Network Working Group J. Wu Internet-Draft J. Bi Intended status: Experimental X. Li Expires: April 14, 2008 G. Ren K. Xu Tsinghua University M. Williams Juniper Networks Oct 12, 2007 SAVA Testbed and Experiences to Date draft-wu-sava-testbed-experience-03 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 14, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Wu, et al. Expires April 14, 2008 [Page 1] Internet-Draft SAVA Testbed Oct 2007 Abstract Since the Internet uses destination-based packet forwarding, malicious attacks have been launched using spoofed source addresses. In an effort to enhance the Internet with IP source address validation, we prototyped an implementation of the IP Source Address Validation Architecture (SAVA) and conducted the evaluation on an IPv6 network. This document reports our prototype implementation and the test results, as well as the lessons and insights gained from our experimentation. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. A Prototype SAVA Implementation . . . . . . . . . . . . . . . 5 2.1. Solution Overview . . . . . . . . . . . . . . . . . . . . 5 2.2. IP Source Address Validation in the Access Network . . . . 6 2.3. IP Source Address Validation at Intra-AS/Ingress Point . . 8 2.4. IP Source Address Validation in Inter-AS Case (Neighboring AS) . . . . . . . . . . . . . . . . . . . . . 8 2.5. IP Source Address Validation in Inter-AS Case (Non-Neighboring AS) . . . . . . . . . . . . . . . . . . . 11 3. SAVA Testbed . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1. CNGI-CERNET2 . . . . . . . . . . . . . . . . . . . . . . . 14 3.2. SAVA Testbed on CNGI-CERNET2 Infrastructure . . . . . . . 14 4. Test Experience and Results . . . . . . . . . . . . . . . . . 17 4.1. Test Experience . . . . . . . . . . . . . . . . . . . . . 17 4.2. Test Results . . . . . . . . . . . . . . . . . . . . . . . 17 5. Design Limitation . . . . . . . . . . . . . . . . . . . . . . 19 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 10.1. Normative References . . . . . . . . . . . . . . . . . . . 24 10.2. Informative References . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 Wu, et al. Expires April 14, 2008 [Page 2] Internet-Draft SAVA Testbed Oct 2007 Intellectual Property and Copyright Statements . . . . . . . . . . 27 Wu, et al. Expires April 14, 2008 [Page 3] Internet-Draft SAVA Testbed Oct 2007 1. Introduction By design the Internet forwards data packets solely based on the destination IP address. The source IP address is not checked during the forwarding process in most cases. This makes it easy for malicious hosts to spoof the source address of the IP packet. We believe that it would be useful to enable the Internet security to enforce the validity of the source IP address for all the packets being forwarded. . Enforcing the source IP address validity can help us achieve the following goals: o The packets which carry spoofed source addresses will not be forwarded, making it impossible to launch network attacks with spoofed source addresses. o The packets which hold a correct source address can be traced back accurately. This can benefit network diagnosis, management, accounting and applications. As part of the effort in developing a Source Address Validation Architecture (SAVA), we have implemented a SAVA prototype on an operational network, a native IPv6 backbone network of the China Next Generation Internet project, and conducted evaluation experiments. In this document we first describe our prototype solutions and then report our experimental results. We hope that this document can provide useful insights to those interested in the subject, and can serve as an initial input to future IETF effort in the same area. In recent years there have been a number of research and engineering efforts to design IP source address validation mechanisms, such as[RFC2827][Park01][Li02][Brem05][Snoe01]. Our SAVA prototype implementation was inspired by some of the schemes from the proposed or existing solutions. The prototype implementation and experimental results presented in this report serve only as an input, and by no means pre-empt any solution development that may be carried out by future IETF effort. Wu, et al. Expires April 14, 2008 [Page 4] Internet-Draft SAVA Testbed Oct 2007 2. A Prototype SAVA Implementation 2.1. Solution Overview In the Internet at large, it is unrealistic to expect any single IP source address validation mechanism to be