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diff --git a/doc/rfc/rfc3006.txt b/doc/rfc/rfc3006.txt new file mode 100644 index 0000000..5aa5cb6 --- /dev/null +++ b/doc/rfc/rfc3006.txt @@ -0,0 +1,731 @@ + + + + + + +Network Working Group B. Davie +Request for Comments: 3006 C. Iturralde +Category: Standards Track D. Oran + Cisco Systems, Inc. + S. Casner + Packet Design + J. Wroclawski + MIT LCS + November 2000 + + + Integrated Services in the Presence of Compressible Flows + +Status of this Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (2000). All Rights Reserved. + +Abstract + + An Integrated Services (int-serv) router performs admission control + and resource allocation based on the information contained in a TSpec + (among other things). As currently defined, TSpecs convey + information about the data rate (using a token bucket) and range of + packet sizes of the flow in question. However, the TSpec may not be + an accurate representation of the resources needed to support the + reservation if the router is able to compress the data at the link + level. This specification describes an extension to the TSpec which + enables a sender of potentially compressible data to provide hints to + int-serv routers about the compressibility they may obtain. Routers + which support appropriate compression take advantage of the hint in + their admission control decisions and resource allocation procedures; + other routers ignore the hint. An initial application of this + approach is to notify routers performing real-time transport protocol + (RTP) header compression that they may allocate fewer resources to + RTP flows. + + + + + + + + +Davie, et al. Standards Track [Page 1] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +Table of Contents + + 1 Introduction ........................................... 2 + 2 Addition of a Hint to the Sender TSpec ................. 3 + 3 Admission Control and Resource Allocation .............. 4 + 4 Object Format .......................................... 8 + 4.1 Hint Numbering ......................................... 9 + 5 Backward Compatibility ................................. 10 + 6 Security Considerations ................................ 10 + 7 IANA Considerations .................................... 11 + 8 Acknowledgments ........................................ 11 + 9 References ............................................. 11 + 10 Authors' Addresses ..................................... 12 + 11 Full Copyright Statement ................................ 13 + +1. Introduction + + In an Integrated Services network, RSVP [RFC 2205] may be used as a + signalling protocol by which end nodes and network elements exchange + information about resource requirements, resource availability, and + the establishment and removal of resource reservations. The + Integrated Services architecture currently defines two services, + Controlled-Load [RFC 2211] and Guaranteed [RFC 2212]. When + establishing a reservation using either service, RSVP requires a + variety of information to be provided by the sender(s) and + receiver(s) for a particular reservation which is used for the + purposes of admission control and allocation of resources to the + reservation. Some of this information is provided by the receiver in + a FLOWSPEC object; some is provided by the sender in a SENDER_TSPEC + object [RFC 2210]. + + A situation that is not handled well by the current specs arises when + a router that is making an admission control decision is able to + perform some sort of compression on the flow for which a reservation + is requested. For example, suppose a router is able to perform + IP/UDP/RTP header compression on one of its interfaces [RFC 2508]. + The bandwidth needed to accommodate a compressible flow on that + interface would be less than the amount contained in the + SENDER_TSPEC. Thus the router might erroneously reject a reservation + that could in fact have been accommodated. At the same time, the + sender is not at liberty to reduce its TSpec to account for the + compression of the data, since it does not know if the routers along + the path are in fact able to perform compression. Furthermore, it is + probable that only a subset of the routers on the path (e.g., those + connected to low-speed serial links) will perform compression. + + + + + + +Davie, et al. Standards Track [Page 2] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + This specification describes a mechanism by which the sender can + provide a hint to network elements regarding the compressibility of + the data stream that it will generate. Network elements may use this + hint as an additional piece of data when making admission control and + resource allocation decisions. + + This specification is restricted to the case where compression is + performed only on a link-by-link basis, as with header compression. + Other cases (e.g., transcoding, audio silence detection) which would + affect the bandwidth consumed at all downstream nodes are for further + study. In these latter cases, it would be necessary to modify a + sender TSpec as it is passed through a compressing node. In the + approach presented here, the sender TSpec that appears on the wire is + never modified, just as specified in [RFC 2210]. + +2. Addition of a Hint to the Sender TSpec + + The appropriate place for a `compressibility hint' is the Sender + TSpec. The reasons for this choice are: + + - The sender is the party who knows best what the