Analysis and comparison of IPV6 and NAT

Summary

Computer networks, telecommunications networks and cable television networks are moving towards a converged next-generation network (NGN) based on IP technology, resulting in a rapid increase in demand for IP address resources, exceeding the initial expected and designed 32bit (IPv4 address length). There are roughly two types of approaches to address resource shortages: 1 "open source", that is, the use of greater address length of the next generation of IP protocol--ipv6, which is a long-term solution; 2 "throttling", that is, to maximize the utilization of existing IPV4 address resources, such as the use of private multiplexing Plus network address translation (NAT) technology , is some medium and short term solution. This paper analyses and compares the present situation of these two technologies and their existing problems.

1 Introduction

The internet has flourished in recent years based on the IPV4 protocol. Whether it is the scope of network coverage and network capacity, or the number of users and business types are growing rapidly. Computer networks, telecommunications networks and cable television networks are moving towards a converged next-generation network of ip-based Technologies (NGN). At the same time, the IP technology obtains the history, the present and the future network construction person favor and the chase stick, must soberly realize that the IPV4 technology itself still has many imperfect places. Issues such as quality of Service (QoS), security, and address shortages are some of the key issues facing the IPV4 network, and these potentially "fatal" drawbacks are hampering the further popularization and application of IP technologies and services. This article discusses the address shortage problem solution, currently has two types: (Computer science)

(1) "Open source", that is, the use of greater address length of the next generation of IP protocol--ipv6, this is a long-term solution;

(2) "throttling", that is, to maximize the utilization of existing IPV4 address resources, such as the use of private multiplexing and various network address (port) translation technology, is some medium and short term solution.

2 Improve Address utilization

Here first introduces "throttling" technology. The methods that have been proposed or have been used to improve IPV4 address utilization are:

* Address recycling: The IP Standardization Organization Internet Engineering Task Force (IETF) has issued a call for institutions and organizations that have been allocated "excessive" addresses in the early days to return the resources they are unlikely to use, but it seems to have had little effect at the moment.

* Stricter address allocation policy: Previous Internet address name Assignment (IANA) organization address allocation policy is based on the "expected largest" allocation of addresses, and now in order to reduce the IP address allocation rate, the policy has been changed to "the current need scale."

* Non-class inter-domain Routing (CIDR): As Class B addresses are nearly depleted, using CIDR technology to break the division of address types (such as Class A, B, and C), multiple consecutive C-class addresses are used to distribute the aggregations. The adoption of CIDR technology has slowed the growth of Internet routing tables in recent years.

* Dial-up Access: Use Point-to-Point Protocol (PPP) and Dynamic Host Configuration Protocol (DHCP) to dynamically assign IP addresses on demand and achieve address reuse when subscriber-dial access.

* Variable eldest child netmask (VLSM): Increase the utilization of address space by dividing an enterprise's enterprise network (Intranet) into subnets of different scales.

* Private address plus network address translation: The use of "private" IP address in the enterprise network, the address between different enterprise networks can be reused. When a user in a private address network communicates with the Internet, a network address translation must be made between them, since the address used by the enterprise network is not in a single space for the internet. The range of private addresses specified by the IETF is 10/8,172.16/12,192.168/16 three (RFC 1918). This is the most frequently used and the most efficient way to solve the problem of address shortages. Of course, the enterprise only chooses to use the private address stipulated in RFC 1918, and sometimes it is not only because of the reason of address reuse, but also for other aspects such as security, control and so on.

3 Problems with NAT

When a private IPv4 is used by the enterprise network, the address to the Internet (public IPv4) is not in a single, unified addressing space. Therefore, when the devices in these networks communicate with the Internet, they must address translation at the boundaries of the network, typical translation techniques including network address Translation (NAT) and network address port translation (NAPT), hereinafter referred to as NAT. The main technical limitations of the "throttling technology" NAT exist are [RFC 2993]:

* When the enterprise network communicates with other networks, NAT can affect network performance and reduce network throughput.

* Disruptive to the original internet End-to-end design concept (end-to-end transparency) only applies to client/server model applications and not to the Peer-to-peer (peer-to-peer) application model. In this model, the promotion of the push business is very restricted.

* In devices that maintain connection state and dynamic mapping information, a single point of failure may occur.

* Increased complexity of multihomed (multi-home) technologies that increase the reliability of enterprise site sites and Internet connectivity.

* Prevents the provision of security services at the network level.

* When the enterprise network needs to be merged with other private networks, there may be an address conflict (overlap) problem.

*NAPT and specific domain IP (Realm specific ip,rsip) increase the complexity of operations.

* The authentication mechanism for the Simple Network Management Protocol (SNMPV3) of version 3 is more complex and even ineffective.

* Many high level application protocols are incompatible with [RFC 3027]. For example, some applications (IPSEC,KERBEROS/5, etc.) can not traverse NAT, and some (such as FTP,H.323,SIP,SMTP,RSVP,DNS,SNMP, etc.) need to use the Application Layer Gateway (ALG) to achieve. With the help of ALG, each new application must consider increasing the support of the application on NAT, which violates the idea that IP technology is independent of high level application.

4 IPV6 controversy

Here is an introduction to "open source" technology. Although IPv4 's design is based on the technical level of the the mid 1970s and the very limited operational experience of the time, the great success of the IPV4 Internet has proven that IPV4 's design is fundamentally successful. When designing IPV6 in the the 1990s, there are plenty of reasons to keep the IPv4 in IPv6 to the fullest, adding only the address length. But based on the experience of the Internet over the years, some "revolutionary" changes should be made to other parts of IPV4. Compared with the IPV4 protocol, the biggest change of the IPV6 protocol is the obvious simplification of the header design, which is mainly embodied in: