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Network Working Group                                         R. Whittle
Internet-Draft                                          First Principles
Intended status: Experimental                             March 06, 2010
Expires: September 7, 2010


         DRTM - Distributed Real Time Mapping for Ivip and LISP
                     draft-whittle-ivip-drtm-01.txt

Abstract

   Distributed Real Time Mapping (DRTM) is intended for Ivip, but may be
   useful for other Core-Edge Separation solutions to the routing
   scaling problem, such as LISP.  End-user networks - or other
   organizations they appoint - control the mapping of each or their one
   or more micronets (ranges of "edge" space with a single mapping) via
   sending commands to the organizations from whom they lease this
   space.  This is conveyed to all ITRs which need it in "real-time"
   such as a second or two, globally.  There is no need for any single
   set of servers to handle all the mapping updates, or to store all the
   mapping databases for all the MABs (Mapped Address Block) of "edge"
   space.  Networks with ITRs use purely caching Resolving query servers
   (QSRs), in contrast to previous Ivip arrangements which required them
   to run a query server which contained the real-time updated full
   mapping database for all MABs.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on September 7, 2010.



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Copyright Notice

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology and overall structure  . . . . . . . . . . . . . .  9
   3.  Development stages . . . . . . . . . . . . . . . . . . . . . . 15
     3.1.  Stage 1 - DITRs only . . . . . . . . . . . . . . . . . . . 15
     3.2.  Stage 2 - Add ITRs in ISPs and EUNs, with purely
           caching QSRs . . . . . . . . . . . . . . . . . . . . . . . 17
     3.3.  Stage 3 (optional) - ISPs/EUNs have non-caching QSRs . . . 20
       3.3.1.  X  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
       3.3.2.  Y  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
       3.3.3.  Z  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
   4.  (continuation from the previous sub-section) . . . . . . . . . 24
   5.  Please refer to the RRG message for the remaining material . . 25
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   8.  Informative References . . . . . . . . . . . . . . . . . . . . 28
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 29

















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1.  Introduction

   (This ID was written in a hurry - so it is lacks sub-headings and has
   rough edges.  Nonetheless, it provides a good description of the new
   mapping distribution system for Ivip, which I think is also
   applicable to LISP.)

   Distributed Real Time Mapping (DRTM) is a complete revision of the
   structure of Ivip's mapping distribution system.  Prior to DRTM's
   announcement on the ITRF Routing Research Group mailing list (2010-
   02-26:
   http://www.ietf.org/mail-archive/web/rrg/current/msg06128.html) and a
   short-lived plan of 2010-02-07, Ivip relied on a single global
   inverted-tree structured system of Replicators, which fanned out all
   the mapping changes for all the MABs (Mapped Address Blocks) in the
   Ivip system.  The Replicator system, and its accompanying Missing
   Payload Servers, enabled tens or hundred of thousands of full
   database query servers (QSDs) in ISP and other networks to maintain a
   full, real-time-updated copy of the mapping for all MABs.  There were
   concerns about the practicality of running and depending upon this
   global, synchronised, full-database mapping structure.

   DRTM makes this system unnecessary.  Perhaps some elements of this
   older system, as described in "Fast Payload Replication mapping
   distribution for Ivip" [I-D.whittle-ivip-fpr] may be useful for
   optional purposes in Ivip as noted in that ID.

   In DRTM, there is no need for any query server to store the full
   mapping database of all MABs.  When an ISP or an end-user network
   wishes to install ITRs, it does not need to run any query server
   which stores the full mapping database of any MABs.  Instead, the ISP
   or end-user network installs one - or ideally two or three - Resolver
   Query Servers (QSRs).  QSRs are caching devices and which pass on
   queries which can't be answered by the mapping they have cached to
   one of several typically nearby Authoritative Query Servers (QSAs)
   which are outside the ISP's network.  These QSAs are typically close
   enough (several thousand km, or less in densely developed areas) to
   send mapping replies without significant delays or risk of packet
   loss.

   Companies which operate MABs are known as MABOCs (MAB Operating
   Companies).  MABOCs run - or contract other organizations (DSOCs -
   DITR-site Operating Companies) to run - a number of widely dispersed
   sites for operate DITRs (Default ITRs in the DFZ).  These DITRs are
   required to tunnel packets sent from hosts in networks without ITRs.
   DITRs are caching ITRs closely connected to QSAs which are sent a
   real-time feed of mapping updates for all the MABs the site supports.




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   At east DITR-site, this QSA - or one or more similar QSAs - are also
   able to accept and respond to queries from QSRs in (typically) nearby
   ISP networks.  Thus, assuming there is no suitable cached mapping, a
   query originates in an ITR and goes directly (or indirectly, through
   one or more levels of optional caching query servers - QSCs) to one
   of the several QSRs in the ISP.  The QSR creates a second map request
   and sends it to one of the typically nearby QSAs which is
   authoritative for the MAB the queried address is within.  The QSA
   responds to the QSR and the QSR responds directly (or indirectly,
   through QSCs) to the ITR.  Since the QSAs are typicaly close enough
   for all this to happen within a few tens of milliseconds, the ITR
   buffers the traffic packet and tunnels it to the ETR specified in the
   mapping as soon as the mapping arrives.

   The ITR caches this mapping, which covers a micronet of address space
   - which may extend beyond the single IPv4 address or the single IPv6
   /64 which was in the ITRs map request.  Likewise, the QSR and any
   intermediate QSCs cache this mapping.  This means that other ITRs in
   this ISP, or in EUNs (end-user networks) served by this ISP, will
   sometimes or often be able to obtain the mapping they need from this
   cached information, without the QSR needing to query a QSA.

