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HRPD Femto Local IP Access: Overview
Peerapol Tinnakornsrisuphap (peerapol@qualcomm.com)
Qualcomm
October 27th, 20083GPP2 Seoul, Korea
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What is Local IP access?
• Previously called “HRPD Femto Local Breakout”• Local IP access provides local IP connectivity from the device connecting through
Femto Access Point – yielding similar functionalities to wireless LAN without requiring additional support for WLAN on handset At the same time, connectivity to operator’s core is still preserved for accessing operator’s
specific contents and for supporting seamless handoff of QoS-sensitive services
• Potential usages Off-load operator’s traffic from operator’s core networks while AT is connected with Femto AP Synchronizing/streaming media on device with media servers, printers, etc. Allow device and Femto AP to be more than “just phone service in poor coverage”
InternetInternet
Femto /Router
ATPDSN
Media
Printer
TVHome
Domain
Operator’s Backhaul
AT in macro
network
Some Use Cases for Local IP Access
1. Share content between phones, bypassing the macro network
2. Stream video stored on home PC to phone
3. Share and stream music between phone and music player
4. Print photos on phone on a home printer
5. Control home appliances (e.g., A/C) from phone
Home Network
Internet
Air Conditioning
Local IP Access (for EV-DO) - Architecture
HRPDFemto
AT
Operator’sNetwork(PDSN)
Correspondent Node(e.g., CNN.com)
DSLRouter(NAT)
Correspondent Node(e.g., local printer)
Correspondent Node(e.g., another AT)
PublicInternet
IPsectunnel
• Red = Traffic Traversing Operator’s network Goal : Allow ATs to be able access services
similar to when AT is on macro network Assumption : There is IPsec tunnel between
Femto cell and the wireless operator’s network
• Blue = IP access to public Internet via Femto Goal : Traffic can bypass home network to save
operator’s resources and improve latency
• Green = Local IP access to local CN Goal : AT can communicate with servers at
home
Local IP Access : Design
• Reuse EV-DO access stream (i.e., AN-terminated stream) and AN-PPP, which is currently only being used for access authentication, to assign local IP address
Legacy AT will reject the request or drop the request
Same call flow with simple IPv4 address assignment on PDSN-PPP
• AN-PPP session and IP interface terminate after AT leaves femto AN
AT can try to request the same IP address (e.g., in enterprise environment)
• Femto AP also configures the AT with the egress filter – for example
Default IP interface is AN-PPP and only packets for operator’s subnet are sent via PDSN
Or default IP interface is PDSN and only packets for local subnet are sent via AN-PPP
• Operator may control whether to enable local IP access during femto configuration phase
• A12 will define a RADIUS attribute to control whether local IP access is allowed for a particular AT
Access Authentication
PPP and LCP Negotiation
Transmitting Packet Data
Session Establishment
AT Femto AP
AT Ready to ExchangeData on AN Stream
IPCP – Config Request [IP = 0.0.0.0, egress filter]
IPCP – Config NAK [IP = Local IP address, egress filter]
IPCP – Config Request [IP = FAP address]
IPCP – Config Ack
IPCP – Config Request [IP = Local IP address,egress filter]
IPCP – Config Ack
Femto APassigns local IP address for AT
Local IP Access Protocol Stack
HRPD air-interfaceSession Layer and below
HRPD air-interface
Session Layer and below
Link-Layer
PL
HRPD air-interface
Session Layer and below
PL
A10
Link-Layer
PL
IP 2
PL
A10
Link-Layer
PL
Link-Layer
PL
IP 1
IP 2
AN-PPP
Packet App
Access Stream
Access Stream
Packet App
AN-PPP
IP 2
IP 1
PDSN-PPP
Packet App
Service Stream
Packet App
Service Stream
PDSN-PPP
IP 1
Access Terminal
Femto AP
Femto AP
Local Correspondent Node
PDSN End Host
Why Femto AP cannot act as “just a pipe” on AN-PPP stream?
• Q: Why Femto AP needs to know local IP address assigned to AT – not just forwarding any packets from the AT to LAN?
• A: Femto AP needs to be aware of the local IP address assigned to the AT so that it can defend the IP address for any packet in the subnet for the AT
Detailed explanation:Assuming Ethernet, when router/gateway receives IP packet for the AT, it will broadcast ARP Request for resolving Ethernet MAC address associated with local IP address of the AT. The Femto AP needs to respond to the request eventhough the request is not for the IP address of the femto AP.
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