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[attachment=7949]
By- Isha Yadav
09-ITMG-2009CS
Introduction
A 4G or 4th generation network is the name given to an IP based mobile system that provides access through a collection of radio interfaces.
Accessing information anywhere, anytime, with a seamless connection to a wide range of information and services, and receiving a large volume of information, data, pictures, video, and so on.
A 4G network promises seamless roaming/handover and best connected service, combining multiple radio access interfaces (such as WLAN, Bluetooth, GPRS) into a single network that subscribers may use.
With this feature, users will have access to different services, increased coverage, the convenience of a single device, one bill with reduced total access cost, and more reliable wireless access even with the failure or loss of one or more networks.
Feature of 4G
High Speed - 4G systems should offer a peak speed of more than 100Mbits per second in stationary mode with an average of 20Mbits per second when travelling.
High Network Capacity – Should be at least 10 times that of 3G systems. This will quicken the download time of a 10-Mbyte file to one second on 4G, from 200 seconds on 3G, enabling high-definition video to stream to phones and create a virtual reality experience on high-resolution handset screens.
Fast/Seamless handover across multiple networks – 4G wireless networks should support global roaming across multiple wireless and mobile networks.
Next-generation multimedia support – The underlying network for 4G must be able to support fast speed volume data transmission at a lower cost than today.
Goal of 4G
The goal of 4G is to replace the current technology of core mobile networks with a single worldwide core network standard, based on IP for control, video, packet data, and voice.
This will provide uniform video, voice, and data services to the mobile host, based entirely in IP. The objective is to offer seamless multimedia services to users accessing an all IP based infrastructure through heterogeneous access technologies.
IP is assumed to act as an adhesive for providing global connectivity and mobility among networks. An all IP-based 4G wireless network has inherent advantages over its predecessors. It is compatible with, and independent of the underlying radio access technology
Mobility Management Issues in 4G Networks
The three main issues regarding mobility management in 4G networks are as follows:
The optimal choice of access technology
The design of a mobility enabled IP networking architecture.
Quality of Service.
Handoffs
The two main Handoff methods are:
Horizontal Handoff.
Vertical Handoff.
Horizontal Handoff
A Horizontal handoff is a handoff between two network access points that use the same network technology and interface. For example, when a mobile device moves in and out of various 802.11b network domains, the handoff activities would be considered as a horizontal handoff, since connection is disrupted solely by device mobility.
Vertical Handoff
A Vertical handoff is a handoff between two network access points, which are using different connection technologies. For example, when mobile device moves out an 802.11b network into a GPRS network, the handoff would be considered a vertical handoff.
Handoff for 4G Networks over MIPv6
Mobility support is the key feature to realize all IP mobile networks. Many mobility technologies have already been introduced and standardized at the Internet Engineering Task Force (IETF).
Mobile IPv6 is a mobility protocols which enables a mobile node to roam between sub-networks without any session break.
Mobile IPv6 allows a mobile node to be addressed by a home address all the time even though the mobile node changes its point of attachment to the Internet.
When the mobile node is attached to a new network, the mobile node sends a binding update to its home agent (called home registration), a router on the mobile node's home page link as shown in Figure 1.
A binding update describes the relation between the home address and an IP address associated with the mobile node while it is on the visiting link, called care of address.
When a correspondent node sends a packet to the home address of the mobile node, the home agent receives the packet by normal routing in the Internet.
Since the home agent has the binding for mobile node, the home agent can forward the packet to the current mobile node's care-of address over the bi-directional tunnel.
After the mobile node receives the tunneled packet, the mobile node may send a binding update, causing the correspondent node to cache the mobile node's binding into its binding cache database.
Though all the Mobile IPv6 related signals must be basically protected by IPsec, Mobile IPv6 employs the different security mechanism, called return routability, to exchange a key to encrypt the binding update. The mobile node sends two messages such as HoTI and CoTI to a correspondent node.
The HoTI must be tunneled through its home agent. The corresponded node will reply HoT and CoT carrying keys. After these messages exchange, the mobile node finally sends a binding update to the correspondent node.
The binding acknowledgment is not mandatory for binding registration to correspondent nodes.
After this binding registration, the correspondent node routes packets directly to the mobile node's care-of address according to the registered binding cache.
Mobile IPv6 Security Threats
Unauthenticated or malicious BUs opens the door for many types of attacks, a few of which are-
False Binding Update attacks
Man-in-the-Middle Attack
Denial-of-Service Attack
False Binding Update attacks
By spoofing Binding Updates, an attacker can redirect traffic to itself or another node and prevent the original node from receiving traffic destined to it.
For example, let us say nodes A and B have been communicating with each other, then, an attacker, node C, sends a spoofed Binding Update packet to node B, claiming to be node A with a care-of-address of node C.
This would cause node B to create a binding for node A’s CoA and subsequent further traffic to node C, believing it to be node A’s new care-of-address. Node A would not receive the data it was intended to receive, and, if the data in the packets is not protected cryptographically, node C will be able to see all of node A’s sensitive information
Man-in-the-Middle Attack
An attacker may also spoof BUs to two corresponding nodes in order to set itself as a Man-in-the-Middle between a MN and a CN.
