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.