Network Working Group B. Carpenter
Internet-Draft Univ. of Auckland
Intended status: Informational B. Liu
Expires: June 15, 2019 Huawei Technologies
December 12, 2018

Limited Domains and Internet Protocols
draft-carpenter-limited-domains-05

Abstract

There is a noticeable trend towards network requirements, behaviours and semantics that are specific to a limited region of the Internet and a particular set of requirements. Policies, default parameters, the options supported, the style of network management and security requirements may vary. This document reviews examples of such limited domains, also known as controlled environments, and emerging solutions, and develops a related taxonomy. It then briefly discusses the standardization of protocols for limited domains. Finally, it shows the needs for a precise definition of limited domain membership and for mechanisms to allow nodes to join a domain securely and to find other members, including boundary nodes.

Status of This Memo

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This Internet-Draft will expire on June 15, 2019.

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Table of Contents

1. Introduction

As the Internet continues to grow and diversify, with a realistic prospect of tens of billions of nodes being connected directly and indirectly, there is a noticeable trend towards local requirements, behaviours and semantics. The word "local" should be understood in a special sense, however. In some cases it may refer to geographical and physical locality - all the nodes in a single building, on a single campus, or in a given vehicle. In other cases it may refer to a defined set of users or nodes distributed over a much wider area, but drawn together by a single virtual network over the Internet, or a single physical network running partially in parallel with the Internet. We expand on these possibilities below. To capture the topic, this document refers to such networks as "limited domains".

Some people have concerns about splintering of the Internet along political or linguistic boundaries by mechanisms that block the free flow of information across the network. That is not the topic of this document, which does not discuss filtering mechanisms and does not apply to protocols that are designed for use across the whole Internet. It is only concerned with domains that have specific technical requirements.

The word "domain" in this document does not refer to naming domains in the DNS, although in some cases a limited domain might incidentally be congruent with a DNS domain.

Another term that has been used in some contexts is "controlled environment". For example, [RFC8085] uses this to delimit the scope within which a particular tunnel encapsulation might be used. A specific example is GRE-in-UDP encapsulation [RFC8086] which explicitly states that "The controlled environment has less restrictive requirements than the general Internet." For example, non-congestion-controlled traffic might be acceptable within the controlled environment. The same phrase has been used to delimit the scope of quality of service or security protocols, e.g. [RFC6398], [RFC6455]. In this document, we assume that "limited domain" and "controlled environment" mean the same thing.

The requirements of limited domains will be different in different scenarios. Policies, default parameters, and the options supported may vary. Also, the style of network management may vary, between a completely unmanaged network, one with fully autonomic management, one with traditional central management, and mixtures of the above. Finally, the requirements and solutions for security and privacy may vary.

This documents analyses and discusses some of the consequences of this trend, and how it impacts the idea of universal interoperability in the Internet. Firstly we list examples of limited domain scenarios and of technical solutions for limited domains, with the main focus being the Internet layer of the protocol stack. Then we develop a taxonomy of the features to be found in limited domains. With this background, we discuss the resulting challenge to the idea that all Internet standards must be universal in scope and applicability. To the contrary, we assert that some protocols need to be specifically limited in their applicability. This implies that the concepts of a limited domain, and of its membership, need to be formalised and supported by secure mechanisms. While this document does not propose a design for such mechanisms, it does outline some resulting functional requirements.

2. Failure Modes in Today's Internet

Today, the Internet does not have a well-defined concept of limited domains. One result of this is that certain protocols and features fail on certain paths. Earlier analyses of this topic have focused either on the loss of transparency of the Internet [RFC2775], [RFC4924] or on the middleboxes responsible for that loss [RFC3234], [RFC7663], [I-D.dolson-plus-middlebox-benefits]. Unfortunately the problems persist, both in application protocols, and even in very fundamental mechanisms. For example, the Internet is not transparent to IPv6 extension headers [RFC7872], and Path MTU Discovery has been unreliable for many years [RFC2923], [RFC4821]. IP fragmentation is also unreliable [I-D.ietf-intarea-frag-fragile], and problems in TCP MSS negotiation have been reported [I-D.andrews-tcp-and-ipv6-use-minmtu].

