Allyn Romanow (Cisco) Internet-Draft Jeff Mogul (HP) Expires: June 2003 Tom Talpey (NetApp) Stephen Bailey (Sandburst) RDMA over IP Problem Statement draft-ietf-rddp-problem-statement-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This draft addresses an IP-based solution to the problem of high system costs due to network I/O copying in end-hosts at high speeds. The problem is due to the high cost of memory bandwidth, and it can be substantially improved using "copy avoidance." The high overhead has prevented TCP/IP from being used as an interconnection network. Romanow, et al Expires June 2003 [Page 1] Internet-Draft RDMA Over IP Problem Statement December 2002 Table Of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 2 2. The high cost of data movement operations in network I/O . 3 2.1. Copy avoidance improves processing overhead . . . . . . . 5 3. Memory bandwidth is the root cause of the problem . . . . 6 4. High copy overhead is problematic for many key Internet applications . . . . . . . . . . . . . . . . . . . . . . . 7 5. Copy Avoidance Techniques . . . . . . . . . . . . . . . . 9 5.1. A Conceptual Framework: DDP and RDMA . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . 11 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 17 Full Copyright Statement . . . . . . . . . . . . . . . . . 17 1. Introduction This draft considers the problem of high host processing overhead associated with network I/O that occurs under high speed conditions. This problem is often referred to as the "I/O bottleneck" [CT90]. More specifically, the source of high overhead that is of interest here is data movement operations - copying. This issue is not be confused with TCP offload, which is not addressed here. High speed refers to conditions where the network link speed is high relative to the bandwidths of the host CPU and memory. With today's computer systems, one Gbits/s and over is considered high speed. High costs associated with copying are an issue primarily for large scale systems. Although smaller systems such as rack-mounted PCs and small workstations would benefit from a reduction in copying overhead, the benefit to smaller machines will be primarily in the next few years as they scale in the amount of bandwidth they handle. Today it is large system machines with high bandwidth feeds, usually multiprocessors and clusters, that are adversely affected by copying overhead. Examples of such machines include all varieties of servers: database servers, storage servers, application servers for transaction processing, for e-commerce, and web serving, content distribution, video distribution, backups, data mining and decision support, and scientific computing. Note that such servers almost exclusively service many concurrent sessions (transport connections), which, in aggregate, are responsible for > 1 Gbits/s of communication. Nonetheless, the cost of copying overhead for a particular load is the same whether from few or many sessions. Romanow, et al Expires June 2003 [Page 2] Internet-Draft RDMA Over IP Problem Statement December 2002 The I/O bottleneck, and the role of data movement operations, have been widely studied in research and industry over the last approximately 14 years, and we draw freely on these results. Historically, the I/O bottleneck has received attention whenever new networking technology has substantially increased line rates - 100 Mbits/s FDDI and Fast Ethernet, 155 Mbits/s ATM, 1 Gbits/s Ethernet. In earlier speed transitions, the availability of memory bandwidth allowed the I/O bottleneck issue to be deferred. Now however, this is no longer the case. While the I/O problem is significant at 1 Gbits/s, it is the introduction of 10 Gbits/s Ethernet which is motivating an upsurge of activity in industry and research [DAFS, IB, VI, CGZ01, Ma02, MAF+02]. Because of high overhead of end-host processing in current implementations, the TCP/IP protocol stack is not used for high speed transfer. Instead, special purpose network fabrics, using a technology generally known as remote direct memory access (RDMA), have been developed and are widely used. RDMA is a set of mechanisms that allow the network adapter, under control of the application, to steer data directly into and out of application buffers. Examples of such interconnection fabrics include Fibre Channel [FIBRE] for block storage transfer, Virtual Interface Architecture [VI] for database clusters, Infiniband [IB], Compaq Servernet [SRVNET], Quadrics [QUAD] for System Area Networks. These link level technologies limit application scaling in both distance and size, meaning that the number of nodes cannot be arbitrarily large. This problem statement substantiates the claim that in network I/O processing, high overhead results from data movement operations, specifically copying; and that copy avoidance significantly decreases the processing overhead. It describes when and why the high processing overheads occur, explains why the overhead is problematic, and points out which applications are most affected. In addition, this document introduces an architectural approach to solving the problem, which is developed in detail in [BT02]. It also discusses how the proposed technology may introduce security concerns and how they should be addressed. 