universally supported. Different operators and vendors may choose to deploy/develop different mechanisms to achieve the same end, and there need to be different mechanisms to solve the problem at different places in the network. Furthermore, implementation bugs or configuration errors can also render the intended implementation in-effective. Therefore our prototype SAVA implementation is a combination of multiple coexisting and cooperating mechanisms. More specifically, we implement source IP address validation at three levels: access network source address validation; intra-AS source address validation; and inter-AS source address validation, as shown in Figure 1.The system details can be found in[WRL2007]. __ ____ __ ____ .-'' `': .-'' `': | | | | | +-+----+ | Inter-AS SAV | +-+----+ | | |Router+--+------------------+---|Router+ + | +--.---+ | | +--.---+ | Intra-AS | | | Intra-AS | | | SAV | +--+---+ | SAV | +--+---+ | | |Router| | | |Router| | '_ +--.---+ _ '_ +--.---+ _ `'---|---''' `'---|---''' _.--|-----. _.--|-----. ,-'' | `--. ,-'' | `--. |'+-----------------+`| |'+-----------------+`| | | Router | | | | Router | | | ++----------------+ | | ++----------------+ | Access | | | | | Access | | | | | Network| | +------++------+ | Network| | +------++------+ | SAV | | |Switch||Router| | SAV | | |Switch||Router| | | | +------++------+ | | | +------++------+ | | | | | | | | | | | |+-+--+ +----+ +----+ | |+-+--+ +----+ +----+ | ||Host| |Host| |Host| | ||Host| |Host| |Host| | `.----+ +----+ +----+,' `.----+ +----+ +----+,' `--. _.-' `--. _.-' `--------'' `--------'' Key: SAV== Source Address Validation Figure 1: Solution Overview It is important to enforce IP source address validity at the access Wu, et al. Expires April 14, 2008 [Page 5] Internet-Draft SAVA Testbed Oct 2007 network. That is, when an IP packet is sent from a host, the routers, switches or other devices ( if you implement the functions in a special device ) should check to make sure that the packet carries a legally assigned source IP address. If this access network source address validation is missing, then a host may be able to spoof the source IP address which belongs to another local host. We use the term "intra-AS source address validation" to mean the IP source address validation at the attachment point of an access network to its provider network, also called the ingress point. IP source address validation at ingress points can enforce the source IP address correctness at the IP prefix level, assuming the access network owns one or more IP address blocks. This practice has been adopted as the Internet Best-Current-Practice [RFC2827][RFC3704]. Even in the absence of the access network source address checking, this ingress checking can still prevent the hosts within one access network from spoofing IP addresses belonging to other networks. In theory, everyone would do validation in the access network level and again at the intra-AS level. In reality, some packets will get validated and some will not get validated. As a result, the Intra-AS validation level will also need to be able to preserve validation status learnt from the Inter-AS validation level (see below) from ingress to egress for transit traffic. This is a topic for further study. Inter-AS IP source address validation refers to mechanisms that enforce packet source address correctness at AS boundaries . The first two steps of source address validation utilize the network physical connectivity of the access network and the ingress points. Because the global Internet has a mesh topology, and because different networks belong to different administrative authorities, IP source address validation at Inter-AS level becomes more challenging. Nevertheless we believe this third level of protection is necessary to detect packets with spoofed source addresses, when the first two levels of source address validation are missing or ineffective . In the rest of this section we describe the specific mechanisms implemented at each of the three levels in detail. 