--- 1/draft-ietf-6man-udpzero-06.txt 2012-10-22 11:14:20.045342337 +0200 +++ 2/draft-ietf-6man-udpzero-07.txt 2012-10-22 11:14:20.105342275 +0200 @@ -1,114 +1,119 @@ Internet Engineering Task Force G. Fairhurst Internet-Draft University of Aberdeen -Intended status: Informational M. Westerlund -Expires: December 20, 2012 Ericsson - June 20, 2012 +Intended status: Standards Track M. Westerlund +Expires: April 25, 2013 Ericsson + October 22, 2012 - IPv6 UDP Checksum Considerations - draft-ietf-6man-udpzero-06 + Applicability Statement for the use of IPv6 UDP Datagrams with Zero + Checksums + draft-ietf-6man-udpzero-07 Abstract - This document examines the role of the UDP transport checksum when - used with IPv6, as defined in RFC2460. It presents a summary of the - trade-offs for evaluating the safety of updating RFC 2460 to permit - an IPv6 UDP endpoint to use a zero value in the checksum field as an + This document provides an applicability statement for the use of UDP + transport checksums when used with IPv6. This defines + recommendations and requirements for use of IPv6 UDP datagrams with a + zero checksum. It examines the role of the IPv6 UDP transport + checksum, as defined in RFC2460 and presents a summary of the trade- + offs for evaluating the safety of updating RFC 2460 to permit an IPv6 + UDP endpoint to use a zero value in the checksum field as an indication that no checksum is present. This method is compared with some other possibilities. The document also describes the issues and design principles that need to be considered when UDP is used with - IPv6 to support tunnel encapsulations. It concludes that UDP with a - zero checksum in IPv6 can safely be used for this purpose, provided - that this usage is governed by a set of constraints. + IPv6 to support tunnel encapsulations. + + XXX NOTE - This revision is a partial response to comments received + during IESG review. There are additional comments to be incorporated + - and updates anticipated to the related PS that updates IPv6. This + is therefore an interim version. XXX Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on December 20, 2012. + This Internet-Draft will expire on April 25, 2013. Copyright Notice - Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal - Provisions Relating to IETF Documents (http://trustee.ietf.org/ - license-info) in effect on the date of publication of this document. - Please review these documents carefully, as they describe your rights - and restrictions with respect to this document. Code Components - extracted from this document must include Simplified BSD License text - as described in Section 4.e of the Trust Legal Provisions and are - provided without warranty as described in the Simplified BSD License. + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1.1. Document Structure . . . . . . . . . . . . . . . . . . . . 3 - 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1.2.1. The Role of a Transport Endpoint . . . . . . . . . . . 4 - 1.2.2. The UDP Checksum . . . . . . . . . . . . . . . . . . . 4 - 1.2.3. Differences between IPv6 and IPv4 . . . . . . . . . . 6 - 1.3. Use of UDP Tunnels . . . . . . . . . . . . . . . . . . . . 6 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 1.1. Document Structure . . . . . . . . . . . . . . . . . . . . 4 + 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 + 1.3. Use of UDP Tunnels . . . . . . . . . . . . . . . . . . . . 5 1.3.1. Motivation for new approaches . . . . . . . . . . . . 6 - 1.3.2. Reducing forwarding cost . . . . . . . . . . . . . . . 7 - 1.3.3. Need to inspect the entire packet . . . . . . . . . . 8 - 1.3.4. Interactions with middleboxes . . . . . . . . . . . . 8 + 1.3.2. Reducing forwarding cost . . . . . . . . . . . . . . . 6 + 1.3.3. Need to inspect the entire packet . . . . . . . . . . 7 + 1.3.4. Interactions with middleboxes . . . . . . . . . . . . 7 1.3.5. Support for load balancing . . . . . . . . . . . . . . 8 - 2. Standards-Track Transports . . . . . . . . . . . . . . . . . . 9 - 2.1. UDP with Standard Checksum . . . . . . . . . . . . . . . . 9 + 2. Standards-Track Transports . . . . . . . . . . . . . . . . . . 8 + 2.1. UDP with Standard Checksum . . . . . . . . . . . . . . . . 8 2.2. UDP-Lite . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 2.2.1. Using UDP-Lite as a Tunnel Encapsulation . . . . . . . 10 - 2.3. General Tunnel Encapsulations . . . . . . . . . . . . . . 10 - 3. Issues Requiring Consideration . . . . . . . . . . . . . . . . 11 + 2.2.1. Using UDP-Lite as a Tunnel Encapsulation . . . . . . . 9 + 2.3. General Tunnel Encapsulations . . . . . . . . . . . . . . 9 + 3. Issues Requiring Consideration . . . . . . . . . . . . . . . . 10 3.1. Effect of packet modification in the network . . . . . . . 11 3.1.1. Corruption of the destination IP address . . . . . . . 12 - 3.1.2. Corruption of the source IP address . . . . . . . . . 13 - 3.1.3. Corruption of Port Information . . . . . . . . . . . . 14 - 3.1.4. Delivery to an unexpected port . . . . . . . . . . . . 14 + 3.1.2. Corruption of the source IP address . . . . . . . . . 12 + 3.1.3. Corruption of Port Information . . . . . . . . . . . . 13 + 3.1.4. Delivery to an unexpected port . . . . . . . . . . . . 13 3.1.5. Corruption of Fragmentation Information . . . . . . . 15 3.2. Validating the network path . . . . . . . . . . . . . . . 17 - 3.3. Applicability of method . . . . . . . . . . . . . . . . . 18 - 3.4. Impact on non-supporting devices or applications . . . . . 19 + 3.3. Applicability of method . . . . . . . . . . . . . . . . . 17 + 3.4. Impact on non-supporting devices or applications . . . . . 18 4. Evaluation of proposal to update RFC 2460 to support zero - checksum . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 + checksum . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1. Alternatives to the Standard Checksum . . . . . . . . . . 19 - 4.2. Comparison . . . . . . . . . . . . . . . . . . . . . . . . 21 - 4.2.1. Middlebox Traversal . . . . . . . . . . . . . . . . . 21 - 4.2.2. Load Balancing . . . . . . . . . . . . . . . . . . . . 22 - 4.2.3. Ingress and Egress Performance Implications . . . . . 22 + 4.2. Comparison . . . . . . . . . . . . . . . . . . . . . . . . 20 + 4.2.1. Middlebox Traversal . . . . . . . . . . . . . . . . . 20 + 4.2.2. Load Balancing . . . . . . . . . . . . . . . . . . . . 21 + 4.2.3. Ingress and Egress Performance Implications . . . . . 21 4.2.4. Deployability . . . . . . . . . . . . . . . . . . . . 22 - 4.2.5. Corruption Detection Strength . . . . . . . . . . . . 23 + 4.2.5. Corruption Detection Strength . . . . . . . . . . . . 22 4.2.6. Comparison Summary . . . . . . . . . . . . . . . . . . 23 - 5. Requirements on the specification of transported protocols . . 25 - 5.1. Constraints required on usage of a zero checksum . . . . . 25 - 6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 - 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 28 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 28 - 10.2. Informative References . . . . . . . . . . . . . . . . . 29 - Appendix A. Document Change History . . . . . . . . . . . . . . . 30 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 + 5. Constraints on implementation of IPv6 nodes supporting + zero checksum . . . . . . . . . . . . . . . . . . . . . . . . 25 + 6. Requirements on the specification of transported protocols . . 25 + 7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 + 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 29 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 + 11.1. Normative References . . . . . . . . . . . . . . . . . . . 29 + 11.2. Informative References . . . . . . . . . . . . . . . . . . 29 + Appendix A. Document Change History . . . . . . . . . . . . . . . 