2. The high cost of data movement operations in network I/O A wealth of data from research and industry shows that copying is responsible for substantial amounts of processing overhead. It further shows that even in carefully implemented systems, eliminating copies significantly reduces the overhead, as referenced below. Romanow, et al Expires June 2003 [Page 3] Internet-Draft RDMA Over IP Problem Statement December 2002 Clark et al. [CJRS89] in 1989 shows that TCP [Po81] overhead processing is attributable to both operating system costs such as interrupts, context switches, process management, buffer management, timer management, and to the costs associated with processing individual bytes, specifically computing the checksum and moving data in memory. They found moving data in memory is the more important of the costs, and their experiments show that memory bandwidth is the greatest source of limitation. In the data presented [CJRS89], 64% of the measured microsecond overhead was attributable to data touching operations, and 48% was accounted for by copying. The system measured Berkeley TCP on a Sun-3/60 using 1460 Byte Ethernet packets. In a well-implemented system, copying can occur between the network interface and the kernel, and between the kernel and application buffers - two copies, each of which are two memory bus crossings - for read and write. Although in certain circumstances it is possible to do better, usually two copies are required on receive. Subsequent work has consistently shown the same phenomenon as the earlier Clark study. A number of studies report results that data- touching operations, checksumming and data movement, dominate the processing costs for messages longer than 128 Bytes [BS96, CGY01, Ch96, CJRS89, DAPP93, KP96]. For smaller sized messages, per- packet overheads dominate [KP96, CGY01]. The percentage of overhead due to data-touching operations increases with packet size, since time spent on per-byte operations scales linearly with message size [KP96]. For example, Chu [Ch96] reported substantial per-byte latency costs as a percentage of total networking software costs for an MTU size packet on SPARCstation/20 running memory-to-memory TCP tests over networks with 3 different MTU sizes. The percentage of total software costs attributable to per-byte operations were: 1500 Byte Ethernet 18-25% 4352 Byte FDDI 35-50% 9180 Byte ATM 55-65% Although many studies report results for data-touching operations including checksumming and data movement together, much work has focused just on copying [BS96, B99, Ch96, TK95]. For example, [KP96] reports results that separate processing times for checksum from data movement operations. For the 1500 Byte Ethernet size, 20% of total processing overhead time is attributable to copying. The study used 2 DECstations 5000/200 connected by an FDDI network. (In this study checksum accounts for 30% of the processing time.) Romanow, et al Expires June 2003 [Page 4] Internet-Draft RDMA Over IP Problem Statement December 2002 2.1. Copy avoidance improves processing overhead A number of studies show that eliminating copies substantially reduces overhead. For example, results from copy-avoidance in the IO-Lite system [PDZ99], which aimed at improving web server performance, show a throughput increase of 43% over an optimized web server, and 137% improvement over an Apache server. The system was implemented in a 4.4BSD derived UNIX kernel, and the experiments used a server system based on a 333MHz Pentium II PC connected to a switched 100 Mbits/s Fast Ethernet. There are many other examples where elimination of copying using a variety of different approaches showed significant improvement in system performance [CFF+94, DP93, EBBV95, KSZ95, TK95, Wa97]. We will discuss the results of one of these studies in detail in order to clarify the significant degree of improvement produced by copy avoidance [Ch02]. Recent work by Chase et al. [CGY01], measuring CPU utilization, shows that avoiding copies reduces CPU time spent on data access from 24% to 15% at 370 Mbits/s for a 32 KBytes MTU using an AlphaStation XP1000 and a Myrinet adapter [BCF+95]. This is an absolute improvement of 9% due to copy avoidance. The total CPU utilization was 35%, with data access accounting for 24%. Thus the relative importance of reducing copies is 26%. At 370 Mbits/s, the system is not very heavily loaded. The relative improvement in achievable bandwidth is 34%. This is the improvement