IPv6 solution for 3G mobile communication system

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IPv6 solution for 3G mobile communication system [Copy link]

1. Market driving force of IPv6

　　Due to the rapid development of the Internet and Internet applications in recent years, the number of people using the Internet and the number of new computers joining the Internet has increased rapidly. The available addresses of the 32-bit IPv4 address structure currently used on the Internet are facing a serious shortage of addresses. The popularization of broadband access modes around the world and the sharp increase in the number of broadband Internet users have changed the way people used to use dial-up Internet access. The large increase in the number of user terminal devices that are always online has intensified the consumption of IPv4 addresses.

　　In addition, the development of WLAN, 2.5, and 3G wireless mobile data networks around the world has accelerated the formation of a communication model centered on the Internet. Since the growth of mobile communication users is much faster than that of fixed network users, especially the rapid development of various mobile terminals with networking functions, considering the need for direct personal multimedia communications anytime, anywhere, in any form, the existing IPv4 is far from meeting the network market's requirements for address space, end-to-end IP connection, quality of service, network security, and mobility performance.

　　2. IPv6 in 3G Mobile Communication System Architecture

　　Wireless communication is the most flexible access method to the communication network, and the technical integration of the data communication industry and the wireless communication industry is the key to finally realize "Any to Any" communication. The development of the Internet and data communication industry has accelerated the evolution of the wireless communication industry, enabling the wireless communication industry to better meet the rapidly growing demand for data services (mainly IP services) in terms of technology. The third-generation mobile communication system 3G will usher in the Internet era of mobile communications.

　　Whether it is 3GPP's UMTS or 3GPP2's CDMA2000 system, their system architecture will evolve and develop in the direction of full IP. The carrying of voice, data, multimedia and other service forms is based on IP; the end-to-end service call model is based on IP; the network switching and call control of RAN and CN core are also based on IP. In the system planning of 3G/B3G, the direction of 3GPP and 3GPP2 specifications has determined that IPv6 is the development direction of 3G/B3G network carrying and service applications. In the IMS stage of 3G/B3G, the network system (including packet domain and circuit domain) will be fully based on or compatible with IPv6.

　　People often get confused when they learn about IPv6 in the 3GPP/3GPP2 system. This is because IPv6 is in two different layers. The first is the data bearer layer, where user data traffic flows from the MS to the PDN through the operator's PLMN. The other is the transport bearer layer, which is a different logical layer from the data bearer layer. In general, IPv6 appears in four areas in the 3GPP/3GPP2 standard. As shown in Figure 2, 2 are in the user data bearer layer and 2 are in the transport bearer layer. The following figure introduces the application environment and role of IPv6 in this system.

　　One thing needs to be clarified. First, "IP bearer service" describes the user data service bearer plane in the PLMN, not the transport bearer plane. To better understand the data bearer plane and the transport bearer plane, please refer to Figure 3. We can see that there are two different IP layers in the figure. The orange part (including the green part used by IMS) is the IP layer that carries user data. It is the network layer used to transmit UDP or TCP between UE and application. In addition, in the PLMN, there is another set of IP protocol stack in the operator's network. But as shown in the figure, it belongs to another layer, namely the transport bearer layer.

　　3. IPv6 at the data bearer level

　　The data bearer layer ranges from the MS to the network (called PDN in 3G standards) equipment that provides services that the MS wants to access, which may be another MS in the end-to-end call model. At the user's data bearer layer, IMS (IP Multimedia Subsystem, the green part in Figure 2) and IPv6 are very important parts, because the 3GPP standard requires IMS to use IPv6 and establishes its uniqueness. Please note that 3GPP2 also adopted this IMS protocol model for the consideration of the integration of the two systems. IMS IPv6 data flow will flow from MS to PDN and enter the IM subdomain of the mobile operator. IMS uses SIP as the control plane to control user data. User data will flow to the Intranet, Internet, ASP or WASP that provides SIP applications. This is exactly the part represented by the green arrows in Figures 2 and 3. Starting from the MS that supports dual stacks (IPv4, IPv6), all network elements related to the IMS call process in the 3G system will have to support IPv6. Including support for dual-stack MS, packet gateway and network address on Pi network side, CSCF of SIP control plane, etc., involving IPv6 address allocation of MS, simple IP, mobile IP service PPP session user routing convergence in PDSN, FA and HA pipeline, HA COA address binding table update, etc. This means that in the implementation stage of IMS, using IPv6 as the bearer network of the core network (including packet and circuit domain) will be the best choice. At the same time, through the implementation of QoS technology in IPv6 network, according to the requirements of different service levels and traffic models, the end-to-end (within the same management domain) service quality assurance is fully guaranteed for different levels of service applications and different SLA requirements of 3G network mobile terminals. There will be different stages before 3G is officially commercialized, such as the integration of equipment from different manufacturers, testing and deployment, etc. The most prominent problem at this stage is the difference between IETF and 3GPP/3GPP2 SIP network elements, and the interoperability between IMS and external SIP devices using IPv4.