31 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33 1. Introduction The User Datagram Protocol (UDP) [RFC0768] transport is defined for the Internet Protocol (IPv4) [RFC0791] and is defined in Internet Protocol, Version 6 (IPv6) [RFC2460] for IPv6 hosts and routers. The UDP transport protocol has a minimal set of features. This limited set has enabled a wide range of applications to use UDP, but these application do need to provide many important transport functions on top of UDP. The UDP Usage Guidelines [RFC5405] provides overall @@ -157,148 +162,53 @@ Section 3 discusses issues with a zero checksum in UDP for IPv6. It considers the impact of corruption, the need for validation of the path and when it is suitable to use a zero checksum. Section 4 evaluates a set of proposals to update the UDP transport behaviour and other alternatives intended to improve support for tunnel protocols. It focuses on a proposal to allow a zero checksum for this use-case with IPv6 and assesses the trade-offs that would arise. - Section 5.1 lists the constraints perceived for safe deployment of - zero-checksum. + Section 5 is an applicability statement that defines requirements and + recommendations on the implementation of IPv6 nodes that support the + use of a UDP zero value in the checksum of a UDP datagram. - Section 6 provides the recommendations for standardization of zero- + Section 6 provides an applicability statement that identifies + requirements and recommendations for protocols and tunnel + encapsulations that are transported over an IPv6 transport connection + that does not perform a UDP checksum calculation to verify the + integrity at the transport endpoints. + + Section 7 provides the recommendations for standardization of zero- checksum with a summary of the findings and notes remaining issues needing future work. -1.2. Background - - This section provides a background on topics relevant to the - following discussion. - -1.2.1. The Role of a Transport Endpoint - - An Internet transport endpoint should concern itself with the - following issues: - - o Protection of the endpoint transport state from unnecessary extra - state (e.g. Invalid state from rogue packets). - - o Protection of the endpoint transport state from corruption of - internal state. - - o Pre-filtering by the endpoint of erroneous data, to protect the - transport from unnecessary processing and from corruption that it - can not itself reject. - - o Pre-filtering of incorrectly addressed destination packets, before - responding to a source address. - -1.2.2. The UDP Checksum - UDP, as defined in [RFC0768], supports two checksum behaviours when - used with IPv4. The normal behaviour is for the sender to calculate a - checksum over a block of data that includes a pseudo header and the - UDP datagram payload. The UDP header includes a 16-bit one's - complement checksum that provides a statistical guarantee that the - payload was not corrupted in transit. This also allows a receiver to - verify that the endpoint was the intended destination of the - datagram, because the transport pseudo header covers the IP - addresses, port numbers, transport payload length, and Next Header/ - Protocol value corresponding to the UDP transport protocol [RFC1071]. - The length field verifies that the datagram is not truncated or - padded. The checksum therefore protects an application against - receiving corrupted payload data in place of, or in addition to, the - data that were sent. Although the IPv4 UDP [RFC0768] checksum may be - disabled, applications are recommended to enable UDP checksums - [RFC5405]. - - The network-layer fields that are validated by a transport checksum - are: - - o Endpoint IP source address (always included in the pseudo header - of the checksum) - - o Endpoint IP destination address (always included in the pseudo - header of the checksum) - - o Upper layer payload type (always included in the pseudo header of - the checksum) - - o IP length of payload (always included in the pseudo header of the - checksum) - - o Length of the network layer extension headers (i.e. by correct - position of the checksum bytes) - - The transport-layer fields that are validated by a transport checksum - are: - - o Transport demultiplexing, i.e. ports (always included in the - checksum) - - o Transport payload size (always included in the checksum) - - Transport endpoints also need to verify the correctness of reassembly - of any fragmented datagram. For UDP, this is normally provided as a - part of the integrity check. Disabling the IPv4 checksum prevents - this check. A lack of the UDP header and checksum in fragments can - lead to issues in a translator or middlebox. For example, many IPv4 - Network Address Translators, NATs, rely on port numbers to find the - mappings, packet fragments do not carry port numbers, so fragments - get dropped. IP/ICMP Translation Algorithm [RFC6145] provides some - guidance on the processing of fragmented IPv4 UDP datagrams that do - not carry a UDP checksum. - - IPv4 UDP checksum control is often a kernel-wide configuration - control (e.g. In Linux and BSD), rather than a per socket call. - There are also Networking Interface Cards (NICs) that automatically - calculate TCP [RFC0793] and UDP checksums on transmission when a - checksum of zero is sent to the NIC, using a method known as checksum - offloading. - -1.2.3. Differences between IPv6 and IPv4 - - IPv6 does not provide a network-layer integrity check. The removal - of the header checksum from the IPv6 specification released routers - from a need to update a network-layer checksum for each router hop as - the IPv6 Hop Count is changed (in contrast to the checksum update - needed when an IPv4 router modifies the Time-To-Live (TTL)). +1.2. Terminology - The IP header checksum calculation was seen as redundant for most - traffic (with UDP or TCP checksums enabled), and people wanted to - avoid this extra processing. However, there was concern that the - removal of the IP header checksum in IPv6 combined with a UDP - checksum set to zero would lessen the protection of the source/ - destination IP addresses and result in a significant (a multiplier of - ~32,000) increase in the number of times that a UDP packet was - accidentally delivered to the wrong destination address and/or - apparently sourced from the wrong source address. This would have - had implications on the detectability of mis-delivery of a packet to - an incorrect endpoint/socket, and the robustness of the Internet - infrastructure. The use of the UDP checksum is therefore required - [RFC2460] when endpoint applications transmit UDP datagrams over - IPv6. + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. 1.3. Use of UDP Tunnels One increasingly popular use of UDP is as a tunneling protocol, where a tunnel endpoint encapsulates the packets of another protocol inside UDP datagrams and transmits them to another tunnel endpoint. Using UDP as a tunneling protocol is attractive when the payload protocol is not supported by the middleboxes that may exist along the path, - because many middleboxes support transmission using UDP. In this use, - the receiving endpoint decapsulates the UDP datagrams and forwards - the original packets contained in the payload [RFC5405]. Tunnels - establish virtual links that appear to directly connect locations - that are distant in the physical Internet topology and can be used to - create virtual (private) networks. + because many middleboxes support transmission using UDP. In this + use, the receiving endpoint decapsulates the UDP datagrams and + forwards the original packets contained in the payload [RFC5405]. + Tunnels establish virtual links that appear to directly connect + locations that are distant in the physical Internet topology and can + be used to create virtual (private) networks. 