On the security side, the widespread insertion of firewalls at domain boundaries that are perceived by humans but unknown to protocols results in arbitrary failure modes as far as the application layer is concerned. There are operational recommendations and practices that effectively guarantee arbitrary failures in realistic scenarios [I-D.ietf-opsec-ipv6-eh-filtering].

The recent discussions about the unreliability of IP fragmentation and the filtering of IPv6 extension headers have clearly shown that at least for some protocol elements, transparency is a lost cause and middleboxes are here to stay. In summary, some application environments require protocol features that cannot cross the whole Internet. Ignoring this during protocol design is not an option.

3. Examples of Limited Domain Requirements

This section describes various examples where limited domain requirements can easily be identified, either based on an application scenario or on a technical imperative. It is of course not a complete list, and it is presented in an arbitrary order, loosely from smaller to bigger.

  1. A home network. It will be unmanaged, constructed by a non-specialist, and will possibly include wiring errors such as physical loops. It must work with devices "out of the box" as shipped by their manufacturers and must create adequate security by default. Remote access may be required. The requirements and applicable principles are summarised in [RFC7368].
  2. A small office network. This is sometimes very similar to a home network, if whoever is in charge has little or no specialist knowledge, but may have differing security and privacy requirements. In other cases it may be professionally constructed using recommended products and configurations, but operate unmanaged. Remote access may be required.
  3. A vehicle network. This will be designed by the vehicle manufacturer but may include devices added by the vehicle's owner or operator. Parts of the network will have demanding performance and reliability requirements with implications for human safety. Remote access may be required to certain functions, but absolutely forbidden for others. Communication with other vehicles, roadside infrastructure, and external data sources will be required. See [I-D.ietf-ipwave-vehicular-networking] for a survey of use cases.
  4. Supervisory Control And Data Acquisition (SCADA) networks, and other hard real time networks. These will exhibit specific technical requirements, including tough real-time performance targets. See for example [I-D.ietf-detnet-use-cases] for numerous use cases. An example is a building services network. This will be designed specifically for a particular building, but using standard components. Additional devices may need to be added at any time. Parts of the network may have demanding reliability requirements with implications for human safety. Remote access may be required to certain functions, but absolutely forbidden for others.
  5. Sensor networks. The two preceding cases will all include sensors, but some networks may be specifically limited to sensors and the collection and processing of sensor data. They may be in remote or technically challenging locations and installed by non-specialists.
  6. Internet of Things (IoT) networks. While this term is very flexible and covers many innovative types of network, including ad hoc networks that are formed spontaneously, it seems reasonable to expect that IoT edge networks will have special requirements and protocols that are useful only within a specific domain, and that these protocols cannot, and for security reasons should not, run over the Internet as a whole.
  7. An important subclass of IoT networks consists of constrained networks [RFC7228] in which the nodes are limited in power consumption and communications bandwidth, and are therefore limited to using very frugal protocols.
  8. Delay tolerant networks may consist of domains that are relatively isolated and constrained in power (e.g. deep space networks) and are connected only intermittently to the outside, with a very long latency on such connections [RFC4838]. Clearly the protocol requirements and possibilities are very specialised in such networks.
  9. "Traditional" enterprise and campus networks, which may be spread over many kilometres and over multiple separate sites, with multiple connections to the Internet. Interestingly, the IETF appears never to have analysed this long-established class of networks in a general way, except in connection with IPv6 deployment (e.g. [RFC7381]).
  10. Data centres and hosting centres, or distributed services acting as such centres. These will have high performance, security and privacy requirements and will typically include large numbers of independent "tenant" networks overlaid on shared infrastructure.
  11. Content Delivery Networks (CDNs), comprising distributed data centres and the paths between them, spanning thousands of kilometres, with numerous connections to the Internet.
  12. Massive Web Service Provider Networks. This is a small class of networks with well known trademarked names, combining aspects of distributed enterprise networks, data centres and CDNs. They have their own international networks bypassing the generic carriers. Like CDNs, they have numerous connections to the Internet, typically offering a tailored service in each economy.