   The longer the caching time, the less often the ITRs, any
   intermediate QSCs and the QSR will need to send a query.  The longer
   caching time increases the memory requirements of these devices - but
   memory and CPU power in COTS (Commercial Off The Shelf) servers is
   exceedingly inexpensive.

   The caching time does not impede the real-time ability of the EUN or
   their appointee to control the tunneling behavior of all ITRs which
   are handling packets addressed to one of the EUN's micronets.  The
   mechanism for this is as follows:

   When a QSA receives a mapping update for a micronet whose mapping it
   recently ("recently" in this discussion means within the previous 10
   minutes, or whatever the map reply caching time is) sent to one or
   more QSRs, it sends each such QSR a Cache Update message.  This is
   secured by the nonce in the QSR's original map request.

   The QSR updates its cache and performs a similar algorithm - to send
   a similar Cache Update message to the one or more queriers to which
   it recently send the mapping for this micronet.  The queriers may be
   ITRs, or caching QSCs.  In the case of a QSC, the QSC receives the
   Cache Update and performs the same algorithm for its queriers, which
   may be ITRs or further QSCs.

   Cache Updates are expected to be securely acknowledged.  Cache
   Updates will be sent on the above basis for as long as the caching



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   time of the original map reply - they do not extend this caching
   time.  After the caching time expires - or just before it does - any
   ITRs which are still handling traffic packets for the micronet will
   request mapping for this micronet again.  This will cause the QSR to
   query the authoritative QSA again, and the process will continue as
   before.

   An additional mechanism is required to protect against the caching of
   stale mapping which is not updated as just described due to the
   upstream device (a QSC, the QSR or the QSA) becoming unreachable or
   being rebooted.  The querier (an ITR, QSC or QSR) must, within some
   time period such as ten seconds or so, check that its source of
   mapping is alive and has not been rebooted.  If this cannot be
   established, then all cached mapping from this upstream query server
   should be flushed, forcing the ITR and upstream query servers to gain
   fresh, up-to-date mapping again.  This may involve using a different
   QSC, QSR or QSA.

   Since MABOCs and any DSOCs they use to run their DITRs and QSAs
   ensure that multiple QSAs are always active (they need them for their
   DITRs anyway) then the system has no single point of failure.  A QSR
   may need to access a more distant QSA, but in general it will use one
   of several "nearby" QSAs and so gain mapping information in a
   sufficiently short time, with high enough reliability that ITRs will
   not delay traffic packets to a degree which is noticeable to users or
   which materially affects the application protocols (except perhaps
   NTP).

   Most MABOCs will be in the business of leasing out the SPI space in
   their MABs to thousands or perhaps millions or billions of EUNs - for
   non-mobile portability, multihoming and inbound TE and for TTR
   Mobility.  The remainder of MABOCs will be large EUNs which run their
   own MABOC for their own sites alone.  Assuming this SPI space - these
   micronets - is to be used at any ISP in the world, MABOCs will be
   motivated to ensure that total path lengths from the sending host, to
   the nearest (in BGP terms) DITR, and then to the ETR are kept as
   short as possible.  The best way they can do this is to have
   multiple, widely dispersed, DITRs so that no matter where the sending
   host and the ETR are located, there will be a DITR not too far away
   from the shortest path between these two.

   As described below, ISPs do not absolutely need ITRs, but as SPI use
   becomes more common, they will be motivated to install their own ITRs
   - which means they need to install one, or ideally two or three,
   QSRs.  It is not absolutely assured that each MABOC will run (or
   contract a DSOC to run for them) widely distributed DITR-sites.
   However, in general MABOCs will want to do this.  This typically
   widespread distribution of DITR-sites, each with a QSA which can be



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   used by any ISP's QSR, plus the mechanisms by which QSRs identify the
   closest such QSAs, ensures that typically, the ITRs will not need to
   wait more than a few tens of milliseconds for their mapping, even if
   no QSC or the QSR it relies on has this mapping cached.

   With DTRM, the MABOCs - the organizations which are providing SPI
   space to their customers (unless the MABOC is itself the only user of
   its space) are the ones deriving revenue from this new form of
   scalable portability, multihoming and inbound TE.  It is the MABOCs
   who need to make the first investments, and who will hopefully derive
   the first profits - not the ISPs.  (Of course a MABOC may be an ISP -
   but the key point is that MABOCs need not be ISPs.)  MABOCs invest in
   the DITR infrastructure and with little extra effort provide QSAs at
   those sites for nearby ISPs (and EUNs too) to use if they want ITRs.
   MABOCs have a keen interest in ISPs and EUNs installing their own
   ITRs, since this takes the load off their DITRs.

   ISPs (and EUNs with ITRs) need only install ITRs, a few QSRs and
   optionally some QSCs to get their own ITRs handling packets for all
   MABs.  The MABOCs typically "go the distance" by reaching out across
   the Earth with their DITR-sites.  ISPs do not need to pay anything to
   use each MABOC's, or each DSOC's QSAs.  If the MABOCs are properly
   supporting global portability and mobility for the SPI space they
   lease to their customers, then the ISPs will find that there are QSAs
   close enough for there to be reliable and low-delay responses to the
   queries sent out by their QSRs.

   QSAs get a robust, secure, real-time feed of mapping updates for all
   the MABs they handle.  This is practical and scalable, since each
   DSOC has a finite number of sites, such as 5 to 30, or in principle
   perhaps a hundred or so - and the secure pushing of mapping to all
   these sites can be done however they like, including with the use of
   private network links.