For example, if node A and node B are communicating, the attacker could send both nodes a spoofed Binding Update with the care-of-address set to its own address.
This would cause both nodes A and B to send all packets to node C rather than to each other.
Denial-of-Service Attack
By sending spoofed BUs, an attacker could also send large amounts of unwanted traffic to overwhelm the resources of a single node or that of a network.
The attacker could first find a site with streaming video or another heavy data stream and establish a connection with it. Then it could send a BU to the corresponding node, saying to redirect subsequent data traffic to the attacker’s new location, that of an arbitrary node.
This arbitrary node would be then bombed with a large amount of unnecessary traffic. Similarly, the attacker could also use spoofed BUs to redirect several streams of data to random addresses with the network prefix of a particular target network, thereby congesting an entire network with unwanted data.
Return Routability Procedure
The Return Routability Procedure protects against Denial of-Service attacks in which an attacker uses the victim's address as its care of address, but it does not defend against attackers that are able to monitor the path between the MN and the CN.
The procedure involves two steps where tokens are exchanged between the MN and CN.
[1] The Home and Care-of Test Init messages,
[2] The Home and Care-of Test Messages
Home and Care-of Test Init messages
The Home and Care-of Test Init messages, shown below, are sent at the same time by the mobile node to the correspondent node and they verify that the MN is reachable at its home and care-of addresses and request keygen tokens to be sent from the CN. Each message also contains an init cookie, a 64-bit random value, which must be returned by the correspondent in the next step to verify the identity of the correspondent node.
Home and Care-of Test Messages
The Home and Care-of Test Messages are sent simultaneously from the CN to the MN, in response to the MN’s test init messages, containing keygen tokens.
Included in both messages are the init cookies, which verify that the message is being received by the CN, or at least by a node in the path to the CN.
Problem of MIPv6
When a mobile node changes its care-of address, it must send a binding update to update all the binding cache entry stored in a home agent and correspondent nodes. While this binding update exchange, the mobile node cannot receive or send packets to the correspondent nodes.
It can send packets to correspondent nodes which it does not notify binding, as soon as home registration is completed. This loss is not negligible when a mobile node run a real-time application.
In addition to that, connection oriented communication such as TCP session will start congestion control for this loss of connectivity caused by this binding update. Therefore, as often as mobile node moves, the performance of communication surely decrease.
PMIPv6
PMIPv6 is based on MIPv6 as it extends MIPv6 signaling and reuses many concepts such as the Home Agent (HA) functionality.
Proxy Mobile IPv6 comprises of two core elements i.e. Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG), which are responsible for mobility management.
Initial Attachment and Signal Flow
Handover between two MAGs
Initial Attachment and Signal Flow
a) Initially on attaching to MAG, MN-Identifier (MN-ID) of Mobile Node is authenticated via access security protocols on the network to be accessed.
b) After successful access authentication MAG obtains the MN’s profile.
c) MAG sends a Proxy Binding Update (PBU) to the LMA of Mobile Node regarding its current location.
d) After receiving the PBU message, LMA assigns a MN-HNP (Home Network Prefix) and creates a Binding Cache Entry (BCE) that binds the Proxy-Care of Address of MAG with MN-HNP.
e) It also establishes a bi-directional tunnel to MAG and sends a Proxy Binding Acknowledgement (PBA) message including the MN-HNP.
f) After receiving the PBA message, tunnel is being sets up between MAG and LMA. After that it sends Router Advertisement (RA) message to MN on the access page link to advertise the MN-HNP as the hosted onlink- prefix.
g) On receiving RA messages Mobile Node configures the IP address. After completion of configuration procedure, MN uses this address for all future packets delivery.
Handover between two MAGs
When MN moves to another access network belonging to MAGnew as shown in Fig.2, MAGprev detects that it has moved away from its access link. Therefore, it follows the following steps for handover.
a) MAGprev sends a DeRegistration PBU (DeReg PBU) to LMA.
b) Once LMA received DeReg PBU, it sends a PBA message to MAGprev
c) On the other hand when MAGnew detects the attachment of MN, it obtains the MN-profile using MN-ID. It uses similar authentication steps as performed during initial attachment.
Problems in PMIPv6
PMIPv6 suffers from unacceptable handover latencies and packet losses. Where, Handover latency means the maximum time interval in which mobile Handover latency means the maximum time interval in which mobile node does not receive any packet due to the process of handover.
And on the other hand packet loss means number of downstream packet lost at the mobile node during handover period. It offers a loose coordination of handover control, there is limited coordination in the LMA, which replaces existing bindings with new ones based on timestamps provided in the proxy binding updates.
Therefore it is necessary to design and specify PMIPv6 extension that enhances its performance.
Future Work
To find an agent based solution for mobile node initial attachment and handover in PMIPv6 environment.
