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Network Working Group                                        P. FergusonRequest for Comments: 2071                           cisco Systems, Inc.Category: Informational                                     H. Berkowitz                                                       PSC International                                                            January 1997Network Renumbering Overview:Why would I want it and what is it anyway?Status of this Memo   This memo provides information for the Internet community.  This memo   does not specify an Internet standard of any kind.  Distribution of   this memo is unlimited.Abstract   The PIER [Procedures for Internet/Enterprise Renumbering] working   group is compiling a series of documents to assist and instruct   organizations in their efforts to renumber.  However, it is becoming   apparent that, with the increasing number of new Internet Service   Providers (ISP's) and organizations getting connected to the Internet   for the first time, the concept of network renumbering needs to be   further defined.  This document attempts to clearly define the   concept of network renumbering and discuss some of the more pertinent   reasons why an organization would have a need to do so.Table of Contents1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .22.   Background . . . . . . . . . . . . . . . . . . . . . . . . .23.   Network Renumbering Defined. . . . . . . . . . . . . . . . .34.   Reasons for Renumbering. . . . . . . . . . . . . . . . . . .35.   Summary. . . . . . . . . . . . . . . . . . . . . . . . . . .126.   Security Considerations  . . . . . . . . . . . . . . . . . .127.   Acknowledgments. . . . . . . . . . . . . . . . . . . . . . .128.   References . . . . . . . . . . . . . . . . . . . . . . . . .139.   Authors' Addresses . . . . . . . . . . . . . . . . . . . . .14Ferguson & Berkowitz         Informational                      [Page 1]

RFC 2071              Network Renumbering Overview          January 19971. Introduction   The popularity of connecting to the global Internet over the course   of the past several years has spawned new problems; what most people   casually refer to as "growing pains" can be attributed to more basic   problems in understanding the requirements for Internet connectivity.   However, the reasons why organizations may need to renumber their   networks can greatly vary. We'll discuss these issues in some amount   of detail below.  It is not within the intended scope of this   document to discuss renumbering methodologies, techniques, or tools.2. Background   The ability for any network or interconnected devices, such as   desktop PCs or workstations, to obtain connectivity to any potential   destination in the global Internet is reliant upon the possession of   unique IP host addresses [1].  A duplicate host address that is being   used elsewhere in the Internet could best be described as   problematic, since the presence of duplicate addresses would cause   one of the destinations to be unreachable from some origins in the   Internet.  It should be noted, however, that globally unique IP   addresses are not always necessary, and is dependent on the   connectivity requirements [2].   However, the recent popularity in obtaining Internet connectivity has   made these types of connectivity dependencies unpredictable, and   conventional wisdom in the Internet community dictates that the   various address allocation registries, such as the InterNIC, as well   as the ISP's, become more prudent in their address allocation   strategies.  In that vein, the InterNIC has defined address   allocation policies [3] wherein the majority of address allocations   for end-user networks are accommodated by their upstream ISP, except   in cases where dual- or multihoming and very large blocks of   addresses are required.  With this allocation policy becoming   standard current practice, it presents unique problems regarding the   portability of addresses from one provider to another.   As a practical matter, end users cannot assume they "own" address   allocations, if their intention is to be to have full connectivity to   the global Internet. Rather, end users will "borrow" part of the   address space of an upstream provider's allocation. The larger   provider block from which their space is suballocated will have been   assigned in a manner consistent with global Internet routing.   Not having "permanent" addresses does not mean users will not have   unique identifiers. Such identifiers are typically Domain Name System   (DNS) [4] names for endpoints such as servers and workstations.   Mechanisms such as the Dynamic Host Configuration Protocol (DHCP) [5]Ferguson & Berkowitz         Informational                      [Page 2]

