication
4. POPA Configuration*
5. EP filter setup
6. IP Session/data traffic
*Only needed if the IP address needs to be reallocated
IETF-71, Philadelphia
Specific example
• Deployment scenario in which:
– DSL Network configuration with:
• PaC in the DSL modem/RG
• BRAS hosting PAA, DHCP Server/Relay, and AAA client
• DSLAM acting as EP
–
–
–
–
–
Link-local IPv4 address as PRPA
DHCP-based PAA discovery
EAP-MD5 Authentication method
POPA configured using DHCPv4
EP is triggered by DHCPACK whose 'yiaddr' field is
filled
IETF-71, Philadelphia
Specific Message flows
DSL Model/RG
or host
DSLAM
(PaC)
(EP)
EP Filter
allowing
only DHCP
and PANA
BRAS
AAA Server
(PAA)
1. Link local PRPA Configuration
2. DHCP Inform *(req PAA option)
No IP
Address
Allocation
3. DHCP Ack (PAA option)
5. PANA Auth Req (EAP-MD5 Challenge)
6. PANA Auth Ans (EAP-MD5 resp)
7. RADIUS Access Req (EAP)
8. RADIUS Access Accept (EAP)
9. PANA Auth Req (EAP Success)
Authentication
4. PANA client initiation
10. PANA Auth Ans (Ack)
11. DHCP Discover
12. DHCP Offer
IP Address
Allocation
13. DHCP Request (with IP address in 'yiaddr')
14. DHCP Ack
15. IP Session/data traffic
EP Filter update
based on DHCP
snooping
IETF-71, Philadelphia
Next Step
• Provide more details on:
– The use of link-local IP@
• Mechanism to avoid/resolve possible address conflict/collision
– PANA impacts on DSL network:
• Host, DSL Modem, DSLAM, BRAS, DHCP server
– DSLAM acting as EP
• And the use of DHCP as EP triggering mechanism
– IP@/Identity binding management
• Tight/loose coupling between DHCP/PANA/AAA
• Investigate/clarify the case of hosts behind a NAT/Router in IPv4
– Does PANA support NAT traversal?
• Consider Unspecified IP address?
– As an alternative to link-local IP address as PRPA
IETF-71, Philadelphia
Thank You
IETF-71, Philadelphia