data will look + like. + + - Unlike the Adspec, the Sender TSpec is not modified in transit + + - From the perspective of RSVP, the Sender TSpec is a set of + opaque parameters that are passed to `traffic control' + (admission control and resource allocation); the + compressibility hint is just such a parameter. + + An alternative to putting this information in the TSpec would be to + use an additional object in the RSVP PATH message. While this could + be made to work for RSVP, it does not address the issue of how to get + the same information to an intserv router when mechanisms other than + RSVP are used to reserve resources. It would also imply a change to + RSVP message processing just for the purposes of getting more + information to entities that are logically not part of RSVP + (admission control and resource allocation). The inclusion of the + information in the TSpec seems preferable and more consistent with + the Integrated Services architecture. + + The contents of the hint are likely to vary depending on the exact + scenario. The hint needs to tell the routers that receive it: + + - the type of compression that is possible on this flow (e.g. + IP/UDP/RTP); + + + + + +Davie, et al. Standards Track [Page 3] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + - enough information to enable a router to determine the likely + compression ratio that may be achieved. + + In a simple case such as IP/UDP/RTP header compression, it may be + sufficient to tell the routers nothing more than the fact that + IP/UDP/RTP data is being sent. Knowing this fact, the maximum packet + size of the flow (from the TSpec), and the local conditions at the + router, may be sufficient to allow the router to determine the + reduction in bandwidth that compression will allow. In other cases, + it may be helpful or necessary for the sender to include additional + quantitative information to assist in the calculation of the + compression ratio. To handle these cases, additional parameters + containing various amounts of information may be added to the sender + TSpec. Details of the encoding of these parameters, following the + approach originally described in [RFC 2210] are described below. + +3. Admission Control and Resource Allocation + + Integrated Services routers make admission control and resource + allocation decisions based on, among other things, information in the + sender TSpec. If a router receives a sender TSpec which contains a + compressibility hint, it may use the hint to calculate a `compressed + TSpec' which can be used as input to the admission control and + resource allocation processes in place of the TSpec provided by the + sender. To make this concrete, consider the following simple + example. A router receives a reservation request for controlled load + service where: + + - The Sender TSpec and Receiver TSpec contain identical token + bucket parameters; + + - The rate parameter in the token bucket (r) is 48 kbps; + + - The token bucket depth (b) is 120 bytes; + + - The maximum packet size (M) in the TSpecs is 120 bytes; + + - The minimum policed unit (m) is 64 bytes; + + - The Sender TSpec contains a compressibility hint indicating + that the data is IP/UDP/RTP; + + - The compressibility hint includes a compression factor of 70%, + meaning that IP/UDP/RTP header compression will cause a + reduction in bandwidth consumed at the link level by a factor + of 0.7 (the result of compressing 40 bytes of IP/UDP/RTP header + to 4 bytes on a 120 byte packet) + + + + +Davie, et al. Standards Track [Page 4] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + - The interface on which the reservation is to be installed is + able to perform IP/UDP/RTP header compression. + + The router may thus conclude that it can scale down the token bucket + parameters r and b by a factor of 0.7, i.e., to 33.6 kbps and 84 + bytes respectively. M may be scaled down by the same factor (to 84 + bytes), but a different calculation should be used for m. If the + sender actually sends a packet of size m, its header may be + compressed from 40 bytes to 4, thus reducing the packet to 28 bytes; + this value should be used for m. + + Note that if the source always sends packets of the same size and + IP/UDP/RTP always works perfectly, the compression factor is not + strictly needed. The router can independently determine that it can + compress the 40 bytes of IP/UDP/RTP header to 4 bytes (with high + probability). To determine the worst-case (smallest) gain provided + by compression, it can assume that the sender always sends maximum + sized packets at 48 kbps, i.e., a 120 byte packet every 20 + milliseconds. The router can conclude that these packets would be + compressed to 84 bytes, yielding a token bucket rate of 33.6 kbps and + a token bucket depth of 84 bytes as before. If the sender is willing + to allow an independent calculation of compression gain by the + router, the explicit compression factor may be omitted from the + TSpec. Details of the TSpec encoding are provided below. + + To generalize the above discussion, assume that the Sender TSpec + consists of values (r, b, p, M, m), that the explicit compression + factor provided by the sender is f percent, and that the number of + bytes saved by compression is N, independent of packet size. The + parameters in the compressed TSpec would be: + + r' = r * f/100 + b' = b * f/100 + p' = p + M' = M-N + m' = m-N + + The calculations for r' and b' reflect that fact that f is