1.3.1. Motivation for new approaches A number of tunnel encapsulations deployed over IPv4 have used the UDP transport with a zero checksum. Users of these protocols expect a similar solution for IPv6. A number of tunnel protocols are also currently being defined (e.g. Automated Multicast Tunnels, AMT [I-D.ietf-mboned-auto-multicast], and the Locator/Identifier Separation Protocol, LISP [LISP]). These @@ -319,32 +229,32 @@ Address Translators, NATs. o A desire to use the port number space to enable load-sharing. 1.3.2. Reducing forwarding cost It is a common requirement to terminate a large number of tunnels on a single router/host. Processing per tunnel concerns both state (memory requirements) and per-packet processing costs. - Automatic IP Multicast Tunneling, known as AMT [I-D.ietf-mboned-auto- - multicast] currently specifies UDP as the transport protocol for - packets carrying tunneled IP multicast packets. The current - specification for AMT requires that the UDP checksum in the outer - packet header should be 0 (see Section 6.6 of [I-D.ietf-mboned-auto- - multicast]). It argues that the computation of an additional - checksum, when an inner packet is already adequately protected, is an - unwarranted burden on nodes implementing lightweight tunneling - protocols. The AMT protocol needs to replicate a multicast packet to - each gateway tunnel. In this case, the outer IP addresses are - different for each tunnel and therefore require a different pseudo - header to be built for each UDP replicated encapsulation. + Automatic IP Multicast Tunneling, known as AMT + [I-D.ietf-mboned-auto-multicast] currently specifies UDP as the + transport protocol for packets carrying tunneled IP multicast + packets. The current specification for AMT requires that the UDP + checksum in the outer packet header should be 0 (see Section 6.6 of + [I-D.ietf-mboned-auto-multicast]). It argues that the computation of + an additional checksum, when an inner packet is already adequately + protected, is an unwarranted burden on nodes implementing lightweight + tunneling protocols. The AMT protocol needs to replicate a multicast + packet to each gateway tunnel. In this case, the outer IP addresses + are different for each tunnel and therefore require a different + pseudo header to be built for each UDP replicated encapsulation. The argument concerning redundant processing costs is valid regarding the integrity of a tunneled packet. In some architectures (e.g. PC- based routers), other mechanisms may also significantly reduce checksum processing costs: There are implementations that have optimised checksum processing algorithms, including the use of checksum-offloading. This processing is readily available for IPv4 packets at high line rates. Such processing may be anticipated for IPv6 endpoints, allowing receivers to reject corrupted packets without further processing. However, there are certain classes of @@ -362,60 +272,60 @@ not provide checksum-offloading. Thus enabling checksum calculation over the complete packet can impact router design, performance improvement, energy consumption and/or cost. 1.3.4. Interactions with middleboxes In IPv4, UDP-encapsulation may be desirable for NAT traversal, since UDP support is commonly provided. It is also necessary due to the almost ubiquitous deployment of IPv4 NATs. There has also been discussion of NAT for IPv6, although not for the same reason as in - IPv4. If IPv6 NAT becomes a reality they hopefully do not present the - same protocol issues as for IPv4. If NAT is defined for IPv6, it + IPv4. If IPv6 NAT becomes a reality they hopefully do not present + the same protocol issues as for IPv4. If NAT is defined for IPv6, it should take UDP zero checksum into consideration. The requirements for IPv6 firewall traversal are likely be to be - similar to those for IPv4. In addition, it can be reasonably expected - that a firewall conforming to RFC 2460 will not regard UDP datagrams - with a zero checksum as valid packets. If a zero-checksum for UDP - were to be allowed for IPv6, this would need firewalls to be updated - before full utility of the change is available. + similar to those for IPv4. In addition, it can be reasonably + expected that a firewall conforming to RFC 2460 will not regard UDP + datagrams with a zero checksum as valid packets. If a zero-checksum + for UDP were to be allowed for IPv6, this would need firewalls to be + updated before full utility of the change is available. It can be expected that UDP with zero-checksum will initially not have the same middlebox traversal characteristics as regular UDP. However, if standardized we can expect an improvement over time of - the traversal capabilities. We also note that deployment of - IPv6-capable middleboxes is still in its initial phases. Thus, it - might be that the number of non-updated boxes quickly become a very - small percentage of the deployed middleboxes. + the traversal capabilities. We also note that deployment of IPv6- + capable middleboxes is still in its initial phases. Thus, it might + be that the number of non-updated boxes quickly become a very small + percentage of the deployed middleboxes. 1.3.5. Support for load balancing The UDP port number fields have been used as a basis to design load- balancing solutions for IPv4. This approach has also been leveraged - for IPv6. An alternate method would be to utilise the IPv6 Flow Label - as basis for entropy for the load balancing. This would have the - desirable effect of releasing IPv6 load-balancing devices from the - need to assume semantics for the use of the transport port field and - also works for all type of transport protocols. This use of the + for IPv6. An alternate method would be to utilise the IPv6 Flow + Label as basis for entropy for the load balancing. This would have + the desirable effect of releasing IPv6 load-balancing devices from + the need to assume semantics for the use of the transport port field + and also works for all type of transport protocols. This use of the flow-label is consistent with the intended use, although further clarity may be needed to ensure the field can be consistently used for this purpose, (e.g. Equal-Cost Multi-Path routing, ECMP [ECMP]). Router vendors could be encouraged to start using the IPv6 Flow Label as a part of the flow hash, providing support for ECMP without requiring use of UDP. However, the method for populating the outer IPv6 header with a value for the flow label is not trivial: If the inner packet uses IPv6, then the flow label value could be copied to the outer packet header. However, many current end-points set the - flow label to a zero value (thus no entropy). The ingress of a tunnel - seeking to provide good entropy in the flow label field would + flow label to a zero value (thus no entropy). The ingress of a + tunnel seeking to provide good entropy in the flow label field would therefore need to create a random flow label value and keep corresponding state, so that all packets that were associated with a flow would be consistently given the same flow label. Although possible, this complexity may not be desirable in a tunnel ingress. The end-to-end use of flow labels for load balancing is a long-term solution. Even if the usage of the flow label is clarified, there would be a transition time before a significant proportion of end- points start to assign a good quality flow label to the flows that they originate, with continued use of load balancing using the @@ -475,45 +385,45 @@ Lite, because UDP-Lite uses a different IPv6 network-layer Next Header value to that of UDP, and few middleboxes are able to interpret UDP-Lite and take appropriate actions when forwarding the packet. This makes UDP-Lite less suited to protocols needing general Internet support, until such time that UDP-Lite has achieved better support in middleboxes and end-points. 