2.2. IP Source Address Validation in the Access Network At the access network level, the solution will make sure the host inside the access network could not use the source address of other host. The host address should be legally assigned to the host in a static way or a dynamic way. A layer-3 source address validation device (SAVA Device) for access network (the device can be a function inside the CPE router or a separate device) is deployed at the exit Wu, et al. Expires April 14, 2008 [Page 6] Internet-Draft SAVA Testbed Oct 2007 of the access network. Some source address validation agents (SAVA Agent) are deployed inside the access network, these agents can be a function inside the first hop router/switch that connected to hosts. Some layer-3 protocols are designed between the host, SAVA Agent and SAVA Device. Only a packet originating from the host that owns the valid source address can finally pass through the SAVA Agent and SAVA Device. Therefore, there are two parts: host-to-agent and agent-to- device (in case that there is no agent can be deployed, the protocol is between the host and SAVA device directly, so we denote it as "host/agent-device part" in the following sections). The main idea of the first-hop part (host-to-agent) is to create a dynamic binding between a switch port and valid source IP address, or a binding between MAC address, source IP address and switch port. For host/agent-device part, we develop a method using source address authentication using session key and hash digest algorithms, and prevent replay attack by combining a sequence number method with a timestamp method. The host-to-agent part has three main modules: Source Address Request Client (SARC) on the host, Source Address Validation Proxy (SAVP) on the switch, and Source Address Management Server (SAMS). The solution has the following basic steps: 1. The SARC on the end host sends an IP address request. The SAVP on the switch relays this request to the SAMS and records the MAC address and incoming port. If the address has already been predetermined by the end host, the end host still needs to put that address in the request message for verification by SAMS. 2. After the SAMS receives the IP address request then allocates a source address for that SARC based on the address allocation and management policy of the access network, it stores the allocation of the IP address in the history database of SAMS for traceback, then sends response message containing the allocated address to the SARC. 3. After the SAVP on the access switch receives the response, it binds the IP address and the former stored MAC address of the request message with the switch port on the binding table. Then, it forwards the issued address to SARC on the end host. 4. The access switch begins to filter packets sent from the end host. Packets which do not conform to the tuple (IP address, Switch Port) are discarded. For the case that IP address was staticly assigned to the host, if the address has been predetermined by the end host, it still needs to Wu, et al. Expires April 14, 2008 [Page 7] Internet-Draft SAVA Testbed Oct 2007 put it in the request datagram for acceptance from SAMS. The host/agent-to-device part includes the following steps (the mechanism details can be found in [XBW07]): 1. When a host wants to access the Internet, it should firstly carry out the access authentication. 2. Then the SAVA Agent generates a session key S and sends it to the SAVA Device via a key exchange mechanisms. The SAVA Device binds the session key and the host's IP address. 3. When the host sends packet M to somewhere outside the access network, the SAVA Agent needs to generate one signature for each packet using the hash digest algorithm (e.g. MD5). Then the signature H[M||S] is carried in a new IPv6 extension header, named 'source address validation header'. 4. The SAVA Device uses the session key to authenticate the signature carried in the packet so that it can validate the source address. 5. The SAVA Device identifies the replay packets by checking whether the sequence number of the packet is increasing within the admission time window T (T is set up by timestamp mechanism). 6. In case there is no SAVA Agent deployed, the host is installed a software to do the above work (exchanging session key and inserting the signature into the packets) by the host itself. 2.3. IP Source Address Validation at Intra-AS/Ingress Point We adopted the solution of the source address validation of IP packets at ingress points described in [RFC2827]and[RFC3704]; the latter describes source address validation at the ingress points of multi-homed access networks. 