Wide Area Network Concepts

Mobile Networking Concepts

• Wide Area Network (WAN) facilitates long-distance communication between various networks.
• Foreign Agent acts as an intermediary in a visited network, managing mobility functions for mobile nodes.

Mobile User Contact Challenges

• Difficulty in contacting a mobile friend who frequently relocates.
• Traditional methods such as searching phone books or contacting relatives may be ineffective.

Basic Service Set (BSS) in Wireless LAN

• Multiple Basic Service Sets (BSSs) are deployed to extend the physical range of wireless LANs in organizations.
• Each BSS operates under the same IP subnet, enhancing mobility for connected devices.

Seamless Mobility Between BSSs

• Wireless stations can transfer between BSSs while maintaining active TCP sessions.
• H1 can transition from BSS1 to BSS2 without changing its IP address, provided the interconnection device is not a router.

Maintaining TCP Connections

• Transitioning within the same IP subnet allows devices to retain their IP and ongoing connections during movement.
• If a router is involved during the transition, a new IP address would be required, disrupting existing TCP connections.

Handoff Process

• As H1 moves from AP1 to AP2, it identifies a stronger signal from AP2 and successfully associates with it.
• The handoff process allows ongoing TCP sessions to continue without interruption.

Switch Self-Learning Capabilities

• Switches autonomously learn and maintain forwarding tables based on the movement of devices within a network.
• Self-learning effectively manages transitions when users change locations infrequently.

Challenges for Highly Mobile Users

• Standard switch operations are insufficient for users who rapidly move between BSSs while needing sustained TCP connections.
• As H1 switches from BSS1 to BSS2, the switch must update its forwarding table to reroute frames to the new access point.

Solution for Mobile Users

• AP2 should broadcast H1's MAC address to the switch after re-association.
• This action prompts the switch to update its forwarding table, redirecting traffic to AP2.

Mobility Management Techniques

• To maintain network application transparency during user mobility, it is advantageous for a mobile node to keep its permanent address.
• When connected to a foreign network, traffic directed to the permanent address is rerouted using a care-of-address (COA).

Care-of-Address (COA) Creation

• Foreign agents create a COA that aligns with the foreign network's address.
• Two addresses are linked to each mobile node: a permanent address and a care-of-address.

Mobility Management Approaches

• Routing Handles Mobility: Routers advertise mobile node addresses within their standard routing table exchanges.
• End-System Handles Mobility:
  • Indirect routing involves communication through a home agent.
  • Direct routing sends data directly to the mobile user’s foreign address.

Triangle Routing Issue

• Direct routing can simplify connectivity but requires the correspondent to acquire the mobile node's care-of-address, complicating communication if the mobile changes networks.

Strategy with Anchor Foreign Agents

• An anchor foreign agent persists in the first visited network and manages data routing.
• When a mobile node shifts to a new foreign agent, data is forwarded from the previous agent, establishing a chaining mechanism.

Conclusion

• Effective mobility management revolves around maintaining constant connections and smooth transitions between varying networks while addressing the challenges associated with user mobility.

Dive into the essentials of wide area networks, focusing on key concepts like foreign agents and mobility functions. This quiz will test your knowledge on the roles and functionalities within a visited network environment. Prepare to enhance your understanding of network communications!