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Proxy Mobile IPv6 (PMIPv6 )

 

Introduction

Service providers are seeking new ways to accommodate the surge in mobile data traffic and the variety of smart, portable devices coming onto their networks.

Fixed and mobile operators are therefore looking at both licensed and unlicensed (Wi-Fi) technologies to meet this demand and to expand their customer footprint. Trusted Wi-Fi hotspots can be integrated into the SP’s existing policy and accounting infrastructure allowing the SP to maintain subscriber accountability. At the same time, traffic from these trusted Wi-Fi hotspots can be integrated into the SP’s existing packet core using standard Proxy Mobile IPv6 (s2a-PMIPv6) interface in order to provide IP mobility across Wi-Fi and 4G networks to enhance subscriber experience.     

This document is an attempt to explain in high level about PMIPv6 .

Proxy Mobile IPv6 (or PMIPv6, or PMIP)

is a network-based mobility management protocol standardized by IETF and is specified in RFC 5213. It is a protocol for building a common and access technology independent of mobile core networks, accommodating various access technologies such as WiMAX, 3GPP, 3GPP2 and WLAN based access architectures. Proxy Mobile IPv6 is the only network-based mobility management protocol standardized by IETF.

Contrary to Mobile IP approach, this functionality is implemented by the network, which is responsible for tracking the movements of the host and initiating the required mobility signalling on its behalf. However in case the mobility involves different network interfaces, the host needs modifications similar to Mobile IP in order to maintain the same IP address across different interfaces.

Network-based mobility management enables IP mobility for a host without requiring its participation in any mobility-related signaling.  The network is responsible for managing IP mobility on behalf of the host.  The mobility entities in the network are responsible for tracking the movements of the host and initiating the required mobility signaling on its behalf.  This specification describes a network-based mobility management protocol and is referred to as Proxy Mobile IPv6.

A proxy mobility agent in the network performs the signaling with the home agent and does the mobility management on behalf of the mobile node attached to the network.  Because of the use and extension of Mobile IPv6 signaling and home agent functionality, this protocol is referred to as Proxy Mobile IPv6 (PMIPv6).

PMIPv6 vs  Mobile IP

MIP (Mobile IP, originally RFC2002) is an early approach to get mobility in the Internet.As mentioned earlier , PMIPv6 does network based mobility  .

Mobile IPv6

  • MIPv6 Home Agent is the Mobility Anchor
  • Care of Address is acquired by MN in the foreign network

PMIPv6

  • LMA is the Mobility Anchor
  • Care of Address is that of MAG

Some of the other challenges seen with Mobile IP :

1. Clients must implement MIP in the kernel (MIP mobility is host-based).

    difficult to implement kernel changes
    difficult to deploy (clients need software upgrade to get MIP support)

[ The main advantage of PMIPv6 is that it needs no additional modifications on the MN (kernel and user space software), therefore it is transparent to the user devices. PMIPv6 is an access technology independent solution, so it can be used with WLAN, WiMAX, 3G UMTS, LTE, LTE-A or any other technology in the future].

2. Large delay in  hand off .

[ PMIPv6  provides fast handovers according to its localized nature, which means that the PMIPv6 has a well-defined domain area (Local Mobility Domain, LMD) where exchanging signaling messages is quite fast ].

3. Security concerns (MIP support in the kernel provides an additional attack vector).

Where can PMIPv6 be deployed?

PMIPv6 is primarily targeted at the following networks:

1. WLAN-based campus-style networks:
    PMIPv6 provides transparent hand off for mobile nodes in campus networks.
2. Advanced 3G/4G networks
    Replace GTP (GPRS tunneling protocol) by PMIP, thus reduce the costs and management in the network .

PMIPv6 Terminologies

Note - There are two new nodes defined in PMIPv6: (1) The Local Mobility Anchor (LMA) and (2) The Mobile Access Gateway (MAG). 

  • Proxy Mobile IPv6 Domain: A network where the mobility management of a mobile node is handled using the Proxy Mobile IPv6 protocol. The domain consists of network entities like MAG & LMA between which Proxy Binding can be maintained on behalf of the mobile nodes.

  • Local Mobility Anchor (LMA): LMA is the home agent for the mobile node in a PMIPv6 domain.  It is the topological anchor point for the mobile node's home network prefix and is the entity that manages the mobile node's binding state.

  • Mobile Access Gateway (MAG): MAG is a function on an access router that manages the mobility-related signaling for a mobile node that is attached to its access link.  It is responsible for tracking the mobile node's movements to and from the access link

  • Mobile Node (MN): An IP host, mobile node or router whose mobility is managed by the network. The MN may be an IPv4-only node, IPv6-only node, or a dual-stack node and is not required to participate in any IP mobility related signaling for achieving mobility for an IP address that is obtained in that PMIPv6 domain.

  • Correspondent Node (CN): The device that the mobile node (MN) is communicating with such as a web server. A correspondent node may be either mobile (e.g. another MN) or stationary (e.g. server).

  • Network Access Identifier (NAI): NAI is the user identity submitted by the client during network access authentication.  In roaming, the purpose of the NAI is to identify the user as well as to assist in the routing of the authentication request. The standard syntax is "user@realm" or as defined in rfc 4282.