Three other aspects, while not tied to specific network types, also strongly depend on the concept of limited domains:

  1. Intent Based Networking. In this concept, a network domain is configured and managed in accordance with an abstract policy known as "Intent", to ensure that the network performs as required [I-D.moulchan-nmrg-network-intent-concepts]. Whatever technologies are used to support this, they will be applied within the domain boundary.
  2. Many of the above types of network may be extended throughout the Internet by a variety of virtual private network (VPN) techniques. Therefore we argue that limited domains may overlap each other in an arbitrary fashion by use of virtualization techniques. As noted above in the discussion of controlled environments, specific tunneling and encapsulation techniques may only be usable within a given domain.
  3. Network Slicing. A network slice is a virtual network that consists of a managed set of resources carved off from a larger network [I-D.geng-netslices-architecture]. Whatever technologies are used to support slicing, they will require a clear definition of the boundary of a given slice.

While it is clearly desirable to use common solutions, and therefore common standards, wherever possible, it is increasingly difficult to do so while satisfying the widely varying requirements outlined above. However, there is a tendency when new protocols and protocol extensions are proposed to always ask the question "How will this work across the open Internet?" This document suggests that this is not always the right question. There are protocols and extensions that are not intended to work across the open Internet. On the contrary, their requirements and semantics are specifically limited (in the sense defined above).

A common argument is that if a protocol is intended for limited use, the chances are very high that it will in fact be used (or misused) in other scenarios including the so-called open Internet. This is undoubtedly true and means that limited use is not an excuse for bad design or poor security. In fact, a limited use requirement potentially adds complexity to both the protocol and its security design, as discussed later.

Nevertheless, because of the diversity of limited domainss with specific requirements that is now emerging, specific standards (and ad hoc standards) will probably emerge for different types of domain. There will be attempts to capture each market sector, but the market will demand standardised solutions. In addition, operational choices will be made that can in fact only work within a limited domain. The history of RSVP illustrates that a standard defined as if it could work over the open Internet may not in fact do so. In general we cannot assume that a protocol designed according to classical Internet guidelines will in fact work reliably across the network as a whole. However, the "open Internet" must remain as the universal method of interconnection. Reconciling these two aspects is a major challenge.

4. Examples of Limited Domain Solutions

This section lists various examples of specific limited domain solutions that have been proposed or defined. It intentionally does not include Layer 2 technology solutions, which by definition apply to limited domains.

  1. Differentiated Services. This mechanism [RFC2474] allows a network to assign locally significant values to the 6-bit Differentiated Services Code Point field in any IP packet. Although there are some recommended codepoint values for specific per-hop queue management behaviours, these are specifically intended to be domain-specific codepoints with traffic being classified, conditioned and re-marked at domain boundaries (unless there is an inter-domain agreement that makes re-marking unnecessary).
  2. Integrated Services. Although it is not intrinsic in the design of RSVP [RFC2205], it is clear from many years' experience that Integrated Services can only be deployed successfully within a limited domain that is configured with adequate equipment and resources.
  3. Network function virtualisation. As described in [I-D.irtf-nfvrg-gaps-network-virtualization], this general concept is an open research topic, in which virtual network functions are orchestrated as part of a distributed system. Inevitably such orchestration applies to an administrative domain of some kind, even though cross-domain orchestration is also a research area.
  4. Service Function Chaining (SFC). This technique [RFC7665] assumes that services within a network are constructed as sequences of individual functions within a specific SFC-enabled domain. As that RFC states: "Specific features may need to be enforced at the boundaries of an SFC-enabled domain, for example to avoid leaking SFC information". A Network Service Header (NSH) [RFC8300] is used to encapsulate packets flowing through the service function chain: "The intended scope of the NSH is for use within a single provider's operational domain."
  5. Firewall and Service Tickets (FAST). Such tickets would accompany a packet to claim the right to traverse a network or request a specific network service [I-D.herbert-fast]". They would only be valid within a particular domain.
  6. Data Centre Network Virtualization Overlays. A common requirement in data centres that host many tenants (clients) is to provide each one with a secure private network, all running over the same physical infrastructure. [RFC8151] describes various use cases for this, and specifications are under development. These include use cases in which the tenant network is physically split over several data centres, but which must appear to the user as a single secure domain.
  7. Segment Routing. This is a technique which "steers a packet through an ordered list of instructions, called segments" [I-D.ietf-spring-segment-routing]. The semantics of these instructions are explicitly local to a segment routing domain or even to a single node. Technically, these segments or instructions are represented as an MPLS label or an IPv6 address, which clearly adds a semantic interpretation to them within the domain.
  8. Autonomic Networking. As explained in [I-D.ietf-anima-reference-model], an autonomic network is also a security domain within which an autonomic control plane [I-D.ietf-anima-autonomic-control-plane] is used by service agents. These service agents manage technical objectives, which may be locally defined, subject to domain-wide policy. Thus the domain boundary is important for both security and protocol purposes.
  9. Homenet. As shown in [RFC7368], a home networking domain has specific protocol needs that differ from those in an enterprise network or the Internet as a whole. These include the Home Network Control Protocol (HNCP) [RFC7788] and a naming and discovery solution [I-D.ietf-homenet-simple-naming].
  10. Creative uses of IPv6 features. As IPv6 enters more general use, engineers notice that it has much more flexibility than IPv4. Innovative suggestions have been made for:

    All of these suggestions are only viable within a specified domain. The case of the extension header is particularly interesting, since its existence has been a major "selling point" for IPv6, but it is notorious that new extension headers are virtually impossible to deploy across the whole Internet

    [RFC7045], [RFC7872]. It is worth noting that extension header filtering is considered as an important security issue [I-D.ietf-opsec-ipv6-eh-filtering]. There is considerable appetite among vendors or operators to have flexibility in defining extension headers for use in limited or specialised domains, e.g. [I-D.voyer-6man-extension-header-insertion] and [BIGIP].
  11. Deterministic Networking (DetNet). The Deterministic Networking Architecture [I-D.ietf-detnet-architecture] and encapsulation [I-D.ietf-detnet-dp-sol] aim to support flows with extremely low data loss rates and bounded latency, but only within a part of the network that is "DetNet aware". Thus, as for differentiated services above, the concept of a domain is fundamental.
  12. Provisioning Domains (PvDs). An architecture for Multiple Provisioning Domains has been defined [RFC7556] to allow hosts attached to multiple networks to learn explicit details about the services provided by each of those networks.

5. Taxonomy of Limited Domains

This section develops a taxonomy for describing limited domains. Several major aspects are considered in this taxonomy:

The following sub-sections analyse each of these aspects.

5.1. The Domain as a Whole

5.2. Individual Nodes

5.3. The Domain Boundary

5.4. Topology

5.5. Technology

5.6. Connection to the Internet

5.7. Security, Trust and Privacy Model

5.8. Operations

5.9. Making use of this taxonomy

This taxonomy could be used to design or analyse a specific type of limited domain. For the present document, it is intended to form a background to the following two sections, concerning the scope of protocols used in limited domains, and mechanisms reuqired to securely define domain membership and properties.

6. The Scope of Protocols in Limited Domains

One consequence of the deployment of limited domains in the Internet is that some protocols will be designed, extended or configured so that they only work correctly between end systems in such domains. This is to some extent encouraged by some existing standards and by the assignment of code points for local or experimental use. In any case it cannot be prevented. Also, by endorsing efforts such as Service Function Chaining, Segment Routing and Deterministic Networking, the IETF is in effect encouraging such deployments. Furthermore, it seems inevitable, if the "Internet of Things" becomes reality, that millions of edge networks containing completely novel types of node will be connected to the Internet; each one of these edge networks will be a limited domain.

It is therefore appropriate to discuss whether protocols or protocol extensions should sometimes be standardised to interoperate only within a Limited Domain Boundary. Such protocols would not be required to interoperate across the Internet as a whole. Several possibly overlapping scenarios could then arise:

To provide an existing example, consider Differentiated Services [RFC2474]. A packet containing any value whatever in the 6 bits of the Differentiated Service Code Point (DSCP) is well-formed and falls into scenario A. However, because the semantics of DSCP values are locally significant, the packet also falls into scenario D. In fact, differentiated services are only interoperable across domain boundaries if there is a corresponding agreement between the operators; otherwise a specific gateway function is required for meaningful interoperability. Much more detailed discussion is to be found in [RFC2474] and [RFC8100].

To provide a provocative example, consider the proposal in [I-D.voyer-6man-extension-header-insertion] that the restrictions in [RFC8200] should be relaxed to allow IPv6 extension headers to be inserted on the fly in IPv6 packets. If this is done in such a way that the affected packets can never leave the specific limited domain in which they were modified, scenario C applies. If the semantic content of the inserted headers is locally defined, scenario D also applies. In neither case is the Internet disturbed.

We conclude that it is reasonable to explicitly define limited-domain protocols, either as standards or as proprietary mechanisms, as long as they describe which of the above scenarios apply and they clarify how the domain is defined. As long as all relevant standards are respected outside the domain boundary, a well-specified limited-domain protocol is not harmful to the Internet. However, as described in the next section, mechanisms are needed to support domain membership operations.

7. Functional Requirements of Limited Domains

As the preceding taxonomy shows, there are very numerous aspects to a domain, so the common features are not immediately obvious. It would be possible, but tedious, to apply the taxonomy to each of the domain types described in Section 3. However, we can deduce some generally required features and functions without doing so.

A basic assumption is that domains should be created and managed as automatically as possible, with minimal human configuration required. We therefore investigate protocol requirements for automating domain creation and management.

Firstly, if we drew a topology map, any domain -- virtual or physical -- will have a well defined boundary between "inside" and "outside". However, that boundary in itself has no technical meaning. What matters in reality is whether a node is a member of the domain, and whether it is at the boundary between the domain and the rest of the Internet. Thus the boundary in itself does not need to be identified. However, a sending node needs to know whether it is sending to an inside or outside destination; a receiving node needs to know whether a packet originated inside or outside; and a boundary node needs to know which of its interfaces are inward-facing or outward-facing. It is irrelevant whether the interfaces involved are physical or virtual.

With this perspective, we can list some general functional requirements. An underlying assumption here is that domain membership operations should be cryptographically secured; a domain without such security cannot be reliably protected from attack.

  1. Domain Identity. A domain must have a unique and verifiable identifier; effectively this should be a public key for the domain. Without this, there is no way to secure domain operations and domain membership. The holder of the corresponding private key becomes the trust anchor for the domain.
  2. Node Eligibility. It must be possible for a node to determine which domain(s) it can potentially join, and on which interface(s).
  3. Secure Enrolment. A node must be able to enrol in a given domain via secure node identfication and to acquire relevant security credentials (authorization) for operations within the domain. If a node has multiple physical or virtual interfaces, they may require to be individually enrolled.
  4. Withdrawal. A node must be able to cancel enrolment in a given domain.
  5. Dynamic Membership. Optionally, a node should be able temporarily leave or rejoin a domain (i.e. enrolment is persistent but membership is intermittent).
  6. Role, implying authorization to perform a certain set of actions. A node must have a verifiable role. In the simplest case, the choices of role are "interior node" and "boundary node". In a boundary node, individual interfaces may have different roles, e.g. "inward facing" and "outward facing".
  7. Verify Peer. A node must be able to verify whether another node is a member of the domain.
  8. Verify Role. A node must be able to learn the verified role of another node. In particular, it must be possible for a node to find boundary nodes (interfacing to the Internet).
  9. Domain Data. In a domain with management requirements, it must be possible for a node to acquire domain policy and/or domain configuration data. This would include, for example, filtering policy to ensure that inappropriate packets do not leave the domain.

These requirements could form the basis for further analysis and solution design.

Another aspect is whether individual packets within a limited domain need to carry any sort of indicator that they belong to that domain, or whether this information will be implicit in the IP addresses of the packet. A related question is whether individual packets need cryptographic authentication. This topic is for further study.

8. Security Considerations

Clearly, the boundary of a limited domain will almost always also act as a security boundary. In particular, it will serve as a trust boundary, and as a boundary of authority for defining capabilities. Within the boundary, limited-domain protocols or protocol features will be useful, but they will be meaningless if they enter or leave the domain.

The security model for a limited-scope protocol must allow for the boundary, and in particular for a trust model that changes at the boundary. Typically, credentials will need to be signed by a domain-specific authority.

9. IANA Considerations

This document makes no request of the IANA.

10. Contributors

Sheng Jiang made important contributions to this document.

11. Acknowledgements

Useful comments were received from Amelia Andersdotter, Edward Birrane, David Black, Ron Bonica, Tim Chown, Darren Dukes, Tom Herbert, John Klensin, Michael Richardson, Rick Taylor, Niels ten Oever, and other members of the ANIMA and INTAREA WGs.

12. Informative References

[BIGIP] Li, R., "HUAWEI - Big IP Initiative.", 2018.
[I-D.andrews-tcp-and-ipv6-use-minmtu] Andrews, M., "TCP Fails To Respect IPV6_USE_MIN_MTU", Internet-Draft draft-andrews-tcp-and-ipv6-use-minmtu-04, October 2015.
[I-D.dolson-plus-middlebox-benefits] Dolson, D., Snellman, J., Boucadair, M. and C. Jacquenet, "Beneficial Functions of Middleboxes", Internet-Draft draft-dolson-plus-middlebox-benefits-03, March 2017.
[I-D.fioccola-v6ops-ipv6-alt-mark] Fioccola, G., Velde, G., Cociglio, M. and P. Muley, "IPv6 Performance Measurement with Alternate Marking Method", Internet-Draft draft-fioccola-v6ops-ipv6-alt-mark-01, June 2018.
[I-D.geng-netslices-architecture] 67, 4., Dong, J., Bryant, S., kiran.makhijani@huawei.com, k., Galis, A., Foy, X. and S. Kuklinski, "Network Slicing Architecture", Internet-Draft draft-geng-netslices-architecture-02, July 2017.
[I-D.herbert-fast] Herbert, T., "Firewall and Service Tickets", Internet-Draft draft-herbert-fast-03, September 2018.
[I-D.ietf-6man-segment-routing-header] Filsfils, C., Previdi, S., Leddy, J., Matsushima, S. and d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header (SRH)", Internet-Draft draft-ietf-6man-segment-routing-header-15, October 2018.
[I-D.ietf-anima-autonomic-control-plane] Eckert, T., Behringer, M. and S. Bjarnason, "An Autonomic Control Plane (ACP)", Internet-Draft draft-ietf-anima-autonomic-control-plane-18, August 2018.
[I-D.ietf-anima-reference-model] Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L. and J. Nobre, "A Reference Model for Autonomic Networking", Internet-Draft draft-ietf-anima-reference-model-10, November 2018.
[I-D.ietf-detnet-architecture] Finn, N., Thubert, P., Varga, B. and J. Farkas, "Deterministic Networking Architecture", Internet-Draft draft-ietf-detnet-architecture-09, October 2018.
[I-D.ietf-detnet-dp-sol] Korhonen, J., Andersson, L., Jiang, Y., Finn, N., Varga, B., Farkas, J., Bernardos, C., Mizrahi, T. and L. Berger, "DetNet Data Plane Encapsulation", Internet-Draft draft-ietf-detnet-dp-sol-04, March 2018.
[I-D.ietf-detnet-use-cases] Grossman, E., "Deterministic Networking Use Cases", Internet-Draft draft-ietf-detnet-use-cases-19, October 2018.
[I-D.ietf-homenet-simple-naming] Lemon, T., Migault, D. and S. Cheshire, "Homenet Naming and Service Discovery Architecture", Internet-Draft draft-ietf-homenet-simple-naming-03, October 2018.
[I-D.ietf-intarea-frag-fragile] Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O. and F. Gont, "IP Fragmentation Considered Fragile", Internet-Draft draft-ietf-intarea-frag-fragile-04, November 2018.
[I-D.ietf-ipwave-vehicular-networking] Jeong, J., "IP Wireless Access in Vehicular Environments (IPWAVE): Problem Statement and Use Cases", Internet-Draft draft-ietf-ipwave-vehicular-networking-07, November 2018.
[I-D.ietf-opsec-ipv6-eh-filtering] Gont, F. and W. LIU, "Recommendations on the Filtering of IPv6 Packets Containing IPv6 Extension Headers", Internet-Draft draft-ietf-opsec-ipv6-eh-filtering-06, July 2018.
[I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S. and R. Shakir, "Segment Routing Architecture", Internet-Draft draft-ietf-spring-segment-routing-15, January 2018.
[I-D.irtf-nfvrg-gaps-network-virtualization] Bernardos, C., Rahman, A., Zuniga, J., Contreras, L., Aranda, P. and P. Lynch, "Network Virtualization Research Challenges", Internet-Draft draft-irtf-nfvrg-gaps-network-virtualization-10, September 2018.
[I-D.jiang-semantic-prefix] Jiang, S., Qiong, Q., Farrer, I., Bo, Y. and T. Yang, "Analysis of Semantic Embedded IPv6 Address Schemas", Internet-Draft draft-jiang-semantic-prefix-06, July 2013.
[I-D.moulchan-nmrg-network-intent-concepts] Sivakumar, K. and M. Chandramouli, "Concepts of Network Intent", Internet-Draft draft-moulchan-nmrg-network-intent-concepts-00, October 2017.
[I-D.voyer-6man-extension-header-insertion] daniel.voyer@bell.ca, d., Leddy, J., Filsfils, C., Dukes, D., Previdi, S. and S. Matsushima, "Insertion of IPv6 Segment Routing Headers in a Controlled Domain", Internet-Draft draft-voyer-6man-extension-header-insertion-04, June 2018.
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, September 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", RFC 2474, DOI 10.17487/RFC2474, December 1998.
[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, DOI 10.17487/RFC2775, February 2000.
[RFC2923] Lahey, K., "TCP Problems with Path MTU Discovery", RFC 2923, DOI 10.17487/RFC2923, September 2000.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K. and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, DOI 10.17487/RFC4838, April 2007.
[RFC4924] Aboba, B. and E. Davies, "Reflections on Internet Transparency", RFC 4924, DOI 10.17487/RFC4924, July 2007.
[RFC6294] Hu, Q. and B. Carpenter, "Survey of Proposed Use Cases for the IPv6 Flow Label", RFC 6294, DOI 10.17487/RFC6294, June 2011.
[RFC6398] Le Faucheur, F., "IP Router Alert Considerations and Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October 2011.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 6455, DOI 10.17487/RFC6455, December 2011.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing of IPv6 Extension Headers", RFC 7045, DOI 10.17487/RFC7045, December 2013.
[RFC7228] Bormann, C., Ersue, M. and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, DOI 10.17487/RFC7228, May 2014.
[RFC7368] Chown, T., Arkko, J., Brandt, A., Troan, O. and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, DOI 10.17487/RFC7368, October 2014.
[RFC7381] Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V., Pouffary, Y. and E. Vyncke, "Enterprise IPv6 Deployment Guidelines", RFC 7381, DOI 10.17487/RFC7381, October 2014.
[RFC7556] Anipko, D., "Multiple Provisioning Domain Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015.
[RFC7663] Trammell, B. and M. Kuehlewind, "Report from the IAB Workshop on Stack Evolution in a Middlebox Internet (SEMI)", RFC 7663, DOI 10.17487/RFC7663, October 2015.
[RFC7665] Halpern, J. and C. Pignataro, "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015.
[RFC7788] Stenberg, M., Barth, S. and P. Pfister, "Home Networking Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 2016.
[RFC7872] Gont, F., Linkova, J., Chown, T. and W. Liu, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", RFC 7872, DOI 10.17487/RFC7872, June 2016.
[RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, March 2017.
[RFC8086] Yong, L., Crabbe, E., Xu, X. and T. Herbert, "GRE-in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, March 2017.
[RFC8100] Geib, R. and D. Black, "Diffserv-Interconnection Classes and Practice", RFC 8100, DOI 10.17487/RFC8100, March 2017.
[RFC8151] Yong, L., Dunbar, L., Toy, M., Isaac, A. and V. Manral, "Use Cases for Data Center Network Virtualization Overlay Networks", RFC 8151, DOI 10.17487/RFC8151, May 2017.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017.
[RFC8300] Quinn, P., Elzur, U. and C. Pignataro, "Network Service Header (NSH)", RFC 8300, DOI 10.17487/RFC8300, January 2018.

Appendix A. Change log [RFC Editor: Please remove]

draft-carpenter-limited-domains-00, 2018-06-11:

Initial version

draft-carpenter-limited-domains-01, 2018-07-01:

Minor terminology clarifications

draft-carpenter-limited-domains-02, 2018-08-03:

Additions following IETF102 discussions

Updated authorship/contributors

draft-carpenter-limited-domains-03, 2018-09-12:

First draft of taxonomy

Editorial improvements

draft-carpenter-limited-domains-04, 2018-10-14:

Reorganized section 3

Newly written sections 6 and 7

Editorial improvements

draft-carpenter-limited-domains-05, 2018-12-12:

Added discussion of transparency/filtering debates

Added discussion of "controlled environment"

Modified assertion about localized standards

Editorial improvements

Authors' Addresses

Brian Carpenter Department of Computer Science University of Auckland PB 92019 Auckland, 1142 New Zealand EMail: brian.e.carpenter@gmail.com
Bing Liu Huawei Technologies Q14, Huawei Campus No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China EMail: leo.liubing@huawei.com