2.3. General Tunnel Encapsulations The IETF has defined a set of tunneling protocols or network layer - encapsulations, e.g., IP-in-IP and GRE. These either do not include a - checksum or use a checksum that is optional, since tunnel + encapsulations, e.g., IP-in-IP and GRE. These either do not include + a checksum or use a checksum that is optional, since tunnel encapsulations are typically layered directly over the Internet layer (identified by the upper layer type in the IPv6 Next Header field) and are also not used as endpoint transport protocols. There is little chance of confusing a tunnel-encapsulated packet with other application data that could result in corruption of application state or data. From the end-to-end perspective, the principal difference is that the network-layer Next Header field identifies a separate transport, which reduces the probability that corruption could result in the packet being delivered to the wrong endpoint or application. Specifically, packets are only delivered to protocol modules that process a specific next header value. The next header field therefore provides a first-level check of correct demultiplexing. In contrast, the UDP port space is shared by many diverse applications and therefore UDP demultiplexing relies solely on the port numbers. 3. Issues Requiring Consideration - This section evaluates issues around the proposal to update IPv6 - [RFC2460], to provide the option of using a UDP transport checksum - set to zero. Some of the identified issues are shared with other - protocols already in use. + This informative section evaluates issues around the proposal to + update IPv6 [RFC2460], to provide the option of using a UDP transport + checksum set to zero. Some of the identified issues are shared with + other protocols already in use. The decision by IPv6 to omit an integrity check at the network level has meant that the transport check was overloaded with many functions, including validating: o the endpoint address was not corrupted within a router, i.e., a packet was intended to be received by this destination and validate that the packet does not consist of a wrong header spliced to a different payload; @@ -571,52 +482,57 @@ When a checksum is used, this significantly reduces the impact of errors, reducing the probability of undetected corruption of state (and data) on both the host stack and the applications using the transport service. The following sections examine the impact of modifying each of these header fields. 3.1.1. Corruption of the destination IP address - An IP endpoint destination address could be modified in the network + An IPv6 endpoint destination address could be modified in the network (e.g. corrupted by an error). This is not a concern for IPv4, because the IP header checksum will result in this packet being discarded by the receiving IP stack. Such modification in the network can not be detected at the network layer when using IPv6. There are two possible outcomes: o Delivery to a destination address that is not in use (the packet will not be delivered, but could result in an error report); o Delivery to a different destination address. This modification will normally be detected by the transport checksum, resulting in - silent discard. Without this checksum, the packet would be passed - to the endpoint port demultiplexing function. If an application - is bound to the associated ports, the packet payload will be - passed to the application (see the subsequent section on port - processing). + silent discard. Without a computed checksum, the packet would be + passed to the endpoint port demultiplexing function. If an + application is bound to the associated ports, the packet payload + will be passed to the application (see the subsequent section on + port processing). 3.1.2. Corruption of the source IP address This section examines what happens when the source address is corrupted in transit. This is not a concern in IPv4, because the IP header checksum will normally result in this packet being discarded by the receiving IP stack. Corruption of an IPv6 source address does not result in the IP packet being delivered to a different endpoint protocol or destination address. If only the source address is corrupted, the datagram will likely be processed in the intended context, although with erroneous - origin information. The result will depend on the application or - protocol that processes the packet. Some examples are: + origin information. When using Unicast Reverse Path Forwarding + [RFC2827], a change in address may result in the router discarding + the packet when the route to the modified source address is different + to that of the source address of the original packet. + + The result will depend on the application or protocol that processes + the packet. Some examples are: o An application that requires a per-established context may disregard the datagram as invalid, or could map this to another context (if a context for the modified source address was already activated). o A stateless application will process the datagram outside of any context, a simple example is the ECHO server, which will respond with a datagram directed to the modified source address. This would create unwanted additional processing load, and generate @@ -765,34 +680,34 @@ fragments resulting when the path MTU results in fragmentation of a larger packet, common when addition of a tunnel encapsulation header expands the size of a packet). Detection of this type of error requires a checksum or other integrity check of the headers and the payload. Such protection is anyway desirable for tunnel encapsulations using IPv4, since the small fragmentation ID can easily result in wrap-around [RFC4963], this is especially the case for tunnels that perform flow aggregation [I-D.ietf-intarea-tunnels]. Tunnel fragmentation behavior matters. There can be outer or inner - fragmentation "Tunnels in the Internet Architecture" [I-D.ietf- - intarea-tunnels]. If there is inner fragmentation by the tunnel, the - outer headers will never be fragmented and thus a zero-checksum in - the outer header will not affect the reassembly process. When a - tunnel performs outer header fragmentation, the tunnel egress needs - to perform reassembly of the outer fragments into an inner packet. - The inner packet is either a complete packet or a fragment. If it is - a fragment, the destination endpoint of the fragment will perform - reassembly of the received fragments. The complete packet or the - reassembled fragments will then be processed according to the packet - next header field. The receiver may only detect reassembly anomalies - when it uses a protocol with a checksum. The larger the number of - reassembly processes to which a packet has been subjected, the - greater the probability of an error. + fragmentation "Tunnels in the Internet Architecture" + [I-D.ietf-intarea-tunnels]. If there is inner fragmentation by the + tunnel, the outer headers will never be fragmented and thus a zero- + checksum in the outer header will not affect the reassembly process. + When a tunnel performs outer header fragmentation, the tunnel egress + needs to perform reassembly of the outer fragments into an inner + packet. The inner packet is either a complete packet or a fragment. + If it is a fragment, the destination endpoint of the fragment will + perform reassembly of the received fragments. The complete packet or + the reassembled fragments will then be processed according to the + packet next header field. The receiver may only detect reassembly + anomalies when it uses a protocol with a checksum. The larger the + number of reassembly processes to which a packet has been subjected, + the greater the probability of an error. o An IP-in-IP tunnel that performs inner fragmentation has similar properties to a UDP tunnel with a zero-checksum that also performs inner fragmentation. o An IP-in-IP tunnel that performs outer fragmentation has similar properties to a UDP tunnel with a zero checksum that performs outer fragmentation. o A tunnel