A Framework for Semantic IPv6 Prefix and Gap Analysis
Author(s): Qiong Sun, Sheng Jiang, Ian Farrer
Some Internet Service Providers and enterprises require detailed information about the payload of traffic, so that packets can be treated differently and efficiently. Packet-level differentiation can also enable flow-level and user-level differentiation....
Network Working Group S. Jiang, Ed. Internet-Draft Huawei Technologies Co., Ltd Intended status: Informational Q. Sun Expires: August 3, 2013 China Telecom I. Farrer Deutsche Telekom AG January 30, 2013 A Framework for Semantic IPv6 Prefix and Gap Analysis draft-jiang-semantic-prefix-04 Abstract Some Internet Service Providers and enterprises require detailed information about the payload of traffic, so that packets can be treated differently and efficiently. Packet-level differentiation can also enable flow-level and user-level differentiation. With its large address space, IPv6 allows semantics to be embedded into addresses by assigning additional significance to specific bits within the prefix. Using these semantics, routers and other intermediary devices can easily apply relevant policies as required. This document describes a framework for such an approach. It also analyses the technical advantages and limitations associated with such an approach. This informational document only discusses the usage of semantics within a single network, or group of interconnected networks which share a common addressing policy, referred to as a Semantic Prefix Domain. The document is NOT intended to suggest the standardization of any common global semantics. Requirements Language 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 RFC 2119 [RFC 2119]. 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 Jiang, et al. Expires August 3, 2013 [Page 1] Internet-Draft Semantic IPv6 Prefix Framework January 2013 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 August 3, 2013. Copyright Notice Copyright (c) 2013 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. Jiang, et al. Expires August 3, 2013 [Page 2] Internet-Draft Semantic IPv6 Prefix Framework January 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Existing Approaches to Traffic Differentiation . . . . . . . . 4 2.1. Differentiated Services . . . . . . . . . . . . . . . . . 4 2.2. Deep Packet Inspection . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Justifcation for Semantics with the IPv6 Prefix . . . . . . . 5 5. The Semantic Prefix Domain . . . . . . . . . . . . . . . . . . 6 6. The Embedded Semantics . . . . . . . . . . . . . . . . . . . . 7 7. Applicability Examples . . . . . . . . . . . . . . . . . . . . 8 7.1. An ISP Semantic Prefix Example . . . . . . . . . . . . . . 8 7.2. A Semantic Prefix for Security Domains . . . . . . . . . . 9 7.3. A Multi-Prefix Semantic . . . . . . . . . . . . . . . . . 9 8. Semantic Prefix Benefits . . . . . . . . . . . . . . . . . . . 9 9. Gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. Semantic Relevant Operations in Networks . . . . . . . . . 11 9.2. Semantic Relevant Interactions with Hosts . . . . . . . . 11 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 12 12. Security Considerations . . . . . . . . . . . . . . . . . . . 12 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 14.1. Normative References . . . . . . . . . . . . . . . . . . . 13 14.2. Informative References . . . . . . . . . . . . . . . . . . 13 Appendix A. Appendix A: Topics for Future Extention . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Jiang, et al. Expires August 3, 2013 [Page 3] Internet-Draft Semantic IPv6 Prefix Framework January 2013 1. Introduction As the global Internet expands, it is being used for an increasingly diverse range of services. These services place differentiated requirements upon packet delivery networks meaning that Internet Service Providers and enterprises need to be aware of more information about each packet in order to best meet a specific service's needs. Within a specific prefix, source/destination location information is used for routing decisions. However, user types, service types, applications, security requirements, traffic identity types, quality requirements and other criteria may also be relevant parameters which a network operator may wish to use to treat packets differently and efficiently. Packet-level differentiation can also be used for flow- level and user-level differentiation. However, almost all of the above mentioned criteria are not expressed explicitly within an packet. Hence, it is difficult for network operators to identify from packet level. 2. Existing Approaches to Traffic Differentiation There are several existing approaches which have been developed that can assist operators in identifying and marking traffic. These solutions were mainly developed in the IPv4 era, where the IP address is used as a host locator and little else. The limited capacity of a 32-bit IPv4 address provides very little room for encoding additional information. Correspondingly, these approaches are indirect, inefficient and expensive for operators. 