we would see if copy avoidance were added when the machine was saturated by network I/O. Note that improvement from the optimization becomes more important if the overhead it targets is a larger share of the total cost. This is what happens if other sources of overhead, such as checksumming, are eliminated. In [CGY01], after removing checksum overhead, copy avoidance reduces CPU utilization from 26% to 10%. This is a 16% absolute reduction, a 61% relative reduction, and a 160% relative improvement in achievable bandwidth. In fact, today's network interface hardware commonly offloads the checksum, which removes the other source of per-byte overhead. They also coalesce interrupts to reduce per-packet costs. Thus, today copying costs account for a relatively larger part of CPU utilization than previously, and therefore relatively more benefit is to be gained in reducing them. (Of course this argument would be specious if the amount of overhead were insignificant, but it has been shown to be substantial.) Romanow, et al Expires June 2003 [Page 5] Internet-Draft RDMA Over IP Problem Statement December 2002 3. Memory bandwidth is the root cause of the problem Data movement operations are expensive because memory bandwidth is scarce relative to network bandwidth and CPU bandwidth [PAC+97]. This trend existed in the past and is expected to continue into the future [HP97, STREAM], especially in large multiprocessor systems. With copies crossing the bus twice per copy, network processing overhead is high whenever network bandwidth is large in comparison to CPU and memory bandwidths. Generally with today's end-systems, the effects are observable at network speeds over 1 Gbits/s. A common question is whether increase in CPU processing power alleviates the problem of high processing costs of network I/O. The answer is no, it is the memory bandwidth that is the issue. Faster CPUs do not help if the CPU spends most of its time waiting for memory [CGY01]. The widening gap between microprocessor performance and memory performance has long been a widely recognized and well-understood problem [PAC+97]. Hennessy [HP97] shows microprocessor performance grew from 1980-1998 at 60% per year, while the access time to DRAM improved at 10% per year, giving rise to an increasing "processor- memory performance gap". Another source of relevant data is the STREAM Benchmark Reference Information website which provides information on the STREAM benchmark [STREAM]. The benchmark is a simple synthetic benchmark program that measures sustainable memory bandwidth (in MBytes/s) and the corresponding computation rate for simple vector kernels measured in MFLOPS. The website tracks information on sustainable memory bandwidth for hundreds of machines and all major vendors. Results show measured system performance statistics. Processing performance from 1985-2001 increased at 50% per year on average, and sustainable memory bandwidth from 1975 to 2001 increased at 35% per year on average over all the systems measured. A similar 15% per year lead of processing bandwidth over memory bandwidth shows up in another statistic, machine balance [Mc95], a measure of the relative rate of CPU to memory bandwidth (FLOPS/cycle) / (sustained memory ops/cycle) [STREAM]. Network bandwidth has been increasing about 10-fold roughly every 8 years, which is a 40% per year growth rate. A typical example illustrates that the memory bandwidth compares unfavorably with link speed. The STREAM benchmark shows that a modern uniprocessor PC, for example the 1.2 GHz Athlon in 2001, Romanow, et al Expires June 2003 [Page 6] Internet-Draft RDMA Over IP Problem Statement December 2002 will move the data 3 times in doing a receive operation - 1 for the network interface to deposit the data in memory, and 2 for the CPU to copy the data. With 1 GBytes/s of memory bandwidth, meaning one read or one write, the machine could handle approximately 2.67 Gbits/s of network bandwidth, one third the copy bandwidth. But this assumes 100% utilization, which is not possible, and more importantly the machine would be totally consumed! (A rule of thumb for databases is that 20% of the machine should be required to service I/O, leaving 80% for the database application. And, the less the better.) In 2001, 1 Gbits/s links were common. An application server may typically have two 1 Gbits/s connections - one connection backend to a storage server and one front-end, say for serving HTTP [FGM+99]. Thus the communications could use 2 Gbits/s. In our typical example, the machine could handle 2.7 Gbits/s at its theoretical maximum while doing nothing else. This means that the machine basically could not keep up with the communication demands in 2001, with the relative growth trends the situation only gets worse. 