that performs outer fragmentation can result in a higher @@ -818,54 +733,55 @@ IP transports designed for use in the general Internet should not assume specific path characteristics. Network protocols may reroute packets that change the set of routers and middleboxes along a path. Therefore transports such as TCP, SCTP and DCCP have been designed to negotiate protocol parameters, adapt to different network path characteristics, and receive feedback to verify that the current path is suited to the intended application. Applications using UDP and UDP-Lite need to provide their own mechanisms to confirm the validity of the current network path. - The zero-checksum in UDP is explicitly disallowed in RFC2460. Thus it - may be expected that any device on the path that has a reason to look - beyond the IP header will consider such a packet as erroneous or + The zero-checksum in UDP is explicitly disallowed in RFC2460. Thus + it may be expected that any device on the path that has a reason to + look beyond the IP header will consider such a packet as erroneous or illegal and may likely discard it, unless the device is updated to support a new behavior. A pair of end-points intending to use a new behavior will therefore not only need to ensure support at each end- point, but also that the path between them will deliver packets with the new behavior. This may require negotiation or an explicit mandate to use the new behavior by all nodes intended to use a new protocol. Support along the path between end points may be guaranteed in limited deployments by appropriate configuration. In general, it can be expected to take time for deployment of any updated behaviour to become ubiquitous. A sender will need to probe the path to verify the expected behavior. Path characteristics may change, and usage therefore should be robust and able to detect a failure of the path under normal usage and re-negotiate. This will require periodic validation of the path, adding complexity to any solution using the new behavior. 3.3. Applicability of method - The expectation of the present proposal defined in [I-D.ietf-6man- - udpchecksums] is that this change would only apply to IPv6 router - nodes that implement specific protocols that permit omission of UDP - checksums. However, the distinction between a router and a host is - not always clear, especially at the transport level. Systems (such - as unix-based operating systems) routinely provide both functions. - There is also no way to identify the role of a receiver from a - received packet. + The expectation of the present proposal defined in + [I-D.ietf-6man-udpchecksums] is that this change would only apply to + IPv6 router nodes that implement specific protocols that permit + omission of UDP checksums. However, the distinction between a router + and a host is not always clear, especially at the transport level. + Systems (such as unix-based operating systems) routinely provide both + functions. There is also no way to identify the role of a receiver + from a received packet. Any new method would therefore need a specific applicability statement indicating when the mechanism can (and can not) be used. + Enabling this, and ensuring correct interactions with the stack, implies much more than simply disabling the checksum algorithm for specific packets at the transport interface. The IETF should carefully consider constraints on sanctioning the use of any new transport mode. If this is specified and widely available, it may be expected to be used by applications that are perceived to gain benefit. Any solution that uses an end-to-end transport protocol, rather than an IP-in-IP encapsulation, needs to minimise the possibility that end-hosts could confuse a corrupted or @@ -895,81 +811,81 @@ this case, applications using other ports would maintain the current IPv6 behavior, discarding incoming UDP datagrams with a zero- checksum. These other applications would not be effected by this changed behavior. An application that allows the changed behavior should be aware of the risk for corruption and the increased level of misdirected traffic, and can be designed robustly to handle this risk. 4. Evaluation of proposal to update RFC 2460 to support zero checksum - This section evaluates the proposal to update IPv6 [RFC2460], to - provide the option that some nodes may suppress generation and - checking of the UDP transport checksum. It also compares the - proposal with other alternatives. + This informative section evaluates the proposal to update IPv6 + [RFC2460], to provide the option that some nodes may suppress + generation and checking of the UDP transport checksum. It also + compares the proposal with other alternatives. 4.1. Alternatives to the Standard Checksum There are several alternatives to the normal method for calculating - the UDP Checksum that do not require a tunnel endpoint to inspect the - entire packet when computing a checksum. These include (in - decreasing order of complexity): + the UDP Checksum [RFC1071]that do not require a tunnel endpoint to + inspect the entire packet when computing a checksum. These include + (in decreasing order of complexity): o Delta computation of the checksum from an encapsulated checksum field. Since the checksum is a cumulative sum [RFC1624], an encapsulating header checksum can be derived from the new pseudo header, the inner checksum and the sum of the other network-layer fields not included in the pseudo header of the encapsulated packet, in a manner resembling incremental checksum update [RFC1141]. This would not require access to the whole packet, but does require fields to be collected across the header, and arithmetic operations on each packet. The method would only work for packets that contain a 2's complement transport checksum (i.e. it would not be appropriate for SCTP or when IP fragmentation is used). o UDP-Lite with the checksum coverage set to only the header portion of a packet. This requires a pseudo header checksum calculation only on the encapsulating packet header. The computed checksum - value may be cached (before adding the Length field) for each flow - /destination and subsequently combined with the Length of each + value may be cached (before adding the Length field) for each + flow/destination and subsequently combined with the Length of each packet to minimise per-packet processing. This value is combined with the UDP payload length for the pseudo header, however this length is expected to be known when performing packet forwarding. o The proposed UDP Tunnel Transport, UDPTT [UDPTT] suggested a method where UDP would be modified to derive the checksum only from the encapsulating packet protocol header. This value does not change between packets in a single flow. The value may be cached per flow/destination to minimise per-packet processing. o There has been a proposal to simply ignore the UDP checksum value on reception at the tunnel egress, allowing a tunnel ingress to insert any value correct or false. For tunnel usage, a non standard checksum value may be used, forcing an RFC 2460 receiver to drop the packet. The main downside is that it would be - impossible to identify a UDP packet (in the network or an + impossible to identify a UDP datagram (in the network or an endpoint) that is treated in this way compared to a packet that has actually been corrupted. o A method has been proposed that uses a new (to be defined) IPv6 Destination Options Header to provide an end-to-end validation check at the network layer. This would allow an endpoint to verify delivery to an appropriate end point, but would also require IPv6 nodes to correctly handle the additional header, and - would require changes to middlebox behavior (e.g. when used with - a NAT that always adjusts the checksum value). + would require changes to middlebox behavior (e.g. when used with a + NAT that always adjusts