Managing the Co-existing Network of IPv6 and IPv4 under Various Transition Mechanisms

Transcription

1 Managing the Co-existing Network of IPv6 and IPv4 under Various Transition Mechanisms I-Ping Hsieh Shang-Juh Kao Department of Computer Science National Chung-Hsing University 250 Kuo-Kuang Rd., Taichung, 402, Taiwan { iphsieh, sjkao }@cs.nchu.edu.tw TEL: #708 FAX: Abstract Even though IPv6 has been developed for more than a decade, IPv4 is still the most commonly adopted network protocol. However, the significant changes in the new version may cause the transition procedure to continue for several years. Currently, three transition mechanisms, Dual Stack, Tunneling, and Translation, are proposed to solve the problems due to the co-existence of IPv6 and IPv4. In many occasions, there could be more than one transition mechanism between network connections. In order to effectively manage the co-existing environment with various transition mechanisms, this paper presents a practical approach to deal with the management of co-existing networks. In this approach, we firstly determine the underlying transitions by gathering and analyzing corresponding IPv6 addresses. Once transitions are discovered, appropriate management facilities are developed and applied accordingly. Keywords: IPv6, co-existing network, network management 1 Introduction It has been more than a decade for the replacement preparation of IPv4 with IPv6. The long duration is due to the significant and essential changes between these two versions. In order to help users and vendors to migrate to IPv6 smoothly, the IETF s ngtrans 1 activity presented several transition operations required either within a host or between hosts. Within a host, equipping the current Internet Protocol with IPv6 software has been widely applied to add a host to IPv6 community. Between two sites, tunneling focus on IPv6-only to IPv6-only communications and translation addresses communications between IPv6-only and IPv4-only nodes. As a consequence, three transition mechanisms[1] have been launched: Dual Stack, Tunneling, and Translation. These transition mechanisms enable IPv6 traffic transferred over existing IP networks. However, the co-existent environment causes management tasks more complicated. Even worse, there could have two or more transition mechanisms which are simultaneously adopted in an existing IP 1

2 network. How to determine which transition mechanism is applied and to effectively manage the co-existing network are the main theme of this paper. Both transition determination and corresponding management functions are reported. During the transition determination phase, gathering and analyzing all IPv6 addresses in managed scope via exchanging a series of ICMPv6[2] messages is applied to distinguish among various transition methods. Regarding of the management task, based on results of transition discovery, appropriate management functions are proposed. In this paper, we present a practical solution for co-existing network management. In Section 2, we review fundamental transition mechanisms and related management tools. An approach to distinguish among various transition mechanisms is presented in Section 3. Also in this section, several co-existent management facilities are reported accordingly. Finally, a conclusion and several future enhancements are given. could be used to distinguish IPv6 from IPv4, as the value 0x86dd and 0x0800 respectively. Under this transition mechanism, management information of both IP versions could be retrieved via IPv4 messages. However, an exceptional restriction is that the management agent or monitoring tool should be able to collect IPv6 traffic, or say that management agent or tool should support IPv6. For instance, NetFlow[3] version 9, a flow monitor developed by Cisco, could collect both IPv6 and IPv4 traffic information of a dual stack host and export them to a back-end NMS via IPv4. 2 Transition Mechanisms and Related Management Tools As mentioned in the previous section, there exist threes transition mechanisms: Dual Stack, Tunneling, and Translation. In this section we will explore these mechanisms and report several related management tools Dual Stack The simplest transition mechanism, dual stack, as illustrated in Figure 2.1, is that a host equipped with both IPv6 and IPv4 protocol stacks. The protocol field of Ethernet header Figure 2.1 Dual Stack Architecture 2.2. Tunneling The second transition mechanism is tunneling. As shown in Figure 2.2, the operational scheme of tunneling treats the whole IPv6 packet as the payload of an IPv4 packet. That is, IPv6 packets are transmitted over IPv4 network. This mechanism allows IPv6 networks to connect with each other using IPv4 traffic.