2.4. IP Source Address Validation in Inter-AS Case (Neighboring AS) Our design for the Inter-AS Source Address Validation aimed at the following characteristics: It should cooperate among different ASes with different administrative authorities and different interests. It should be light-weight to support high throughput and not to influence forwarding efficiency. The inter-AS level of SAVA can be classified into two sub-cases: o Two SAVA-compliant ASes exchanging traffic are directly connected; Wu, et al. Expires April 14, 2008 [Page 8] Internet-Draft SAVA Testbed Oct 2007 o Two SAVA-compliant ASes are separated by one or more intervening, SAVA-non-compliant providers. --------- | AIMS | ------|- | -------------- -----------|----- | AS-4 |-------- --------| AS-1 | |------- Global | ------ |ASBR,VE|->|ASBR,VE| ------|- |ASBR,VE|--->IPv6 | |VRGE| |-------- --------| | VRGE | |------- Network | ------ | | -------- | --------------- ----- ----------------- |ASBR,VE| |ASBR,VE| --------- --------- / | / | / | / | ---------- -------- |ASBR, VE| |ASBR,VE| --------------- ------------- | AS-2 | | AS-3 | | ----- | | ----- | | |VRGE| | | |VRGE| | | ----- | | ------ | --------------- ------------- Key: AIMS == AS-IPv6 prefix Mapping Server, VRGE == Validation Rule Generating Engine, VE == Validating Engine, ASBR = AS Border Router, VR==Validation Rule Figure 2: Inter-ISP (Neighboring AS) Solution An AS relation based mechanism is proposed for neighboring SAVA- compliant ASes. The basic ideas of this AS-relation based mechanism are as follows. It builds a VR table that associates each incoming interface of the router with a set of valid source address blocks, and then uses it to filter spoofed packets. The VR is generated from the AS relation of neighboring SAVA-compliant ASes. In the solution implemented on the testbed, the solution for the validation of IPv6 prefixes is separated into three functional modules: The Validation Rule Generating Engine (VRGE), the Validation Engine (VE) and the the AS-IPv6 prefix Mapping Server(AIMS). Validation rules (VR) that are generated by the VRGE are expressed as IPv6 address prefixes. The VRGE generates validation rules which are derived according to Wu, et al. Expires April 14, 2008 [Page 9] Internet-Draft SAVA Testbed Oct 2007 the table shown in figure 3, and each AS has a VRGE. The VE loads validation rules generated by VRGE to filter packets passed between ASes (in the case of Figure 2, from neighboring ASes into AS-1). In the SAVA testbed, the VE is implemented as a simulated L2 device on a Linux-based machine inserted into the data path just outside each ASBR interface that faces a neighboring AS, but in a real-world implementation, it would probably be implemented as a packet filtering set on the ASBR. The AS-IPv6 prefix mapping server is also implemented on a Linux machine and derives a mapping between IPv6 prefix and the AS number of that prefix. --------------------------------------------------------------------------- | \Export| Own | Customer's| Sibling's | Provider's | Peer's | |To \ | Address | Address | Address | Address | Address | |-----\-------------------------------------------------------------------| | Provider | Y | Y | Y | | | |-------------------------------------------------------------------------| | Customer | Y | Y | Y | Y | Y | |-------------------------------------------------------------------------| | Peer | Y | Y | Y | | | |-------------------------------------------------------------------------| | Sibling | Y | Y | Y | Y | Y | --------------------------------------------------------------------------- Figure 3: AS-Relation Based Inter-AS Filtering Different ASes exchange and transmit VR information using the AS- Relation Based Export Rules in the VRGE. As per Figure 3, an AS exports the address prefixes of its own, its customers, its providers, its siblings and its peers to its customers and siblings as valid prefixes, while it only exports the address prefixes of its own, its customers and its siblings to its providers and peers as valid prefixes. With the support of AS Number to IPv6 Address Mapping service, only AS numbers of valid address prefixes are transferred between ASes and the AS number is mapped to address prefixes at the VRGE. Only changes of AS relation and changes of IP address prefixes belonging to an AS require the generation of VR updates. The procedure's principle steps are as follows (Seeing from AS-1 in Figure 2): 1. When the VRGE has initialized, it reads its neighboring SAVA- compliant AS table and establishes connections to all the VEs in its own AS. 2. The VRGE initiates a VR renewal. According to its exporting table, it sends its own originated VR to VRGEs of neighboring ASes. In this process, VR are expressed as AS numbers. Wu, et al. Expires April 14, 2008 [Page 10] Internet-Draft SAVA Testbed Oct 2007 3. When a VRGE receives the new VR from its neighbor, it uses its own export table to decide whether it should accept the VR and, if it accepts a VR, whether or not it should re-export the VR to other neighboring ASes. 4. If the VRGE accepts a VR, it uses the AIMS to transform AS- expressed VR into IPv6 prefix-expressed VR. 5. The VRGE pushes the VR to all the VEs in its AS. The VEs use these prefix-based VRs to validate the source IP addresses of incoming packets. 