4. High copy overhead is problematic for many key Internet applications If a significant portion of resources on an application machine is consumed in network I/O rather than in application processing, it makes it difficult for the application to scale - to handle more clients, to offer more services. Several years ago the most affected applications were streaming multimedia, parallel file systems and supercomputing on clusters [BS96]. In addition, today the applications that suffer from copying overhead are more central in Internet computing - they store, manage, and distribute the information of the Internet and the enterprise. They include database applications doing transaction processing, e-commerce, web serving, decision support, content distribution, video distribution, and backups. Clusters are typically used for this category of application, since they have advantages of availability and scalability. Today these applications, which provide and manage Internet and corporate information, are typically run in data centers that are organized into three logical tiers. One tier is typically a set of web servers connecting to the WAN. The second tier is a set of application servers that run the specific applications usually on more powerful machines, and the third tier is backend databases. Physically, the first two tiers - web server and application server - are usually combined [Pi01]. For example an e-commerce server communicates with a database server and with a customer site, or a Romanow, et al Expires June 2003 [Page 7] Internet-Draft RDMA Over IP Problem Statement December 2002 content distribution server connects to a server farm, or an OLTP server connects to a database and a customer site. When network I/O uses too much memory bandwidth, performance on network paths between tiers can suffer. (There might also be performance issues on SAN paths used either by the database tier or the application tier.) The high overhead from network-related memory copies diverts system resources from other application processing. It also can create bottlenecks that limit total system performance. There are a large and growing number of these application servers distributed throughout the Internet. In 1999 approximately 3.4 million server units were shipped, in 2000, 3.9 million units, and the estimated annual growth rate for 2000-2004 was 17 percent [Ne00, PA01]. There is high motivation to maximize the processing capacity of each CPU, as scaling by adding CPUs one way or another has drawbacks. For example, adding CPUs to a multiprocessor will not necessarily help, as a multiprocessor improves performance only when the memory bus has additional bandwidth to spare. Clustering can add additional complexity to handling the applications. In order to scale a cluster or multiprocessor system, one must proportionately scale the interconnect bandwidth. Interconnect bandwidth governs the performance of communication-intensive parallel applications; if this (often expressed in terms of "bisection bandwidth") is too low, adding additional processors cannot improve system throughput. Interconnect latency can also limit the performance of applications that frequently share data between processors. So, excessive overheads on network paths in a "scalable" system both can require the use of more processors than optimal, and can reduce the marginal utility of those additional processors. Copy avoidance scales a machine upwards by removing at least two- thirds the bus bandwidth load from the "very best" 1-copy (on receive) implementations, and removes at least 80% of the bandwidth overhead from the 2-copy implementations. An example showing poor performance with copies and improved scaling with copy avoidance is illustrative. The IO-Lite work [PDZ99] shows higher server throughput servicing more clients using a zero-copy system. In an experiment designed to mimic real world web conditions by simulating the effect of TCP WAN connections on the server, the performance of 3 servers was compared. One server Romanow, et al Expires June 2003 [Page 8] Internet-Draft RDMA Over IP Problem Statement December 2002 was Apache, another an optimized server called Flash, and the third the Flash server running IO-Lite, called Flash-Lite with zero copy. The measurement was of throughput in requests/second as a function of the number of slow background clients that could be served. As the table shows, Flash-Lite has better throughput, especially as the number of clients increases. Apache Flash Flash-Lite ------ ----- ---------- #Clients Thruput reqs/s Thruput Thruput 0 520 610 890 16 390 490 890 32 360 490 850 64 360 490 890 128 310 450 880 256 310 440 820 Traditional Web servers (which mostly send data and can keep most of their content in the file cache) are not the worst case for copy overhead. Web proxies (which often receive as much data as they send) and complex Web servers based on SANs or multi-tier systems will suffer more from copy overheads than in the example above. 