　　4. IPv6 at the transport bearer level

　　There are two important parts to consider at the transport bearer level. In 3GPP/3GPP2 terms, they are the core network (CN) and the radio access network (RAN), both of which can or should use IPv6. The transport bearer level exists in the bearer layer of the RAN network, the RP/Gn interface, and the 3G CN network layer (such as the Gp interface), and IPv6 appears as an option.

　　The transport bearer plane does not make any data forwarding decisions for the user interface in the CN and RAN. Only at the PDSN/GGSN does a part of the forwarding decision based on the IP packet header begin. More intelligent routing processing occurs behind the Gi interface of the GGSN and the Pi interface of the PDSN. Between the MS and the PDSN/GGSN, the IP layer of the application is transmitted through a tunnel. In the 3GPP UMTS system, the CN transmission uses the tunnel protocol GTP (GPRS Tunnel Protocol) to support the connection between the MS and the GGSN. In GPRS (2.5G), GTP only appears between the SGSN and the GGSN; in the UMTS environment, GTP is also connected to the relevant RNC (Radio Network Controller) and the SGSN. GTP can use IPv4 or IPv6. As we mentioned earlier, the IP version of the transport bearer plane (here the GTP IP layer) is completely independent of the data bearer plane. From the MS to the PDSN/GGSN via the uplink link, or from the GGSN to the MS via the downlink. When an IP data packet is delivered from the MS to the PDSN/GGSN, its IP routing and forwarding will actually begin.

　　5. 3G-oriented IPV6 core network solution

　　IPv6 is a basic requirement for the development of future 3G system networks. It has a huge address space, which can accommodate the development of mobile networks and a large number of "peer-to-peer" and "any-to-any" communications. IMS also adopts IPv6 technology for the above reasons. There are many ways to integrate IPv6 services on the core backbone network of operators: running IPv6 private networks on multiple different data link layers, dual-stack IPv4-IPv6 backbone networks, or using existing MPLS backbone networks. If the IPv6 data traffic and the operating income generated meet the necessary investment and risks agreed by both parties, then users can deploy these solutions on the backbone network.

　　We need a way to build a reliable IP core network in a commercial environment to serve current technology needs (such as GPRS) and carry IPv6. This is a basic requirement for tools that solve the transition and coexistence issues from IPv4 to IPv6. To address the different requirements of various services, the network needs to provide a range of reliability and scalability capabilities. MPLS is a key part of IP core network design.

　　5.1. Cisco 6PE Solution

　　6PE provides an MPLS backbone with the same capabilities, flexibility and scalability for both IPv4 and IPv6: fast forwarding, traffic engineering with fast reroute, VPN and DiffServ without impacting core network performance. All IPv6 functions are handled at the edge of the network, enabling smooth injection of IPv6 traffic. 6PE avoids the business risks of not being able to support IPv6 today, and also avoids the risks of modifying the current core network to do so. For the data bearer plane (GPRS and IMS), the PDN routes IPv6 data traffic to the APN and the communicating peers. The PDN can be a single network (such as a mobile operator's PDN) or a series of networks from a mobile operator to an application provider. The same MPLS features can be used for IPv4 and IPv6. In any case, the PE device is responsible for routing IP data, and the core network is only responsible for forwarding data. We have shown how an MPLS network can support mobile wireless IP transport between user terminal devices. Figure 5 summarizes the PDN.

　　6PE is a very easy-to-deploy solution that can quickly implement IPv6 for operators when they need it. With MPLS 6PE, any IPv6 traffic will not affect other traffic within the unified backbone network. Application services will not be affected by the introduction of IPv6. IPv6 services are flexibly introduced from the edge of the network in a scalable manner, without any IPv6 addressing restrictions and without putting the stable and controllable IPv4 backbone network at risk.

　　Cisco is working with the IETF to ensure the smooth progress of the corresponding standardization work. Specifically, the Cisco 6PE solution complies with the latest version of the draft standard issued by the IETF for "Using BGP to connect IPv6 domains across multiple IPv4 clouds" [IPv6_BGP].

　　5.2. Pure IPv6 MPLS Core Network Solution

　　Another way is to use an MPLS core router running IPv6 to build a new pure IPv6 network, or to completely upgrade the P and PE routers of the existing MPLS backbone network and provide dual control interfaces for IPv4 and IPv6. The core IGP and label distribution protocol require upgrades.

　　Cisco's IPv6 network solution will meet the network evolution requirements of 3G at different stages. We can divide the network evolution of 3G system into two major steps, namely the evolution from traditional mobile circuit domain to full IP and the evolution of the entire system to IMS. In the first stage, Cisco's IPv6 solution can provide reliable guarantee for the overall requirements of circuit domain IPization; in the IMS system evolution stage, Cisco's IPv6 network can be fully utilized to provide efficient bearer services and business optimization for the network and business of 3G system.