the checksum value). - o UDP modified to disable checksum processing [I-D.ietf-6man- - udpchecksums]. This requires no checksum calculation, but would - require constraints on appropriate usage and updates to end-points - and middleboxes. + o UDP modified to disable checksum processing + [I-D.ietf-6man-udpchecksums]. This requires no checksum + calculation, but would require constraints on appropriate usage + and updates to end-points and middleboxes. o IP-in-IP tunneling. As this method completely dispenses with a transport protocol in the outer-layer it has reduced overhead and complexity, but also reduced functionality. There is no outer checksum over the packet and also no ports to perform demultiplexing between different tunnel types. This reduces the information available upon which a load balancer may act. These options are compared and discussed further in the following sections. @@ -984,24 +900,24 @@ Regular UDP with a standard checksum or the delta encoded optimization for creating correct checksums have the best possibilities for successful traversal of a middlebox. No new support is required. A method that ignores the UDP checksum on reception is expected to have a good probability of traversal, because most middleboxes perform an incremental checksum update. UDPTT may also traverse a middlebox with this behaviour. However, a middlebox on the path that attempts to verify a standard checksum will not forward packets using - either of these methods, preventing traversal. The methods that - ignores the checksum has an additional downside in that middlebox - traversal can not be improved, because there is no way to identify - which packets use the modified checksum behaviour. + either of these methods, preventing traversal. A method that ignores + the checksum has an additional downside in that it prevents + improvement of middlebox traversal, because there is no way to + identify packets that use the modified checksum behaviour. IP-in-IP or GRE tunnels offer good traversal of middleboxes that have not been designed for security, e.g. firewalls. However, firewalls may be expected to be configured to block general tunnels as they present a large attack surface. A new IPv6 Destination Options header will suffer traversal issues with middleboxes, especially Firewalls and NATs, and will likely require them to be updated before the extension header is passed. @@ -1115,34 +1031,35 @@ support, limited middlebox traversal, but possible to improve over time, currently poor load balancing support that could improve over time, in most cases requiring application level negotiation and validation. The delta-checksum is an optimization in the processing of UDP, as such it exhibits some of the drawbacks of using regular UDP. The remaining proposals may be described in similar terms: - Zero-Checksum: A low complexity encapsulation, with good multiplexing - support, limited middlebox traversal that could improve over time, - good load balancing support, in most cases requiring application - level negotiation and validation. + Zero-Checksum: A low complexity encapsulation, with good + multiplexing support, limited middlebox traversal that could + improve over time, good load balancing support, in most cases + requiring application level negotiation and validation. UDPTT: A medium complexity encapsulation, with good multiplexing support, limited middlebox traversal, but possible to improve over time, good load balancing support, in most cases requiring application level negotiation and validation. - IPv6 Destination Option IP in IP tunneling: A medium complexity, with - no multiplexing support, limited middlebox traversal, currently - poor load balancing support that could improve over time, in most - cases requiring application level negotiation and validation. + IPv6 Destination Option IP in IP tunneling: A medium complexity, + with no multiplexing support, limited middlebox traversal, + currently poor load balancing support that could improve over + time, in most cases requiring application level negotiation and + validation. IPv6 Destination Option combined with UDP Zero-checksuming: A medium complexity encapsulation, with good multiplexing support, limited load balancing support that could improve over time, in most cases requiring application level negotiation and validation. Ignore the checksum on reception: A low complexity encapsulation, with good multiplexing support, medium middlebox traversal that never can improve, good load balancing support, in most cases requiring application level negotiation and validation. @@ -1181,121 +1098,155 @@ o Are there other avenues of change that will resolve the issue in a better way and sufficiently quickly ? o Do we accept the complexity cost of having one more solution in the future? The authors do think the answer to the above questions are such that zero-checksum should be standardized for use by tunnel encapsulations. -5. Requirements on the specification of transported protocols +5. Constraints on implementation of IPv6 nodes supporting zero checksum - This section identifies requirements for the protocols that are - transported over a transport connection that does not perform a UDP - checksum calculation to verify the integrity at the transport - endpoints. + This section is an applicability statement that defines requirements + and recommendations on the implementation of IPv6 nodes that support + the use of a UDP zero value in the checksum of a UDP datagram. -5.1. Constraints required on usage of a zero checksum + 1. IPv6 nodes SHOULD by default NOT allow the zero checksum method + for transmission or reception. - If a zero checksum approach were to be adopted by the IETF, the - specification should consider adding the following constraints on - usage: + 2. The default node receiver behaviour MUST discard all IPv6 packets + carrying UDP datagrams with a zero checksum. IPv6 nodes MUST + provide a way for the application/protocol to indicate the set of + ports that will be enabled to send UDP datagrams with a zero + checksum. This may be implemented via a socket API call, or + similar mechanism. It may also be implemented by enabling the + method for a pre-assigned static port used by a specific tunnel + protocol. - 1. IPv6 protocol stack implementations should not by default allow - the new method. The default node receiver behaviour must discard - all IPv6 packets carrying UDP packets with a zero checksum. + 3. IPv6 nodes MUST provide a way for the application/protocol to + indicate the set of ports that will be enabled to receive UDP + datagrams with a zero checksum. - 2. Implementations must provide a way to signal the set of ports - that will be enabled to receive UDP datagrams with a zero - checksum. An IPv6 node that enables reception of UDP packets - with a zero-checksum, must enable this only for a specific port - or port-range. This may be implemented via a socket API call, or - similar mechanism. + 4. RFC 2460 specifies that IPv6 nodes SHOULD log received UDP + datagrams with a zero-checksum. This should remain the case for + any datagram received on a port that does not explicitly enable + zero-checksum processing. A port for which zero-checksum has + been enabled MUST NOT log the datagram solely because the + checksum is zero, but MAY log this to support other functions + (such as a security policy). - 3. RFC 2460 specifies that IPv6 nodes should log UDP datagrams with - a zero-checksum. This should remain the case for any datagram - received on a port that does not explicitly enable zero-checksum - processing. A port for which zero-checksum has been enabled must - not log the datagram. + 5. IPv6 nodes MAY separately identify received UDP datagrams that + are discarded with a zero checksum. It SHOULD NOT add these to + the standard log, since the endpoint has not been verified. - 4. A stack may separately