RFC 2071              Network Renumbering Overview          January 1997   can help automate the assignment and maintenance of host names, as   well as the 'borrowed' addresses required for routing-level   connectivity.   The PIER Working Group is developing procedures and guidelines for   detailed renumbering of specific technologies, such as routers [6].   PIER WG documents are intended to suggest methods both for making   existing networks prepared for convenient renumbering, as well as for   operational transition to new addressing schemes.   Also, in many instances, organizations who have never connected to   the Internet, yet have been using arbitrary blocks of addresses since   their construction, have different and unique challenges.3. Network Renumbering Defined   In the simplest of definitions, the exercise of renumbering a network   consists of changing the IP host addresses, and perhaps the network   mask, of each device within the network that has an address   associated with it. This activity may or may not consist of all   networks within a particular domain, such as FOO.EDU, or networks   which comprise an entire autonomous system.   Devices which may need to be renumbered, for example, are networked   PC's, workstations, printers, file servers, terminal servers, and   routers. Renumbering a network may involve changing host parameters   and configuration files which contain IP addresses, such as   configuration files which contain addresses of DNS and other servers,   addresses contained in SNMP [7] management stations, and addresses   configured in access control lists. While this is not an all-   inclusive list, the PIER working group is making efforts to compile   documentation to identify these devices in a more detailed fashion.   Network renumbering need not be sudden activity, either; in most   instances, an organization's upstream service provider(s) will allow   a grace period where both the "old" addresses and the "new" addresses   may be used in parallel.4. Reasons for Renumbering   The following sections discuss particular reasons which may   precipitate network renumbering, and are not presented in any   particular order of precedence.  They are grouped into reasons that   primarily reflect decisions made in the past, operational   requirements of the present, or plans for the future.Ferguson & Berkowitz         Informational                      [Page 3]

RFC 2071              Network Renumbering Overview          January 1997   Some of these requirements reflect evolution in the organization's   mission, such as a need to communicate with business partners, or to   work efficiently in a global Internet.  Other requirements reflect   changes in network technologies.4.1  Past   Many organizations implemented IP-based networks not for connectivity   to the Internet, but simply to make use of effective data   communications mechanisms.  These organizations subsequently found   valid reasons to connect to other organizations or the Internet in   general, but found the address structures they chose incompatible   with overall Internet practice.   Other organizations connected early to the Internet, but did so at a   time when address space was not scarce.  Yet other organizations   still have no requirement to connect to the Internet, but have legacy   addressing structures that do not scale to adequate size.4.1.1  Initial addressing using non-unique addresses   As recently as two years ago, many organizations had no intention of   connecting to the Internet, and constructed their corporate or   organizational network(s) using unregistered, non-unique network   addresses.  Obviously, as most problems evolve, these same   organizations determined that Internet connectivity had become a   valuable asset, and subsequently discovered that they could no longer   use the same unregistered, non-unique network addresses that were   previously deployed throughout their organization.  Thus, the labor   of renumbering to valid network addresses is now upon them, as they   move to connect to the global Internet.   While obtaining valid, unique addresses is certainly required to   obtain full Internet connectivity in most circumstances, the number   of unique addresses required can be significantly reduced by the   implementation of Network Address Translation (NAT) devices [8] and   the use of private address space, as specified in [9].  NAT reduces   not only the number of required unique addresses, but also localizes   the changes required by renumbering.   It should also be noted that NAT technology may not always be a   viable option, depending upon scale of addressing, performance or   topological constraints.Ferguson & Berkowitz         Informational                      [Page 4]

RFC 2071              Network Renumbering Overview          January 19974.1.2  Legacy address allocation   There are also several instances where organizations were originally   allocated very large amounts of address space, such as traditional   "Class A" or "Class B" allocations, while the actual address   requirements are much less than the total amount of address space   originally allocated.  In many cases, these organizations could   suffice with a smaller CIDR allocation, and utilize the allocated   address space in a more efficient manner.  As allocation requirements   become more stringent, mechanisms to review how these organizations   are utilizing their address space could, quite possibly, result in a   request to return the original allocation to a particular registry   and renumber with a more appropriately sized address block.4.1.3  Limitations of Bridged Internetworks   Bridging has a long and distinguished history in legacy networks.  As   networks grow, however, traditional bridged networks reach   performance- and stability-related limits, including (but not limited   to) broadcast storms.   Early routers did not have the speed to handle the needs of some   large networks.  Some organizations were literally not able to move   to routers until router forwarding performance improved to be   comparable to bridges.  Now that routers are of comparable or   superior speed, and offer more robust features, replacing bridged   networks becomes reasonable.   IP addresses assigned to pure bridged networks tend not to be   subnetted, yet subnetting is a basic approach for router networks.   Introducing subnetting is a practical necessity in moving from   bridging to routing.   Special cases of bridging are realized in workgroup switching   systems, discussed below.4.1.4  Limitations of Legacy Routing Systems   Other performance problems might come from routing mechanisms that   advertise excessive numbers of routing updates (e.g., RIP, IGRP).   Likewise, appropriate replacement protocols (e.g., OSPF, EIGRP, S-IS)   will work best with a structured addressing system that encourages   aggregation.Ferguson & Berkowitz         Informational                      [Page 5]

RFC 2071              Network Renumbering Overview          January 19974.1.5  Limitations of System Administration Methodologies   There can be operational limits to growth based on the difficulty of   adds, moves and changes.  As enterprise networks grow, it may be   necessary to delegate portions of address assignment and maintenance.   If address space has been assigned randomly or inefficiently, it may   be difficult to delegate portions of the address space.   It is not unusual for organizational networks to grow sporadically,   obtaining an address prefix here and there, in a non-contiguous   fashion.  Depending on the number of prefixes that an organization   acquires over time, it may become increasingly unmanageable or demand   higher levels of maintenance and administration when individual   prefixes are acquired in this way.   Reasonable IP address management may in general simplify continuing   system administration; a good numbering plan is also a good   renumbering plan.  Renumbering may force a discipline into system   administration that will reduce long-term support costs.   It has been observed "...there is no way to renumber a network   without an inventory of the hosts (absent DHCP). On a large network   that needs a database, plus tools and staff to maintain the   database."[10] It can be argued that a detailed inventory of router   configurations is even more essential.4.2  Present   Organizations now face needs to connect to the global Internet, or at   a minimum to other organizations through bilateral private links.   Certain new transmission technologies have tended to redefine the   basic notion of an IP subnet.  An IP numbering plan needs to work   with these new ideas. Legacy bridged networks and leading-edge   workgroup switched networks may very well need changes in the   subnetting structure.  Renumbering needs may also develop due to the   characteristics of new WAN technologies, especially nonbroadcast   multi-access (NBMA) services such as Frame-Relay and Asynchronous   Transfer Mode (ATM).   Increased use of telecommuting by mobile workers, and in small and   home offices, need on-demand WAN connectivity, using modems or ISDN.   Effective use of demand media often requires changes in numbering and   routing.Ferguson & Berkowitz         Informational                      [Page 6]

RFC 2071              Network Renumbering Overview          January 19974.2.1   Change in organizational structure or network topology   As companies grow, through mergers, acquisitions and reorganizations,   the need may arise for realignment and modification of the various   organizational network architectures.  The connectivity of disparate   corporate networks present unique challenges in the realm of   renumbering, since one or more individual networks may have to be   blended into a much larger architecture consisting a different IP   address prefix altogether.4.2.2  Inter-Enterprise Connectivity   Even if they do not connect to the general Internet, enterprises may   interconnect to other organizations which have independent numbering   systems. Such connectivity can be as simple as bilateral dedicated   circuits. If both enterprises use unregistered or private address   space, they run the risk of using duplicate addresses.   In such cases, one or both organizations may need to renumber into   different parts of the private address space, or obtain unique   registered addresses.4.2.3   Change of Internet Service Provider   As mentioned previously inSection 2, it is increasingly becoming   current practice for organizations to have their IP addresses   allocated by their upstream ISP.  Also, with the advent of Classless   Inter Domain Routing (CIDR) [11], and the considerable growth in the   size of the global Internet table, Internet Service Providers are   becoming more and more reluctant to allow customers to continue using   addresses which were allocated by the ISP, when the customer   terminates service and moves to another ISP.  The prevailing reason   is that the ISP was previously issued a CIDR block of contiguous   address space, which can be announced to the remainder of the   Internet community as a single prefix. (A prefix is what is referred   to in classless terms as a contiguous block of IP addresses.)  If a   non-customer advertises a specific component of the CIDR block, then   this adds an additional routing entry to the global Internet routing   table.  This is what is commonly referred to as "punching holes" in a   CIDR block. Consequently, there are usually no routing anomalies in   doing this since a specific prefix is always preferred over an   aggregate route.  However, if this practice were to happen on a large   scale, the growth of the global routing table would become much   larger, and perhaps too large for current backbone routers to   accommodate in an acceptable fashion with regards to performance of   recalculating routing information and sheer size of the routing table   itself.  For obvious reasons, this practice is highly discouraged by   ISP's with CIDR blocks, and some ISP's are making this a contractualFerguson & Berkowitz         Informational                      [Page 7]

RFC 2071              Network Renumbering Overview          January 1997   issue, so that customers understand that addresses allocated by the   ISP are non-portable.   It is noteworthy to mention that the likelihood of being forced to   renumber in this situation is inversely proportional to the size of   the customer's address space.  For example, an organization with a   /16 allocation may be allowed to consider the address space   "portable", while an organization with multiple non-contiguous /24   allocations may not.  While the scenarios may be vastly different in   scope, it becomes an issue to be decided at the discretion of the   initial allocating entity, and the ISP's involved; the major deciding   factor being whether or not the change will fragment an existing CIDR   block and whether it will significantly contribute to the overall   growth of the global Internet routing tables.   It should also be noted that (contrary to opinions sometimes voiced)   this form of renumbering is a technically necessary consequence of   changing ISP's, rather than a commercial or political mandate.4.2.3  Internet Global Routing   Even large organizations, now connected to the Internet with   "portable" address space, may find their address allocation too   small. Current registry guidelines require that address space usage   be justified by an engineering plan. Older networks may not have   efficiently utilized existing address space, and may need to make   their existing structures more efficient before new address   allocations can be made.4.2.4  Internal Use of LAN Switching   Introducing workgroup switches may introduce subtle renumbering   needs.  Fundamentally, workgroup switches are specialized, high-   performance bridges, which make their main forwarding decisions based   on Layer 2 (MAC) address information. Even so, they rarely are   independent of Layer 3 (IP) address structure.  Pure Layer 2   switching has a "flat" address space that will need to be renumbered   into a hierarchical, subnetted space consistent with routing.   Introducing single switches or stacks of switches may not have   significant impact on addressing, as long as it is understood that   each system of switches is a single broadcast domain. Each broadcast   domain should map to a single IP subnetwork.   Virtual LANs (VLANs) further extend the complexity of the role of   workgroup switches. It is generally true that moving an end station   from one switch port to another within the same VLAN will not cause   major changes in addressing. Many overview presentations of thisFerguson & Berkowitz         Informational                      [Page 8]

RFC 2071              Network Renumbering Overview          January 1997   technology do not make it clear that moving the same end station   between different VLANs will move the end station into another IP   subnet, requiring a significant address change.   Switches are commonly managed by SNMP applications. These network   management applications communicate with managed devices using IP.   Even if the switch does not do IP forwarding, it will itself need IP   addresses if it is to be managed. Also, if the clients and servers in   the workgroup are managed by SNMP, they will also require IP   addresses. The workgroup, therefore, will need to appear as one or   more IP subnetworks.   Increasingly, internetworking products are not purely Layer 2 or   Layer 3 devices. A workgroup switch product often includes a routing   function, so the numbering plan must support both flat Layer 2 and   hierarchical Layer 3 addressing.4.2.4  Internal Use of NBMA Cloud Services   "Cloud" services such as frame relay often are more economical than   traditional services. At first glance, when converting existing   enterprise networks to NBMA, it might appear that the existing subnet   structure should be preserved, but this is often not the case.   Many organizations often  began by treating the "cloud" as a single   subnet, but experience has shown it is often better to treat the   individual virtual circuits as separate subnets, which appear as   traditional point-to-point circuits.  When the individual point-to-   point VCs become separate subnets, efficient address utilization   requires the use of long prefixes (i.e., 30 bit) for these subnets.   In practice, obtaining 30 bit prefixes means the logical network   should support variable length subnet masks (VLSM).  VLSMs are the   primary method in which an assigned prefix can be subnetted   efficiently for different media types. This is accomplished by   establishing one or more prefix lengths for LAN media with more than   two hosts, and subdividing one or more of these shorter prefixes into   longer /30 prefixes that minimize address loss.   There are alternative ways to configure routing over NBMA, using   special mechanisms to exploit or simulate point-to-multipoint VCs.   These often have a significant performance impact, and may be less   reliable because a single routing point of failure is created.   Motivations for such alternatives tend to include:Ferguson & Berkowitz         Informational                      [Page 9]

RFC 2071              Network Renumbering Overview          January 1997      1.  A desire not to use VLSM. This is often founded in fear          rather than technology.      2.  Router implementation issues that limit the number of subnets          or interfaces a given router can support.      3.  An inherently point-to-multipoint application (e.g., remote          hosts to a data center). In such cases, some of the          limitations are due to the dynamic routing protocol in use.          In such "hub-and-spoke" implementations, static routing can          be preferable from a performance and flexibility standpoint,          since it does not produce routing protocol chatter and is          unaffected by split horizon constraints (namely, the inability          to build an adjacency with a peer within the same IP          subnetwork).4.2.5  Expansion of Dialup Services   Dialup services, especially public Internet access providers, are   experiencing explosive growth. This success represents a particular   drain on the available address space, especially with a commonly used   practice of assigning unique addresses to each customer.   In this case, individual users announce their address to the access   server using PPP's IP control protocol (IPCP) [12]. The server may   validate the proposed address against some type of user   identification, or simply make the address active in a subnet to   which the access server (or set of bridged access servers) belongs.   The preferred technique is to allocate dynamic addresses to the user   from a pool of addresses available to the access server.4.2.6  Returning non-contiguous prefixes for an aggregate   In many instances, an organization can return their current, non-   contiguous prefix allocations for a contiguous block of address space   of equal or greater size, which can be accommodated with CIDR.  Also,   many organizations have begun to deploy classless interior routing   protocols within their domains that make use of route summarization   and other optimized routing features, effectively reducing the total   number of routes being propagated within their internal network(s),   and making it much easier to administer and maintain.   Hierarchical routing protocols such as OSPF scale best when the   address assignment of a given network reflects the topology, and the   topology of the network can often be fluid. Given that the network is   fluid, even the best planned address assignment scheme, given time,   will diverge from the actual topology. While not required, someFerguson & Berkowitz         Informational                     [Page 10]

RFC 2071              Network Renumbering Overview          January 1997   organization may choose to gain the benefit of both technical and   administrative scalability of their IGP by periodically renumbering   to have address assignments reflect the network topology. Patrick   Henry once said "the tree of liberty must from time to time be   watered with the blood of patriots." In the Internet, routing trees   of the best-planned networks need from time to time be watered with   at least the sweat of network administrators.  Improving aggregation   is also highly encouraged to reduce the size of not only the global   Internet routing table, but also the size and scalability of interior   routing within the enterprise.4.3  Future   Emerging new protocols will most definitely affect addressing plans   and numbering schemes.4.3.1  Internal Use of Switched Virtual Circuit Services   Services such as ATM virtual circuits, switched frame relay, etc.,   present challenges not considered in the original IP design.  The   basic IP decision in forwarding a packet is whether the destination   is local or remote, in relation to the source host's subnet. Address   resolution mechanisms are used to find the medium address of the   destination in the case of local destinations, or to find the medium   address of the router in the case of remote routers.   In these new services, there are cases where it is far more effective   to "cut-through" a new virtual circuit to the destination. If the   destination is on a different subnet than the source, the cut-through   typically is to the egress router that serves the destination subnet.   The advantage of cut-through in such a case is that it avoids the   latency of multiple router hops, and reduces load on "backbone"   routers. The cut-through decision is usually made by an entry router   that is aware of both the routed and switched environments.   This entry router communicates with a address resolution server using   the Next Hop Resolution Protocol (NHRP) [13]. This server maps the   destination network address to either a next-hop router (where cut-   through is not appropriate) or to an egress router reached over the   switched service. Obviously, the data base in such a server may be   affected by renumbering. Clients may have a hard-coded address of the   server, which again may need to change.  While the NHRP protocol   specifications are still evolving at the time of this writing,   commercial implementations based on drafts of the protocol standard   are in use.Ferguson & Berkowitz         Informational                     [Page 11]

RFC 2071              Network Renumbering Overview          January 19974.3.2  Transitioning to IP version 6   Of course, when IPv6 [14] deployment is set in motion, and as   methodologies are developed to transition to IPv6, renumbering will   also be necessary, but perhaps not immediately mandatory.  To aid in   the transition to IPv6, mechanisms to deploy dual- IPv4/IPv6 stacks   on network hosts should also become available. It is also envisioned   that Network Address Translation (NAT) devices will be developed to   assist in the IPv4 to IPv6 transition, or perhaps supplant the need   to renumber the majority of interior networks altogether, but that is   beyond the scope of this document. At the very least, DNS hosts will   need to be reconfigured to resolve new host names and addresses, and   routers will need to be reconfigured to advertise new prefixes.   IPv6 address allocation will be managed by the Internet Assigned   Numbers Authority (IANA) as set forth in [15].5. Summary   As indicated by the Internet Architecture Board (IAB) in [16], the   task of renumbering networks is becoming more widespread and   commonplace.  Although there are numerous reasons why an organization   would desire, or be required to renumber, there are equally as many   reasons why address allocation should be done with great care and   forethought at the onset, in order to minimize the impact that   renumbering would have on the organization. Even with the most   forethought and vision, however, an organization cannot foresee the   possibility for renumbering. The best advice, in this case, is to be   prepared, and get ready for renumbering.6. Security Considerations   Although no obvious security issues are discussed in this document,   it stands to reason that renumbering certain devices can defeat   security systems designed and based on static IP host addresses.   Care should be exercised by the renumbering entity to ensure that all   security systems deployed with the network(s) which may need to be   renumbered be given special consideration and significant forethought   to provide continued functionality and adequate security.7. Acknowledgments   Special acknowledgments to Yakov Rekhter [cisco Systems, Inc.], Tony   Bates [cisco Systems, Inc.] and Brian Carpenter [CERN] for their   contributions and editorial critique.Ferguson & Berkowitz         Informational                     [Page 12]

RFC 2071              Network Renumbering Overview          January 19978. References [1] Gerich, E., "Unique Addresses are Good",RFC 1814, IAB, July 1995. [2] Crocker, D., "To Be `On' the Internet",RFC 1775, March 1995. [3] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and J.     Postel, "INTERNET REGISTRY IP ALLOCATION GUIDELINES",BCP 12,RFC 2050, November 1996. [4] Mockapetris, P., "Domain Names - Concepts and Facilities",     and  "Domain Names - Implementation and Specification",     STD 13, RFCs 1034, 1035, November 1987. [5] Droms, R., "Dynamic Host Configuration Protocol",RFC 1541,     October 1993. [6] Berkowitz, H., "Router Renumbering Guide",RFC 2072,     January 1997. [7] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "A Simple     Network Management Protocol (SNMP)", STD 15,RFC 1157,     May 1990. [8] Egevang,, K., and P. Francis, "The IP Network Address Translator     (NAT)",RFC 1631, May 1994. [9] Rekhter, Y., Moskowitz, R., Karrenberg, D., de Groot, G-J., and E.     Lear, "Address Allocation for Private Internets",RFC 1918,     February 1996. [10] Messages to PIER list on CERN renumbering; Brian Carpenter, CERN.      Available in PIER WG mailing list archives. [11] Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless      Inter-Domain Routing (CIDR): an Address Assignment and      Aggregation Strategy",RFC 1519, October 1993. [12] McGregor, G., "The PPP Internet Protocol Control Protocol      (IPCP)",RFC 1332, May 1992. [13] Luciani, J., Katz, D., Piscitello, D., and Cole, B., "NBMA Next      Hop Resolution Protocol (NHRP)", Work in Progress. [14] Deering, S., and R. Hinden, "Internet Protocol, Version 6 (IPv6)      Specification",RFC 1883, December 1995.Ferguson & Berkowitz         Informational                     [Page 13]

RFC 2071              Network Renumbering Overview          January 1997 [15] IAB and IESG, "IPv6 Address Allocation Management",RFC 1881,      December 1995. [16] Carpenter, B., and Y. Rekhter, "Renumbering Needs Work",RFC 1900,      February 1996.9. Authors' Addresses   Paul Ferguson   cisco Systems, Inc.   1875 Campus Commons Road   Suite 210   Reston, VA 22091   Phone: (703) 716-9538   Fax: (703) 716-9599   EMail: pferguso@cisco.com   Howard C. Berkowitz   PSC International   1600 Spring Hill Road   Vienna, VA 22182   Phone (703) 998-5819   Fax:  (703) 998-5058   EMail:  hcb@clark.netFerguson & Berkowitz         Informational                     [Page 14]