IPv6 Working Group T. Hain Internet-Draft Cisco Systems, Inc. Expires: February 11, 2004 F. Templin Nokia August 13, 2003 Addressing Requirements for Local Communications within Sites draft-hain-templin-ipv6-limitedrange-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 11, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract The IPv6 addressing architecture specifies global and local-use unicast addressing schemes, but provides no operational guidelines or requirements for their use. There is a strong requirement for addressing to support local communications within sites. Of special interest are "active sites", e.g., sites that are intermittently-connected or disconnected from the global Internet, sites that frequently change provider points of attachment, sites that temporarily or permanently merge with other sites, multi-homed sites, etc. This memo will discuss addressing requirements for local communications within sites. Hain & Templin Expires February 11, 2004 [Page 1] Internet-Draft Local Addressing Requirements August 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1 Easy to Acquire . . . . . . . . . . . . . . . . . . . . . . 4 3.2 Stable . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3 Multiple Link Support . . . . . . . . . . . . . . . . . . . 4 3.4 Well-known Prefix . . . . . . . . . . . . . . . . . . . . . 4 3.5 Global Uniqueness . . . . . . . . . . . . . . . . . . . . . 5 3.6 Provider Independence . . . . . . . . . . . . . . . . . . . 5 3.7 Applicable in Managed/Unmanaged Environments . . . . . . . . 6 3.8 Compatible with Site Naming System . . . . . . . . . . . . . 6 3.9 Compatible with VPN . . . . . . . . . . . . . . . . . . . . 6 3.10 Multiple Addressing . . . . . . . . . . . . . . . . . . . . 6 4. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1 Applications of Private Addressing Today . . . . . . . . . . 7 4.2 Mobile Router with Personal Area Network . . . . . . . . . . 8 4.3 Mobile Ad-hoc Networks that Travel Together . . . . . . . . 8 4.4 Vehicular Networks . . . . . . . . . . . . . . . . . . . . . 8 4.5 Asset Protection in Enterprise Networks . . . . . . . . . . 9 4.6 Home Networks . . . . . . . . . . . . . . . . . . . . . . . 9 5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . 10 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 Normative References . . . . . . . . . . . . . . . . . . . . 11 Informative References . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 11 A. Filtering Considerations . . . . . . . . . . . . . . . . . . 12 B. Routing Considerations . . . . . . . . . . . . . . . . . . . 12 C. Multiple Addressing Considerations . . . . . . . . . . . . . 14 D. Potential Applications of Limited Range Address Space . . . 15 E. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 17 Intellectual Property and Copyright Statements . . . . . . . 18 Hain & Templin Expires February 11, 2004 [Page 2] Internet-Draft Local Addressing Requirements August 2003 1. Introduction The IPv6 addressing architecture [RFC3513] specifies global and local-use unicast address formats. Global addresses are understood to have unlimited range and may be used as the source and destination addresses in packets that originate from any point on the connected global IPv6 Internet. Local-use addresses are intended for use only within the range of a single link/site, but their specification does not address operational considerations and does not account for the esoteric aspects of terms such as "site". There is a strong requirement for addressing that supports local communications within sites. Of special interest are "active sites", e.g., sites that are intermittently-connected or disconnected from the global Internet, sites that frequently change provider points of attachment, sites that temporarily or permanently merge with other sites, multi-homed sites, etc. This memo will discuss addressing requirements for local communications within sites in the context of real world deployment scenarios. 2. Terminology site: an entity autonomously operating a network using IP and, in particular, determining the addressing plan and routing policy for that network. This is the same definition as [MULTI6]. active site: a site that may be intermittently-connected or disconnected from the global Internet, may frequently change provider points of attachment, may have multiple concurrent provider points of attachment, may temporarily or permanently merge with other sites, etc. range: domain of applicability. identifier range: range within which an address uniquely identifies an entity. Addresses that may possibly identify multiple entities within a limited range are said to be ambiguous. locator range: filtering and/or routing functions set by operational policy that determine a limited range. Hain & Templin Expires February 11, 2004 [Page 3] Internet-Draft Local Addressing Requirements August 2003 3. Requirements There is a strong requirement for addressing that supports local communications within sites. An obvious solution alternative is an easy-to-get, stable, private address space for use within a limited range as this is consistent with current practices familiar to IPv4 network managers. Alternative solution proposals should be made available in a timely fashion through full disclosure to the public domain so that their merits can be evaluated. The following sections present addressing requirements for local communications within sites. 3.1 Easy to Acquire Addresses must be made available that require no public registration, payment, customer/provider relationship, or approval. Network managers have stated, and historical experience has shown, that there is a need for addresses that do not require public registration. These addresses must be architecturally supported and end-user-controlled. 3.2 Stable Applications require addresses that remain stable during intermittent connectivity, site mergers, change to a new provider, etc. In particular, applications should not be affected by address renumbering events [BAKER]. The addressing scheme should also support stable communications within sites that are mobile. In particular, addresses should remain stable as the site moves to new topological points of attachment or geographical coordinates. 3.3 Multiple Link Support Addressing for local communications within sites should support operation over multiple links, e.g., via L3 routing, L2 bridging or some combination thereof. As such, subnetting consistent with the recommendations in ([RFC3177], section 3) should be supported. Link-local addresses in IPv6: "are designed to be used for addressing on a single link for purposes such as automatic address configuration, neighbor discovery, or when no routers are present" ([RFC3513], section 2.5.6). By definition, link-local addressing has a single link range of operation and will not meet this requirement. 3.4 Well-known Prefix Hain & Templin Expires February 11, 2004 [Page 4] Internet-Draft Local Addressing Requirements August 2003 Placing portions of the address space in a common short prefix allows everyone to filter it which prevents unwanted exposure in the case of single point configuration errors. In this solution alternative, the common prefix must not end up in the global routing system, even accidentally. Using a well-known prefix provides a hint that a filtering policy has been applied somewhere in the network, though it does not by itself indicate where the boundaries are. Alternative solution proposals should be made available in a timely fashion through full disclosure to the public domain so that their merits can be evaluated. Given the presence of the well-known prefix, an application that chooses to check can infer that there is an explicit filter somewhere in the network. That filter may or may not be between it and the application peer. 3.5 Global Uniqueness /48 prefixes used by sites [RFC3177] must be globally-unique such that site mergers will not result in collisions. Global uniqueness is based on the statistical properties of the prefix assignment, therefore a suitable means for random prefix generation must be specified. Sufficient global uniqueness is required to support: o VPNs between enterprises o dynamically created VPNs in support of temporary virtual organizations o service provider co-location of hosts that reside in the address space of multiple customers o formation of virtual organizations (Grids) among enterprises o mergers and acquisitions of enterprises such that address spaces do not collide Achieving these goals does not require absolute uniqueness, but an extremely low probability of collisions resulting in conflict is required. The addressing scheme must also provide a means for conflict resolution, e.g., certification through a central registry, distributed database, etc. 3.6 Provider Independence Active sites require addresses that are provider independent (PI) and Hain & Templin Expires February 11, 2004 [Page 5] Internet-Draft Local Addressing Requirements August 2003 do not create a real or artificial lock-in to any provider. In the case of intermittently-connected sites, provider aggregated prefixes may be unavailable for long periods but this must not disrupt local communications within the site. In the case of movement to new providers, frequent site renumbering events may occur but, again, local communications must not be affected. The strong demand for PI addressing also applies to cases where network managers want global access. The issue is that PI addresses have no designed aggregation properties, thus advertising them outside the site may lead to global routing table explosion given current routing technologies. For this reason: o a PI mechanism with reasonable aggregation properties should be investigated. o a feasibility study for routing technologies with better scaling properties should be undertaken. 3.7 Applicable in Managed/Unmanaged Environments Some sites (e.g., large enterprises) may have network management teams responsible for address planning while others (e.g., home networks and personal area networks) may require unmanaged operation. The addressing scheme must provide general applicability in any environment - be it managed or unmanaged. 3.8 Compatible with Site Naming System Addresses for local communications within sites must be compatible with the site's naming system. Examples include DNS, multicast name resolution, static configuration, etc. In practice, it is expected that addresses will be resolved only within the range of operation of the naming system. 3.9 Compatible with VPN The addressing scheme should support VPN connections between multiple sites, e.g., to form geographically-extended organizations. Prefix delegations in effect at each constituent site must remain valid when connected via VPN. 3.10 Multiple Addressing A well-known address prefix provides an opportunity to move beyond the common IPv4 model where all nodes in a network use the same single range of filtered space, by providing simultaneous support for Hain & Templin Expires February 11, 2004 [Page 6] Internet-Draft Local Addressing Requirements August 2003 local and global space. To gain the acceptance of network managers, tools they use as security measures must start from exactly the same point they are in IPv4. Concurrent use of limited & global range addresses allows neighboring nodes on a network to have individual policies about global visibility. This moves the policy decision from the edge to the originating device, which allows the application which has enough information decide the appropriate action, rather than the alternative brute force edge approach one-size-fits-all policy. In the case of devices that move between subnets, it also mitigates the need for continuous changes of access controls at the edge. Alternative solution proposals should be made available in a timely fashion through full disclosure to the public domain so that their merits can be evaluated. 4. Scenarios Many anticipated IPv6 deployment scenarios require an addressing scheme that meets the requirements outlined in Section 3. An example real life deployment scenario is as follows: o site A sets up a local network with no ISP connection; the network should "just work" out of the box o site A later connects to an ISP for external connectivity, but uses filtering to avoid exposing internal addressing to the outside o in the meantime, site B performs corresponding actions o sometime later, sites A and B connect, e.g., via VPN, shared link, etc. The sites can send local traffic to each other as well as traffic out either of the sites' ISPs o sometime later, site A disconnects from its ISP and site B's ISP is used o sometime later, site A disconnects from site B o sometime later, site A registers with a new ISP Addressing schemes for local communications within sites should support this scenario as well as others described in the following subsections: 4.1 Applications of Private Addressing Today Hain & Templin Expires February 11, 2004 [Page 7] Internet-Draft Local Addressing Requirements August 2003 Network managers limit specific applications to internal use, so they configure them to only work with a filtered address range. This simplifies the border filter to an address prefix, rather than needing to employ deep packet inspection to track a potentially dynamic range of ports. Private space may be used to avoid exposing to competitors what internal networks they are deploying and which office is coordinating that effort. Network managers also don't have to expose business plans to a registrar for evaluation for networks that are not attached to the global Internet. Some have stated that if they are required to register for public space for every internal use network, they are more likely to pick random numbers than tip off the competition. Another significant use of private address space is test networks. Frequently these are large, elaborate networks with a mix of public and private address space. Use of random unallocated space runs the risk of collision with legitimate addresses on remote networks. 4.2 Mobile Router with Personal Area Network Multiaccess terminals that serve as routers between the operator and a personal area network (PAN) of the user's locally-connected devices are seen as a near-term deployment scenario. Access to the operator may be intermittent, yet local communications within the PAN must be supported even when no connection to the global Internet is available. As mobile users travel about, multiple PANs may come together in a common space such that two or more PANs merge. As such, the address prefixes used in each PAN should be globally unique to avoid collisions and provide a means for verifying ownership to resolve conflicts. 4.3 Mobile Ad-hoc Networks that Travel Together As with the mobile PAN in Section 4.2, mobile ad-hoc networks of nodes that travel together as a group may have long periods of intermittent/disconnected access to the global Internet. Such applications as disaster relief, coordinated missions, and expeditionary forces may comprise numerous ad-hoc networks that may merge, partition, or lose global connectivity from time to time. An addressing scheme is needed for the continuous support of local communications in such mobile ad-hoc networks. 4.4 Vehicular Networks Vehicular networks may connect elements in an automobile to provide sensory and situational awareness data to the driver. Periodic Hain & Templin Expires February 11, 2004 [Page 8] Internet-Draft Local Addressing Requirements August 2003 contact with roadside Internet access points, other vehicles, etc. may entail sharing public information (e.g., road conditions encountered) while protecting private information (e.g., the vehicle's speedometer reading). The addressing scheme should provide a means for denoting both public and private components, e.g., for filtering at site borders. Research ships at sea intermittently connect via INMARSAT, or when in port, the shipboard network is connected to shore via Ethernet. Of utmost importance is that the systems on board the ship all function, providing data collection and analysis without interruption. Static addressing is used on most intra-ship network components and servers. It's quite expensive to operate a research ship, so eliminating points of failure is important. Scientists on board collaborate with colleagues back home by sharing of data and email. Currently private address space is employed for several reasons: 1) it provides the ability to allocate significant address space to each ship without needing to worry about how many computers will be on a given cruise. 2) it provides separate address space for each ship. 3) it simplifies filtering to ensure shipboard traffic is not permitted to transmit out or bring up expensive satellite links. 4.5 Asset Protection in Enterprise Networks Enterprise networks that protect private corporate assets (e.g., printers, faxes, robotics, sensors, etc.) require an addressing scheme that remains stable even when VPN connections from outside sites occur. Such VPN connections may arise from home users, corporate mergers and acquisitions, bridging remote sites together, etc. Prefixes used for protecting private assets must not end up in the global routing system, even by accident. 4.6 Home Networks Home networks with intermittent access to a service provider require an addressing scheme that supports local communications even when the service is unavailable. The addressing scheme should also protect private assets from exposure to the global Internet and should allow continuous operation when VPN connections to the office or other extended sites are used. 5. Summary Filtering creates addressing boundaries, no matter where the bits come from. The point is that some addresses are only valid within the range defined by the local network manager. In the simple case, hosts that are allowed external access have a Hain & Templin Expires February 11, 2004 [Page 9] Internet-Draft Local Addressing Requirements August 2003 policy that allows them to configure both global and limited range prefixes, while those that are not allowed global access have a policy that only allows limited range. Address selection rules will prefer the smallest range, so internal communications are forced to stay internal by the hard filter at the border. If an application chooses to assert a policy that is different from the network manager's filtering rules, it will fail. Having a well defined limited range address space that is known to have filtering applied allows applications to have a hint about potential range restrictions. We can choose to leave the network managers to figure out their own adhoc mechanisms, or we can put them in a structured limited range address space so that applications will have a chance to react appropriately. A limited range addressing scheme would seem a logical choice to satisfy the requirments and real-life scenarios outlined in this document, but the authors recognize that it may not be the ONLY choice. Alternative solution proposals should be made available in a timely fashion through full disclosure to the public domain so that their merits can be evaluated. 6. IANA Considerations This requirements document does not introduce any IANA requirements, though mechanisms that meet these requirements may. 7. Security Considerations The concept of route filtering is frequently used as a tool to aid in network security, so having a well-known range to filter enhances the deployment of that tool. Access control is one aspect of what limited range addressing provides. It is a clear address space that service providers can put in filters, and enterprise managers can filter without having to go into detail about which specific devices on a subnet are allowed. It does not comprise a full service security solution, and should not be represented as such. 8. Acknowledgements The authors acknowledge the contributions of numerous postings on the ipng mailing list [IPNG] that led to a better community understanding of addressing issues for local communications within sites. In particular, the following individuals provided valuable input for this document: Brian Carpenter, Tim Hartrick, Eliot Lear, Michel Py, Daniel Senie, Stephen Sprunk, and Michael Thomas. Special thanks to Hain & Templin Expires February 11, 2004 [Page 10] Internet-Draft Local Addressing Requirements August 2003 Andrew White for supplying an example real-life scenario. Normative References [RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 3513, April 2003. Informative References [BAKER] Baker, F., "Procedures for Renumbering an IPv6 Network without a Flag Day", draft-baker-ipv6-renumber-procedure-00 (work in progress), April 2003. [HAIN] Hain, T., "Application and Use of the IPv6 Provider Independent Global Unicast Address Format", draft-hain-ipv6-pi-addr-use-04 (work in progress), April 2003. [IPNG] "IPng mailing list archive: ftp://playground.sun.com/pub/ ipng/mail-archive". [MULTI6] Abley, J., Black, B. and V. Gill, "Goals for IPv6 Site-Multihoming Architectures", draft-ietf-multi6-multihoming-requirements-07 (work in progress), June 2003. [RFC3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address", RFC 3177, September 2001. Authors' Addresses Tony Hain Cisco Systems, Inc. 500 108th Ave. NE Bellevue, WA EMail: alh-ietf@tndh.net Fred L. Templin Nokia 313 Fairchild Drive Mountain View, CA 94043 Phone: +1 650 625 2331 EMail: ftemplin@iprg.nokia.com Hain & Templin Expires February 11, 2004 [Page 11] Internet-Draft Local Addressing Requirements August 2003 Appendix A. Filtering Considerations The only difference between an individual network defined non- routable global prefix and a well-known local use prefix is the coordination and verification of filters. Any prefix can be used in a local-only context, but the ability to detect a configuration error which leads to open routing is limited unless it is well- known. The concept of address scoping is nothing more than a formalization of the existing deployments of limited route announcements, or explicit filtering. Defining a well-known address range for local use allows broad deployment of filters at the edge of the public network without additional site specific coordination. A defined prefix for local use uniquely identifies addresses that have a limited administrative domain of applicability. This prefix provides a network manager with a stable address range, as well as establishes a clear filter to limit introduction into the public network. As such, one common use instance of a site border will be the boundary between the IGP and EGP. Use of limited range addresses for connections external to a site is strongly discouraged, because it is difficult to know when applications will encounter the boundary of the domain of reference. When applications are expected to work across the site boundary, care should be taken to ensure all participating nodes have global addresses available. Appendix B. Routing Considerations The term 'site' is not rigorously defined by intent (just as Areas are not rigorously defined in an IGP), but is typically expected to cover a region of topology that belongs to a single organization, and may be located within a single geographic location, such as an office, an office complex, or a campus. An organization should probably start with the assumption that a site boundary is exactly congruent with an IGP area or IGP/EGP boundary, but they may choose to restrict it further, or expand it when it makes sense for their network. The concepts of sites and IGP areas are similar in that they are about limiting how much information is exposed across administrative borders. In any case a policy boundary will exist at any attachment point to the public Internet, so that is a very likely place to implement at least part of the site boundary. A limited range address space is any set of addresses that can not be reached from a significant portion of the public Internet. The reasons for lack of ability to reach these addresses are based on policy local to the network(s) using them vs. policy at an arbitrary remote network. Hain & Templin Expires February 11, 2004 [Page 12] Internet-Draft Local Addressing Requirements August 2003 The implementation mechanism used to accomplish that policy could be simply restricting the range of routing announcements, or explicit access controls in a device along the path. In either of those cases, the result is a local range with a well defined boundary controlled by the network manager using the addresses. A consequence of the implemented policy is that any packets destined for locations within the limited range, must originate and stay within that range, as there is no way to deliver packets from outside the defined range. As a simple example, take the case below where A & B have a choice of addresses that they can use to reach each other, but C can only reach the Public addresses of either. ---- A ---- | | L P o u c b a l ---- C l i | c | | ---- B ---- One of the requirements of this network environment is that any process that intends to provide C with topology information for reaching A or B, needs to understand the topology so that it can provide C with correct and useful information. An alternate way to draw the example network is: ---- A ---- - | | | L G P o l u c o b a b - R - l ---- C l a i | l c | | | ---- B ---- - This alternate view correlates the public side of A & B where they share some aspect of the routing hierarchy. The result still requires that any process that intends to provide C with topology information understands the topology to recognize the local and global range differences to provide useful information. Hain & Templin Expires February 11, 2004 [Page 13] Internet-Draft Local Addressing Requirements August 2003 To simplify subsequent discussion, the labels will be changed using that same view. The local prefix will be shown as P(l), while the global public prefix will be shown as P(g). ---- A ---- - | | | | | P | | u | | b P(l) P(g) - R - l ---- C | | i | | c | | | ---- B ---- - This sequence of network drawings has been presented to show that limited ranges exist in many IPv4 network deployments today. Additional discussion of the policies that drive these deployments can be found in a discussion on deployment and use of a proposed Provider Independent (PI) address space [HAIN]. Any specific PI mechanism is not the issue here, so much as the policies that drive deployment of an address space that is not controlled by the public network service provider. Further discussion of the requirements for site controlled space follow in the next section. Applications that insist on passing topology information outside the domain of applicability will fail to operate correctly in this environment. Appendix C. Multiple Addressing Considerations While the earlier examples showed a physical separation between the local and global topology, the scenario is identical between multiple interfaces with a single address, and individual interfaces with multiple addresses. This characteristic results in another view of the example network: A ---- - | | | P | u | b P(l)&P(g) - R - l ---- C | i | c | | B ---- - Hain & Templin Expires February 11, 2004 [Page 14] Internet-Draft Local Addressing Requirements August 2003 This configuration is not typical in IPv4 networks, because implementing multiple addresses per interface is operationally challenging, making it relatively difficult. In this view, the router R either informs the public network of only the global prefix A & B are using, or if the local use prefix is a subset of the global prefix, R explicitly controls access to the local use portion. Either way, C can only reach A(g) & B(g), while A & B can reach either P(g) or P(l). In any case, the issues raised by the limited routing range of P(l) are the same as they were in the multiple interface case we started with, and completely independent of the allocation source of P(l). Adding a little more detail to the drawing, shows the distinction between the customer premise equipment (CPE) router, and the provider edge (PE) router: A ---- - | | | P | u | b P(l)&P(g) - R(cpe) - R(pe) - l ---- C | i | c | | B ---- - Again, the issues don't change, this simply allows discussion about how P(g) & P(l) are handled at each of those points. Placing all the local use prefixes under a common shorter prefix allows the service provider to have a common filter at all R(pe) borders. This additional level of filtering provides a backup in the case that R(cpe) is misconfigured in a way that would allow access to P(l) from the public network. Accomplishing the same degree of isolation when P(l) is a subset of P(g), would require a unique configuration for every R(pe), and would explicitly expose P(l) to global access in the case of a configuration error in R(cpe). Appendix D. Potential Applications of Limited Range Address Space A well-known prefix that can be embedded in appliances so they are easy to sell to the average consumer and a simple filter limits access to the home network. Such a prefix would also simplify the case of file system mounts between nodes on an intermittently connected network. If the mount dropped every time a connect event caused addresses to change, the consumer would quickly find another product. Hain & Templin Expires February 11, 2004 [Page 15] Internet-Draft Local Addressing Requirements August 2003 For example, company X has 125,000 employees globally, with regular reorganizations causing constant office shuffles between regions. Each employee has a laptop, which will have global access, and a network connected printer which will not have global access. There are 100 touch-points to the Internet, with the 3 primary ones running multiple OC-48 access loops. The 'explicit filter lists at the border' model requires keeping 100 tables in sync in the face of constant change, and parsing a 125,000 entry list at OC-48 rates for every packet at 3 of the borders. The 'well-known limited range address filter at the border' model requires the organization to tell their printer manufacturer to preconfigure all the devices they buy to only accept and auto-configure limited range prefixes from the RA (likely a widely demanded item), and put in a 2 entry list that remains static at every border. In addition, it is reasonable and expected that the peer across the border will maintain a matching version of the filter list. The compromise model of 'using 2 public prefixes per segment' allows for a 2 entry static list at every border, which may or may not be considered reasonable to match by the border peer. It does not provide the printer manufacturer a preconfiguration option that matches other customers, and even if it was done, as soon as Company X changes providers, they have to manually touch every printer for the new configuration. To make the name service simple in these 3 cases, Company X chooses to run back-to-back normal dns servers. The primary set facing internally to accommodate dynamic updates, with a slave set facing externally. A periodic process will replicate the information from the source-of-truth internal facing servers to the external ones, but the security team requires it to scrub out all records for internal-only nodes. For model 1, the scrubbing process would have to contact the border filter list (after deciding which was the current source of truth), then parse through it for all 250,000 entries to decide which are replicated. For model 2, the scrubbing process simply has to drop records with the limited range address prefix and replicate all others. For model 3, the scrubbing process has to look for the set of prefixes that identify private-use, and replicate all others. Once any one of these processes completes, all nodes are accessible Hain & Templin Expires February 11, 2004 [Page 16] Internet-Draft Local Addressing Requirements August 2003 by name in the internal range, and all nodes that should be accessed from the outside are accessible by name in the global range. Applications that are expected to work across the border will have global addresses to use. Multi-party apps that use name-string referrals will work across the border, but those that use limited range literals will fail by design (note: use of limited range addresses == expected to fail across border). Use of filtered global addresses makes it impossible for the application to know why it failed to connect. Appendix E. Change Log Changes since draft-00: o Changed title, and removed linkage of requirments and the particular solution alternative referred to as "limited range addressing" in the previous draft. Thanks to Eliot Lear and Michael Thomas for suggesting the change. o Added real life example scenario from Andrew White Hain & Templin Expires February 11, 2004 [Page 17] Internet-Draft Local Addressing Requirements August 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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