2.1. Differentiated Services Quality of Service (QoS) based on and Differentiated Services [RFC2474] is a widely deployed framework specifying a simple, scalable and coarse-grained mechanism for classifying and managing network traffic. But in a service provider's network, DiffServ codepoint (DSCP) values cannot be trusted when they are set by the customer as these are arbitrary values. In real-world scenarios, ISPs deploy "remarking" points at the customer edge of their network, re-classifying received packets by rewriting the DSCP field according to local policy using information such as the source/destination address, IP protocol number and transport layer source/destination ports. The traffic classification process leads to increased packet Jiang, et al. Expires August 3, 2013 [Page 4] Internet-Draft Semantic IPv6 Prefix Framework January 2013 processing overhead and complexity at the edge of the service provider's network. The DSCP in the IPv6 header traffic class field allows 6-bits for encoding service provider specific information related to the contents of the packet. Whilst this is a useful part of an overall packet differentiation architecture, the relative small number of available bits (when compared to the available number of bits within the service providers prefix) means that it cannot be used in isolation. 2.2. Deep Packet Inspection Deep Packet Inspection (DPI) may also be used by ISPs to learn the characteristics of users packets. This involves looking into the packet well beyond the network-layer header to identify the specific application traffic type. Once identified, the traffic type can be used as an input for setting the packet's DSCP or other actions. But DPI is expensive both in processing costs and latency. The processing costs means that dedicated infrastructure is necessary to carry out the function. The incurred latency may be too much for use with any delay/jitter sensitive applications. As a result, DPI is difficult for large-scale deployment and it's usage is usually limited to small and specific functions in the network. 3. Terminology The following terms are used throughout this document: Semantic Prefix: A flexible-length IPv6 prefix which embeds certain semantics. Semantic Prefix Domain: A portion of the Internet over which a consistent semantic-prefix based policy is in operation. Semantic Prefix Policy: [IF - I think that this could simplify wording elsewhere in the document] Write this 4. Justifcation for Semantics with the IPv6 Prefix The IPv6 address can remove such limitations due to its large address space. This can be used by service provides to embed certain pre- defined semantics into an address so that intermediate devices can easily apply relevant forwarding operations each packet based solely on network layer source and destination address information. Jiang, et al. Expires August 3, 2013 [Page 5] Internet-Draft Semantic IPv6 Prefix Framework January 2013 Using semantic prefix information for this function also makes it possible for the service provider to increase the level of trust in a customer-generated packet. If the packet has an incorrectly set source or destination address, then a session will simply fail to establish. This document describes a framework for embedding semantics into IPv6 prefixes so that network devices can process and forward packets based on these semantics. This approach diverts much network complexity to the planning and management of IPv6 address and IP address based policies. It indeed simplifies the management of ISP networks. Different service providers may make very different choices regarding the specific semantics which are relevant to their networks. Semantic prefix definitions are only meaningful within a domain which implements a single policy. Therefore, it is not possible or desirable to attempt to standardize a general semantic prefix policy. Although the interface identifier portion of an IPv6 address has arbitrary bits and extension headers can carry significantly more information, these fields can not be trusted by network operators. Users may easily change the setting of interface identifier or extension header in order to obtain undeserved priorities/privileges, while servers or enterprise users may be much more self-restricted since they are charged accordingly. The prefix can offer a higher level of trust for the network operator because it is delegated by the network and therefore the network is better able to detect any undesired modifications and filter the packet accordingly. If a user manipulated the destination address, the packet will never arrive at the desired service; if the source address is altered, then the return packet will not be received. 