DNS Gateway NAT Mapping for Mobile Node Routing
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Solution Overview
Problem
Current communication systems face challenges in establishing data connections between a mobile node behind a Network Address Translator (NAT) and external devices, as the mobile node does not have a permanently allocated external IP address and port number, making it difficult for external devices to initiate communication sessions.
Innovation Solution
A method is introduced that involves allocating a private network IP address and hostname to the mobile node, creating a mapping between the private and public IP addresses at a gateway, and using the Domain Name System (DNS) to resolve the hostname to a public IP address, allowing external nodes to initiate connections by forwarding requests through the gateway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Network Address Translation (NAT) is used to allow mobile devices to access IP data services with limited IPv4 addresses, then the number of mobile users that can access the network is improved, but the ability of external devices to initiate communication sessions with mobile nodes deteriorates
Solution Approach 1:
The system pre-registers mobile nodes in the DNS before external communication is needed. When a mobile node joins the network, its hostname and current IP address are registered in advance in the DNS system, so that when external devices need to communicate, the routing information is already available, eliminating the need for real-time discovery or complex signaling.
Solution Approach 2:
The gateway acts as an intermediary between the private mobile network and the public internet. It maintains a mapping between hostnames and current IP addresses of mobile nodes, and intercepts DNS queries from external devices to provide the correct routing information, thereby mediating the communication between external devices and mobile nodes behind NAT.
2Adaptability or versatility
If mobile nodes use dynamically allocated IP addresses through NAT, then IPv4 address space limitations are addressed, but the stability and predictability of the mobile node's external identifier deteriorates
Solution Approach 1:
Hostnames are assigned to mobile nodes in advance before they connect to the network, similar to how email addresses work. This preliminary assignment of stable identifiers allows the system to adapt to dynamic IP allocation while maintaining stable external identifiers that can be used consistently for communication.
Solution Approach 2:
The system creates a virtual representation of the mobile node's identity through its hostname, which is stored in the DNS system. This hostname copy serves as a stable external identifier that resolves to the current IP address, allowing the mobile node to have both dynamic IP allocation and stable external identification simultaneously.
3Ease of operation
If the NAT maintains a mapping table between external and private IP addresses, then address translation functionality is provided, but the complexity of the gateway system increases
Solution Approach 1:
The patent combines the DNS service and NAT mapping table into a single integrated system at the gateway. Instead of maintaining separate DNS infrastructure and NAT translation tables, the gateway's DNS resolver directly queries its own NAT mapping table, merging two functions into one and reducing overall system complexity.
Solution Approach 2:
The gateway's DNS resolver serves itself by querying its own NAT mapping table for hostname-to-IP translations. This self-service approach eliminates the need for external DNS servers or additional translation layers, as the gateway provides its own routing information directly from its existing NAT data structures.
Data Source
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AI summary
A method of allowing a data connection to be made between a first node attached to a private IP network and a second node external to the private IP network and connected to a public IP network. The method comprises allocating a private network IP address, a hostname, and a service name to said first node, the service name being associated with a service provided by the first node. At a gateway interconnecting said private and public IP networks, a unique public network side port number is allocated to the first node. A mapping between said private network IP address (and optionally the private network side port number) and said public network side port is included in a connection table. The following records are installed in a Domain Name System, DNS, of the public IP network: a service, SRV, record defining said hostname and public network side port number as the location for said service name, and an address, A, record defining a public IP address of said gateway as the location for said hostname. Said second node is thereafter able to perform a DNS lookup in the public IP network in order to resolve said service name into a public IP address and port number and said gateway listens at said public side network port number for connection attempts to said first node.