identify UDP datagrams that are discarded - with a zero checksum. It should not add these to the standard - log, since the endpoint has not been verified. + 6. IPv6 nodes that receive ICMPv6 messages that refer to packets + with a zero UDP checksum MUST provide appropriate checks + concerning the consistency of the reported packet to verify that + the reported packet actually originated from the node, before + acting upon the information (e.g. validating the address and port + numbers in the ICMPv6 message body). - 5. Tunnels that encapsulate IP may rely on the inner packet +6. Requirements on the specification of transported protocols + + This section is an applicability statement that identifies + requirements and recommendations for protocols and tunnel + encapsulations that are transported over an IPv6 transport connection + that does not perform a UDP checksum calculation to verify the + integrity at the transport endpoints. + + 1. UDP Tunnels that enable the use of zero checksum MUST only enable + this only for a specific port or port-range. + + 2. UDP Tunnels that encapsulate IP MAY rely on the inner packet integrity checks provided that the tunnel will not significantly increase the rate of corruption of the inner IP packet. If a significantly increased corruption rate can occur, then the - tunnel must provide an additional integrity verification - mechanism. An integrity mechanisms is always recommended at the - tunnel layer to ensure that corruption rates of the inner most - packet are not increased. + tunnel MUST provide an additional integrity verification + mechanism. Early detection is desirable to avoid wasting + unneccessary computation/storage for packets that will + subsequently be discarded. - 6. Tunnels that encapsulate Non-IP packets must have a CRC or other - mechanism for checking packet integrity, unless the Non-IP packet - specifically is designed for transmission over lower layers that - do not provide any packet integrity guarantee. In particular, - the application must be designed so that corruption of this - information does not result in accumulated state or incorrect - processing of a tunneled payload. + 3. An integrity mechanisms is always RECOMMENDED at the tunnel layer + to ensure that corruption rates of the inner-most packet are not + increased. A mechanism that isolates the causes of corruption + (e.g. identifying mis-delivery, IPv6 header corruption, tunnel + header corruption) is expected to also provide additional + information about the status of the tunnel (e.g. to suggest a + security attack). - 7. UDP applications that support use of a zero-checksum, should not - rely upon correct reception of the IP and UDP protocol - information (including the length of the packet) when decoding - and processing the packet payload. In particular, the - application must be designed so that corruption of this - information does not result in accumulated state or incorrect - processing of a tunneled payload. + 4. UDP Tunnels that encapsulate non-IP packets MUST have a CRC or + other mechanism for checking packet integrity, unless the non-IP + packet specifically is designed for transmission over lower + layers that do not provide any packet integrity guarantee. In + particular, the tunnel endpoint MUST be designed so that + corruption of this information does not result in accumulated + state or incorrect processing of a tunneled payload. - 8. If a method proposes recursive tunnels, it needs to provide - guidance that is appropriate for all use-cases. Restrictions may - be needed to the use of a tunnel encapsulations and the use of - recursive tunnels (e.g. Necessary when the endpoint is not - verified). + 5. UDP Tunnels that support use of a zero-checksum, SHOULD NOT rely + upon correct reception of the IP and UDP protocol information + (including the length of the packet) when decoding and processing + the packet payload. In particular, the application MUST be + designed so that corruption of this information does not result + in accumulated state or incorrect processing of a tunneled + payload. - 9. IPv6 nodes that receive ICMPv6 messages that refer to packets - with a zero UDP checksum must provide appropriate checks - concerning the consistency of the reported packet to verify that - the reported packet actually originated from the node, before - acting upon the information (e.g. validating the address and - port numbers in the ICMPv6 message body). + 6. A UDP Tunnel egress that supports a zero UDP checksum MUST also + allow reception using a standard UDP checksum. The encapsulating + endpoint may choose to compute the UDP checksum, or the sending + endpoint IPv6 stack may enable this by default. In either case, + the remote endpoint uses the reception method specified in + RFC2460. - Deployment of the new method needs to remain restricted to endpoints - that explicitly enable this mode and adopt the above procedures. Any - middlebox that examines or interacts with the UDP header over IPv6 - should support the new method. + 7. UDP Tunnels with control feedback need to be robust to changes in + network path. The set of middleboxes on a path may vary during + the life of an association. Endpoints need to discover paths + with middleboxes that drop packets with a zero UDP checksum. + Therefore keep-alive messages SHOULD include both UDP datagrams + with a checksum and UDP datagrams with a zero checksum. This + will enable the remote endpoint to distinguish between a path + failure and dropping of UDP datagrams with a zero checksum. Note + that path validation need only be performed for each pair of + tunnel endpoints, not for each tunnel context. -6. Summary + 8. Middleboxes implementations MUST allow IPv6 packets forward both + a zero and standard UDP checksum. A middlebox MAY configure + specific port ranges that forward UDP datagrams with a zero UDP + checksum. These middleboxes MUST forward both standard and zero + checksum UDP datagrams within the configured range, but may drop + IPv6 UDP datagrams with a zero checksum that are outside the + configured ranges. + +7. Summary This document examines the role of the transport checksum when used with IPv6, as defined in RFC2460. It presents a summary of the trade-offs for evaluating the safety of updating RFC 2460 to permit an IPv6 UDP endpoint to use a zero value in the checksum field to indicate that no checksum is present. A decision not to include a UDP checksum in received IPv6 datagrams could impact a tunnel application that receives these packets. However, a well-designed tunnel application should include consistency checks to validate any header information encapsulated with a packet. In most cases tunnels encapsulating IP packets can rely on the inner packets own integrity protection. When correctly implemented, such a tunnel endpoint will not be negatively impacted by omission of the transport-layer checksum. Recursive tunneling and fragmentation is a potential issue that can raise corruption rates significantly, and requires careful consideration. Other applications at the intended destination node or another IPv6 - node can be impacted if they are allowed to receive datagrams without - a transport-layer checksum. It is particularly important that - already deployed applications are not impacted by any change at the - transport layer. If these applications execute on nodes that + node can be impacted if they are allowed to receive datagrams that do + not have a transport-layer checksum. It is particularly important + that already deployed applications are not impacted by any change at + the transport layer. If these applications execute on nodes that implement RFC 2460, they will reject all datagrams with a zero UDP checksum, thus this is not an issue. For nodes that implement support for zero-checksum it is important to ensure that only UDP applications that desire zero-checksum