expressed + as a percentage and must therefore be divided by 100. The + calculations for M' and m' hold only in the case where the + compression algorithm reduces packets by a certain number of bytes + independent of content or length of the packet, as is true for header + compression. Other compression algorithms may not have this + property. In determining the value of N, the router may need to make + worst case assumptions about the number of bytes that may be removed + by compression, which depends on such factors as the presence of UDP + checksums and the linearity of RTP timestamps. + + + + +Davie, et al. Standards Track [Page 5] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + All these adjusted values are used in the compressed TSpec. The + router's admission control and resource allocation algorithms should + behave as if the sender TSpec contained those values. [RFC 2205] + provides a set of rules by which sender and receiver TSpecs are + combined to calculate a single `effective' TSpec that is passed to + admission control. When a reservation covering multiple senders is + to be installed, it is necessary to reduce each sender TSpec by its + appropriate compression factor. The set of sender TSpecs that apply + to a single reservation on an interface are added together to form + the effective sender TSpec, which is passed to traffic control. The + effective receiver TSpec need not be modified; traffic control takes + the greatest lower bound of these two TSpecs when making its + admission control and resource allocation decisions. + + The handling of the receiver RSpec depends on whether controlled load + or guaranteed service is used. In the case of controlled load, no + additional processing of RSpec is needed. However, a guaranteed + service RSpec contains a rate term R which does need to be adjusted + downwards to account for compression. To determine how R should be + adjusted, we note that the receiver has chosen R to meet a certain + delay goal, and that the terms in the delay equation that depend on R + are b/R and C/R (when the peak rate is large). The burstsize b in + this case is the sum of the burstsizes of all the senders for this + reservation, and each of these numbers has been scaled down by the + appropriate compression factor. Thus, R should be scaled down using + an average compression factor + + f_avg = (b1*f1 + b2*f2 + ... + bn*fn)/(b1 + b2 + ... bn) + + where bk is the burstsize of sender k and fk is the corresponding + compression factor for this sender. Note that f_avg, like the + individual fi's, is a percentage. Note also that this results in a + compression factor of f in the case where all senders use the same + compression factor f. + + To prevent an increase in delay caused by the C/R term when the + reduced value of R is used for the reservation, it is necessary for + this hop to `inflate' its value of C by dividing it by (f_avg/100). + This will cause the contribution to delay made by this hop's C term + to be what the receiver would expect when it chooses its value of R. + + There are certain risks in adjusting the resource requirements + downwards for the purposes of admission control and resource + allocation. Most compression algorithms are not completely + deterministic, and thus there is a risk that a flow will turn out to + be less compressible than had been assumed by admission control. + This risk is reduced by the use of the explicit compression factor + provided by the sender, and may be minimized if the router makes + + + +Davie, et al. Standards Track [Page 6] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + worst case assumptions about the amount of compression that may be + achieved. This is somewhat analogous to the tradeoff between making + worst case assumptions when performing admission control or making + more optimistic assumptions, as in the case of measurement-based + admission control. If a flow turns out to be less compressible that + had been assumed when performing admission control, any extra traffic + will need to be policed according to normal intserv rules. For + example, if the router assumed that the 48 kbps stream above could be + compressed to 33.6 kbps and it was ultimately possible to compress it + to 35 kbps, the extra 1.4 kbps would be treated as excess. The exact + treatment of such excess is service dependent. + + A similar scenario may arise if a sender claims that data for a + certain session is compressible when in fact it is not, or overstates + the extent of its compressibility. This might cause the flow to be + erroneously admitted, and would cause insufficient resources to be + allocated to it. To prevent such behavior from adversely affecting + other reserved flows, any flow that sends a compressibility hint + should be policed (in any router that has made use of the hint for + its admission control) on the assumption that it is indeed + compressible, i.e., using the compressed TSpec. That is, if the flow + is found to be less compressible than advertised, the extra traffic + that must be forwarded by the router above the compressed TSpec will + be policed according to intserv rules appropriate for the service. + Note that services that use the maximum datagram size M for policing + purposes (e.g. guaranteed service [RFC 2210]) should continue to use + the uncompressed value of M to allow for the possibility that some + packets may not be successfully compressed. + + Note that RSVP does not generally require flows to be policed at + every hop. To quote [RFC 2205]: + + Some QoS services may require traffic policing at some or all of + (1) the edge of the network, (2) a merging point for data from + multiple senders, and/or (3) a branch point where traffic flow + from upstream may be greater than the downstream reservation being + requested. RSVP knows where such points occur and must so + indicate to the traffic control mechanism. + + For the purposes of policing, a router which makes use of the + compressibility hint in a sender TSpec should behave as if it is at + the edge of the network, because it is in a position to receive + traffic from a sender that, while it passed through policing at the + real network edge, may still need to be policed if the amount of data + sent exceeds the amount described by the compressed TSpec. + + + + + + +Davie, et al. Standards Track [Page 7] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +4. Object Format + + The compressibility hint may be included in the sender TSpec using + the encoding rules of Appendix A in [RFC 2210]. The complete sender + TSpec is as follows: + + 31 24 23 16 15 8 7 0 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 1 | 0 (a) | reserved | 10 (b) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 2 | 1 (c) |0| reserved | 9 (d) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 3 | 127 (e) | 0 (f) | 5 (g) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 4 | Token Bucket Rate [r] (32-bit IEEE floating point number) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 5 | Token Bucket Size [b] (32-bit IEEE floating point number) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 6 | Peak Data Rate [p] (32-bit IEEE floating point number) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 7 | Minimum Policed Unit [m] (32-bit integer) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 8 | Maximum Packet Size [M] (32-bit integer) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 9 | 126 (h) | 0 (i) | 2 (j) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 10 | Hint (assigned number) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 11 | Compression factor [f] (32-bit integer) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + (a) - Message format version number (0) + (b) - Overall length (10 words not including header) + (c) - Service header, service number 1 (default/global + information) + (d) - Length of service 1 data, 9 words not including header + (e) - Parameter ID, parameter 127 (Token_Bucket_TSpec) + (f) - Parameter 127 flags (none set) + (g) - Parameter 127 length, 5 words not including header + (h) - Parameter ID, parameter 126 (Compression_Hint) + (i) - Parameter 126 flags (none set) + (j) - Parameter 126 length, 2 words not including header + + The difference between this TSpec and the one described in [RFC 2210] + is that the overall length contained in the first word is increased + by 3, as is the length of the `service 1 data', and the original + TSpec parameters are followed by a new parameter, the compressibility + hint. This parameter contains the standard parameter header, and an + + + +Davie, et al. Standards Track [Page 8] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + + assigned number indicating the type of compression that is possible + on this data. Different values of the hint would imply different + compression algorithms may be applied to the data. Details of the + numbering scheme for hints appear below. + + Following the hint value is the compression factor f, expressed as a + 32 bit integer representing the factor as a percentage value. The + valid range for this factor is (0,100]. A sender that does not know + what value to use here or wishes to leave the compression factor + calculation to the routers' discretion may use the reserved value 0 + to indicate this fact. Zero is reserved because it is not possible + to compress a data stream to zero bits per second. The value 100 + indicates that no compression is expected on this stream. + + In some cases, additional quantitative information about the traffic + may be required to enable a router to determine the amount of + compression possible. In this case, a different encoding of the + parameter would be required. + + In some cases it may be desirable to include more than one hint in a + Tspec (e.g., because more than one compression scheme could be + applied to the data.) In this case, multiple instances of parameter + 126 may appear in the Tspec and the overall length of the Tspec and + the length of the Service 1 data would be increased accordingly. + + Note that the Compression_Hint is, like the Token_Bucket_Tspec, not + specific to a single service, and thus has a parameter value less + than 128. It is also included as part of the default/global + information (service number 1). + +4.1. Hint Numbering + + Hints are represented by a 32 bit field, with the high order 16 bits + being the IP-compression-protocol number as defined in [RFC 1332] and + [RFC 2509]. The low order 16 bits are a sub-option for the cases + where the IP-compression-protocol number alone is not sufficient for + int-serv purposes. The following hint values are required at the + time of writing: + + - hint = 0x002d0000: IP/TCP data that may be compressed according + to [RFC 1144] + + - hint = 0x00610000: IP data that may be compressed according to + [RFC 2507] + + - hint = 0x00610100: IP/UDP/RTP data that may be compressed + according to [RFC 2508] + + + + +Davie, et