   The DSOC needs to receive real-time mapping updates from the one or
   more MABOCs whose MABs its DITR-sites handle.  This too is a finite
   problem with practical solutions, since the DSOC only needs to work
   with its chosen number of MABOCs.  Within the MABOCs, the same
   principles apply - they can build their own internal mechanisms for
   accepting mapping change commands from EUNs or whoever the EUN
   appoints to control the mapping of their micronets.  They can then
   pass this to the DSOC, via secure, real-time and ideally redundant
   mechanisms.  No MABOC or DSOC needs to handle the entire set of
   MABOCs, so their systems are not required to scale beyond what is
   practical and desirable for them.  Very large numbers of DSOCs, and
   therefore of QSAs, can be securely, automatically and scalably
   handled by each QSR, using a DNS-based discovery mechanism described
   below.



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   To the extent that scaling difficulties present barriers to any one
   MABOC or any one DSOC handling large numbers of micronets, these can
   be overcome by there being larger numbers of MABOCs and DSOCS.

   As long as there are no more than 100k to perhaps 200k MABs, and
   assuming each MAB contains at least dozens of micronets (many will
   have hundreds of thousands or perhaps millions) then the system will
   be perfectly scalable and will serve very large numbers of EUNs
   without excessive load on the DFZ control plane.

   A crucial part of the scalability of this system is the ability of
   the QSR to automatically discover the "nearest" two or three QSAs for
   each MAB.  Since multiple MABs will generally be run by one MABOC,
   and multiple MABOCs will usually have their MABs supported by the
   DITR-sites of a single DSOC, it follows that there will be many less
   DSOCs than there are MABs.  Whether a DSOC runs a handful of DITR
   sites or hundreds, the QSRs will still be able to reliably find the
   two or three "nearest" QSAs at these sites.

   When fully developed, DRTM will contain some additional mechanisms to
   aid scaling, load balancing and robustness.  Firstly, map replies and
   Cache Updates from QSAs will optionally contain additional
   information advising the querying QSR to what extent this QSA should
   be used for further queries - with suggestions on which other ones
   should be used as alternatives.  This will enable one DSOC's system
   to dynamically load-share the burden of QSR queries across its QSAs.

   Sometimes, a QSR may need to query a distant QSA - such as one on
   another continent.  This will be a failing of the DSOC/MABOC to
   properly reach out to the ISPs - not a failure of the architecture.
   MABOCs earn money from their MABs, so to remain competitive against
   other MABOCs, they will need to run a good DITR system and handle
   mapping queries from all QSRs as quickly and reliably as possible.

   It will be technically possible for a MABOC to run its one or more
   MABs with a single DITR, at a single DITR-site - while providing a
   single QSA for all the QSRs in the world to send their queries to.
   This would not be a good service for its SPI-leasing customers
   compared to the best services of other MABOCs, but it does show how a
   company could start up in business as a MABOC with simply a DITR-site
   and some address space.  DITRs are most likely to be, initially at
   least, COTS servers.  However a DITR is not just a server in a data-
   center - it needs direct connection to other routers at an Internet
   exchange since it needs to advertise the one or more MABs it serves
   to the DFZ and be able to forward encapsulated packets to other DFZ
   routers.

   DRTM is firstly a new approach to CES mapping distribution, secondly



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   a new approach for Ivip which is not subject to some important
   concerns which applied to earlier approaches, and thirdly it is a
   model of introducing a new form of address space and DITR service for
   scalable routing without ISPs needing to make any initial investment.















































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2.  Terminology and overall structure

   DRTM involves new protocols, servers with new functions and
   organizations playing new roles - with some flexibility.  In order to
   keep the IDs as short as possible, please refer to the Ivip Glossary
   [I-D.whittle-ivip-glossary]for fuller descriptions of the following
   terms: DITR - Default ITR in the DFZ; DSOC - DITR-site Operating
   Company; EUN - End-User Network; ITFH - ITR Function in sending Host;
   ITR - Ingress Tunnel Router; MAB - Mapped Address Block; MABOC - MAB
   Operating Company; Mapping; Mapping Distribution System; Micronet;
   Mobility; MN - Mobile Node; Multihoming; Portability; QSA -
   Authoritative Query Server; QSC - Caching Query Server; QSD (obsolete
   term); QSR - Resolving Query Server; Replicator (obsolete term); SPI
   - Scalable Provider Independent address space; TE - Traffic
   Engineering; TTR Mobility architecture; TTROC - TTR Operating
   Company; and, UAB - User Address Block.  The Glossary also contains
   the history of Ivip's mapping system, but this can be ignored by
   anyone who is not familiar with Ivip before mid-March 2010.

   For a general overview of Ivip, including its goals and non-goals,
   please refer to the Ivip-arch ID [I-D.whittle-ivip-arch].

