Mobile IPv6 & Cellular Telephony

Charles E. Perkins

Nokia Research Center

Mountain View, CA USA

http://www.iprg.nokia.com/~charliep

charliep@iprg.nokia.com

Why Mobile IP?

• Both ends of a TCP session (connection) need to keep the same IP address for the life of the session.

• IP needs to change the IP address when a network node moves to a new place in the network.

Mobile IPv4 changes the mobility problem into a routing problem

Mobile IPv4 protocol overview

• Advertisement from foreign agent• Seamless Roaming: mobile node keeps home address• Foreign agent offers care-of address• Mobile Node “always on” by way of home agent

Foreign Agent

178.24.9.36

Home Agent

correspondent node

The Mobile IP(v4) solution

• Mobile node always uses the same IP address (called the home address) for communication  

• The care-of address is used for routing• The home agent manages home network

operations for the mobile node while it is away from home:– encapsulation– proxy ARP

• Specified in RFCs 2002-2006

Foreign Agents & Triangles

• The foreign agent advertises the care-of address, and terminates the tunnel from the home network

• All traffic to the mobile node is sent to the mobile node's home address. Traffic from the mobile node does not have to traverse the home network.

• This leads to the phenomenon of triangle routing.

Ingress Filtering

• Ingress filtering routers prevent packets from entering the Internet unless the source IP address is topologically correct.

• This leads to the possibility of reverse tunneling (RFC 2344) from the care-of address to the home agent.

Cellular architectures

• Involve SS7 over "control plane" to set up virtual circuits for "user plane" traffic

• Are highly optimized for voice traffic (low delay, guaranteed bandwidth), not data

• Tend toward "intelligent network" philosophy which for IP is a misplaced locus of control.

• Operators want to migrate towards "All-IP" solutions (whatever that means…).

Mobile IPv6 Design Points

• Enough Addresses

• Enough Security

• Address Autoconfiguration

• Route Optimization

• Destination Options

• Reduced Soft-State

Mobile IPv6 protocol overview

• Advertisement from local router• Seamless Roaming: mobile node keeps home address• Address autoconfiguration for care-of address• Binding Updates sent to correspondent nodes• Mobile Node “always on” by way of home agent

Local Router

charliep@nokia.com

Home Agent

correspondent node

Enough Addresses

• 340 undecillion addresses (340,282,366,920,938,463,463,374,607,431,768,211,456) total

• Billions of IP-addressable wireless handsets• Address space crunch is already evident

– recent unfulfilled request to RIPE

• Multi-level NAT unknown/unavailable• Even more addresses for embedded wireless• Especially interesting for China now

Enough Security (almost)

• Authentication Header• Needed for Binding Update

– Remote Redirect problem

• Encapsulating Security Payload• Required from every IPv6 node• Key distribution still poorly understood

– PKI?– AAA?

Address Autoconfiguration

• A new care-of address on every link

• Stateless Address Autoconfiguration

• Link-Local Address Global Address

• Stateful Autoconfiguration (DHCPv6)

• Movement Detection

Routing Prefix MAC address

Destination Options

• Binding Updates without control packets– allows optimal routing– replaces IPv4 Registration Request messages

• Home Address option– better interaction with ingress filtering– supported by all IPv6 network nodes

• Binding Acknowledgement– replaces Registration Reply

Route Optimization

• Reduces network load by ~50%– (depending on your favorite traffic model)

• Most Internet devices will be mobile

• Route Optimization could double Internet-wide performance levels!

• Binding Update SHOULD be part of every IPv6 node implementation

Improved ICMP messages

• IPv4 ICMP returns only 8 payload bytes

• IPv4 home agents could not relay errors– insufficient inner header information– some data sources might never find out about

broken links

• IPv6 ICMP messages return enough data

• Also used for anycast home agent discovery

Mobile IPv6 status

• Interactions with IPsec fully worked out

• Mobile IPv6 testing event Sept 15-17– Bull, Ericsson, NEC, INRIA

• Connectathon last month – success!

• Internet Draft is ready for Last Call

• Another bake-off likely by fall

AAAv4 and Cellular Telephony

• Terminology

• Protocol overview

• Key Distribution

• Scalability and Performance

• IETF Status

• How can we make it work for Mobile IPv6?

Terminology

• Authentication – verifying a node’s identity• Authorization – for access to resources

– according to authentication and policy

• Accounting – measuring utilization• Network Access Identifier (NAI) – user@realm• Challenge – replay protection from local attendant• AAAF for foreign domain• AAAH for home domain

AAA & Mobile IP protocol overview

• Advertisement from local attendant (e.g., router)• Connectivity request w/MN-NAI from Mobile Node• Local Attendant asks AAAF for help• AAAF looks at realm to contact AAAH• AAAH authenticates & authorizes, starts accounting• AAAH, optionally, allocates a home address• AAAH contacts & initializes Home Agent

AAAF AAAH

Local AttendantHome Agent

charliep@nokia.com

Key Distribution

• New security model– just one SA: mobile node AAAH

• So, association needed HA mobile node

• TR45.6, others, want also:– local attendant mobile node

• AAAH can allocate the keys for this

Brokers

• Needed when there are 1000’s of domains• NAI is perfect to enable this• AAAF decides whether to use per realm

– may prefer bilateral arrangement

• iPASS, GRIC

AAAHAAAF

Local AttendantHome Agent

Scalability and Performance

• Single Internet Traversal• Brokers• Eliminate all unnecessary AAA interaction• Handoff between local attendants (routers)

– can use keys from previous router

• Regional Registration• HA can use single care-of address per

domain

Mobile IP/AAA Status

• AAA working group has been formed• Taking a page from the existing model with

RADIUS • Mobile IP (v4) AAA requirements draft

– Last Call “over”

• Several 3G requirements documents online• Mobile IP/AAA extensions draft• AAAv6 Internet Draft(s) submitted

– stateless and stateful variations

Other features (needed for IPv6)

• Routers used instead as mobility agents• Regional registration

– eliminates most location update traffic– GGSNs/border routers are candidates

• UDP Lite• Robust Header Compression• AAA HLR adaptation layer• Challenge generation (not from HLR?)• Privacy considerations

Hierarchical Foreign Agents

Home Agent

GFA

Home Agent stores GFA address as the Care-of Address

Mobile Node registers only once with Home Agent Mobile node registers locally with GFA

Often, only one level of hierarchy is being considered

LFA

3GPP with GPRS

InternetInternet

PSTN

HSS

Subscription andLocation Directory

Call ProcessingServer/Gatekeeper

CPS/GK

SGSN

Evolution from cellular packet/GPRS

BSC/RNC

BSS

GGSN

GPRS

GW

Traditional BSS withpacket data QoS enhancements

Mobility agentAt GGSN

One (of many) “ALL-IP” visions

PSTN

HA(mobility within

serving ntw)

HA

FW

AAA Server AAA Server

Internet, Intranets

Subscriberdatabase

FW

CPS

GW

"Slim RNC/BSC"

Evolution from general IP networks

CDMA2000 3G micromobility

AAA Server

HA

AAA Server

Subscriberdatabase

PDSN

RNN

CDMA2000 3G micromobility

• Terminate physical layer distant from “FA”

• Protected, private n/w between FA and MN

• PDSN (Packet Data Serving Node) ~ GFA

• RNN (Radio Network Node) ~ LFA

• RNN manages the physical layer connection to the mobile node

CDMA2000 3G Requirements

• GRE encapsulation (but will it survive?)

• Reverse Tunneling (RFC 2344)

• Registration Update

• Registration Acknowledge

• Session-specific registration extension– contains MN-ID, type, MN Connection-ID– contains Key field for GRE

CDMA2000 Registration Update

• Used for handovers to new RNN

• Acknowledgement required– allows PDSN/old RNN to reclaim resources

• New authentication extension required

• Home address 0

• Home agent PDSN

• Care-of address RNN

IMT-2000/UMTS/EDGE reqt’s

• Independent of access technology– so should work for non-GSM also

• Interoperation with existing cellular

• Privacy/encryption (using IPsec)

• QoS for Voice/IP and videoconferencing– particular concern during handover

• Fixed/mobile convergence desired

IMT-2000 reqt’s, continued

• Charge according to QoS attribute request

• Roaming to diverse access technologies– e.g., Vertical IP

• Route optimization

• Identification/authorization based on NAI

• Proxy registration for legacy mobile nodes

• Signaling for firewall traversal

IMT-2000 reqt’s, continued

• Reverse tunneling• Private networks

– but, still allow access to networks other than the mobile node’s home network

• Dynamic home address assignment• Dynamic home agent assignment

– even in visited network– even when roaming from one visited network to

another

IPv6 status for cellular telephony

• Seems highly likely to be mandated for 3GPP, with IPv4 support optional only

• MWIF recommendation for IPv6• 3GPP2 study group favorable towards IPv6• Seems difficult to make a phone call to a

handset behind a NAT (not impossible, just expensive and cumbersome and protocol-rich)

Summary and Conclusions

• Future Internet is largely wireless/mobile• IPv6 needed for billions of wireless devices• Mobile IPv6 is far better and more efficient• Autoconfiguration suitable for the mobile Internet• Security is a key component for success• AAA has a big role to play for cellular rollout• Leverage from current cellular interest