3 Figure 2.2 IPv6 Tunneling over IPv4 Based on the operation of packet encapsulating, various implementations of tunneling, such as 6to4[4], ISATAP[5], and Teredo[5], were developed. 6to4 is the most popular one. It effectively enables the communication between two IPv6-only networks over existing IPv4 environment. Another popular tunneling implementation could be ISATAP. ISATAP allows an isolated IPv6 host, in fact, a Dual Stack host, to connect to IPv6-only networks. These two methods could be well operated if the IPv4 NAT[7] mechanism is not adopted in between two IPv6 networks. Teredo was developed so that a tunnel can be constructed even when the NAT exists. With tunneling, all management components such as agent, MIB, NMS, and management protocol itself, must cooperate using the elements of IPv6. The latest version of HP OpenView[8], a network management system, provides such solution but it s expensive Translation To connect IPv6-only and IPv4-only networks, translation gateway is applied. As shown in Figure 2.3, translation mechanism works as a gateway to translate between IPv6 and IPv4 packet headers. The SIIT[9] algorithm was developed to build bidirectional translation rules between IPv6 and IPv4 header, as well as between ICMPv6 and ICMPv4 packets. The well-known translator, NAT-PT[10], was implemented based on SIIT. Figure 2.3 Translation Mechanism Figure 2.4 Management via proxy Agent To deal with management tasks across both sides of a translation gateway, in [11], the authors proposed an approach that the translation gateway plays as a proxy agent. Figure 2.4 shows the architecture. Management commands from one side should be translated, if necessary, and forwarded to the target device. The management tool, IPv6 Management Gateway[12], allows, under an existing IPv4 network management platform, a manager to manage the native IPv6 network by translating SNMP, ICMP and TCP protocol messages between IPv4 and IPv6 networks Variations of Transition Mechanisms Of various transition implementations, not only the operational flow but also the address specifications are different. Practically, IPv6 address plays an important role in discovering the implementation of each transition type. In fact, every transition implementation has its own specific address requirement. Table 2.1 lists the differentiation of various common transition

4 implementations. Table 2.1 Classifying Several Transition Mechanisms Types Connectivity Transition Address Specification Dual Stack 4-to-4 over 4 6-to-6 over 6 Dual Stack IPv4 address IPv6 address 6to4 6-to-6 over 4 Tunnel 2002:IPv4 address/48 ISATAP 6-to-6 over 4 Tunnel IPv6 Prefix/64+ ::5EFE:IPv4 address/64 Teredo 6-to-6 over 4 Tunnel 3FFE:831F/32 SIIT 6-to-4, 4-to-6 Translation ::FFFF: IPv4 address/96 In reality, more than one transition type s could be involved in a co-existing network. For example, in Figure 2.2, tunneling is used to connect two IPv6-only networks, while both routers are dual-stacked. In such hybrid environment, a NMS must handle management tasks under multiple transition mechanisms. sition type is adopted in a co-existing network. Thus, to gather all IPv6 addresses assigned to all interfaces inside the managed network is the first step for managing a co-existing network. The operational procedure of gathering all IP addresses within managed scope is first to get one legal IPv6 address of managed scope and then to 3 Co-existing Network Management Each of three transition mechanisms mentioned query all IP addresses by exchanging ICMP messages with other interfaces. Ipv6 supports two automatic address configuration mechanisms, Stateless Address Autoconfiguration[13] and Dynamic Host Configuration in the last section may have many imple- mentations. In order to manage a co-existing network, it is necessary to differentiate among various transition mechanisms as well as different implementations of each transition. Consequently, an appropriate management approach for co-existing networks should include two parts. First of all, distinction among detailed transition methods is carried out. Secondly, appropriate management facilities are developed and applied correspondingly. Protocol version 6[14]. Initially, an IPv6 address could be assigned via either configuration. If the managed network does not provide either mechanism or the NMS doesn t appear in the managed network, the manager should manually enter a legal IPv6 address. After obtaining an address, we send ICMPv6 Neighbor Solicitation[15] messages to network to be managed, and then, all active interfaces would respond ICMPv6 Neighbor Advertisement[15] messages. Eventually, all MAC addresses of active interfaces can be obtained. Next, we send 3.1. Determination of Transition Types out Inverse Neighbor Solicitation[16] messages to all alive interfaces, and receive the replied As indicated in Table 2.1, IPv6 address is a valuable information for determining which tran- Inverse Neighbor Advertisement[16] messages. From the reply messages, all IPv6 addresses are