   Figure 1 illustrates the minimal configuration for DRTM.  All ITRs
   are assumed to be in an ISP network, and there are no QSCs.  The ISP
   network has two QSRs.  One is theoretically sufficient, but two,
   three or perhaps more should be used for robustness and load sharing.
   The query-response paths are shown between the ITRs and the QSRs, and
   between QSR-1 and the two nearest QSAs of two separate sets of DITR-
   sites, run by two separate DSOCs A and B. The links (perhaps via
   private networks) between the sites of DSOC-A are shown as "AA.." and
   likewise as "BB.." for DSOC-B




















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       Inside the ISP          .          Outside the ISP, two sets
                               .          of DITR-sites A and B,
                               .          showing the two closest
    Multiple ITRs     Two QSRs .          QSAs in of each set.
                               .
                               .                    [QSA-A4]
                               .                           A
    [ITR-1]------------[QSR-1]--------------[QSA-A5]AAAAAAAAAAA<->
            \         /        \                            A
             \       /         .\--------------[QSA-B9]B    A
              \     /          . \                      B   A
    [ITR-2]------------[QSR-2] .  \---------[QSA-A6]AAAAAAAAA
                               .   \                      B
                               .    \-------------[QSA-B8]BBBB<->
                               .                          B
                               .                  [QSA-B7]BBBBBBB<->

   Figure 1: Minimal structure for DRTM.

   Figure 2 depicts the direction of flow of messages between the
   querier and the upstream query server.  This is true for the pair
   "ITR -> QSR" and for the pair "QSR -> QSA".  Not shown in Figure 1 is
   one or more levels of optional QSC caching query servers.  The same
   pattern of messages applies to the pair "QSC-downstream -> QSC-
   upstream", and to the pairs "ITR -> QSC" and "QSC -> QSR".  At
   present, there are no plans for any intermediate servers between QSRs
   and QSAs.  Inside each DITR-site, the DITRs are assumed to either
   query directly a QSA, or if there are multiple DITRs, they may do so
   via QSCs.

   The internal operations of DITR sites are not our primary concern,
   since these are inherently scalable and are a matter only for the
   DSOCs and MABOCs who run them.  Our primary concern is with the
   scaling, robustness, performance and security by which ISPs (or any
   EUN which has its own ITRs and QSRs) can work with sufficient QSAs
   for the ITRs to be able to handle packets addressed to all the MABs
   in the entire Ivip system.

   Note that an ITR has one or a few upstream query servers, and so does
   a QSC.  In later work, some automatic discovery methods by which ITRs
   and QSCs can discover their upstream query servers will be proposed.

   Although Figure 1 depicts QSR-1 as having just four upstream query
   servers, in reality, there may be dozens or even hundreds of DSOC
   systems such as A and B, and each QSR will automatically discover
   (before it needs to send any Map Request queries) the addresses of
   two or three of the nearest QSAs in each such system of DSOCs.  QSR-2
   would do the same in principle as QSR-1.  Perhaps it would use



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   identical QSAs as QSR-1, or perhaps it would use somewhat or
   completely different QSAs.  The latter would provide greater
   resilience in the event of some QSAs becoming unreachable or going
   down.

   In Figure 2, the messages are shown in the order they would occur.
   All these messages are currently assumed to be UDP packets, but
   perhaps SCTP could be used as an option

   Future work will involve describing how ITRs automatically discover,
   via the one or more QSRs theirs queries go directly or indirectly to,
   what the current complete set of MABs is.  As described in a separate
   section below, QSRs automatically discover this from a DNS-based
   mechanism.  This could be quite a large body of information, but
   there needs to be a reliable and automated way that all ITRs know the
   complete set of MABs.  They need this to advertise all these MABs in
   the local routing system, and so they only attempt to get mapping
   for, and tunnel to an ETR, those packets whose destination addresses
   match one of the MABs.

   When an ITR receives a traffic packet whose destination address
   matches a MAB, but not any micronet it currently has cached mapping
   for, it buffers the traffic packet and sends a Map Request containing
   the destination address, which is an SPI ("edge") address.  The Map
   Request contains the ITR's address in the source field, and it also
   contains a nonce which the ITR generated and uses only for this Map
   Request.

   This Map Request may go to the QSR directly (as shown in Figure 1) or
   it may go via one or more layers of QSCs before it reaches one of the
   network's QSRs.  If it goes directly to the QSR, this is a single Map
   Request.  If it goes to a QSC-n, that is one Map Request.  Assuming
   QSC-n does not have the mapping cached, then QSC-n will generate a
   separate Map Request, with a separate nonce, and send this to one of
   its upstream query servers, which may be either another QSC or one of
   the network's QSRs.  While the two Map Requests are for the same SPI
   address, they are separate Map Requests, with separate queriers and
   upstream query servers.  The two Map Requests have separate nonces.
   Similarly, the Map Replies and the Acknowledgements are separate for
   the two legs of the path: "ITR --- QSC-n" and "QSC-n --- QSR".











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          Querier:                     Upstream query server:
          ITR or                       QSR or
          QSR                          QSA

               Map Request ----------->
                            (<------------ Map Request Ack)
                             <------------ Map Reply
             Map Reply Ack ----------->

     Later, perhaps:

                             <------------ Cache Update
          Cache Update Ack ----------->


   Figure 2: Direction of flow of various messages.

   The typical operation, for instance from ITR-1 to QSR-1 in Figure 1,
   would be:

   ITR-1 sends Map Request to QSR-1.

   The diagram shows a Map Request Ack being sent from QSR-1 to ITR-1.
   Whether this will be necessary is TBD.  Normally, the Map Reply will
   come back to the ITR-1 soon enough that the retry time-constant can
   be short enough for rapidly trying to send a second request, perhaps
   to QSR-2.  If QSR-2 has the mapping already cached, the it will be
   able to send the Map Reply very rapidly - such as within a few
   milliseconds.  Since the all the ITRs and QSRs are in the same ISP
   network (in this example at least) the delay times between them
   sending and receiving packets will be a sub-millisecond or a few
   milliseconds at most.