2.5. IP Source Address Validation in Inter-AS Case (Non-Neighboring AS) In the case where two ASes do not exchange packets directly, it is not possible to deploy a solution like that in the previous section. However, it is highly desirable for non-neighboring ISPs to be able to form a trust alliance such that packets leaving one AS will be recognized by the other and inherit the validation status they possessed on leaving the first AS. There is more than one way to do this. For the SAVA experiments to date, a signature method has been used. This solution is inspired by the work [Brem05]. The basic ideas of this light-weight signature based mechanism are as follows. For every two SAVA-compliant ASes, there is a pair of unique temporary signatures. All SAVA-compliant ASes form SAVA AS Alliance. When a packet is leaving its own AS, if the destination IP address belongs to an AS in the SAVA AS Alliance, the edge router of this AS looks up for the signature based on the destination AS number, and tags a signature to the packet. When a packet is arriving at the destination AS, if the source address of the packet belongs to an AS in the SAVA AS Alliance, the edge router of the destination AS looks up for the signature based on the source AS number, and the signature carried in the packet is verified and removed. This particular method uses a light-weight signature. For every packet forwarded, the signature can be put in an IPv6 hop-by-hop extension header. We can use a 128-bit shared random number as the signature, instead of using cryptographic method to generate the signature. Wu, et al. Expires April 14, 2008 [Page 11] Internet-Draft SAVA Testbed Oct 2007 +-----+ .-----------------+.REG |-----------------. | +-----+ | | | ,-----+-------- ,------+------- ,' `| `. ,' ` | `. / | \ / | \ / | \ / | \ ; +--'--+ +----+ +----+ +-----+ ; | | ASC +------+ASBR| |ASBR+-----+ ASC | | : +--.--+ +----+` +----+ +--+--+ : \ |__________________________________________| / \ / \ / `. ,' `. ,' '-------------' '-------------' AS-1 AS-2 KEY: REG == Registration Server, ASC == AS Control Server, ASBR == AS Border Router. Figure 4: Inter-AS (Non-neighboring AS) Solution There are three major components in the system: the Registration Server (REG), the AS Control Server (ASC), and the AS Border Router (ASBR). The Registration Server is the "center" of the trust alliance (TA) . It maintains a member list for the TA. It performs two major functions: o Processes requests from the AS Control Server, to get the member list for the TA. o When the member list is changed, notifies each AS Control Server. Each AS deploying the method has an AS Control Server. The AS Control Server has three major functions: o Communicates with the Registration Server, to get the up-to-date member list of TA. o Communicates with the AS Control Server in other member AS in the TA, to exchange updates of prefix ownership information, and to exchange signatures. o Communicates with all AS Border routers of the local AS, to configure the processing component on the AS Border routers. The AS Border Router does the work of adding signature to the packet Wu, et al. Expires April 14, 2008 [Page 12] Internet-Draft SAVA Testbed Oct 2007 at the sending AS, and the work of verifying and removing the signature at the destination AS. In the design of this system, in order to decrease the burden on the REG, most of the control traffic happens between ASCs. The signature needs to be changed frequently, Although the overhead of maintaining and exchanging signatures between AS pairs is not O(N^2), but O(N), the traffic and processing overhead increase as the number of ASes increases. Therefore an automatic signature changing method is utilized in this solution. Wu, et al. Expires April 14, 2008 [Page 13] Internet-Draft SAVA Testbed Oct 2007 3. SAVA Testbed 3.1. CNGI-CERNET2 The prototypes of our solutions for SAVA are implemented and tested on CNGI-CERNET2. CNGI-CERNET2 is one of the China Next Generation Internet (CNGI) backbones. CNGI-CERNET2 connects 25 core nodes distributed in 20 cities in China at speeds of 2.5-10 Gb/s. The CNGI-CERNET2 backbones are IPv6-only networks, not a mixed IPv4/IPv6 infrastructure. The CNGI-CERNET2 backbones, CNGI-CERNET2 CPNs, and CNGI-6IX all have globally unique AS numbers. Thus a multi-AS testbed environment is provided. 