5. Copy Avoidance Techniques There have been extensive research investigation and industry experience with two main alternative approaches to eliminating data movement overhead, often along with improving other Operating System processing costs. In one approach, hardware and/or software changes within a single host reduce processing costs. In another approach, memory-to-memory networking [MAF+02], hosts communicate via information that allows them to reduce processing costs. The single host approaches range from new hardware and software architectures [KSZ95, Wa97, DWB+93] to new or modified software systems [BP96, Ch96, TK95, DP93, PDZ99]. In the approach based on using a networking protocol to exchange information, the network adapter, under control of the application, places data directly into and out of application buffers, reducing the need for data movement. Commonly this approach is called RDMA, Remote Direct Memory Access. As discussed below, research and industry experience has shown that copy avoidance techniques within the receiver processing path alone have proven to be problematic. The research special purpose host adapter systems had good performance and can be seen as precursors Romanow, et al Expires June 2003 [Page 9] Internet-Draft RDMA Over IP Problem Statement December 2002 for the commercial RDMA-based NICs [KSZ95, DWB+93]. In software, many implementations have successfully achieved zero-copy transmit, but few have accomplished zero-copy receive. And those that have done so make strict alignment and no-touch requirements on the application, greatly reducing the portability and usefulness of the implementation. In contrast, experience has proven satisfactory with memory-to- memory systems that permit RDMA - performance has been good and there have not been system or networking difficulties. RDMA is a single solution. Once implemented, it can be used with any OS and machine architecture, and it does not need to be revised when either of these changes. In early work, one goal of the software approaches was to show that TCP could go faster with appropriate OS support [CJR89, CFF+94]. While this goal was achieved, further investigation and experience showed that, though possible to craft software solutions, specific system optimizations have been complex, fragile, extremely interdependent with other system parameters in complex ways, and often of only marginal improvement [CFF+94, CGY01, Ch96, DAPP93, KSZ95, PDZ99]. The network I/O system interacts with other aspects of the Operating System such as machine architecture and file I/O, and disk I/O [Br99, Ch96, DP93]. For example, the Solaris Zero-Copy TCP work [Ch96], which relies on page remapping, shows that the results are highly interdependent with other systems, such as the file system, and that the particular optimizations are specific for particular architectures, meaning for each variation in architecture optimizations must be re-crafted [Ch96]. A number of research projects and industry products have been based on the memory-to-memory approach to copy avoidance. These include U-Net [EBBV95], SHRIMP [BLA+94], Hamlyn [BJM+96], Infiniband [IB], Winsock Direct [Pi01]. Several memory-to-memory systems have been widely used and have generally been found to be robust, to have good performance, and to be relatively simple to implement. These include VI [VI], Myrinet [BCF+95], Quadrics [QUAD], Compaq/Tandem Servernet [SRVNET]. Networks based on these memory-to-memory architectures have been used widely in scientific applications and in data centers for block storage, file system access, and transaction processing. By exporting direct memory access "across the wire", applications may direct the network stack to manage all data directly from application buffers. A large and growing class of applications has already emerged which takes advantage of such capabilities, Romanow, et al Expires June 2003 [Page 10] Internet-Draft RDMA Over IP Problem Statement December 2002 including all the major databases, as well as file systems such as DAFS [DAFS] and network protocols such as Sockets Direct [SDP]. 5.1. A Conceptual Framework: DDP and RDMA An RDMA solution can be usefully viewed as being comprised of two distinct components: "direct data placement (DDP)" and "remote direct memory access (RDMA) semantics". They are distinct in purpose and also in practice - they may be implemented as separate protocols. The more fundamental of the two is the direct data placement facility. This is the means by which memory is exposed to the remote peer in an appropriate fashion, and the means by which the peer may access it, for instance reading and writing. The RDMA control functions are semantically layered atop direct data placement. Included are operations that provide "control" features, such as connection and termination, and the ordering of operations and signaling their completions. A "send" facility is provided. While the functions (and potentially protocols) are distinct, historically both aspects taken together have been referred as "RDMA". The facilities of direct data placement are useful in and of themselves, and may be employed by other upper layer protocols to facilitate data transfer. Therefore, it is often useful to refer to DDP as the data placement functionality and RDMA as the control aspect. [BT02] develops an architecture for DDP and RDMA, and is a companion draft to this problem statement. 