   If QSR-1 already has the mapping cached, it will send back the Map
   Reply.  If not, it will send a separate Map Request to one of the
   QSAs, and when that is replied to, it will send the Map Reply back to
   ITR-1.

   It may not be necessary for the requester - ITR-1 in this example, to
   acknowledge the receipt of the Map Reply, but such a message is shown
   here.  If this is part of the protocol, then QSR-1 would time-out
   after a few milliseconds of not receiving it, and resend the same Map
   Reply, at least for a few attempts before giving up.

   In this exchange, the Map Request included a nonce unique to this Map
   Request, and this is used to secure the Map Reply, and any Map
   Request Ack. In a fully developed version of the protocol, the Map
   Request may also have a sequence number generated by ITR-1, which is



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   returned in the Map Reply and any Map Request Ack, so it can more
   easily index into the information it needs to relate these to.
   Likewise, the Map Reply and the Cache Update (to be described below)
   may have sequence numbers generated by the sender - QSC-1 in this
   example - to aid it in keeping a track of the Map Reply Ack and Cache
   Update Acks which result, and which would include copies of these
   sequence numbers.

   At a later time, but within the caching time specified in the Map
   Reply message, if the upstream query server is notified of a mapping
   change to the micronet whose mapping was returned in the Map Reply
   message, then that upstream query server (QSR-1 in this example) will
   generate a Cache Update message.

   The most common change to the mapping of a micronet is a change to
   its ETR address.  In this case, the Cache Update specifies the
   micronet (its start and either its end, or its length) and then
   specifies the new ETR address.  The Cache Update carries the nonce
   and any sequence number contained in the original Map Request which
   lead to the Map Reply with this micronet's previous mapping.

   The querier, ITR-1 in this example, simply updates its cache and from
   that point on, will tunnel any packets whose destination address
   matches this micronet to the new ETR address.

   There are other changes to mapping than simply changing the ETR
   address of a micronet.  The ETR address in the new mapping could be
   zero (0.0.0.0 in IPv4).  That is processed as described above, but
   the ITR interprets it as an instruction to drop any packets whose
   destination address matches this micronet.

   Another change is that the EUN or their appointee could command the
   MABOC to delete this micronet, and perhaps at the same time to make
   its space become part of another one or more micronets.  For instance
   the existing range could be split into two, or used as part of a
   bigger micronet.  Also, the new micronets may not have boundaries at
   the boundaries of the old one.  While it is possible to imagine
   complex Cache Update commands to convey all this information, it is
   almost certainly the case that the best approach is to simply send a
   special Cache Update message to the effect that the cached mapping
   for this micronet should be deleted (AKA "flushed") from the cache of
   the querier.  In this example, the querier is an ITR.  If the querier
   was a QSC, or a QSR, then it would generate similar Cache Update
   messages to the one or more downstream devices which it recently
   (inside the current caching time) send mapping for this micronet.

   When a micronet is deleted from the cache of an ITR, the next
   matching packet (and there may be none, for a long time, or perhaps



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   ever) will cause the ITR to start afresh and request mapping for the
   destination address of the new traffic packet.  Since its upstream
   query servers will just have had their cached mapping for this
   micronet deleted, then unless one of them has already requested and
   received mapping which matches this new packet's address, then a Map
   Request message will be sent by a QSR to a QSA, and the reply will
   soon come back, as described above, giving the ITR the up-to-date
   mapping for whatever new micronet this destination address matches.
   To implement this "delete cached mapping" command without any special
   flags in the message, it would suffice to define an ETR address such
   as 0.0.0.1 to have this specific meaning.

   The fully developed DRTM protocol will specify timeouts for retrying
   these communications.  For instance, if an ITR sends a packet to its
   first choice of three upstream query servers and doesn't receive a
   response within 50ms, it would send a separate Map Request, with a
   separate nonce, either to the same upstream query server, or probably
   better to another one.  For instance, if, as in Figure 1, the
   upstream query servers were QSR-1 and QSR-2, and if the first query
   went to QSR-1, then the retry would go to QSR-2.  Similarly, if QSR-1
   sent a Map Request to QSA-A6 and didn't get back a reply in some
   predetermined time, it would send a fresh Map Request to QSA-A5.

   The time constants for these retries need to be set with care.  Also
   there needs to be some limit to the number of retries, with error
   reporting if no mapping can be found.  In the case of a QSR which
   can't get a reply from any of the QSAs it has currently chosen for a
   given MAB or set of MABs, this would be a reason for it to recheck,
   via the DNS mechanism, which QSAs are authoritative for this MAB and
   to choose some other ones to try instead.

   Future work will include describing how a QSR chooses generally
   "nearby" QSAs - such as by sending a null Map Request and timing how
   long after this the Map Reply arrives - whilst also considering any
   instructions in the Map Reply about whether to continue to send
   requests to this QSA, and perhaps with suggestions as to which
   alternative QSAs to use.  (The suggested QSA addresses or FQDNs must
   match one already returned by the DNS mechanism.)  As part of this,
   the QSR would determine the typical time it takes this QSR to
   respond.  If a significantly longer time elapsed after a real Map
   Request, without a Map Reply arriving, then this would constitute a
   time-out and be cause for sending a second Map Request to an
   alternative QSA.








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3.  Development stages

3.1.  Stage 1 - DITRs only

   For non-mobile services, one or more MABOCs set themselves up in
   business, with one or more MABs, some method of accepting map change
   commands from their EUN customers (or whoever the EUN appoints to
   control the mapping of the SPI space they lease, divide into
   micronets etc.) and with at least one, but probably half a dozen or
   more DITRs at DITR-Sites around the world.  For simplicity in this
   example I will assume the MABOC runs its own DITR sites, so it is its
   own DSOC.

