1. Field of the Invention
The present invention relates to a method and apparatus for reserving a session resource in an IPv4/IPv6 combination network system, and more particularly, to a method and apparatus for reserving a session resource in an IPv4/IPv6 combination network system that is capable of notifying a starting node of a tunnel session about whether a last node supports RSVP or not while assigning IPv4 address information to an IPv6 host according to a dual stack transition mechanism (DSTM), or Dual IP Layer Stack Transition Mechanism (DSTM), when reserving a resource according to an RSVP mechanism in a 4over6 DSTM environment.
2. Description of the Related Art
The Internet is a core infrastructure of information society. With the development of real-time, high quality service such as voice over IP (VoIP) and Internet TV, most Internet traffic has changed from traffic including text information to multimedia traffic including voice, image, and video information. In addition, traffic has dramatically increased.
The current Internet protocol version 4 (IPv4)-based Internet uses a short address and a complex header structure to accommodate the rapidly increasing number of hosts and multimedia traffic. This degrades the processing speed of a router and a node that process traffic and, in turn, the overall performance of the Internet.
Internet protocol version 6 (IPv6) developed to solve such problems associated with IPv4-based Internet has features such as an expanded 128 bit address system, a simplified header structure, improved quality of service (QoS), and enhanced security.
In reality, the current Internet cannot be completely converted into an IPv6 network within a short period of time since it is widely used as an IPv4 network. The IPv4 network and IPv6 network will coexist for the time being while the IPv4 network is gradually replaced by the IPv6 network.
Coexistence of IPv6 hosts/routers and IPv4 hosts/routers in a current IPv4 network is critical to successfully build the IPv6 network.
Efficient accommodation of rapidly increasing traffic requires an Internet infrastructure capable of providing QoS required for traffic having different features, such as voice, video, and data. It is also necessary to define a model capable of providing QoS for multimedia traffic in an IPv4/IPv6 combination network including both the IPv4 network and the IPv6 network.
Methods for processing packets in such an IPv4/IPv6 combination network including IPv4 hosts and routers and IPv6 hosts and routers have been proposed by the Internet Engineering Task Force (IETF). The methods include a dual stack-based method, a header translation method, and a tunneling method.
In the dual stack based method, all hosts and routers have a dual stack protocol prior to completely shifting to an IPv6 network. That is, the method allows both IPv4 and IPv6 to be used until all systems on the Internet use IPv6.
The header translation method is useful when most systems on the Internet use IPv6 but some still use IPv4. A sender translates a header of an IPv6 packet into an IPv4 header for transmission to a recipient when the recipient does not understand IPv6.
The tunneling method is used when two hosts using IPv6 have to communicate through an IPv4 network. An IPv6 packet is encapsulated in an IPv4 packet upon entrance into an IPv4 area and decapsulated from the IPv4 packet upon exit from the IPv4 region.
Resource reservation protocol (RSVP), a tunneling method for processing packets in the IPv4/IPv6 combination network, is a mechanism that reserves network resources in advance in order to accommodate traffic requiring different QoS in an IP layer.
RSVP may be a flow-based model that allows a user to establish a flow as a kind of virtual line from a source to a destination and to reserve flow-specific resources required by all routers between the source and the destination, thereby guaranteeing QoS.
Here, flow refers to a collection of packets that have the same source and destination address information, the same source and destination port information, and the same session identifier information.
The current RSVP allows the same resource as used for an end-to-end (EtoE) session to be reserved even within the tunnel by dividing an RSVP session for one flow into an end-to-end session and a tunnel session, mapping the two sessions to each other, and separately reserving a resource for each session in order to support end-to-end RSVP on a path including a tunnel.
Among transition mechanisms proposed by IETF Next Generation Transition Working Group (Ngtrans WG), etc., an IPv6 translation mechanism such as network address translation protocol translation (NAT-PT) provides protocol stack translation to enable communication between an IPv6 host and an IPv4 host.
However, because such a translation mechanism translates an IPv6 packet into an IPv4 packet or an IPv4 packet into an IPv6 packet, it is unable to support end-to-end security in a network layer and a transport layer. The translation mechanism is also unable to support perfect translation between the IPv6 header and the IPv4 header.
When an application layer protocol has data containing an IP address, the translation mechanism does not support the translation. To accommodate this application layer protocol, an application layer gateway (ALG) for the application layer protocol is required.
In contrast, a dual stack transition mechanism (DSTM), using a dual stack having both an IPv4 stack and an IPv6 stack as well as tunneling, supports a transparent connection between the dual stack host and the IPv4 host without causing any problem due to protocol translation.
However, the DSTM considers only the initialization of a connection from the dual stack host to the IPv4 host and provides no connection from the IPv4 node to the dual stack host in the IPv6 network.
To solve such problems associated with the original DSTM, a 4over6 DSTM has been proposed. The 4over6 DSTM is able to provide a transparent connection between the IPv4 host and the dual stack host in the IPv6 network even when the IPv4 host establishes the connection to the dual stack host.
Since QoS (Quality of Service) is not considered in the 4over6 DSTM, a tunnel RSVP mechanism capable of reserving resources for end-to-end session, including a tunnel section, is used to provide end-to-end QoS in the 4over6 DSTM environment.
Network Working Group Request for Comments (RFC) 2746 (RSVP Operation Over IP Tunnels) describes an approach for providing RSVP protocol services over IP tunnels. In the RFC 2746, however, there is a limitation that a starting node of the tunnel is only allowed to establish a RSVP session on the tunnel after receiving a reservation (Resv) message containing “NODE_CHAR object” from a last node of the tunnel. This limitation is caused because the starting node of the tunnel cannot be aware of whether the last node supports the tunnel RSVP mechanism.