5. The Semantic Prefix Domain A Semantic Prefix Domain is analagous to a Differentiated Services Domain [RFC2474]. It can be described as a portion of the Internet over which a consistent set of semantic-prefix-based policies are administered in a coordinated fashion. Some of the characteristics of a single Semantic Prefix Domain could represent include: o Administrative domains o Autonomous systems Jiang, et al. Expires August 3, 2013 [Page 6] Internet-Draft Semantic IPv6 Prefix Framework January 2013 o Trust regions o Network technologies o Hosts o Routers o User groups o Services o Traffic groups o Applications An enterprise Semantic Prefix Domain may span several physical networks and traverse ISP networks. However, when an interim network is traversed (such as when an intermediary ISP is used for interconnectivity), the relevance of the semantics is limited to network domains that share a common Semantic Prefix Policy. The selection of semantics vary between different Semantic Prefix Domains. Network operators should choose semantics according to their network and service management needs. If an ISP has several non-contiguous address blocks, they may be organized as a single Semantic Prefix Domain if the same Semantic Prefix Policy is shared across these non-contiguous address blocks. A Semantic Prefix Domain has a set of pre-defined semantic definitions, which are only meaningful locally. Without an efficient semantics notification, exchanging mechanism or service agreement, the definitions of semantics are only meaningful within local Semantic Prefix Domain. Manual interactions between network operators may also work out. However, this may involve trust models among network operators. Sharing semantic definition among Semantic Prefix Domains enables more semantic based network operations. 6. The Embedded Semantics The size of the operator assigned prefix means that there is potentially much more scope for embedding semantics than has previously been possible. The following list describes some suggested semantics which may be useful to network operators besides source/destination location: Jiang, et al. Expires August 3, 2013 [Page 7] Internet-Draft Semantic IPv6 Prefix Framework January 2013 o User types o Applications o Security domain o Traffic identity types o Quality requirements Consideration must also be given to the complexity that is created within the semantic prefix policy. Whilst it may be desirable to encode as much information within the prefix so that it is possible to have a high level of granularity, this can come at the expense of future addressing flexibility and could also lead to a high amount of address wastage. In the same time, embedding too many semantics may waste addressing space and induce semantic overlap. It should be taken into careful consideration on semantics definition. 7. Applicability Examples The following sections provide some examples of how semantics prefixes could be applied in different use cases. The network operators could also choose to combine ideas from the following examples, or create their own as best suits their requirements. 7.1. An ISP Semantic Prefix Example Current ISP networks are mainly aggregated by using the IP prefix as a geographical locator. The ISP semantic prefix example below uses the left most bits of the prefix for the locator function and lower bits for semantics. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IANA assigned block | locator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | locator (Cont.) | Semantic Field|Subscriber bits| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ An ISP semantic prefix example In this example, the service provider has been allocated a /20 prefix. This means that the Semantic Prefix Domain is potentially up to 44-bits long. The 28 left-most bits (starting at bit-20) are allocated for use as geographical locators. These provide the facility for topolgy based network aggregation. The semantic prefix Jiang, et al. Expires August 3, 2013 [Page 8] Internet-Draft Semantic IPv6 Prefix Framework January 2013 is assigned to bits 48 to 55. The remaining /56 is delegated as prefixes for subscribers. 7.2. A Semantic Prefix for Security Domains In some networks, the locator function of the IP address may be considered to be secondary to the geographical locator function. An example application could be where an operator wishes to use the semantic field to separate services across their entire network to create security domains. Implementing the semantic field in the left-most bits means that a single, simple access-control list implemented across all networking devices would be enough to enforce effective traffic segregation. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ISP assigned block | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ISP assigned block | Security Domain Bits | Locator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ An Semantic Prefix example for Security Domains 7.3. A Multi-Prefix Semantic A multiple-site enterprise may have been assigned several prefixes of different lengths by its upstream ISPs. In this situation, in order to create a single, contiguous Semantic Prefix Domain, it is necessary to base the semantic prefix policy on the longest assigned prefix to ensure that there in enough addressing space to encode a consistent set of semantics across all of the assigned prefixes. In this example, an enterprise has received a /38 address block for one site (A) and a /44 for a second site (B) . They can be organized in the same Semantic Prefix Domain. The most-left 18 (site A) and 12 (site B) bits are allocated as locator. It provides topology based network aggregation. The 8 right-most bits (from bits 56 to 63) are assigned as the semantic field. In this design, the multiple-site enterprise that has been assigned two prefixes of different lengths can be organized as the same Semantic Prefix Domain. 8. Semantic Prefix Benefits This section describes some of the benefits associated with the semantic prefix approach, depending on the semantics which are embedded. Jiang, et al. Expires August 3, 2013 [Page 9] Internet-Draft Semantic IPv6 Prefix Framework January 2013 - Simplified measurement and statistics gathering The semantic prefix provides explicit identifiers which can be used for measurement and statistical information collection. This can be achieved by checking certain bits of the source and/or destination address in each packet. - Simplified flow control By applying policies according to certain bit values, packets carrying the same semantics in their source/destination addresses can. - Service Segregation When service related information is encoded within the semantic prefix, this can be used to create simple access-control lists which can be applied uniformly across all network devices. This means that it is easy to - Policy aggregation The semantic prefix allows many policies to be aggregated according to the same semantics within the policy based routing system [RFC1104]. - Easy dynamic reconfiguration of semantic oriented policy Network operators may want to dynamically change the policy actions that are operated on certain semantic packets. The semantic prefix allows such changes be operated easily, as only a small number of consistent policy rules need to be updated on all devices within the semantic prefix domain. - Application-aware routing Embedding application information into IP addresses is the simplest way to realize application aware routing. - Easy virtualization Virtual network based on any semantics can be easily deployed using the semantic prefix mechanism. 9. Gaps The simplest semantic prefix model is to embed only abstracted user Jiang, et al. Expires August 3, 2013 [Page 10] Internet-Draft Semantic IPv6 Prefix Framework January 2013 type semantics into the prefix. Current network architectures can support this as each subscriber is still assigned a single prefix, while they are not notified the semantic within it. In order to maximise the benefits of the semantic prefix design, additional functions are needed to allow semantic relevant operations in networks and semantic relevant interactions with hosts. IPv6 provides a facility for multiple addresses to be configured on a single interface. This creates a precondition for the approach that user chooses addresses differently for different purposes/usages. 9.1. Semantic Relevant Operations in Networks In order to manage semantic prefixes and their relevant network actions, the network should provide the following semantic relevant functions: - Notification of semantics within the managed network When an prefix is delegated using a DHCPv6 IA_PD [RFC3633], the associated semantics should also be propogated to the requesting router. This is particularly useful for autonomic process when a new device is connected. 9.2. Semantic Relevant Interactions with Hosts The more that semantics are embedded into a prefix, the more that complicated functions are needed for semantic relevant interactions between hosts and the network, such as prefix delegation, host notification and address selections, etc. In practice, a single host may belong to multiple semantics. This means that several IPv6 addresses are configured on a single physical interface and should be selected for use depending on the service that a host wishes to access. A certain packet would only serve a certain semantic. The host's IPv6 stack must have a mechanism for understanding these semantics in order to choose right source address when forming a packet. If the embedded semantic is application relevant, applications on the hosts should also be involved in the address choosing process: the host IPv6 stack reports multiple available addresses to the application through socket API (one example is "IPv6 Socket API for Source Address Selection" [RFC5014]). The application then needs to apply the semantic logic so that it can correctly select from the offered candidate addresses. Jiang, et al. Expires August 3, 2013 [Page 11] Internet-Draft Semantic IPv6 Prefix Framework January 2013 Although [RFC6724] provides an algorithm for source address selection, some semantic prefix policies may conflict with this algorithm. In this case, the source address selection mechanism may also further supporting functions to be developed. 