   A MABOC doesn't absolutely need more than one DITR or multiple DITRs
   at sites all over the world.  They can still make their MAB work with
   a single DITR or DITRs only in a given region.  If, for instance, the
   MABOC's SPI-using EUN customers for some reason always use their SPI
   space via ISPs in Europe, then for the purely DITR purposes, it would
   be fine for the MABOC to run a handful of DITRs just in European
   sites.

   If a Sending Host (SH) was in Adelaide (Australia) and was sending
   packets to a host in a micronet which is mapped to an ETR accessible
   via an ISP in Dusseldorf, then it will be fine if these packets
   traverse most of the DFZ in their raw SPI-addressed state, to be
   tunneled to the ETR by a DITR in Amsterdam, London or Zurich.

   However, later in the development phase when the MABOC wants to
   encourage ISPs and EUNs all over the world to run their own ITRs,
   then it really needs to do better than just have DITR-Sites in
   Europe.  Also, its a second-rate service to only have DITRs in a
   given region - since at least some of its European companies might
   want to use their space in branch offices in Asia, North and South
   America etc.  If the sending host in Adelaide was in an EUN or ISP
   with ITRs, then it would be best if the caching MR those ITRs depend
   on can send queries to a DITR-Site-QSD a lot closer than Europe.

   DRTM doesn't absolutely ensure that the closest QSA or closest
   several QSAs to any QSR in the world will be "nearby".  Firstly, as
   just noted, there may only be a single DITR site with a single QSA.
   This would be a pretty lousy service by the MABOC, but perhaps it
   would suit a start-up company, or be suitable for a smaller EUN who
   has converted its own PI prefix into a single MAB and is now using it
   as SPI space, being its own MABOC.

   If the MABOC company is providing a good service to its customers (or
   to itself, it this is a EUN only using the space for itself), it will
   ensure it has DITRs widely scattered around the Net and the nearest



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   DITR-site - and therefore the nearest QSA - will be "nearby" or "near
   enough to generally provide a fast response with little chance of the
   query or response packets being lost" to QSRs all over the world.

   If a MR in Dallas Fort-Worth finds that the closest DITR-Site is in
   London, then its not disastrous.  When I wrote the original version
   of this DRTM material on 2010-02-26, there was a 104ms RTT to London
   via Houston (I think "IAH"), LA and Washington DC.  As long as the
   query or response packet isn't dropped, this shouldn't cause much
   complaint about slow starts to communications.  But it is not ideal,
   and it would be much better if the nearest DITR-Site-QSD was in San
   Jose, which should be a RTT of 40msec or probably much less (though
   on 2010-02-26 I got a traceroute from DFW to San Jose via Amsterdam
   and London with a RTT of 172ms!).

   For Stage 1 - DITRs only - as long as the DITR-Sites are reasonably
   close to wherever the SPI space is being used, and as long as they
   can handle the traffic loads, then the only other things which are
   needed are:



      1.  The DITRs need to have a tunneling and PMTUD protocol which is
          compatible with the ETR functionality of whatever the SPI-
          using EUNs (SPI-leasing customers of this MABOC) are using on
          their PA addresses.  For now, I am assuming that the ETR
          functionality can be provided by the MABOC for free - such as
          being downloaded from somewhere and run on a COTS server of
          the SPI-EUN - or, ideally, be implemented on a router which
          the SPI-using EUN already owns.

      2.  The ISPs these EUNs connect with must allow them to emit
          packets using these SPI addresses as source addresses.

   In this simple arrangement multiple EUNs EUN-0000 to EUN-0999 are
   customers of this MABOC-X and are using micronets in one or more of
   MABOC-X's MABs.  Maybe another set of EUNs EUN-1xxx are leasing space
   from another MABOC-Y.  Assuming any EUN-0xxx is only using SPI space
   from MABOC-X, then their ETR functions only have to be compatible
   with the DITRs run by MABOC-X.  So far, there's no absolute need for
   standardization.

   Ideally there would be RFC standards for ITRs and ETRs and all the
   DITRs in the world would support this one standard.  Then EUNs could
   lease SPI space from multiple MABOC companies and know that the one
   ETR function could handle packets tunneled by the ITRs run by their
   two or more different MABOCs.




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   The real need for standardization of ITR and ETR functions comes when
   parties other than MABOCs are running ITRs, and/or if parties other
   than MABOC customers are running ETRs.  In the latter case, perhaps
   an ISP runs an ETR which connects to the networks of multiple SPI-
   using EUNs.  They don't want to be mucking around with different ETRs
   for customers using different MABOCs, and therefore relying on
   different sets of technically different DITRs.

3.2.  Stage 2 - Add ITRs in ISPs and EUNs, with purely caching QSRs

   This Stage 2 is the main part of DRTM.  As far as I know, it should
   suffice for Ivip scaling to the largest imaginable numbers of MABs,
   SPI-using EUNs (including billions of TTR Mobile MNs) and so billions
   of micronets.