5 expected to be included. And, this is the way we gather all IPv6 addresses within the managed network. Finally, we deliver IPv4 RARP[17] messages to detect any IPv4 capable node inside managed network. Once all addresses are obtained, we are able to determine which types of transitions are utilized in the co-existing network, by the address specification in Table Management Facilities The second part of co-existence network management is to develop appropriate management facilities. The facilities are strongly relied upon the designated transition types over the co-existing network. Three management facilities: topology discovery, detection of IP misusing, and traffic monitoring, which are well-developed in IPv4 networks, are taken as examples to demonstrate the co-existing network management. Network topology plays a critical role for managing a network system efficiently. In [18], the authors proposed an excellent topology discovery algorithm which mainly adopts SNMP to get related MIBs in IPv4 network. Under the translation mechanism, the algorithm could be effectively executed to depict the native IPv6 network topology. IPv6 Management Gateway, an implementation of translation mechanism, could switch related SNMP commands and target MIB objects between heterogeneous IP networks. However, two management components, agent and MIB, should support IPv6 when the network devices are located within the IPv6 network. In order to execute the algorithm in tunneling environment, not only all management components, but also the algorithm itself should support IPv6. Modification of target MIB objects for retrieving exact information should be done to guarantee the correct execution. Under dual stack mechanism, the management protocol remains unchanged since the communication could be constructed via IPv4 messages. To provide a fair network access environment, preventing IP address from misusing and equally distributing network bandwidth are imperatively. In [19], the authors presented an approach to deal with these two problems via SNMP. Along with the utilization of topology discovery algorithm, it is useful and easy to implement under translation gateway. However, modifications are necessary in order to apply to the co-existing network using dual stack or tunneling mechanism. Of these three management facilities, the IPv6 supporting status under various transition mechanisms can be summarized as listed in Table 3.1. In this table, U indicates that the management components are not necessary to support IPv6, while N denotes that the IPv6 support is necessary for management components. Table 3.1 Conditions of Management components under transition mechanisms Agent MIB Protocol Tools Dual Stack N N U N Tunneling N N N N Translation N N U U N: necessary for supporting IPv6 U: unnecessary for supporting IPv6 4 Conclusions Due to the significant differences of both IP versions, fully deployment of IPv6 could take for

6 years. Until then, management of co-existing network remains and is more challenging. More than one transitions could be employed in a network connection, which cause the co-existing management even more difficult. In this paper, we first review various transition mechanisms. Then, we propose a practical solution to manage co-existing networks. In our approach, transition methods deployed in the system is first determined. Both ICMPv6 and ICMPv4 messages are used to gather all IP addresses within the network for the determination of transition mechanisms. Depending upon the discovery, several management facilities are developed to support the co-existing network management. Management facilities including topology discovery, detection of IP misusing, and traffic monitoring are reported. Since the co-existent environment is transient, our network management system should be flexible to cope with whatever changes in the future. Consequently, modular design and robustness are preferred. As mobile devices gaining popular, how to safely provide a network services also imposes another challenge to the management problem. In addition, mobility issue and security concern are getting apparent and important, and must be cooperated with the management system. References [1] R. Gilligan, and E. Nordmark, Transitions Mechanisms for IPv6 Hosts and Routers, RFC2893. [2] A. Conta, and S. Deering, Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification, RFC2463. [3] NetFlow, protocol_family_home.html. [4] B. Carpenter, and K. Moore, Connection of IPv6 Domains via IPv4 Clouds, RFC3056 [5] F. Templin, T. Gleeson, M. Talwar, and D. Thaler, Intra-Site Automatic Tunnel Addressing Protocol (ISATAP), IETF draft, draft-ietf-ngtransisatap-14.txt, work in progress, Aug [6] C. Huitema, Teredo: Tunneling IPv6 over UDP through NATs, IETF draft, draft-huitema-v6ops-teredo-00.txt, work in progress, June [7] P. Srisuresh, and K. Egevang, Traditional IP Network Address Translator (Traditional NAT), RFC3022. [8] HP OpenView, ucts/. [9] E. Nordmark, Stateless IP/ICMP Translation Algorithm (SIIT), RFC2765. [10] G. Tsirtsis, and P. Srisuresh, Network Address Translation - Protocol Translation (NAT-PT), RFC2766. [11] G.M. Keeni,, K. Koide, D. Chakraborty, and N. Shiratori, SNMP in the IPv6 context, Applications and the Internet Workshops, Jan. 2003, pp [12] IPv6 Management Gateway, [13] S. Thomson, and T. Narten, IPv6 Stateless Address Autoconfiguration, RFC2462. [14] R. Droms, Ed., J. Bound, B. Volz, T. Lemon, C. Perkins, and M. Carney, Dynamic Host Configuration Protocol for IPv6 (DHCPv6), RFC3315. [15] T. Narten, E. Nordmark, and W. Simpson,

7 Neighbor Discovery for IP Version 6 (IPv6), RFC2461 [16] A. Conta, Extensions to IPv6 Neighbor Discovery for Inverse Discovery Specification, RFC3122 [17] R. Finlayson, T. Mann, J.C. Mogul, and M. Theimer, Reverse Address Resolution Protocol, RFC903. [18] Fu-Min Chang, Lai-Ming Shiue, and Shang-Juh Kao, "A Practical Approach for Network Topology Discovery", The 8th World Multi-Conference on Systemics, Cybernetics and Informatics, Orlando, Florida, USA, July 18-21, [19] I-Ping Hsieh, Lai-Ming Shiue, and Shang-Juh Kao, "Implementation of a Department Local Area Network Management System", 33rd International Conference on Computer and Industrial Engineering, Jeju, Korea, March 25-27, 2004.