3.2. SAVA Testbed on CNGI-CERNET2 Infrastructure It is intended that eventually the SAVA testbed will be implemented directly on the CNGI-CERNET2 backbone, but in the early stages the testbed has been implemented across 12 universities connected to CNGI-CERNET2. This is because first, some of the algorithms need to be implemented in the testbed routers themselves and to date they have not been implemented on any of the commercial routers forming the CNGI-CERNET2 backbone. Second, since CNGI-CERNET2 is a operational backbone, any new protocols and networking techniques need to be tested in a non- disruptive way. Wu, et al. Expires April 14, 2008 [Page 14] Internet-Draft SAVA Testbed Oct 2007 __ ,' \ _,...._ ,' \____---------------+ ,'Beijing`. / \ | Inter-AS SAV |-----| Univ | +---------------+ | | +---------------+ `-._____,' | Inter-AS SAV +-----| | +------.--------+ | CNGI- | _,...._ | | CERNET2 |__---------------+ ,Northeast`. | | | |Inter-AS SAV |-----| Univ | Tsinghua|University | Backbone| +---------------+ `-._____,' ,,-|-._ | | ,' | `. | | ,'+---------+\ | | | |Intra-AS | | | | ... | | SAV | | | | | +---------+ | | | | | | | | _,...._ | +---------+ | | |__---------------+ ,Chongqing`. | | Access | | | | |Inter-AS SAV |-----|Univ | | | Network | | | | +---------------+ `-._____,' | | SAV | | | | \ +---------+.' \ .' \ ,' \ | `. ,' \ / ``---' -_,' KEY: SAV=Source Address Validation Figure 5: CNGI-CERNET2 SAVA Testbed Notwithstanding the aforementioned restrictions on the early testbed, the testbed is fully capable of functional testing of solutions for all parts of the SAVA solutions. Namely, it is possible to test procedures for ensuring the validity of IPv6 source addresses in the access network and in packets sent from the access network to an IPv6 service provider, packets sent within one service provider's network, packets sent between neighboring service providers and packets sent between service providers separated by an intervening transit network. The testbed is distributed across 12 universities connected to CNGI- CERNET2, namely Tsinghua University, Beijing University, Beijing University of Post and Telecommunications, Shanghai Jiaotong University, Huazhong University of Science and Technology in Wuhan, Southeast University in Nanjing, and South China University of Technology in Guangzhou, Northeast University in Shenyang, Xi'an Jiaotong University, Shandong University in Jinan, University of Electronic Science and Technology of China in Chengdu and Chongqing University. Wu, et al. Expires April 14, 2008 [Page 15] Internet-Draft SAVA Testbed Oct 2007 Each of the university installations is connected to the CNGI-CERNET2 backbone through a set of inter-AS Source Address Validation prototype equipment and traffic monitoring equipment for test result display. Of the installations, the installation at Tsinghua University is the most fully-featured, with inter-AS, intra-AS and access network level validation all able to be tested. In addition, a suite of applications that could be subject to spoofing attacks or which can be subverted to carry out spoofing attacks are installed on a variety of servers. Wu, et al. Expires April 14, 2008 [Page 16] Internet-Draft SAVA Testbed Oct 2007 4. Test Experience and Results The solutions outlined in section 2 have been implemented on the testbed described in section 3. Successful testing of all solutions has been carried out, as detailed in the following sections. 4.1. Test Experience We have test in Tsinghua University and tests between Tsinghua University and other universities. We have Inter-AS (non-neighboring AS) SAVA solution test, Inter-AS (neighboring AS) SAVA solution test, Intra-AS SAVA solution test, and Access Network SAVA solution test. For each one of the test scenarios, we have tested many cases. Taking Inter-AS (non-neighboring AS) SAVA solution test as an example, we classified the test cases into three classes: normal class, dynamic class and anti-spoofing class. 