   Stage 3 goes beyond the primary purpose of DRTM to allow for
   arrangements which have something in common with previous approaches
   to Ivip's mapping system, but not the global inverted tree of
   Replicators.  Specifically, Stage 3 in some ways resembles the so-far
   only partly documented, short-lived "Plan-C" arrangement of
   2010-02-17 as described in the History of Ivip mapping systems at the
   end of Ivip-glossary.  There may be no reason to go beyond this Stage
   2 arrangement, since as far as I know it will scale very well.  Stage
   3 is documented because it is possible and there may be some benefits
   for certain ISPs or other networks to pursue it.  The Stage 3
   arrangements are absolutely not required of any participant in Ivip -
   and perhaps they will never be developed or deployed.

   In all stages the MABOCs charge their SPI-leasing customers for the
   use these customers make of their DITRs - or rather, the use of these
   DITRs by packets sent to the SPI addresses of each of their SPI-
   leasing customers.  If the MABOC uses another company - a DSOC - to
   run its DITRs, then the DSOC needs to monitor DITR usage and present
   statistics to the MABOC, both for the total uses of DITRs by packets
   addressed to MABs run by this MABOC and in greater detail by
   micronet, so the MABOC can charge its SPI-using EUN customers
   accordingly.

   The MABOCs will also charge their customers for each mapping change -
   probably a few cents or similar.  This is in part to deter EUNs from
   making frivolous and repeated mapping changes, and also to help pay
   for the cost of running DITR sites and QSAs, and for fanning out the
   mapping change to all the DITR sites which support this MABOC's MABs.

   The MABOCs would be happier if some, most or ideally all of the
   tunneling of the traffic addressed to their SPI-leasing customer EUNs
   was done by someone else's ITRs: the ITRs of the EUNs or ISPs of the
   sending hosts (SHs).  To this end, *perhaps* the MABOCs would want to



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   pay ISPs and large EUNs to run ITRs covering their MABs.

   (There is an unresolved question regarding a scenario in which an EUN
   very frequently changes the mapping of its micronets, and this
   results in very frequent mapping updates being sent to QSRs and ITRs
   in ISPs whose ITRs are tunneling packets to this micronet.  The ISP
   may be unhappy about this high level of updates giving their QSR and
   ITRs a workout.  Should the MABOC, which is charging money for these
   updates, use some of that revenue keep ISPs happy to receive and act
   on these frequent mapping updates?)

   As the use of SPI space becomes more widespread, the ISPs themselves
   would want to have their own ITRs.  If an ISP has one or more
   customers with SPI space (either with their own ETRs, or using an
   ISP-supplied ETR) and there are other customers of this ISP sending
   packets to these SPI addresses, then the ISP would prefer to have its
   own ITR to tunnel these directly, rather than let the packets go out
   the upstream link, to a DITR, and return in encapsulated form via
   that link.

   If the ISP had its own ITR, at least to cover the MABs of these SPI-
   using customers, it could reduce the traffic on its expensive
   upstream links - and provide faster packet delivery times.

   For this discussion, I will assume that an ISP installing an ITR will
   make that ITR advertise, in its internal routing system, all the MABs
   of the complete Ivip system.  This is not necessarily the case, but
   it makes the discussion less complex to assume this.

   So the ISP wishes to run one or more ITRs which cover all MABs.

   Also, individual EUNs using this ISP may wish to run their own ITRs
   so their outgoing packets addressed to SPI addresses will definitely
   takes the shortest path to the ETR, rather than going by some
   potentially longer path to the "nearest" DITR.  (After seeing a
   Dallas Fort-Worth to San Jose traceroute go via Amsterdam and London,
   I am keen to put the word _nearest_ in inverted commas if I mean
   "nearest in terms of the current state of the DFZ"!)

   This is for EUNs on conventional PI space, PA space or SPI space.
   The question of an EUN having its own ITRs, or wanting its ISP to
   have ITRs, is independent of whether the EUN is using conventional PI
   or PA space, or is using SPI space via an ETR.  In Ivip, ITRs can be
   on SPI addresses.  They can also be implemented in sending hosts on
   any global unicast address (PI, PA or SPI).  (At present, I don't
   have arrangements for ITRs to be behind NAT, but it could be done
   with a different protocol between the ITR and the upstream query
   server - QSC or QSR - it queries.)



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   In all cases, these ITRs need a "local" QSR to send their queries to.
   (I don't plan for ITRs to directly query QSAs, which are typically
   outside the ISP's network, at DITR-sites.  It would probably be
   technically possible, since the ITR -> QSC/QSR query protocol would
   similar or identical to the QSC -> QSC, QSC -> QS and the QSR -> QSA
   protocols.)

   So in all the above circumstances, to accommodate one to hundreds or
   thousands of ITRs in an ISP's network (including in the EUN customers
   of this ISP) then the ISP should install two or more QSRs.  (I will
   refer to ISPs doing this, but the same principles apply to any EUN
   which wants to run a QSR itself.)

   These ITRs need to be configured - or ideally automatically discover
   - the two or more QSRs of this ISP, or the upstream QSCs if these are
   used.  I haven't worked on how to do this, but I am sure it will be
   possible.

   In some networks the ITRs would query the QSRs directly.  In others,
   they would query a QSC first, which handles a bunch of ITRs and which
   queries either the QSR directly, or the QSR via one or more other
   QSCs.  One way or another, each ITR needs at least two upstream QSCs
   or QSRs to query.  It would typically send a query to one, and if
   nothing came back within some time like 100ms, it would send a fresh
   Map Request query for the same address (with a different nonce) to
   the other upstream query server.

   Then the task of designing the DRTM system is to devise a method by
   which these two QSRs know at least two (ideally nearby) QSAs to query
   for each of the MABs in the entire Ivip system.  This can be done by
   a new DNS-based system I describe in a section below.  There could be
   other, better, ways - but this will do for now.