al. Standards Track [Page 9] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +5. Backward Compatibility + + It is desirable that an intserv router which receives this new TSpec + format and does not understand the compressibility hint should + silently ignore the hint rather than rejecting the entire TSpec (or + the message containing it) as malformed. While [RFC 2210] clearly + specifies the format of TSpecs in a way that they can be parsed even + when they contain unknown parameters, it does not specify what action + should be taken when unknown objects are received. Thus it is quite + possible that some RSVP implementations will discard PATH messages + containing a TSpec with the compressibility hint. In such a case, + the router should send a PathErr message to the sending host. The + message should indicate a malformed TSpec (Error code 21, Sub-code + 04). The host may conclude that the hint caused the problem and send + a new PATH without the hint. + + For the purposes of this specification, it would be preferable if + unknown TSpec parameters could be silently ignored. In the case + where a parameter is silently ignored, the node should behave as if + that parameter were not present, but leave the unknown parameter + intact in the object that it forwards. This should be the default + for unknown parameters of the type described in [RFC 2210]. + + It is possible that some future modifications to [RFC 2210] will + require unknown parameter types to cause an error response. This + situation is analogous to RSVP's handling of unknown objects, which + allows for three different response to an unknown object, based on + the highest two bits of the Class-Num. One way to handle this would + be to divide the parameter space further than already done in [RFC + 2216]. For example, parameter numbers of the form x1xxxxxx could be + silently ignored if unrecognized, while parameter numbers of the form + x0xxxxxx could cause an error response if unrecognized. (The meaning + of the highest order bit is already fixed by [RFC 2216].) A third + possibility exists, which is to remove the unrecognized parameter + before forwarding, but this does not seem to be useful. + +6. Security Considerations + + The extensions defined in this document pose essentially the same + security risks as those of [RFC 2210]. The risk that a sender will + falsely declare his data to be compressible is equivalent to the + sender providing an insufficiently large TSpec and is dealt with in + the same way. + + + + + + + + +Davie, et al. Standards Track [Page 10] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +7. IANA Considerations + + This specification relies on IANA-assigned numbers for the + compression scheme hint. Where possible the existing numbering + scheme for compression algorithm identification in PPP has been used, + but it may in the future be necessary for IANA to assign hint numbers + purely for the purposes of int-serv. + +8. Acknowledgments + + Carsten Borman and Mike DiBiasio provided much helpful feedback on + this document. + +9. References + + [RFC 1144] Jacobson, V., "Compressing TCP/IP Headers for Low-Speed + Serial Links", RFC 1144, February 1990. + + [RFC 1332] McGregor, G., "The PPP Internet Protocol Control Protocol + (IPCP)", RFC 1332, May 1992. + + [RFC 2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. + Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 + Functional Specification", RFC 2205, September 1997. + + [RFC 2210] Wroclawski, J., "The Use of RSVP with IETF Integrated + Services", RFC 2210, September 1997. + + [RFC 2211] Wroclawski, J., "Specification of the Controlled-Load + Network Element Service", RFC 2211, September 1997. + + [RFC 2212] Shenker, S., Partridge, C. and R. Guerin, "Specification + of Guaranteed Quality of Service", RFC 2212, September + 1997. + + [RFC 2216] Shenker, S. and J. Wroclawski, "Network Element Service + Specification Template", RFC 2216, September 1997. + + [RFC 2507] Degermark, M., Nordgren, B. and S. Pink,"Header + Compression for IP", RFC 2507, February 1999. + + [RFC 2508] Casner, S. and V. Jacobson, "Compressing IP/UDP/RTP + Headers for Low-Speed Serial Links", RFC 2508, February + 1999. + + [RFC 2509] Engan, M., Casner, S. and C. Bormann, "IP Header + Compression over PPP", RFC 2509, February 1999. + + + + +Davie, et al. Standards Track [Page 11] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +10. Authors' Addresses + + Bruce Davie + Cisco Systems, Inc. + 250 Apollo Drive + Chelmsford, MA, 01824 + + EMail: bsd@cisco.com + + + Carol Iturralde + Cisco Systems, Inc. + 250 Apollo Drive + Chelmsford, MA, 01824 + + EMail: cei@cisco.com + + + Dave Oran + Cisco Systems, Inc. + 170 Tasman Drive + San Jose, CA, 95134 + + EMail: oran@cisco.com + + + Stephen L. Casner + Packet Design + 66 Willow Place + Menlo Park, CA 94025 + + EMail: casner@acm.org + + + John Wroclawski + MIT Laboratory for Computer Science + 545 Technology Sq. + Cambridge, MA 02139 + + EMail: jtw@lcs.mit.edu + + + + + + + + + + + +Davie, et al. Standards Track [Page 12] + +RFC 3006 Integrated Services in Compressible Flows November 2000 + + +Full Copyright Statement + + Copyright (C) The Internet Society (2000). All Rights Reserved. + + This document and translations of it may be copied and furnished to + 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. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + + + + + + + + + + + + + +Davie, et al. Standards Track [Page 13] + |