1. For normal class, there are three cases: Adding Signature Test, Removing Signature Test and Forwarding packets with valid source address. 2. For dynamic class, there are four cases: Updating the signature between ASes, The protection for newly joined member AS, Adding address space and Deleting address space. 3. For anti-spoofing class, there is one case: Filtering of packets with forged IP address. As is shown in Fig.5, we have "multiple-fence" design for our SAVA testbed. If source address validation is deployed in the access network, we can get a host granularity validation. If source address validation is deployed at intra-AS level, we can guarantee that the packets sent from this point have a correct IP prefix. If source address validation is deployed at inter-AS level, we can guarantee that the packets sent from this point are from a correct AS. 4.2. Test Results 1. The test results are consistent with the expected ones. For an AS which has fully-featured SAVA deployment with inter-AS, intra-AS and access network level validation, packets that do not hold an authenticated source address will not be forwarded in network. As a result, it is not possible to launch network attacks with spoofed source addresses. Moreover, the traffic in the network can be traced back accurately. Wu, et al. Expires April 14, 2008 [Page 17] Internet-Draft SAVA Testbed Oct 2007 2. For the Inter-AS (non-neighboring AS) SAVA solution, during the period of signature update, the old and the new signature are both valid for source address validation, thus there are no packet loss. 3. For the Inter-AS (non-neighboring AS) SAVA solution, the validation function is implemented in software on a device running Linux, which simulates the source address validation functions of a router line card interface. It is a layer-two device because it has to be transparent to router interface, During the test, If the devices were connected directly, it could achieve a normal line rate forwarding. If the devices were connected with routers from another vendor, it could only achieve a very limited line speed. The reason is that the signatures are added on the IPv6 hop-by-hop option header and the network devices from other vendors handled the hop-by-hop options just by software. Wu, et al. Expires April 14, 2008 [Page 18] Internet-Draft SAVA Testbed Oct 2007 5. Design Limitation There are several design limitations for the solutions deployed in CNGI-CERNET2 testbed. 1. For the Inter-AS (non-neighboring AS) SAVA solution, the difficulty for guessing the signature between two AS members was discussed in [Brem05]. It is relatively difficult and we can increase the difficulty of guess by increasing the length of the signature. In current CNGI-CERNET2 SAVA testbed, a 128-bit signature is designed in IPv6 hop-by-hop option header. The size of the packets increases with the signatures. Because this IPv6 hop-by-hop option has to be looked at by all intervening routers, it still needs further discussion whether the IPv6 hop-by-hop option is the right tool for the task. Although the overhead is relatively low, the addition of the option and the calculation of the signature can consume valuable resources on the forwarding path. 2. The Inter-AS (neighboring AS) SAVA solution is based on AS relation, thus it can not synchronized with the dynamics of route changes very quickly. 3. The first hop solution in access network needs to be widely deployed in the access network switches. For the environment where source address validation is not deployed in the access network, because we have a "multiple-fence" design for SAVA, we can still get a source address validation by the SAVA Device at the exit of the access network. Currently we use an authentication based method for host/agent-to-device part. The performance of current solution also needs to be further studied. 4. Given that a large fraction of current denial-of-service attacks are employing legitimate IP addresses belonging to botnet clients, even universal deployment of better source address validation techniques would be unable to prevent these attacks. However, tracing these attacks would be easier given that there would be more reliance on the validity of source address. Wu, et al. Expires April 14, 2008 [Page 19] Internet-Draft SAVA Testbed Oct 2007 6. Conclusion Several conclusions can be made from the test experience and results. It is possible to devise a loosely-coupled, and "multiple-fence" design for SAVA. This provides for different granularities of authenticity of source IP addresses. It also allows for different providers to use different solutions, and the coupling of components at different levels of granularity of authenticity can be loose enough to allow component substitution. Incremental deployment is another design principle for SAVA. The tests have demonstrated that benefit is derived even when deployment is incomplete, which gives providers an incentive to be early adopters of the framework. Some DiffServ mechanism could also be considered. That is, traffic from SAVA-compliant ASes could be given a higher priority, especially when attacks happening. Access network source address validation is an important part of SAVA to achieve an authenticity of host IP granularity. There are multiple access cases: local subnet in enterprise networks, residential broadband, and wireless mobile, etc. For enterprise networks, there are multiple solutions from the research and engineering community. Focusing on the appropriate framework and solutions for access network source address validation could be a valuable initial step for solving the source address spoofing problem in IETF. SAVA must be capable of scaling to the size of the global Internet. The scalability of SAVA still needs further consideration. CNGI- CERNET2 testbed merely provides an initial testbed for SAVA. To study the scalabity of the current solutions, we need to extend the scale of the testbed. Wu, et al. Expires April 14, 2008 [Page 20] Internet-Draft SAVA Testbed Oct 2007 7. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. Wu, et al. Expires April 14, 2008 [Page 21] Internet-Draft SAVA Testbed Oct 2007 8. Security Considerations The purpose of the draft is to report experimental results. The security considerations of the solution mechanisms of testbed are not mentioned in this document. Wu, et al. Expires April 14, 2008 [Page 22] Internet-Draft SAVA Testbed Oct 2007 9. Acknowledgements The authors would like to thank Jari Arkko and Lixia Zhang for their detailed review comments on this draft, and thank Paul Ferguson and Ron Bonica for their valuable advices on the solution development and the testbed implementation. Wu, et al. Expires April 14, 2008 [Page 23] Internet-Draft SAVA Testbed Oct 2007 10. References 10.1. Normative References [RFC2827] Paul, F. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed Networks", BCP 84, RFC 3704, 2004. 10.2. Informative References [Brem05] Bremler-Barr, A. and H. Levy, "Spoofing Prevention Method", INFOCOM 2005. [Li02] Li,, J., Mirkovic, J., Wang, M., Reiher, P., and L. Zhang, "SAVE: Source Address Validity Enforcement Protocol", INFOCOM 2002. [Park01] Park, K. and H. Lee, "On the effectiveness of route-based packet filtering for distributed DoS attack prevention in power-law internets", SIGCOMM 2001. [Snoe01] Snoeren, A., Partridge, C., Sanchez, L., and C. Jones......, "A Hash-based IP traceback", SIGCOMM 2001. [WRL2007] Wu, J., Ren, G., and X. Li, "Source Address Validation: Architecture and Protocol Design", ICNP 2007. [XBW07] Xie, L., Bi, J., and J. Wu, "An Authentication based Source Address Spoofing Prevention Method Deployed in IPv6 Edge Network", ICCS 2007. Wu, et al. Expires April 14, 2008 [Page 24] Internet-Draft SAVA Testbed Oct 2007 Authors' Addresses Jianping Wu Tsinghua University Computer Science, Tsinghua University Beijing 100084 China Email: jianping@cernet.edu.cn Jun Bi Tsinghua University Network Research Center, Tsinghua University Beijing 100084 China Email: junbi@cernet.edu.cn Xing Li Tsinghua University Electronic Engineering, Tsinghua University Beijing 100084 China Email: xing@cernet.edu.cn Gang Ren Tsinghua University Computer Science, Tsinghua University Beijing 100084 China Email: rg03@mails.tsinghua.edu.cn Ke Xu Tsinghua University Computer Science, Tsinghua University Beijing 100084 China Email: xuke@csnet1.cs.tsinghua.edu.cn Wu, et al. Expires April 14, 2008 [Page 25] Internet-Draft SAVA Testbed Oct 2007 Mark I. Williams Juniper Networks Suite 1508, W3 Tower, Oriental Plaza, 1 East Chang'An Ave Dong Cheng District, Beijing 100738 China Email: miw@juniper.net Wu, et al. Expires April 14, 2008 [Page 26] Internet-Draft SAVA Testbed Oct 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Wu, et al. Expires April 14, 2008 [Page 27]