can receive and originate zero-checksum packets. Thus, the enabling of zero-checksum needs to be at a port level, not for the entire host or for all use of an interface. The implications on firewalls, NATs and other middleboxes need to be considered. It is not expected that IPv6 NATs handle IPv6 UDP @@ -1324,137 +1275,146 @@ and possibly consider a solution that at least provides the same delivery protection as for IPv4, for example by utilizing UDP-Lite, or by enabling the UDP checksum. Tunnel applications using UDP for encapsulation can in many case use zero-checksum without significant impact on the corruption rate. In some cases, the use of checksum off-loading may help alleviate the checksum processing cost. Recursive tunneling and fragmentation is a difficult issue relating to tunnels in general. There is an increased risk of an error in the inner-most packet when fragmentation when several layers of tunneling - and several different reassembly processes are run without any + and several different reassembly processes are run without verification of correctness. This issue requires future thought and consideration. The conclusion is that UDP zero checksum in IPv6 should be standardized, as it satisfies usage requirements that are currently difficult to address. We do note that a safe deployment of zero- - checksum will need to follow a set of constraints listed in Section - 5.1. + checksum will need to follow a set of constraints listed in + Section 5. -7. Acknowledgements +8. Acknowledgements Brian Haberman, Brian Carpenter, Magaret Wasserman, Lars Eggert, others in the TSV directorate. Thanks also to: Remi Denis-Courmont, Pekka Savola and many others who contributed comments and ideas via the 6man, behave, lisp and mboned lists. -8. IANA Considerations +9. IANA Considerations This document does not require any actions by IANA. -9. Security Considerations +10. Security Considerations Transport checksums provide the first stage of protection for the stack, although they can not be considered authentication mechanisms. These checks are also desirable to ensure packet counters correctly log actual activity, and can be used to detect unusual behaviours. -10. References +11. References -10.1. Normative References +11.1. Normative References - [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September - 1981. + [I-D.ietf-6man-udpchecksums] + Eubanks, M., Chimento, P., and M. Westerlund, "UDP + Checksums for Tunneled Packets", + draft-ietf-6man-udpchecksums-04 (work in progress), + September 2012. - [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC - 793, September 1981. + [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, + September 1981. - [RFC1071] Braden, R., Borman, D., Partridge, C. and W. Plummer, - "Computing the Internet checksum", RFC 1071, September - 1988. + [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, + RFC 793, September 1981. - [RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version - 6 (IPv6) Specification", RFC 2460, December 1998. + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. -10.2. Informative References + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, December 1998. - [ECMP] "Using the IPv6 flow label for equal cost multipath - routing in tunnels (draft-carpenter-flow-ecmp)", . +11.2. Informative References - [I-D.ietf-6man-udpchecksums] - Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled - Packets", Internet-Draft draft-ietf-6man-udpchecksums-02, - March 2012. + [ECMP] "Using the IPv6 flow label for equal cost multipath + routing in tunnels (draft-carpenter-flow-ecmp)". [I-D.ietf-intarea-tunnels] Touch, J. and M. Townsley, "Tunnels in the Internet - Architecture", Internet-Draft draft-ietf-intarea- - tunnels-00, March 2010. + Architecture", draft-ietf-intarea-tunnels-00 (work in + progress), March 2010. [I-D.ietf-mboned-auto-multicast] - Bumgardner, G., "Automatic Multicast Tunneling", Internet- - Draft draft-ietf-mboned-auto-multicast-14, June 2012. + Bumgardner, G., "Automatic Multicast Tunneling", + draft-ietf-mboned-auto-multicast-14 (work in progress), + June 2012. - [LISP] D. Farinacci et al, , "Locator/ID Separation Protocol + [LISP] D. Farinacci et al, "Locator/ID Separation Protocol (LISP)", March 2009. [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. + [RFC1071] Braden, R., Borman, D., Partridge, C., and W. Plummer, + "Computing the Internet checksum", RFC 1071, + September 1988. + [RFC1141] Mallory, T. and A. Kullberg, "Incremental updating of the Internet checksum", RFC 1141, January 1990. [RFC1624] Rijsinghani, A., "Computation of the Internet Checksum via Incremental Update", RFC 1624, May 1994. - [RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. + [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: + Defeating Denial of Service Attacks which employ IP Source + Address Spoofing", BCP 38, RFC 2827, May 2000. + + [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., - Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J. and L. + Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. Wood, "Advice for Internet Subnetwork Designers", BCP 89, RFC 3819, July 2004. - [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E. and + [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., and G. Fairhurst, "The Lightweight User Datagram Protocol (UDP-Lite)", RFC 3828, July 2004. - [RFC4443] Conta, A., Deering, S. and M. Gupta, "Internet Control + [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 4443, March 2006. - [RFC4963] Heffner, J., Mathis, M. and B. Chandler, "IPv4 Reassembly + [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly Errors at High Data Rates", RFC 4963, July 2007. [RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines - for Application Designers", BCP 145, RFC 5405, November - 2008. + for Application Designers", BCP 145, RFC 5405, + November 2008. - [RFC5415] Calhoun, P., Montemurro, M. and D. Stanley, "Control And + [RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And Provisioning of Wireless Access Points (CAPWAP) Protocol Specification", RFC 5415, March 2009. [RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments", RFC 5722, December 2009. - [RFC6145] Li, X., Bao, C. and F. Baker, "IP/ICMP Translation + [RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation Algorithm", RFC 6145, April 2011. [Sigcomm2000] - Jonathan Stone and Craig Partridge , , "When the CRC and - TCP Checksum Disagree", 2000. + Jonathan Stone and Craig Partridge , "When the CRC and TCP + Checksum Disagree", 2000. - [UDPTT] G Fairhurst, , "The UDP Tunnel Transport mode", Feb 2010. + [UDPTT] G Fairhurst, "The UDP Tunnel Transport mode", Feb 2010. Appendix A. Document Change History {RFC EDITOR NOTE: This section must be deleted prior to publication} Individual Draft 00 This is the first DRAFT of this document - It contains a compilation of various discussions and contributions from a variety of IETF WGs, including: mboned, tsv, 6man, lisp, and behave. This includes contributions from Magnus with text on RTP, and various updates. @@ -1507,28 +1468,39 @@ Working Group Draft 05 * Resubmission to correct editorial NiTs - thanks to Bill Atwood for noting these.Group Draft 05. Working Group Draft 06 * Resubmission to keep draft alive (spelling updated from 05). + WoIt that UDP with a zero checksum in IPv6 can safely be used for + this purpose, provided that this usage is governed by a set of + constraints.rking Group Draft 07 + + * Resubmission after IESG Feedback + * This document becomes a PS Applicability Statement + Authors' Addresses Godred Fairhurst University of Aberdeen School of Engineering Aberdeen, AB24 3UE, Scotland, UK + Phone: Email: gorry@erg.abdn.ac.uk URI: http://www.erg.abdn.ac.uk/users/gorry + Magnus Westerlund Ericsson Farogatan 6 Stockholm, SE-164 80 Sweden Phone: +46 8 719 0000 + Fax: Email: magnus.westerlund@ericsson.com + URI: