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rfc:rfc4984

Network Working Group D. Meyer, Ed. Request for Comments: 4984 L. Zhang, Ed. Category: Informational K. Fall, Ed.

                                                        September 2007
       Report from the IAB Workshop on Routing and Addressing

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Abstract

 This document reports the outcome of the Routing and Addressing
 Workshop that was held by the Internet Architecture Board (IAB) on
 October 18-19, 2006, in Amsterdam, Netherlands.  The primary goal of
 the workshop was to develop a shared understanding of the problems
 that the large backbone operators are facing regarding the
 scalability of today's Internet routing system.  The key workshop
 findings include an analysis of the major factors that are driving
 routing table growth, constraints in router technology, and the
 limitations of today's Internet addressing architecture.  It is hoped
 that these findings will serve as input to the IETF community and
 help identify next steps towards effective solutions.
 Note that this document is a report on the proceedings of the
 workshop.  The views and positions documented in this report are
 those of the workshop participants and not of the IAB.  Furthermore,
 note that work on issues related to this workshop report is
 continuing, and this document does not intend to reflect the
 increased understanding of issues nor to discuss the range of
 potential solutions that may be the outcome of this ongoing work.

Meyer, et al. Informational [Page 1] RFC 4984 IAB Workshop on Routing & Addressing September 2007

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Key Findings from the Workshop . . . . . . . . . . . . . . . .  4
   2.1.  Problem #1: The Scalability of the Routing System  . . . .  4
     2.1.1.  Implications of DFZ RIB Growth . . . . . . . . . . . .  5
     2.1.2.  Implications of DFZ FIB Growth . . . . . . . . . . . .  6
   2.2.  Problem #2: The Overloading of IP Address Semantics  . . .  6
   2.3.  Other Concerns . . . . . . . . . . . . . . . . . . . . . .  7
   2.4.  How Urgent Are These Problems? . . . . . . . . . . . . . .  8
 3.  Current Stresses on the Routing and Addressing System  . . . .  8
   3.1.  Major Factors Driving Routing Table Growth . . . . . . . .  8
     3.1.1.  Avoiding Renumbering  . . . . . . . . . . . . . . . . . 9
     3.1.2.  Multihoming  . . . . . . . . . . . . . . . . . . . . . 10
     3.1.3.  Traffic Engineering  . . . . . . . . . . . . . . . . . 10
   3.2.  IPv6 and Its Potential Impact on Routing Table Size  . . . 11
 4.  Implications of Moore's Law on the Scaling Problem . . . . . . 11
   4.1.  Moore's Law  . . . . . . . . . . . . . . . . . . . . . . . 12
     4.1.1.  DRAM . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.1.2.  Off-chip SRAM  . . . . . . . . . . . . . . . . . . . . 13
   4.2.  Forwarding Engines . . . . . . . . . . . . . . . . . . . . 13
   4.3.  Chip Costs . . . . . . . . . . . . . . . . . . . . . . . . 14
   4.4.  Heat and Power . . . . . . . . . . . . . . . . . . . . . . 14
   4.5.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . 15
 5.  What Is on the Horizon . . . . . . . . . . . . . . . . . . . . 15
   5.1.  Continual Growth . . . . . . . . . . . . . . . . . . . . . 15
   5.2.  Large Numbers of Mobile Networks . . . . . . . . . . . . . 16
   5.3.  Orders of Magnitude Increase in Mobile Edge Devices  . . . 16
 6.  What Approaches Have Been Investigated . . . . . . . . . . . . 17
   6.1.  Lessons from MULTI6  . . . . . . . . . . . . . . . . . . . 17
   6.2.  SHIM6: Pros and Cons . . . . . . . . . . . . . . . . . . . 18
   6.3.  GSE/Indirection Solutions: Costs and Benefits  . . . . . . 19
   6.4.  Future for Indirection . . . . . . . . . . . . . . . . . . 20
 7.  Problem Statements . . . . . . . . . . . . . . . . . . . . . . 21
   7.1.  Problem #1: Routing Scalability  . . . . . . . . . . . . . 21
   7.2.  Problem #2: The Overloading of IP Address Semantics  . . . 22
     7.2.1.  Definition of Locator and Identifier . . . . . . . . . 22
     7.2.2.  Consequence of Locator and Identifier Overloading  . . 23
     7.2.3.  Traffic Engineering and IP Address Semantics
             Overload . . . . . . . . . . . . . . . . . . . . . . . 24
   7.3.  Additional Issues  . . . . . . . . . . . . . . . . . . . . 24
     7.3.1.  Routing Convergence  . . . . . . . . . . . . . . . . . 24
     7.3.2.  Misaligned Costs and Benefits  . . . . . . . . . . . . 25
     7.3.3.  Other Concerns . . . . . . . . . . . . . . . . . . . . 25
   7.4.  Problem Recognition  . . . . . . . . . . . . . . . . . . . 26
 8.  Criteria for Solution Development  . . . . . . . . . . . . . . 26
   8.1.  Criteria on Scalability  . . . . . . . . . . . . . . . . . 26
   8.2.  Criteria on Incentives and Economics . . . . . . . . . . . 27

Meyer, et al. Informational [Page 2] RFC 4984 IAB Workshop on Routing & Addressing September 2007

   8.3.  Criteria on Timing . . . . . . . . . . . . . . . . . . . . 28
   8.4.  Consideration on Existing Systems  . . . . . . . . . . . . 28
   8.5.  Consideration on Security  . . . . . . . . . . . . . . . . 29
   8.6.  Other Criteria . . . . . . . . . . . . . . . . . . . . . . 29
   8.7.  Understanding the Tradeoff . . . . . . . . . . . . . . . . 29
 9.  Workshop Recommendations . . . . . . . . . . . . . . . . . . . 30
 10. Security Considerations  . . . . . . . . . . . . . . . . . . . 31
 11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 31
 12. Informative References . . . . . . . . . . . . . . . . . . . . 31
 Appendix A.  Suggestions for Specific Steps  . . . . . . . . . . . 35
 Appendix B.  Workshop Participants . . . . . . . . . . . . . . . . 35
 Appendix C.  Workshop Agenda . . . . . . . . . . . . . . . . . . . 36
 Appendix D.  Presentations . . . . . . . . . . . . . . . . . . . . 37

1. Introduction

 It is commonly recognized that today's Internet routing and
 addressing system is facing serious scaling problems.  The ever-
 increasing user population, as well as multiple other factors
 including multi-homing, traffic engineering, and policy routing, have
 been driving the growth of the Default Free Zone (DFZ) routing table
 size at an increasing and potentially alarming rate [DFZ][BGT04].
 While it has been long recognized that the existing routing
 architecture may have serious scalability problems, effective
 solutions have yet to be identified, developed, and deployed.
 As a first step towards tackling these long-standing concerns, the
 IAB held a "Routing and Addressing Workshop" in Amsterdam,
 Netherlands on October 18-19, 2006.  The main objectives of the
 workshop were to identify existing and potential factors that have
 major impacts on routing scalability, and to develop a concise
 problem statement that may serve as input to a set of follow-on
 activities.  This document reports on the outcome from that workshop.
 The remainder of the document is organized as follows: Section 2
 provides an executive summary of the workshop findings.  Section 3
 describes the sources of stress in the current global routing and
 addressing system.  Section 4 discusses the relationship between
 Moore's law and our ability to build large routers.  Section 5
 describes a few foreseeable factors that may exacerbate the current
 problems outlined in Section 2.  Section 6 describes previous work in
 this area.  Section 7 describes the problem statements in more
 detail, and Section 8 discusses the criteria that constrain the
 solution space.  Finally, Section 9 summarizes the recommendations
 made by the workshop participants.

Meyer, et al. Informational [Page 3] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 The workshop participant list is attached in Appendix B.  The agenda
 can be found in Appendix C, and Appendix D provides pointers to the
 presentations from the workshop.
 Finally, note that this document is a report on the outcome of the
 workshop, not an official document of the IAB.  Any opinions
 expressed are those of the workshop participants and not of the IAB.

2. Key Findings from the Workshop

 This section provides a concise summary of the key findings from the
 workshop.  While many other aspects of a routing and addressing
 system were discussed, the first two problems described in this
 section were deemed the most important ones by the workshop
 participants.
 The clear, highest-priority takeaway from the workshop is the need to
 devise a scalable routing and addressing system, one that is scalable
 in the face of multihoming, and that facilitates a wide spectrum of
 traffic engineering (TE) requirements.  Several scalability problems
 of the current routing and addressing systems were discussed, most
 related to the size of the DFZ routing table (frequently referred to
 as the Routing Information Base, or RIB) and its implications.  Those
 implications included (but were not limited to) the sizes of the DFZ
 RIB and FIB (the Forwarding Information Base), the cost of
 recomputing the FIB, concerns about the BGP convergence times in the
 presence of growing RIB and FIB sizes, and the costs and power (and
 hence heat dissipation) properties of the hardware needed to route
 traffic in the core of the Internet.

2.1. Problem #1: The Scalability of the Routing System

 The shape of the growth curve of the DFZ RIB has been the topic of
 much research and discussion since the early days of the Internet
 [H03].  There have been various hypotheses regarding the sources of
 this growth.  The workshop identified the following factors as the
 main driving forces behind the rapid growth of the DFZ RIB:
 o  Multihoming,
 o  Traffic engineering,
 o  Non-aggregatable address allocations (a big portion of which is
    inherited from historical allocations), and
 o  Business events, such as mergers and acquisitions.

Meyer, et al. Informational [Page 4] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 All of the above factors can lead to prefix de-aggregation and/or the
 injection of unaggregatable prefixes into the DFZ RIB.  Prefix de-
 aggregation leads to an uncontrolled DFZ RIB growth because, absent
 some non-topologically based routing technology (for example, Routing
 On Flat Labels [ROFL] or any name-independent compact routing
 algorithm, e.g., [CNIR]), topological aggregation is the only known
 practical approach to control the growth of the DFZ RIB.  The
 following section reviews the workshop discussion of the implications
 of the growth of the DFZ RIB.

2.1.1. Implications of DFZ RIB Growth

 Presentations made at the workshop showed that the DFZ RIB has been
 growing at greater than linear rates for several years [DFZ].  While
 this has the obvious effects on the requirements for RIB and FIB
 memory sizes, the growth driven by prefix de-aggregation also exposes
 the core of the network to the dynamic nature of the edges, i.e., the
 de-aggregation leads to an increased number of BGP UPDATE messages
 injected into the DFZ (frequently referred to as "UPDATE churn").
 Consequently, additional processing is required to maintain state for
 the longer prefixes and to update the FIB.  Note that, although the
 size of the RIB is bounded by the given address space size and the
 number of reachable hosts (i.e., O(m*2^32) for IPv4, where <m> is the
 average number of peers each BGP router may have), the amount of
 protocol activity required to distribute dynamic topological changes
 is not.  That is, the amount of BGP UPDATE churn that the network can
 experience is essentially unbounded.  It was also noted that the
 UPDATE churn, as currently measured, is heavy-tailed [ATNAC2006].
 That is, a relatively small number of Autonomous Systems (ASs) or
 prefixes are responsible for a disproportionately large fraction of
 the UPDATE churn that we observe today.  Furthermore, much of the
 churn may turn out to be unnecessary information, possibly due to
 instability of edge ASs being injected into the global routing system
 [DynPrefix], or arbitrage of some bandwidth pricing model (see [GIH],
 for example, or the discussion of the behavior of AS 9121 in
 [BGP2005]).
 Finally, it was noted by the workshop participants that the UPDATE
 churn situation may be exacerbated by the current Regional Internet
 Registry (RIR) policy in which end sites are allocated Provider-
 Independent (PI) addresses.  These addresses are not topologically
 aggregatable, and as such, bring the churn problem described above
 into the core routing system.  Of course, as noted by several
 participants, the RIRs have no real choice in this matter, as many
 enterprises demand PI addresses that allow them to multihome without
 the "provider lock" that Provider-Allocated (PA) [PIPA] address space
 creates.  Some enterprises also find the renumbering cost associated
 with PA address assignments unacceptable.

Meyer, et al. Informational [Page 5] RFC 4984 IAB Workshop on Routing & Addressing September 2007

2.1.2. Implications of DFZ FIB Growth

 One surprising outcome of the workshop was the observation made by
 Tony Li about the relationship between "Moore's Law" [ML] and our
 ability to build cost-effective, high-performance routers (see
 Appendix D).  "Moore's Law" is the empirical observation that the
 transistor density of integrated circuits, with respect to minimum
 component cost, doubles roughly every 24 months.  A commonly held
 wisdom is that Moore's law would save the day by ensuring that
 technology will continue to scale at historical rates that surpass
 the growth rate of routing information handled by core router
 hardware.  However, Li pointed out that Moore's Law does not apply to
 building high-end routers as far as the cost is concerned.
 Moore's Law applies specifically to the high-volume portion of the
 semiconductor industry, while the low-volume, customized silicon used
 in core routing is well off Moore's Law's cost curve.  In particular,
 off-chip SRAM is commonly used for storing FIB data, and the driver
 for low-latency, high-capacity SRAM used to be PC cache memory.
 However, recently cache memory has been migrating directly onto the
 processor die, and cell phones are now the primary driver for off-
 chip SRAM.  Given cell phones require low-power, small-capacity parts
 that are not applicable to high-end routers, the SRAMs that are
 favored for router design are not volume parts and do not track with
 Moore's law.

2.2. Problem #2: The Overloading of IP Address Semantics

 One of the fundamental assumptions underlying the scalability of
 routing systems was eloquently stated by Yakov Rekhter (and is
 sometimes referred to as "Rekhter's Law"), namely:
      "Addressing can follow topology or topology can follow
       addressing. Choose one."
 The same idea was expressed by Mike O'Dell's design of an alternate
 address architecture for ipv6 [GSE], where the address structure was
 designed specifically to enable "aggressive topological aggregation"
 to scale the routing system.  Noel Chiappa has also written
 extensively on this topic (see, e.g., [EID]).
 There is, however, a difficulty in creating (and maintaining) the
 kind of congruence envisioned by Rekhter's Law in today's Internet.
 The difficulty arises from the overloading of addressing with the
 semantics of both "who" (endpoint identifier, as used by transport
 layer) and "where" (locators for the routing system); some might also
 add that IP addresses are also overloaded with "how" [GIH].  In any

Meyer, et al. Informational [Page 6] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 event, this kind of overloading is felt to have had deep implications
 for the scalability of the global routing system.
 A refinement to Rekhter's Law, then, is that for the Internet routing
 system to scale, an IP address must be assigned in such a way that it
 is congruent with the Internet's topology.  However, identifiers are
 typically assigned based upon organizational (not topological)
 structure and have stability as a desirable property, a "natural
 incongruence" arises.  As a result, it is difficult (if not
 impossible) to make a single number space serve both purposes
 efficiently.
 Following the logic of the previous paragraphs, workshop participants
 concluded that the so-called "locator/identifier overload" of the IP
 address semantics is one of the causes of the routing scalability
 problem as we see today.  Thus, a "split" seems necessary to scale
 the routing system, although how to actually architect and implement
 such a split was not explored in detail.

2.3. Other Concerns

 In addition to the issues described in Section 2.1 and Section 2.2,
 the workshop participants also identified the following three
 pressing, but "second tier", issues.
 The first one is a general concern with IPv6 deployment.  It is
 commonly believed that the IPv4 address space has put an effective
 constraint on the IPv4 RIB growth.  Once this constraint is lifted by
 the deployment of IPv6, and in the absence of a scalable routing
 strategy, the rapid DFZ RIB size growth problem today can potentially
 be exacerbated by IPv6's much larger address space.  The only routing
 paradigm available today for IPv6 is a combination of Classless
 Inter-Domain Routing (CIDR) [RFC4632] and Provider-Independent (PI)
 address allocation strategies [PIPA] (and possibly SHIM6 [SHIM6] when
 that technology is developed and deployed).  Thus, the opportunity
 exists to create a "swamp" (unaggregatable address space) that can be
 many orders of magnitude larger than what we faced with IPv4.  In
 short, the advent of IPv6 and its larger address space further
 underscores both the concerns raised in Section 2.1, and the
 importance of resolving the architectural issue raised in
 Section 2.2.
 The second issue is slow routing convergence.  In particular, the
 concern was that growth in the number of routes that service
 providers must carry will cause routing convergence to become a
 significant problem.

Meyer, et al. Informational [Page 7] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 The third issue is the misalignment of costs and benefits in today's
 routing system.  While the IETF does not typically consider the
 "business model" impacts of various technology choices, many
 participants felt that perhaps the time has come to review that
 philosophy.

2.4. How Urgent Are These Problems?

 There was a fairly universal agreement among the workshop
 participants that the problems outlined in Section 2.1 and
 Section 2.2 need immediate attention.  This need was not because the
 participants perceived a looming, well-defined "hit the wall" date,
 but rather because these are difficult problems that to date have
 resisted solution, are likely to get more unwieldy as IPv6 deployment
 proceeds, and the development and deployment of an effective solution
 will necessarily take at least a few years.

3. Current Stresses on the Routing and Addressing System

 The primary concern voiced by the workshop participants regarding the
 state of the current Internet routing system was the rapid growth of
 the DFZ RIB.  The number of entries in 2005 ranged from about 150,000
 entries to 175,000 entries [BGP2005]; this number has reached 200,000
 as of October 2006 [CIDRRPT], and is projected to increase to 370,000
 or more within 5 years [Fuller].  Some workshop participants
 projected that the DFZ could reach 2 million entries within 15 years,
 and there might be as many as 10 million multihomed sites by 2050.
 Another related concern was the number of prefixes changed, added,
 and withdrawn as a function of time (i.e., BGP UPDATE churn).  This
 has a detrimental impact on routing convergence, since UPDATEs
 frequently necessitate a re-computation and download of the FIB.  For
 example, a BGP router may observe up to 500,000 BGP updates in a
 single day [DynPrefix], with the peak arrival rates over 1000 updates
 per second.  Such UPDATE churn problems are not limited to DFZ
 routes; indeed, the number of internal routes carried by large ISPs
 also threatens convergence times, given that such internal routes
 include more specifics, Virtual Private Network (VPN) routes, and
 other routes that do not appear in the DFZ [ATNAC2006].

3.1. Major Factors Driving Routing Table Growth

 The growth of the DFZ RIB results from the addition of more prefixes
 to the table.  Although some of this growth is organic (i.e., results
 simply from growth of the Internet), a large portion of the growth
 results from de-aggregation of address prefixes (i.e., more specific

Meyer, et al. Informational [Page 8] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 prefixes).  In this section, we discuss in more detail why this trend
 is accelerating and may be cause for concern.
 An increasing fraction of the more-specific prefixes found in the DFZ
 are due to deliberate action on the part of operators [ATNAC2006].
 Motivations to advertise these more-specifics include:
 o  Traffic Engineering, where load is balanced across multiple links
    through selective advertisement of more-specific routes on
    different links to adjust the amount of traffic received on each;
    and
 o  Attempts to prevent prefix-hijacking by other operators who might
    advertise more-specifics to steer traffic toward them; there are
    several known instances of this behavior today [BHB06].

3.1.1. Avoiding Renumbering

 The workshop participants noted that customers generally prefer to
 have PI address space.  Doing so gives them additional agility in
 selecting ISPs and helps them avoid the need to renumber.  Many end-
 systems use DHCP to assign addresses, so a cursory analysis might
 suggest renumbering might involve modification of a modest number of
 routers and servers (perhaps rather than end hosts) at a site that
 was forced to renumber.
 In reality, however, renumbering can be more cumbersome because IP
 addresses are often used for other purposes such as access control
 lists.  They are also sometimes hard-coded into applications used in
 environments where failure of the DNS would be catastrophic (e.g.,
 some remote monitoring applications).  Although renumbering may be a
 mild inconvenience for some sites and guidelines have been developed
 for renumbering a network without a flag day [RFC4192], for others,
 the necessary changes are sufficiently difficult so as to make
 renumbering effectively impossible.
 For these reasons, PI address space is sought by a growing number of
 customers.  Current RIR policy reflects this trend, and their policy
 is to allocate PI prefixes to all customers who claim a need.
 Routing PI prefixes requires additional entries in the DFZ routing
 and forwarding tables.  At present, ISPs do not typically charge to
 route PI prefixes.  Therefore, the "costs" of the additional
 prefixes, in terms of routing table entries and processing overhead,
 is born by the global routing system as a whole, rather than directly
 by the users of PI space.  The workshop participants observed that no
 strong disincentive exists to discourage the increasing use of PI
 address space.

Meyer, et al. Informational [Page 9] RFC 4984 IAB Workshop on Routing & Addressing September 2007

3.1.2. Multihoming

 Multihoming refers generically to the case in which a site is served
 by more than one ISP [RFC4116].  There are several reasons for the
 observed increase in multihoming, including the increased reliance on
 the Internet for mission- and business-critical applications and the
 general decrease in cost to obtain Internet connectivity.
 Multihoming provides backup routing -- Internet connection
 redundancy; in some circumstances, multihoming is mandatory due to
 contract or law.  Multihoming can be accomplished using either PI or
 PA address space, and multihomed sites generally have their own AS
 numbers (although some do not; this generally occurs when such
 customers are statically routed).
 A multihomed site using PI address space has its prefixes present in
 the forwarding and routing tables of each of its providers.  For PA
 space, each prefix allocated from one provider's address allocation
 will be aggregatable for that provider but not the others.  If the
 addresses are allocated from a 'primary' ISP (i.e., one that the site
 uses for routing unless a failure occurs), then the additional
 routing table entries only appear during path failures to that
 primary ISP.  A problem with multihoming arises when a customer's PA
 IP prefixes are advertised by AS(es) other than their 'primary'
 ISP's.  Because of the longest-matching prefix forwarding rule, in
 this case, the customer's traffic will be directed through the non-
 primary AS(s).  In response, the primary ISP is forced to de-
 aggregate the customer's prefix in order to keep the customer's
 traffic flowing through it instead of the non-primary AS(s).

3.1.3. Traffic Engineering

 Traffic engineering (TE) is the act of arranging for certain Internet
 traffic to use or avoid certain network paths (that is, TE puts
 traffic where capacity exists, or where some set of parameters of the
 path is more favorable to the traffic being placed there).  TE is
 performed by both ISPs and customer networks, for three primary
 reasons:
 o  First, as mentioned above, to match traffic with network capacity,
    or to spread the traffic load across multiple links (frequently
    referred to as "load balancing").
 o  Second, to reduce costs by shifting traffic to lower cost paths or
    by balancing the incoming and outgoing traffic volume to maintain
    appropriate peering relations.

Meyer, et al. Informational [Page 10] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 o  Finally, TE is sometimes deployed to enforce certain forms of
    policy (e.g., Canadian government traffic may not be permitted to
    transit through the United States).
 Few tools exist for inter-domain traffic engineering today.  Network
 operators usually achieve traffic engineering by "tweaking" the
 processing of routing protocols to achieve desired results.  At the
 BGP level, if the address range requiring TE is a portion of a larger
 PA address aggregate, network operators implementing TE are forced to
 de-aggregate otherwise aggregatable prefixes in order to steer the
 traffic of the particular address range to specific paths.
 In today's highly competitive environment, providers require TE to
 maintain good performance and low cost in their networks.  However,
 the current practice of TE deployment results in an increase of the
 DFZ RIB; although individual operators may have a certain gain from
 doing TE, it leads to an overall increased cost for the Internet
 routing infrastructure as a whole.

3.2. IPv6 and Its Potential Impact on Routing Table Size

 Due to the increased IPv6 address size over IPv4, a full immediate
 transition to IPv6 is estimated to lead to the RIB and FIB sizes
 increasing by a factor of about four.  The size of the routing table
 based on a more realistic assumption, that of parallel IPv4 and IPv6
 routing for many years, is less clear.  An increasing amount of
 allocated IPv6 address prefixes is in PI space.  ARIN [ARIN] has
 relaxed its policy for allocation of such space and has been
 allocating /48 prefixes when customers request PI prefixes.  Thus,
 the same pressures affecting IPv4 address allocations also affect
 IPv6 allocations.

4. Implications of Moore's Law on the Scaling Problem

 [Editor's note: The information in this section is gathered from
 presentations given at the workshop.  The presentation slides can be
 retrieved from the pointer provided in Appendix D.  It is worth
 noting that this information has generated quite a bit of discussion
 since the workshop, and as such requires further community input.]
 The workshop heard from Tony Li about the relationship between
 Moore's law and the ability to build cost-effective, high-performance
 routers.  The scalability of the current routing subsystem manifests
 itself in the forwarding table (FIB) and routing table (RIB) of the
 routers in the core of the Internet.  The implementation choices for
 FIB storage are on-chip SRAM, off-chip SRAM, or DRAM.  DRAM is
 commonly used in lower end devices.  RIB storage is done via DRAM.

Meyer, et al. Informational [Page 11] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 [Editor's note: The exact implementation of a high-performance
 router's RIB and FIB memories is the subject of much debate; it is
 also possible that alternative designs may appear in the future.]
 The scalability question then becomes whether these memory
 technologies can scale faster than the size of the full routing
 table.  Intrinsic in this statement is the assumption that core
 routers will be continually and indefinitely upgraded on a periodic
 basis to keep up with the technology curve and that the costs of
 those upgrades will be passed along to the general Internet
 community.

4.1. Moore's Law

 In 1965, Gordon Moore projected that the density of transistors in
 integrated circuits could double every two years, with respect to
 minimum component cost.  The period was subsequently adjusted to be
 between 18-24 months and this conjecture became known as Moore's Law
 [ML].  The semiconductor industry has been following this density
 trend for the last 40 or so years.
 The commonly held wisdom is that Moore's law will save the day by
 ensuring that technology will continue to scale at the historical
 rate that will surpass the growth rate of routing information.
 However, it is vital to understand that Moore's law comes out of the
 high-volume portion of the semiconductor industry, where the costs of
 silicon are dominated by the actual fabrication costs.  The
 customized silicon used in core routers is produced in far lower
 volume, typically in the 1,000-10,000 parts per year, whereas
 microprocessors are running in the tens of millions per year.  This
 places the router silicon well off the cost curve, where the
 economies of scale are not directly inherited, and yield improvements
 are not directly inherited from the best current practices.  Thus,
 router silicon benefits from the technological advances made in
 semiconductors, but does not follow Moore's law from a cost
 perspective.
 To date, this cost difference has not shown clearly.  However, the
 growth in bandwidth of the Internet and the steady climb of the speed
 of individual links has forced router manufacturers to apply more
 sophisticated silicon technology continuously.  There has been a new
 generation of router hardware that has grown at about 4x the
 bandwidth every three years, and increases in routing table size have
 been absorbed by the new generations of hardware.  Now that router
 hardware is nearing the practical limits of per-lambda bandwidth, it
 is possible that upgrades solely for meeting the forwarding table
 scaling will become more visible.

Meyer, et al. Informational [Page 12] RFC 4984 IAB Workshop on Routing & Addressing September 2007

4.1.1. DRAM

 In routers, DRAM is used for storing the RIB and, in lower-end
 routers, is also used for storing the FIB.  Historically, DRAM
 capacity grows at about 4x every 3.3 years.  This translates to 2.4x
 every 2 years, so DRAM capacity actually grows faster than Moore's
 law would suggest.  DRAM speed, however, only grows about 10% per
 year, or 1.2x every 2 years [DRAM] [Molinero].  This is an issue
 because BGP convergence time is limited by DRAM access speeds.  In
 processing a BGP update, a BGP speaker receives a path and must
 compare it to all of the other paths it has stored for the prefix.
 It then iterates over all of the prefixes in the update stream.  This
 results in a memory access pattern that has proven to limit the
 effectiveness of processor caching.  As a result, BGP convergence
 time degrades at the routing table growth rate, divided by the speed
 improvement rate of DRAM.  In the long run, this is likely to become
 a significant issue.