10. IANA Considerations This document has no IANA considerations. 11. Change Log draft-jiang-semantic-prefix-04: new coauthor and re-organize the content, 2013-1-31. draft-jiang-semantic-prefix-03: add the concept of hierarchical Semantic Prefix Domain and more gap analysis, 2012-10-22. draft-jiang-semantic-prefix-02: resubmitted to v6ops WG. Removed detailed examples and recommendations for semantics bits, 2012-10-15. draft-jiang-semantic-prefix-01: added enterprise considerations and scenarios, emphasizing semantics only for local meaning and no intend to standardize any common global semantics, 2012-07-16. draft-jiang-semantic-prefix-00: original version, 2012-07-09 12. Security Considerations Embedding semantics in prefix is actually exposing more information of packets explicit. These informations may also provide convenient for malicious attackers to track or attack certain type of packets. When networks announce their local prefix semantics to their peer networks, it may increase the vulnerable risk. Prefix-based filters should be deployed, in order to protect against address spoofing attacks or denial of service for packets with forged source addresses. 13. Acknowledgements Useful comments were made by Erik Nygren, Nick Hilliard, Ray Hunter, David Farmer, and other participants in the V6OPS working group. Jiang, et al. Expires August 3, 2013 [Page 12] Internet-Draft Semantic IPv6 Prefix Framework January 2013 14. References 14.1. Normative References [RFC1104] Braun, H., "Models of policy based routing", RFC1104, June 1989. [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC2474, December 1998. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC3315, July 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC3633, December 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC4291, February 2006. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC4862, September 2007. [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, "Default Address Selection for Internet Protocol Version 6 (IPv6)", RFC6724, September 2012. 14.2. Informative References [RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 Socket API for Source Address Selection", RFC5014, September 2007. [RFC5401] Adamson, B., Bormann, C., Handley, M., and J. Macker, "Multicast Negative-Acknowledgment (NACK) Building Blocks", RFC5401, November 2008. Appendix A. Appendix A: Topics for Future Extention There are several areas in which the semantic prefix could be extended in order to increase the usefulness and applicability of the Jiang, et al. Expires August 3, 2013 [Page 13] Internet-Draft Semantic IPv6 Prefix Framework January 2013 concept. They are complementarity besides the main framework. These are being described here as topics for possible future work. Each of them may deserve a separated document for technical details. - Dynamic Policy Configuration Dynamic policy configuration would simplify the distribution of policy across devices in the semantic prefix domain. New functions or protocol extension are needed to enable dynamic changes to the policy actions in operation on certain semantic packets. - Semantics Announcements to peer networks A network may announce all, or some of its Semantic Prefix Policy to connected peer networks. This could be used to enable more dynamic configuration and enable traffic from different semantic prefix domains to traverse different networks whilst having the same semantic prefix policy applied. Again, this would require new functions or protocol extensions to realise. This also would allow enterprise semantics to be able to traverse ISP networks. - Extension of Prefix Semantics beyond the left-most 64-bits The prefix concept refers here to the left-most bits in the IP addresses delegated by the network management plane. The prefix could be longer than 64-bits if the network operators strictly manage the address assignment by using Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315] (but in this case standard Stateless Address Autoconfiguration - SLAAC [RFC4862] cannot be used). Authors' Addresses Sheng Jiang (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beijing Road Hai-Dian District, Beijing, 100095 P.R. China Email: email@example.com Jiang, et al. Expires August 3, 2013 [Page 14] Internet-Draft Semantic IPv6 Prefix Framework January 2013 Qiong Sun China Telecom Room 708, No.118, Xizhimennei Street Beijing 100084 P.R. China Email: firstname.lastname@example.org Ian Farrer Deutsche Telekom AG Bonn 53227 Germany Email: email@example.com Jiang, et al. Expires August 3, 2013 [Page 15]