6. Security Considerations Solutions to the problem of reducing copying overhead in high bandwidth transfers via one or more protocols may introduce new security concerns. Any proposed solution must be analyzed for security threats and any such threats addressed. [BSW02] brings up potential security weaknesses due to resource issues that might lead to denial-of-service attacks, overwrites and other concurrent operations, the ordering of completions as required by the RDMA protocol, and the granularity of transfer. Each of these concerns plus any other identified threats need to be examined, described and an adequate solution to them found. Layered atop Internet transport protocols, the RDMA protocols will gain leverage from and must permit integration with Internet Romanow, et al Expires June 2003 [Page 11] Internet-Draft RDMA Over IP Problem Statement December 2002 security standards, such as IPSec and TLS [IPSEC, TLS]. A thorough analysis of the degree to which these protocols solve threats is required. Security for an RDMA design requires more than just securing the communication channel. While it is necessary to be able to guarantee channel properties such as privacy, integrity, and authentication, these properties cannot defend against all attacks from properly authenticated peers, which might be malicious, compromised, or buggy. For example, an RDMA peer should not be able to read or write memory regions without prior consent. Further, it must not be possible to evade consistency checks at the recipient. For example, the RDMA design should not allow a peer to update a region after the completion of an authorized update. The RDMA protocols must ensure that regions addressable by RDMA peers be under strict application control. Remote access to local memory by a network peer introduces a number of potential security concerns. This becomes particularly important in the Internet context, where such access can be exported globally. The RDMA protocols carry in part what is essentially user information, explicitly including addressing information and operation type (read or write), and implicitly including protection and attributes. As such, the protocol requires checking of these higher level aspects in addition to the basic formation of messages. The semantics associated with each class of error must be clearly defined, and the expected action to be taken on mismatch be specified. In some cases, this will result in a catastrophic error on the RDMA association, however in others a local or remote error may be signalled. Certain of these errors may require consideration of abstract local semantics, which must be carefully specified so as to provide useful behavior while not constraining the implementation. 7. Acknowledgements Jeff Chase generously provided many useful insights and information. Thanks to Jim Pinkerton for many helpful discussions. 8. References [BCF+95] N. J. Boden, D. Cohen, R. E. Felderman, A. E. 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Khalidi, "An efficient zero-copy I/O framework for UNIX", Technical Report, SMLI TR-95-39, May 1995 [VI] Virtual Interface Architecture Specification Version 1.0. http://www.viarch.org/html/collateral/san_10.pdf [Wa97] J. R. Walsh, "DART: Fast application-level networking via Romanow, et al Expires June 2003 [Page 16] Internet-Draft RDMA Over IP Problem Statement December 2002 data-copy avoidance", IEEE Network, July/August 1997, pp. 28-38 Authors' Addresses Stephen Bailey Sandburst Corporation 600 Federal Street Andover, MA 01810 USA Phone: +1 978 689 1614 Email: steph@sandburst.com Jeffrey C. Mogul Western Research Laboratory Hewlett-Packard Company 1501 Page Mill Road, MS 1251 Palo Alto, CA 94304 USA Phone: +1 650 857 2206 (email preferred) Email: JeffMogul@acm.org Allyn Romanow Cisco Systems, Inc. 170 W. Tasman Drive San Jose, CA 95134 USA Phone: +1 408 525 8836 Email: allyn@cisco.com Tom Talpey Network Appliance 375 Totten Pond Road Waltham, MA 02451 USA Phone: +1 781 768 5329 Email: thomas.talpey@netapp.com Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to Romanow, et al Expires June 2003 [Page 17] Internet-Draft RDMA Over IP Problem Statement December 2002 others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Romanow, et al Expires June 2003 [Page 18]