  • Mobile Node Identifier: The identity of a mobile node in the PMIPv6 domain. This is the stable identifier and is typically an identifier such as a Network Access Identifier (NAI) or other identifier such as a Media Access Control (MAC) address.

  • Proxy Binding Update (PBU): A request message sent by MAG to LMA for establishing a binding between the MN's home network prefix and the MAG to which MN is attached

  • Proxy Binding Acknowledgement (PBA): A reply message from LMA in response to a PBU message from MAG.

Wi-Fi Mobility

Lets look at different types of Wifi PMIPv6 deployments .

WiFi Aggregation with Standalone LMA

This deployment scenario is termed as “standalone” since there is no requirement of integrating LMA with the Evolved Packet Core.In this model, PMIPv6 facilitates IP mobility to a client less mobile node while roaming across Wi-Fi access network.

 

WiFi Aggregation with Mobile Packet Core (MPC)

In this model, PMIPv6 facilitates IP mobility to a clientless mobile node not only while roaming across Wi-Fi access network but also while roaming across Wi-Fi and 4G/LTE infrastructure, since the subscriber session is anchored at the Packet Gateway or Evolved Packet Core.

 

WiFi Aggregation with Multiple Mobile Network Operator (MNO)

This deployment model is an extension of the previous model and targeted for deploying Wi-Fi access as a Layer-2 wholesale service. Layer-2 wholesale allows a wireline or wireless service provider deploying Wi-Fi access network to partner with retail service providers, MNOs or MVNOs for use of their Wi-Fi infrastructure. The retail SP/MNO/MVNO has the direct business relationship (accounting, billing, policy etc.) with the end subscribers while having service level agreement with the Wi-Fi wholesale access provider.

Useful Show Commands

The following show commands can be used to verify the PMIPv6 client connectivity

show pmipv6 domain

This command displays summary information of a PMIPv6 domain

> show pmipv6 domain <domain_name> profile <profile_name>
NAI: @vodfone.com
APN: VodafoneLMA: Vodafonelma
NAI: *APN: ciscoapn
LMA: ciscolma

Note: Note that the domain name and the profile name can be up to 127 case-sensitive  alphanumeric characters.

show pmipv6 mag bindings

To display the binding information of a mobile access gateway (MAG), use this command.

> show pmipv6 mag binding
[Binding][MN]: Domain: D1, 
Nai: MN1@xyz.com        
[Binding][MN]: State: ACTIVE       
[Binding][MN]: Interface: Management        
[Binding][MN]: Hoa: 0xE0E0E02, att: 3, llid: aabb.cc00.c800        
[Binding][MN][LMA]: Id: LMA1       
[Binding][MN][LMA]: lifetime: 3600        
Binding][MN][GREKEY]: Upstream: 100, Downstream: 1

show pmipv6 mag globals

This command displays the global PMIPv6 parameters of a Mobile Access Gateway.

> show pmipv6 mag globals

Domain  : D1 MAG Identifier  : M1         MAG Interface                   : Management         Max Bindings                    : 10000         Registration Lifetime           : 3600 (sec)         BRI Init-delay time             : 1000 (msec)         BRI Max-delay time              : 2000 (msec)         BRI Max retries                 : 1         Refresh time                    : 300 (sec)         Refresh RetxInit time           : 1000 (msec)         Refresh RetxMax time            : 32000 (msec)         Timestamp option                : Enabled         Validity Window                 : 7         Peer#1:                 LMA Name: AN-LMA-5K      LMA IP: 209.105.210.10         Peer#2:                 LMA Name: AN-LMA         LMA IP: 209.105.210.4         Peer#3:                 LMA Name: AN-LMA         LMA IP: 209.105.210.4

show pmipv6 mag stats

In order to display the statistics of the Mobile Access Gateway (MAG), use this command.

> show pmipv6 mag stats    
[M1]: Total Bindings    : 1 [M1]: PBU Sent          : 7 [M1]: PBA Rcvd          : 4 [M1]: PBRI Sent         : 0 [M1]: PBRI Rcvd         : 0 [M1]: PBRA Sent         : 0 [M1]: PBRA Rcvd         : 0 [M1]: No Of handoff     : 0

show pmipv6 profile summary

Using this command, you can verify the summary of the PMIPv6 profiles.

> show pmipv6 profile summary     Profile Name     WLAN IDS (Mapped) ------------    -----------------   Group1            6

Note: To debug various PMIPv6 related events messages use the command  debug proxy-mobility.

 

To see the PMIPv6 configuration details, use the following show commands

To see the details of a profile of a PMIPv6 domain, enter this command:

show pmipv6 domain domain-name profile profile-name
To see a summary of all the PMIPv6 profiles, enter this command:

show pmipv6 profile summary
To see the global information about the PMIPv6 for a MAG, enter this command:

show pmipv6 mag globals
To see information about the MAG bindings for LMA or NAI, enter this command:

show pmipv6 mag bindings {lma lma-name | nai nai-name}
To see statistical information about MAG, enter this command:

show pmipv6 mag stats domain domain-name peer peer-name
To see information about PMIPv6 for all clients, enter this command:

show client summary
To see information about PMIPv6 for a client, enter this command:

show client details client-mac-address
 To see information about PMIPv6 for a WLAN, enter this command:

show wlan wlan-id

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