4.1.2. Off-chip SRAM

 Storing the FIB in off-chip SRAM is a popular design decision.  For
 high-speed interfaces, this requires low-latency, high-capacity
 parts.  The driver for this type of SRAM was formerly PC cache
 memory.  However, this cache memory has recently been migrating
 directly onto the processor die, so that the volumes of cache memory
 have fallen off.  Today, the primary driver for off-chip SRAM is cell
 phones, which require low-power, small-capacity parts that are not
 applicable to high-end router design.  As a result, the SRAMs that
 are favored for router design are not volume parts.  They have fallen
 off the cost curve and do not track with Moore's law.

4.2. Forwarding Engines

 For many years, router companies have been building special-purpose
 silicon to provide high-speed packet-forwarding capabilities.  This
 has been necessary because the architectural limitations of general
 purpose CPUs make them incapable of providing the high-bandwidth, low
 latency, low-jitter I/O interface for making high speed forwarding
 decisions.
 As a result, the forwarding engines being built for high-end routers
 are some of the most sophisticated Application-specific Integrated
 Circuits (ASICs) being built, and are currently only one
 technological step behind general-purpose CPUs.  This has been
 largely driven by the growth in bandwidth and has already pushed the
 technology well beyond the knee in the price/performance curve.
 Given that this level of technology is already a requirement to meet
 the performance goals, using on-chip SRAM is an interesting design

Meyer, et al. Informational [Page 13] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 alternative.  If this choice is selected, then growth in the
 available FIB is tightly coupled to process technology improvements,
 which are driven by the general-purpose CPU market.  While this
 growth rate should suffice, in general, the forwarding engine market
 is decidedly off the high-volume price curve, resulting in spiraling
 costs to support basic forwarding.
 Moreover, if there is any change in Moore's law or decrease in the
 rate of processor technology evolution, the forwarding engine could
 quickly become the technological leader of silicon technology.  This
 would rapidly result in forwarding technology becoming prohibitively
 expensive.

4.3. Chip Costs

 Each process technology step in chip development has come at
 increasing cost.  The milestone of sending a completed chip design to
 a fabricator for manufacturing is known as 'tapeout', and is the
 point where the designer pays for the fixed overhead of putting the
 chip into production.  The costs of taping out a chip have been
 rising about 1.5x every 2 years, driven by new process technology.
 The actual design and development costs have been rising similarly,
 because each new generation of technology increases the device count
 by roughly a factor of 2.  This allows new features and chip
 architectures, which inevitably lead to an increase in complexity and
 labor costs.  If new chip development was driven solely by the need
 to scale up memory, and if memory structures scaled, then we would
 expect labor costs to remain fixed.  Unfortunately, memory structures
 typically do not seem to scale linearly.  Individual memory
 controllers have a non-negligible cost, leading to the design for an
 internal on-chip interconnect of memories.  The net result is that we
 can expect that chip development costs to continue to escalate
 roughly in line with the increases in tapeout costs, leading to an
 ongoing cost curve of about 1.5x every 2 years.  Since each
 technology step roughly doubles memory, that implies that if demand
 grows faster than about (2x/1.5x) = 1.3x per year, then technology
 refresh will not be able to remain on a constant cost curve.

4.4. Heat and Power

 Transistors consume power both when idle ("leakage current") and when
 switching.  The smaller and hotter the transistors, the larger the
 leakage current.  The overall power consumption is not linear with
 the density increase.  Thus, as the need for more powerful routers
 increases, cooling technology grows more taxed.  At present, the
 existing air cooling system is starting to be a limiting factor for
 scaling high-performance routers.

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 A key metric for system evaluation is now the unit of forwarding
 bandwidth per Watt-- [(Mb/s)/W].  About 60% of the power goes to the
 forwarding engine circuits, with the rest divided between the
 memories, route processors, and interconnect.  Using parallelization
 to achieve higher bandwidths can aggravate the situation, due to
 increased power and cooling demands.
 [Editor's note: Many in the community have commented that heat, power
 consumption, and the attendant heat dissipation, along with size
 limitations of fabrication processes for high speed parallel I/O
 interfaces, are the current limiting factors.]

4.5. Summary

 Given the uncontrolled nature of its growth rate, there is some
 concern about the long-term prospects for the health and cost of the
 routing subsystem of the Internet.  The ongoing growth will force
 periodic technology refreshes.  However, the growth rate can possibly
 exceed the rate that can be supported at constant cost based on the
 development costs seen in the router industry.  Since high-end
 routing is based on low-volume technology, the cost advantages that
 the bulk of the broader computing industry see, based on Moore's law,
 are not directly inherited.  This leads to a sustainable growth rate
 of 1.3x/2yrs for the forwarding table and 1.2x/2yrs for the routing
 table.  Given that the current baseline growth is at 1.3x/2yrs
 [CIDRRPT], with bursts that even exceed Moore's law, the trend is for
 the costs of technology refresh to continue to grow, indefinitely,
 even in constant dollars.

5. What Is on the Horizon

 Routing and addressing are two fundamental pieces of the Internet
 architecture, thus any changes to them will likely impact almost all
 of the "IP stack", from applications to packet forwarding.  In
 resolving the routing scalability problems, as agreed upon by the
 workshop attendees, we should aim at a long-term solution.  This
 requires a clear understanding of various trends in the foreseeable
 future: the growth in Internet user population, the applications, and
 the technology.

5.1. Continual Growth

 The backbone operators expect that the current Internet user
 population base will continue to expand, as measured by the traffic
 volume, the number of hosts connected to the Internet, the number of
 customer networks, and the number of regional providers.

Meyer, et al. Informational [Page 15] RFC 4984 IAB Workshop on Routing & Addressing September 2007

5.2. Large Numbers of Mobile Networks

 Boeing's Connexion service pioneered the deployment of commercial
 mobile networks that may change their attachment points to the
 Internet on a global scale.  It is believed that such in-flight
 Internet connectivity would likely become commonplace in the not-too-
 distant future.  When that happens, there can be multiple thousands
 of airplane networks in the air at any given time.
 Given that today's DFZ RIB already handles over 200,000 prefixes
 [CIDRRPT], several thousands of mobile networks, each represented by
 a single prefix announcement, may not necessarily raise serious
 routing scalability or stability concerns.  However, there is an open
 question regarding whether this number can become substantially
 larger if other types of mobile networks, such as networks on trains
 or ships, come into play.  If such mobile networks become
 commonplace, then their impact on the global routing system needs to
 be assessed.

5.3. Orders of Magnitude Increase in Mobile Edge Devices

 Today's technology trend indicates that billions of hand-held gadgets
 may come online in the next several years.  There were different
 opinions regarding whether this would, or would not, have a
 significant impact on global routing scalability.  The current
 solutions for mobile hosts, namely Mobile IP (e.g., [RFC3775]),
 handle the mobility by one level of indirection through home agents;
 mobile hosts do not appear any different, from a routing perspective,
 than stationary hosts.  If we follow the same approach, new mobile
 devices should not present challenges beyond the increase in the size
 of the host population.
 The workshop participants recognized that the increase in the number
 of mobile devices can be significant, and that if a scalable routing
 system supporting generic identity-locator separation were developed
 and introduced, billions of mobile gadgets could be supported without
 bringing undue impact on global routing scalability and stability.
 Further investigation is needed to gain a complete understanding of
 the implications on the global routing system of connecting many new
 mobile hand-held devices (including mobile sensor networks) to the
 Internet.

Meyer, et al. Informational [Page 16] RFC 4984 IAB Workshop on Routing & Addressing September 2007

6. What Approaches Have Been Investigated

 Over the years, there have been many efforts designed to investigate
 scalable inter-domain routing for the Internet [IDR-REQS].  To
 benefit from the insights obtained from these past results, the
 workshop reviewed several major previous and ongoing IETF efforts:
 1.  The MULTI6 working group's exploration of the solution space and
     the lessons learned,
 2.  The solution to multihoming being developed by the SHIM6 Working
     Group, and its pros and cons,
 3.  The GSE proposal made by O'Dell in 1997, and its pros and cons,
     and
 4.  Map-and-Encap [RFC1955], a general indirection-based solution to
     scalable multihoming support.

6.1. Lessons from MULTI6

 The MULTI6 working group was chartered to explore the solution space
 for scalable support of IPv6 multihoming.  The numerous proposals
 collected by MULTI6 working group generally fell into one of two
 major categories: resolving the above-mentioned conflict by using
 provider-independent address assignments, or by assigning multiple
 address prefixes to multihomed sites, one for each of its providers,
 so that all the addresses can be topologically aggregatable.
 The first category includes proposals of (1) simply allocating
 provider-independent address space, which is effectively the current
 practice, and (2) assigning IP addresses based on customers'
 geographical locations.  The first approach does not scale; the
 second approach represents a fundamental change to the Internet
 routing system and its economic model, and imposes undue constraints
 on ISPs.  These proposals were found to be incomplete, as they
 offered no solutions to the new problems they introduced.
 The majority of the proposals fell into the second category--
 assigning multiple address blocks per site.  Because IP addresses
 have been used as identifiers by higher-level protocols and
 applications, these proposals face a fundamental design decision
 regarding which layer should be responsible for mapping the multiple
 locators (i.e., the multiple addresses received from ISPs) to an
 identifier.  A related question involves which nodes are responsible
 for handling multiple addresses.  One can implement a multi-address
 scheme at either each individual host or at edge routers of a site,
 or even both.  Handling multiple addresses by edge routers provides

Meyer, et al. Informational [Page 17] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 the ability to control the traffic flow of the entire site.
 Conversely, handling multiple addresses by individual hosts offers
 each host the flexibility to choose different policies for selecting
 a provider; it also implies changes to all the hosts of a multihomed
 site.
 During the process of evaluating all the proposals, two major lessons
 were learned:
 o  Changing anything in the current practice is hard: for example,
    inserting an additional header into the protocol would impact IP
    fragmentation processing, and the current congestion control
    assumes that each TCP connection follows a single routing path.
    In addition, operators ask for the ability to perform traffic
    engineering on a per-site basis, and specification of site policy
    is often interdependent with the IP address structure.
 o  The IP address has been used as an identifier and has been
    codified into many Internet applications that manipulate IP
    addresses directly or include IP addresses within the application
    layer data stream.  IP addresses have also been used as
    identifiers in configuring network policies.  Changing the
    semantics of an IP address, for example, using only the last 64-
    bit as identifiers as proposed by GSE, would require changes to
    all such applications and network devices.

6.2. SHIM6: Pros and Cons

 The SHIM6 working group took the second approach from the MULTI6
 working group's investigation, i.e., supporting multihoming through
 the use of multiple addresses.  SHIM6 adopted a host-based approach,
 where the host IP stack includes a "shim" that presents a stable
 "upper layer identifier" (ULID) to the upper layer protocols, but may
 rewrite the IP packets sent and received so that a currently working
 IP address is used in the transmitted packets.  When needed, a SHIM6
 header is also included in the packet itself, to signal to the remote
 stack.
 With SHIM6, protocols above the IP layer use the ULID to identify
 endpoints (e.g., for TCP connections).  The current design suggests
 choosing one of the locators as the ULID (borrowing a locator to be
 used as an identifier).  This approach makes the implementation
 compatible with existing IPv6 upper layer protocol implementations
 and applications.  Many of these applications have inherited the long
 time practice of using IP addresses as identifiers.
 SHIM6 is able to isolate upper layer protocols from multiple IP layer
 addresses.  This enables a multihomed site to use provider-allocated

Meyer, et al. Informational [Page 18] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 prefixes, one from each of its multiple providers, to facilitate
 provider-based prefix aggregation.  However, this gain comes with
 several significant costs.  First, SHIM6 requires modifications to
 all host stack implementations to support the shim processing.
 Second, the shim layer must maintain the mapping between the
 identifier and the multiple locators returned from IPv6 AAAA name
 resolution, and must take the responsibility to try multiple locators
 if failures ever occur during the end-to-end communication.  At this
 time, the host has little information to determine the order of
 locators it should use in reaching a multihomed destination, however,
 there is ongoing effort in addressing this issue.
 Furthermore, as a host-based approach, SHIM6 provides little control
 to the service provider for effective traffic engineering.  At the
 same time, it also imposes additional state information on the host
 regarding the multiple locators of the remote communication end.
 Such state information may not be a significant issue for individual
 user hosts, but can lead to larger resource demands on large
 application servers that handle hundreds of thousands of simultaneous
 TCP connections.
 Yet another major issue with the SHIM6 solution is the need for
 renumbering when a site changes providers.  Although a multihomed
 site is assigned multiple address blocks, none of them can be treated
 as a persistent identifier for the site.  When the site changes one
 of its providers, it must purge the address block of that provider
 from the entire site.  The current practice of using the IP address
 as both an identifier and a locator has been strengthened by the use
 of IP addresses in access control lists present in various types of
 policy-enforcement devices (e.g., firewalls).  If SHIM6's ULIDs are
 to be used for policy enforcement, a change of providers may
 necessitate the re-configuration of many such devices.

6.3. GSE/Indirection Solutions: Costs and Benefits

 The use of indirection for scalable multihoming was discussed at the
 workshop, including the GSE [GSE] and indirection approaches, such as
 Map-and-Encap [RFC1955], in general.  The GSE proposal changes the
 IPv6 address structure to bear the semantics of both an identifier
 and a locator.  The first n bytes of the 16-byte IPv6 address are
 called the Routing Goop (RG), and are used by the routing system
 exclusively as a locator.  The last 8 bytes of the IPv6 address
 specify an interface on an end-system.  The middle (16 - n - 8) bytes
 are used to identify site local topology.  The border routers of a
 site re-write the source RG of each outgoing packet to make the
 source address part of the source provider's address aggregation;
 they also re-write the destination RG of each incoming packet to hide
 the site's RG from all the internal routers and hosts.  Although GSE

Meyer, et al. Informational [Page 19] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 designates the lower 8 bytes of the IPv6 address as identifiers, the
 extent to which GSE could be made compatible with increasingly-
 popular cryptographically-generated addresses (CGA) remains to be
 determined [dGSE].
 All identifier/locator split proposals require a mapping service that
 can return a set of locators corresponding to a given identifier.  In
 addition, these proposals must also address the problem of detecting
 locator failures and redirecting data flows to remaining locators for
 a multihomed site.  The Map-and-Encap proposal did not address these
 issues.  GSE proposed to use DNS for providing the mapping service,
 but it did not offer an effective means for locator failure recovery.
 GSE also requires host stack modifications, as the upper layers and
 applications are only allowed to use the lower 8-bytes, rather than
 the entire, IPv6 address.

6.4. Future for Indirection

 As the saying goes, "There is no problem in computer science that
 cannot be solved by an extra level of indirection".  The GSE proposal
 can be considered a specific instantiation of a class of indirection-
 based solutions to scalable multihoming.  Map-and-Encap [RFC1955]
 represents a more general form of this indirection solution, which
 uses tunneling, instead of locator rewriting, to cross the DFZ and
 support provider-based prefix aggregation.  This class of solutions
 avoids the provider and customer conflicts regarding PA and PI
 prefixes by putting each in a separate name space, so that ISPs can
 use topologically aggregatable addresses while customers can have
 their globally unique and provider-independent identifiers.  Thus, it
 supports scalable multihoming, and requires no changes to the end
 systems when the encapsulation is performed by the border routers of
 a site.  It also requires no changes to the current practice of both
 applications as well as backbone operations.
 However, all gains of an effective solution are accompanied with
 certain associated costs.  As stated earlier in this section, a
 mapping service must be provided.  This mapping service not only
 brings with it the associated complexity and cost, but it also adds
 another point of failure and could also be a potential target for
 malicious attacks.  Any solution to routing scalability is
 necessarily a cost/benefit tradeoff.  Given the high potential of its
 gains, this indirection approach deserves special attention in our
 search for scalable routing solutions.

Meyer, et al. Informational [Page 20] RFC 4984 IAB Workshop on Routing & Addressing September 2007

7. Problem Statements

 The fundamental goal of this workshop was to develop a prioritized
 problem statement regarding routing and addressing problems facing us
 today, and the workshop spent a considerable amount of time on
 reaching that goal.  This section provides a description of the
 prioritized problem statement, together with elaborations on both the
 rationale and open issues.
 The workshop participants noted that there exist different classes of
 stakeholders in the Internet community who view today's global
 routing system from different angles, and assign different priorities
 to different aspects of the problem set.  The prioritized problem
 statement in this section is the consensus of the participants in
 this workshop, representing primarily large network operators and a
 few router vendors.  It is likely that a different group of
 participants would produce a different list, or with different
 priorities.  For example, freedom to change providers without
 renumbering might make the top of the priority list assembled by a
 workshop of end users and enterprise network operators.

7.1. Problem #1: Routing Scalability

 The workshop participants believe that routing scalability is the
 most important problem facing the Internet today and must be solved,
 although the time frame in which these problems need solutions was
 not directly specified.  The routing scalability problem includes the
 size of the DFZ RIB and FIB, the implications of the growth of the
 RIB and FIB on routing convergence times, and the cost, power (and
 hence, heat dissipation) and ASIC real estate requirements of core
 router hardware.
 It is commonly believed that the IPv4 RIB growth has been constrained
 by the limited IPv4 address space.  However, even under this
 constraint, the DFZ IPv4 RIB has been growing at what appears to be
 an accelerating rate [DFZ].  Given that the IPv6 routing architecture
 is the same as the IPv4 architecture (with substantially larger
 address space), if/when IPv6 becomes widely deployed, it is natural
 to predict that routing table growth for IPv6 will only exacerbate
 the situation.
 The increasing deployment of Virtual Private Network/Virtual Routing
 and Forwarding (VPN/VRF) is considered another major factor driving
 the routing system growth.  However, there are different views
 regarding whether this factor has, or does not have, a direct impact
 to the DFZ RIB.  A common practice is to delegate specific routers to
 handle VPN connections, thus backbone routers do not necessarily hold

Meyer, et al. Informational [Page 21] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 state for individual VPNs.  Nevertheless, VPNs do represent
 scalability challenges in network operations.

7.2. Problem #2: The Overloading of IP Address Semantics

 As we have reported in Section 3, multihoming, along with traffic
 engineering, appear to be the major factors driving the growth of the
 DFZ RIB.  Below, we elaborate their impact on the DFZ RIB.

7.2.1. Definition of Locator and Identifier

 Roughly speaking, the Internet comprises a large number of transit
 networks and a much larger number of customer networks containing
 hosts that are attached to the backbone.  Viewing the Internet as a
 graph, transit networks have branches and customer networks with
 hosts hang at the edges as leaves.
 As its name suggests, locators identify locations in the topology,
 and a network's or host's locator should be topologically constrained
 by its present position.  Identifiers, in principle, should be
 network-topology independent.  That is, even though a network or host
 may need to change its locator when it is moved to a different set of
 attachment points in the Internet, its identifier should remain
 constant.
 From an ISP's viewpoint, identifiers identify customer networks and
 customer hosts.  Note that the word "identifier" used here is defined
 in the context of the Internet routing system; the definition may
 well be different when the word "identifier" is used in other
 contexts.  As an example, a non-routable, provider-independent IP
 prefix for an enterprise network could serve as an identifier for
 that enterprise.  This block of IP addresses can be used to route
 packets inside the enterprise network.  However, they are independent
 from the DFZ topology, which is why they are not globally routable on
 the Internet.
 Note that in cases such as the last example, the definition of
 locators and identifiers can be context-dependent.  Following the
 example further, a PI address may be routable in an enterprise but
 not the global network.  If allowed to be visible in the global
 network, such addresses might act as identifiers from a backbone
 operator's point of view but locators from an enterprise operator's
 point of view.

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7.2.2. Consequence of Locator and Identifier Overloading

 In today's Internet architecture, IP addresses have been used as both
 locators and identifiers.  Combined with the use of CIDR to perform
 route aggregation, a problem arises for either providers or customers
 (or both).
 Consider, for example, a campus network C that received prefix
 x.y.z/24 from provider P1.  When C multihomes with a second provider
 P2, both P1 and P2 must announce x.y.z/24 so that C can be reached
 through both providers.  In this example, the prefix x.y.z/24 serves
 both as an identifier for C, as well as a (non-aggregatable) locator
 for C's two attachment points to the transit system.
 As far as the DFZ RIB is concerned, the above example shows that
 customer multihoming blurs the distinction between PA and PI
 prefixes.  Although C received a PA prefix x.y.z/24 from P1, C's
 multihoming forced this prefix to be announced globally (equivalent
 to a PI prefix), and forced the prefix's original owner, provider P1,
 to de-aggregate.  As a result, today's multihoming practice leads to
 a growth of the routing table size in proportion to the number of
 multihomed customers.  The only practical way to scale a routing
 system today is topological aggregation, which gets destroyed by
 customer multihoming.
 Although multihoming may blur the PA/PI distinction, there exists a
 big difference between PA and PI prefixes when a customer changes its
 provider(s).  If the customer has used a PA prefix from a former
 provider P1, the prefix is supposed to be returned to P1 upon
 completion of the change.  The customer is supposed to get a new
 prefix from its new provider, i.e., renumbering its network.  It is
 necessary for providers to reclaim their PA prefixes from former
 customers in order to keep the topological aggregatiblity of their
 prefixes.  On the other hand, renumbering is considered very painful,
 if not impossible, by many Internet users, especially large
 enterprise customers.  It is not uncommon for IP addresses in such
 enterprises to penetrate deeply into various parts of the networking
 infrastructure, ranging from applications to network management
 (e.g., policy databases, firewall configurations, etc.).  This shows
 how fragile the system becomes due to the overloading of IP addresses
 as both locators and identifiers; significant enterprise operations
 could be disrupted due to the otherwise simple operation of switching
 IP address prefix assignment.

Meyer, et al. Informational [Page 23] RFC 4984 IAB Workshop on Routing & Addressing September 2007

7.2.3. Traffic Engineering and IP Address Semantics Overload

 In today's practice, traffic engineering (TE) is achieved by de-
 aggregating IP prefixes.  One can effectively adjust the traffic
 volume along specific routing paths by adjusting the prefix lengths
 and the number of prefixes announced through those paths.  Thus, the
 very means of TE practice directly conflicts with constraining the
 routing table growth.
 On the surface, traffic engineering induced prefix de-aggregation
 seems orthogonal to the locator-identifier overloading problem.
 However, this may not necessarily be true.  Had all the IP prefixes
 been topologically aggregatable to start with, it would make re-
 aggregation possible or easier, when the finer granularity prefix
 announcements propagate further away from their origins.

7.3. Additional Issues

7.3.1. Routing Convergence

 There are two kinds of routing convergence issues, eBGP (global
 routing) convergence and IGP (enterprise or provider) routing
 convergence.  Upon isolated topological events, eBGP convergence does
 not suffer from extensive path explorations in most cases [PathExp],
 and convergence delay is largely determined by the minimum route
 advertisement interval (MRAI) timer [RFC4098], except those cases
 when a route is withdrawn.  Route withdrawals tend to suffer from
 path explorations and hence slow convergence; one participant's
 experience suggests that the withdrawal delays often last up to a
 couple of minutes.  One may argue that, if the destination becomes
 unreachable, a long convergence delay would not bring further damage
 to applications.  However, there are often cases where a more
 specific route (a longer prefix) has failed, yet the destination can
 still be reached through an aggregated route (a shorter prefix).  In
 these cases, the long convergence delay does impact application
 performance.
 While IGPs are designed to and do converge more quickly than BGP
 might, the workshop participants were concerned that, in addition to
 the various special purpose routes that IGPs must carry, the rapid
 growth of the DFZ RIB size can effectively slow down IGP convergence.
 The IGP convergence delay can be due to multiple factors, including
 1.  Delays in detecting physical failures,
 2.  The delay in loading updated information into the FIB, and

Meyer, et al. Informational [Page 24] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 3.  The large size of the internal RIB, often twice as big as the DFZ
     RIB, which can lead to both longer route computation time and
     longer FIB loading time.
 The workshop participants hold different views regarding (1) the
 severity of the routing convergence problem; and (2) whether it is an
 architectural problem, or an implementation issue.  However, people
 generally agree that if we solve the routing scalability problem,
 that will certainly help reduce the convergence delay or make the
 problem a much easier one to handle because of the reduced number of
 routes to process.

7.3.2. Misaligned Costs and Benefits

 Today's rapid growth of the DFZ RIB is driven by a few major factors,
 including multihoming and traffic engineering, in addition to the
 organic growth of the Internet's user base.  There is a powerful
 incentive to deploy each of the above features, as they bring direct
 benefits to the parties who make use of them.  However, the
 beneficiaries may not bear the direct costs of the resulting routing
 table size increase, and there is no measurable or enforceable
 constraint to limit such increase.
 For example, suppose that a service provider has two bandwidth-
 constrained transoceanic links and wants to split its prefix
 announcements in order to fully load each link.  The origin AS
 benefits from performing the de-aggregation.  However, if the de-
 aggregated announcements propagate globally, the cost is born by all
 other ASs.  That is, the costs of this type of TE practice are not
 contained to the beneficiaries.  Multihoming provides a similar
 example (in this case, the multihomed site achieves a benefit, but
 the global Internet incurs the cost of carrying the additional
 prefix(es)).
 The misalignment of cost and benefit in the current routing system
 has been a driver for acceleration of the routing system size growth.

7.3.3. Other Concerns

 Mobility was among the most frequently mentioned issues at the
 workshop.  It is expected that billions of mobile gadgets may be
 connected to the Internet in the near future.  There was also a
 discussion on network mobility as deployed in the Connexion service
 provided by Boeing over the last few years.  However, at this time it
 seems unclear (1) whether the Boeing-like network mobility support
 would cause a scaling issue in the routing system, and (2) exactly
 what would be the impact of billions of mobile hosts on the global

Meyer, et al. Informational [Page 25] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 routing system.  These discussions were covered in Section 5 of this
 report.
 Routing security is another issue that was brought up a number of
 times during the workshop.  The consensus from the workshop
 participants was that, however important routing security may be, it
 was out of scope for this workshop, whose main goal was to produce a
 problem statement about addressing and routing scalability.  It was
 duly considered that security must be one of the top design goals
 when we get to a solution development stage.  It was also noted that,
 if we continue to allow the routing table to grow indefinitely, then
 it may be impossible to add security enhancements in the future.

7.4. Problem Recognition

 The first step in solving a problem is recognizing its existence as
 well as its importance.  However, recognizing the severity of the
 routing scaling issue can be a challenge by itself, because there
 does not exist a specific hard limit on routing system scalability
 that can be easily demonstrated, nor is there any specific answer to
 the question of how much time we may have in developing a solution.
 Nevertheless, a general consensus among the workshop participants is
 that we seem to be running out of time.  The current RIB scaling
 leads to both accelerated hardware cost increases, as explained in
 Section 4, as well as pressure for shorter depreciation cycles, which
 in turn also translates to cost increases.

8. Criteria for Solution Development

 Any common problem statement may admit multiple different solutions.
 This section provides a set of considerations, as identified from the
 workshop discussion, over the solution space.  Given the
 heterogeneity among customers and providers of the global Internet,
 and the elasticity of the problem, none of these considerations
 should inherently preclude any specific solution.  Consequently,
 although the following considerations were initially deemed as
 constraints on solutions, we have instead opted to adopt the term
 'criteria' to be used in guiding solution evaluations.

8.1. Criteria on Scalability

 Clearly, any proposed solution must solve the problem at hand, and
 our number one problem concerns the scalability of the Internet's
 routing and addressing system(s) as outlined in previous sections.
 Under the assumption of continued growth of the Internet user
 population, continued increases of multihoming and RFC 2547 VPN
 [RFC2547] deployment, the solution must enable the routing system to
 scale gracefully, as measured by the number of

Meyer, et al. Informational [Page 26] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 o  DFZ Internet routes, and
 o  Internal routes.
 In addition, scalable support for traffic engineering (TE) must be
 considered as a business necessity, not an option.  Capacity planning
 involves placing circuits based on traffic demand over a relatively
 long time scale, while TE must work more immediately to match the
 traffic load to the existing capacity and to match the routing policy
 requirements.
 It was recognized that different parties in the Internet may have
 different specific TE requirements.  For example,
 o  End site TE: based on locally determined performance or cost
    policies, end sites may wish to control the traffic volume exiting
    to, or entering from specific providers.
 o  Small ISP to transit ISP TE: operators may face tight resource
    constraints and wish to influence the volume of entering traffic
    from both customers and providers along specific routing paths to
    best utilize the limited resources.
 o  Large ISP TE: given the densely connected nature of the Internet
    topology, a given destination normally can be reached through
    different routing paths.  An operator may wish to be able to
    adjust the traffic volume sent to each of its peers based on
    business relations with its neighbor ASs.
 At this time, it remains an open issue whether a scalable TE solution
 would be necessarily inside the routing protocol, or can be
 accomplished through means that are external to the routing system.

8.2. Criteria on Incentives and Economics

 The workshop attendees concluded that one important reason for
 uncontrolled routing growth was the misalignment of incentives.  New
 entries are added to the routing system to provide benefit to
 specific parties, while the cost is born by everyone in the global
 routing system.  The consensus of the workshop was that any proposed
 solutions should strive to provide incentives to reward practices
 that reduce the overall system cost, and punish the "bad" behavior
 that imposes undue burden on the global system.
 Given the global scale and distributed nature of the Internet, there
 can no longer (ever) be a flag day on the Internet.  To bootstrap the
 deployment of new solutions, the solutions should provide incentives
 to first movers.  That is, even when a single party starts to deploy

Meyer, et al. Informational [Page 27] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 the new solution, there should be measurable benefits to balance the
 costs.
 Independent of what kind of solutions the IETF develops, if any, it
 is unlikely that the resulting routing system would stay constant in
 size.  Instead, the workshop participants believed the routing system
 will continue to grow, and that ISPs will continue to go through
 system and hardware upgrade cycles.  Many attendees expressed a
 desire that the scaling properties of the system can allow the
 hardware to keep up with the Internet growth at a rate that is
 comparable to the current costs, for example, allowing one to keep a
 5-year hardware depreciation cycle, as opposed to a situation where
 scaling leads to accelerated cost increases.

8.3. Criteria on Timing

 Although there does not exist a specific hard deadline, the unanimous
 consensus among the workshop participants is that the solution
 development must start now.  If one assumes that the solution
 specification can get ready within a 1 - 2 year time frame, that will
 be followed by another 2-year certification cycle.  As a result, even
 in the best case scenario, we are facing a 3 - 5 year time frame in
 getting the solutions deployed.

8.4. Consideration on Existing Systems

 The routing scalability problem is a shared one between IPv4 and
 IPv6, as IPv6 simply inherited IPv4's CIDR-style "Provider-based
 Addressing".  The proposed solutions should, and are also expected
 to, solve the problem for both IPv4 and IPv6.
 Backwards compatibility with the existing IPv4 and IPv6 protocol
 stack is a necessity.  Although a wide deployment of IPv6 is yet to
 happen, there has been substantial investment into IPv6
 implementation and deployment by various parties.  IPv6 is considered
 a legacy with shipped code.  Thus, a highly desired feature of any
 proposed solution is to avoid imposing backwards-incompatible changes
 on end hosts (either IPv4 or IPv6).
 In the routing system itself, the solutions must allow incremental
 changes from the current operational Internet.  The solutions should
 be backward compatible with the routing protocols in use today,
 including BGP, OSPF, IS-IS, and others, possibly with incremental
 enhancements.
 The above backward-compatibility considerations should not constrain
 the exploration of the solution space.  We need to first find right
 solutions, and look into their backward-compatibility issues after

Meyer, et al. Informational [Page 28] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 that.  This way enables us to gain a full understanding of the
 tradeoffs, and what potential gains, if any, that we may achieve by
 relaxing the backward-compatibility concerns.
 As a rule of thumb for successful deployment, for any new design, its
 chance of success is higher if it makes fewer changes to the existing
 system.

8.5. Consideration on Security

 Security should be considered from day one of solution development.
 If nothing else, the solutions must not make securing the routing
 system any worse than the situation today.  It is highly desirable to
 have a solution that makes it more difficult to inject false routing
 information, and makes it easier to filter out DoS traffic.
 However, securing the routing system is not considered a requirement
 for the solution development.  Security is important; having a
 working system in the first place is even more important.

8.6. Other Criteria

 A number of other criteria were also raised that fall into various
 different categories.  They are summarized below.
 o  Site renumbering forced by the routing system should be avoided.
 o  Site reconfiguration driven by the routing system should be
    minimized.
 o  The solutions should not force ISPs to reveal internal topology.
 o  Routing convergence delay must be under control.
 o  End-to-end data delivery paths should be stable enough for good
    Voice over IP (VoIP) performance.

8.7. Understanding the Tradeoff

 As the old saying goes, every coin has two sides.  If we let the
 routing table continue to grow at its present rate, rapid hardware
 and software upgrade and replacement cycles for deployed core routing
 equipment may become cost prohibitive.  In the worst case, the
 routing table growth may exceed our ability to engineer the global
 routing system in a cost-effective way.  On the other hand, solutions
 for stopping or substantially slowing down the growth in the Internet
 routing table will necessarily bring their own costs, perhaps showing
 up elsewhere and in different forms.  Examples of such tradeoffs are

Meyer, et al. Informational [Page 29] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 presented in Section 6, where we examined the gains and costs of a
 few different approaches to scalable multihoming support (SHIM6, GSE,
 and a general tunneling approach).  A major task in the solution
 development is to understand who may have to give up what, and
 whether that makes a worthy tradeoff.
 Before ending this discussion on the solution criteria, it is worth
 mentioning the shortest presentation at the workshop, which was made
 by Tony Li (the presentation slides can be found from Appendix D).
 He asked a fundamental question: what is at stake?  It is the
 Internet itself.  If the routing system does not scale with the
 continued growth of the Internet, eventually the costs might spiral
 out of control, the digital divide widen, and the Internet growth
 slow down, stop, or retreat.  Compared to this problem, he considered
 that none of the criteria mentioned so far (except solving the
 problem) was important enough to block the development and deployment
 of an effective solution.

9. Workshop Recommendations

 The workshop attendees would like to make the following
 recommendations:
 First of all, the workshop participants would like to reiterate the
 importance of solving the routing scalability problem.  They noted
 that the concern over the scalability and flexibility of the routing
 and addressing system has been with us for a very long time, and the
 current growth rate of the DFZ RIB is exceeding our ability to
 engineer the routing infrastructure in an economically feasible way.
 We need to start developing a long-term solution that can last for
 the foreseeable future.
 Second, because the participants of this workshop consisted of mostly
 large service providers and major router vendors, the workshop
 participants recommend that IAB/IESG organize additional workshops or
 use other venues of communication to reach out to other stakeholders,
 such as content providers, retail providers, and enterprise
 operators, both to communicate to them the outcome of this workshop,
 and to solicit the routing/addressing problems they are facing today,
 and their requirements on the solution development.
 Third, the workshop participants recommend conducting the solution
 development in an open, transparent way, with broad-ranging
 participation from the larger networking community.  A majority of
 the participants indicated their willingness to commit resources
 toward developing a solution.  We must also invite the participation
 from the research community in this process.  The locator-identifier
 split represents a fundamental architectural issue, and the IAB

Meyer, et al. Informational [Page 30] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 should lead the investigation into understanding of both how to make
 this architectural change and the overall impact of the change.
 Fourth, given the goal of developing a long-term solution, and the
 fact that development and deployment cycles will necessarily take
 some time, it may be helpful (or even necessary) to buy some time
 through engineering feasible short- or intermediate-term solutions
 (e.g., FIB compression).
 Fifth, the workshop participants believe the next step is to develop
 a roadmap from here to the solution deployment.  The IAB and IESG are
 expected to take on the leadership role in this roadmap development,
 and to leverage on the momentum from this successful workshop to move
 forward quickly.  The roadmap should provide clearly defined short-,
 medium-, and long-term objectives to guide the solution development
 process, so that the community as a whole can proceed in an
 orchestrated way, seeing exactly where we are going when engineering
 necessary short-term fixes.
 Finally, the workshop participants also made a number of suggestions
 that the IETF might consider when examining the solution space.
 These suggestions are captured in Appendix A.

10. Security Considerations

 While the security of the routing system is of great concern, this
 document introduces no new protocol or protocol usage and as such
 presents no new security issues.

11. Acknowledgments

 Jari Arkko, Vince Fuller, Darrel Lewis, Tony Li, Eric Rescorla, and
 Ted Seely made many insightful comments on earlier versions of this
 document.  Finally, many thanks to Wouter Wijngaards for the fine
 notes he took during the workshop.

12. Informative References

 [RFC1955]    Hinden, R., "New Scheme for Internet Routing and
              Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.
 [RFC2547]    Rosen, E. and Y. Rekhter, "BGP/MPLS VPNs", RFC 2547,
              March 1999.
 [RFC3775]    Johnson, D., Perkins, C., and J. Arkko, "Mobility
              Support in IPv6", RFC 3775, June 2004.

Meyer, et al. Informational [Page 31] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 [RFC4098]    Berkowitz, H., Davies, E., Hares, S., Krishnaswamy, P.,
              and M. Lepp, "Terminology for Benchmarking BGP Device
              Convergence in the Control Plane", RFC 4098, June 2005.
 [RFC4116]    Abley, J., Lindqvist, K., Davies, E., Black, B., and V.
              Gill, "IPv4 Multihoming Practices and Limitations",
              RFC 4116, July 2005.
 [RFC4192]    Baker, F., Lear, E., and R. Droms, "Procedures for
              Renumbering an IPv6 Network without a Flag Day",
              RFC 4192, September 2005.
 [RFC4632]    Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, August 2006.
 [IDR-REQS]   Doria, A. and E. Davies, "Analysis of IDR requirements
              and History", Work in Progress, February 2007.
 [ARIN]       "American Registry for Internet Numbers",
               http://www.arin.net/index.shtml.
 [PIPA]       Karrenberg, D., "IPv4 Address Allocation and Assignment
              Policies for the RIPE NCC Service Region",
              RIPE-387 http://www.ripe.net/docs/ipv4-policies.html,
              2006.
 [SHIM6]      "Site Multihoming by IPv6 Intermediation (shim6)",
               http://www.ietf.org/html.charters/shim6-charter.html.
 [EID]        Chiappa, J., "Endpoints and Endpoint Names: A Proposed
              Enhancement to the Internet Architecture",
               http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999.
 [GSE]        O'Dell, M., "GSE - An Alternate Addressing Architecture
              for IPv6", Work in Progress, 1997.
 [dGSE]       Zhang, L., "An Overview of Multihoming and Open Issues
              in GSE", IETF Journal, http://www.isoc.org/tools/blogs/
              ietfjournal/?p=98#more-98, 2006.
 [PathExp]    Oliveira, R. and et. al., "Quantifying Path Exploration
              in the Internet", Internet Measurement Conference (IMC)
              2006, http://www.cs.ucla.edu/~rveloso/papers/
              imc175f-oliveira.pdf.

Meyer, et al. Informational [Page 32] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 [DynPrefix]  Oliveira, R. and et. al., "Measurement of Highly Active
              Prefixes in BGP", IEEE GLOBECOM 2005
              http://www.cs.ucla.edu/~rveloso/papers/activity.pdf.
 [BHB06]      Boothe, P., Hielbert, J., and R. Bush, "Short-Lived
              Prefix Hijacking on the Internet", NANOG 36
              http://www.nanog.org/mtg-0602/pdf/boothe.pdf, 2006.
 [ROFL]       Caesar, M. and et. al., "ROFL: Routing on Flat Labels",
              SIGCOMM 2006, http://www.sigcomm.org/sigcomm2006/
              discussion/showpaper.php?paper_id=34, 2006.
 [CNIR]       Abraham, I. and et. al., "Compact Name-Independent
              Routing with Minimum Stretch", ACM Symposium on Parallel
              Algorithms and Architectures,
              http://citeseer.ist.psu.edu/710757.html, 2004.
 [BGT04]      Bu, T., Gao, L., and D. Towsley, "On Characterizing BGP
              Routing Table Growth", J. Computer and Telecomm
              Networking V45N1, 2004.
 [Fuller]     Fuller, V., "Scaling issues with ipv6 routing+
              multihoming",  http://www.iab.org/about/workshops/
              routingandaddressing/vaf-iab-raws.pdf, 2006.
 [H03]        Huston, G., "Analyzing the Internet's BGP Routing
              Table",  http://www.potaroo.net/papers/ipj/
              2001-v4-n1-bgp/bgp.pdf, 2003.
 [BGP2005]    Huston, G., "2005 -- A BGP Year in Review",  http://
              www.apnic.net/meetings/21/docs/sigs/routing/
              routing-pres-huston-routing-update.pdf.
 [DFZ]        Huston, G., "Growth of the BGP Table - 1994 to Present",
               http://bgp.potaroo.net, 2006.
 [GIH]        Huston, G., "Wither Routing?",
               http://www.potaroo.net/ispcol/2006-11/raw.html, 2006.
 [ATNAC2006]  Huston, G. and G. Armitage, "Projecting Future IPv4
              Router Requirements from Trends in Dynamic BGP
              Behaviour",  http://www.potaroo.net/papers/phd/
              atnac-2006/bgp-atnac2006.pdf, 2006.
 [CIDRRPT]    "The CIDR Report",  http://www.cidr-report.org.

Meyer, et al. Informational [Page 33] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 [ML]         "Moore's Law",
              Wikipedia http://en.wikipedia.org/wiki/Moore's_law,
              2006.
 [Molinero]   Molinero-Fernandez, P., "Technology trends in routers
              and switches", PhD thesis, Stanford University  http://
              klamath.stanford.edu/~molinero/thesis/html/
              pmf_thesis_node5.html, 2005.
 [DRAM]       Landler, P., "DRAM Productivity and Capacity/Demand
              Model", Global Economic Workshop http://
              www.sematech.org/meetings/archives/GES/19990514/docs/
              07_econ.pdf, 1999.

Meyer, et al. Informational [Page 34] RFC 4984 IAB Workshop on Routing & Addressing September 2007

Appendix A. Suggestions for Specific Steps

 At the end of the workshop there was a lively round-table discussion
 regarding specific steps that IETF may consider undertaking towards a
 quick solution development, as well as potential issues to avoid.
 Those steps included:
 o  Finding a home (mailing list) to continue the discussion started
    from the workshop with wider participation.  [Editor's note: Done
    -- This action has been completed.  The list is ram@iab.org.]
 o  Considering a special process to expedite solution development,
    avoiding the lengthy protocol standardization cycles.  For
    example, IESG may charter special design teams for the solution
    investigation.
 o  If a working group is to be formed, care must be taken to ensure
    that the scope of the charter is narrow and specific enough to
    allow quick progress, and that the WG chair be forceful enough to
    keep the WG activity focused.  There was also a discussion on
    which area this new WG should belong to; both routing area ADs and
    Internet area ADs are willing to host it.
 o  It is desirable that the solutions be developed in an open
    environment and free from any Intellectual Property Right claims.
 Finally, given the perceived severity of the problem at hand, the
 workshop participants trust that IAB/IESG/IETF will take prompt
 actions.  However, if that were not to happen, operators and vendors
 would be most likely to act on their own and get a solution deployed.

Appendix B. Workshop Participants

 Loa Anderson (IAB)
 Jari Arkko (IESG)
 Ron Bonica
 Ross Callon (IESG)
 Brian Carpenter (IAB)
 David Conrad (IANA)
 Leslie Daigle (IAB Chair)
 Elwyn Davies (IAB)
 Terry Davis
 Weisi Dong
 Aaron Falk (IRTF Chair)
 Kevin Fall (IAB)
 Dino Farinacci
 Vince Fuller
 Vijay Gill

Meyer, et al. Informational [Page 35] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 Russ Housley (IESG)
 Geoff Huston
 Daniel Karrenberg
 Dorian Kim
 Olaf Kolkman (IAB)
 Darrel Lewis
 Tony Li
 Kurtis Lindqvist (IAB)
 Peter Lothberg
 David Meyer (IAB)
 Christopher Morrow
 Dave Oran (IAB)
 Phil Roberts (IAB Executive Director)
 Jason Schiller
 Peter Schoenmaker
 Ted Seely
 Mark Townsley (IESG)
 Iljitsch van Beijnum
 Ruediger Volk
 Magnus Westerlund (IESG)
 Lixia Zhang (IAB)

Appendix C. Workshop Agenda

 IAB Routing and Addressing Workshop Agenda
             October 18-19
          Amsterdam, Netherlands
 DAY 1: the proposed goal is to collect, as complete as possible, a
 set of scalability problems in the routing and addressing area facing
 the Internet today.
 0815-0900: Welcome, framing up for the 2 days
            Moderator: Leslie Daigle
 0900-1200: Morning session
            Moderator: Elwyn Davies
            Strawman topics for the morning session:
            - Scalability
            - Multihoming support
            - Traffic Engineering
            - Routing Table Size: Rate of growth, Dynamics
              (this is not limited to DFZ, include iBGP)
            - Causes of the growth
            - Pains from the growth
              (perhaps "Impact on routers" can come here?)
            - How big a problem is BGP slow convergence?

Meyer, et al. Informational [Page 36] RFC 4984 IAB Workshop on Routing & Addressing September 2007

 1015-1030: Coffee Break
 1200-1300: Lunch
 1330-1730: Afternoon session: What are the top 3 routing problems
            in your network?
            Moderator: Kurt Erik Lindqvist
 1500-1530: Coffee Break
 Dinner at Indrapura (http://www.indrapura.nl), sponsored by Cisco
  1. ——–

DAY 2: The proposed goal is to formulate a problem statement

 0800-0830: Welcome
 0830-1000: Morning session: What's on the table
            Moderator: Elwyn Davies
            - shim6
            - GSE
 1000-1030: Coffee Break
 1030-1200: Problem Statement session #1: document the problems
            Moderator: David Meyer
 1200-1300: Lunch
 1300-1500: Problem Statement session # 2, cont;
            Moderator: Dino Farinacci
             - Constraints on solutions
 1500-1530: Coffee Break
 1530-1730: Summary and Wrap-up
            Moderator: Leslie Daigle

Appendix D. Presentations

 The presentations from the workshop can be found on
    http://www.iab.org/about/workshops/routingandaddressing

Meyer, et al. Informational [Page 37] RFC 4984 IAB Workshop on Routing & Addressing September 2007

Authors' Addresses

 David Meyer (editor)
 EMail: dmm@1-4-5.net
 Lixia Zhang (editor)
 EMail: lixia@cs.ucla.edu
 Kevin Fall (editor)
 EMail: kfall@intel.com

Meyer, et al. Informational [Page 38] RFC 4984 IAB Workshop on Routing & Addressing September 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Meyer, et al. Informational [Page 39]

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