   This is a highly scalable arrangement.

   The MABOCs directly or indirectly push their own mapping, for their
   own MABs, in real-time, highly reliably, to all their DITR-Sites.
   They need to do this to have full-database query servers in the same
   rack (or even the same server) as their DITRs.  Theoretically, DITRs
   could rely on a distant full database query server, but this would be
   pretty sloppy - and the DITR is surely going to be getting a lot of
   packets, so it makes sense for the MABOC to push its full mapping for
   each MAB to a QSA query server at each DITR-Site which is full-
   database for all the MABs covered by that DITR-Site.

   So it is not much extra work to use this fresh, reliable, feed of
   real-time mapping to drive one or more a publicly accessible QSAs at
   each DITR-site.



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   For the MABOC or whoever runs the DITR-Site (the DSOC), it will be a
   lot less effort easier answering queries and so allow other
   organizations' ITRs to tunnel a bunch of packets, than for this DITR-
   Site's DITRs to tunnel the same packets.

   The ITRs, QSCs and QSRs in the ISP and its EUNs do not store the
   entire mapping database, or the full mapping database of any of the
   MABs.  The QSRs can boot up very quickly, as described below - they
   only need to discover the current set of MABs and the DITR-Site-QSDs
   they will query for each MAB.  (If the QSR was full-database for one
   or more MABs - as mentioned below in Stage 3, which is entirely
   optional - it would need to download snapshots as described in Ivip-
   fpr.  These snapshots could be quite bulky if there were billions of
   micronets, as there will be with widely deployed TTR Mobility.)

   The DITR-Site can scale well by spreading the load of traffic for
   multiple MABs (including potentially every MAB in the whole Ivip
   system, if for some reason one DITR-Site was working for all the
   MABOCs) over multiple separate DITRs, each of which advertises to the
   DFZ a subset of these MABs.  A single MAB could, in principle, be
   split between two DITRs if necessary, but each advertising half, or a
   quarter of it.  The DITRs would presumably be either acting as DFZ
   routers, advertising MABs and emitting packets back over the same
   link, or perhaps another link, to be forwarded by other DFZ routers -
   or they could be behind a single DFZ router.  In the latter case, if
   four DITRs advertised a quarter of a MAB, then their common router
   should aggregate these into a single shorter prefix of the original
   MAB for its DFZ neighbours.

   The overall load of traffic can be shared by creating more DITR-Sites
   in the areas where they are most needed.  Larger DITR-Sites - such as
   those which are not operated by a single MABOC, but which serve the
   MABs of multiple MABOCs - including perhaps every MAB in the Ivip
   system - would also offer scaling benefits by sharing the various
   peaks in traffic for particular MABs in the system.

   It is possible that the ITRs of a given ISP and its dependent EUNs
   might not advertise, into their local routing systems, all the MABs -
   but in this discussion, I assume that they do.  Then, the QSRs they
   use need to know how to send queries to (ideally) nearby QSAs for
   every MAB in the system.  More on this in the section below on the
   new DNS-based mechanism.

3.3.  Stage 3 (optional) - ISPs/EUNs have non-caching QSRs

   This stage may never be developed or implemented - because I suspect
   it may never be needed.  Nonetheless, it exists as a technical
   possibility and is described here in case it turns out to be useful.



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   This involves some things which people have concerns about - real-
   time pushing of mapping changes to query servers which are full-
   database for some or all MABs.  In Stage 2, which is what DRTM is
   intended to achieve, there is a need to push real-time mapping to
   query servers.  However, these are the QSA query servers at DITR
   sites, and the pushing only happens within or between the DITR-sites
   operated by a single DSOC - though the DSOC has to get the real-time
   mapping changes from as many MABOCs as it chooses to run DITRs for.
   The fact that the number of DITR-sites is limited, such as to dozens
   or at the very most a few hundred, makes the system much less open to
   objections about scaling problems.  Also, the fact that the real-time
   pushing largely or only occurs in a single organizations system,
   albeit a globally distributed system, means that it is more scalable
   and secure than trying to build a single system to be shared by many
   organizations, which was the plan for Ivip until late February 2010.

   A further reason this Stage 2 pure DRTM arrangement is more scalable
   is that no DITR-site and so no DSOC has to carry the whole set of
   MABs.  To whatever extent there are scaling problems or other
   objections to this real-time distribution of mapping to multiple
   QSAs, they can be avoided in total by the natural result of each
   system operating to its limit, and there being multiple independent
   systems operating in parallel to meet the total demand.

   Stage 3 resembles - or could be the same as - what I described on the
   RRG list on 2010-02-07 ("Plan-C" in the history at the end of Ivip-
   glossary).  With Stage 2 looking so powerful and scalable, with no
   need for QSRs to get a feed of mapping updates for any of the MABs -
   there may still be some situations I have neither foreseen or ruled
   out the existence of yet where it would be desirable to have the QSR
   get a full feed for real-time mapping changes for some MABs.  This
   means a QSR, or probably all the QSRs in a given ISP or EUN with
   ITRs, would then be "full-database" for one or more MABs.  In
   principle, this could be extended to the QSRs being full database for
   all MABs.  This would be "Plan C" as noted above.

   Maybe there would be a scenario where it would make sense for all
   MABs - I can't rule it out, but I can't think of one either, other
   than as noted above with networks being on passenger jets, ocean
   liners, Antarctica or the Moon.

   In Stage 3, each QSR could use three methods to get its mapping.  Of
   the three methods mentioned below, it could use X alone, X and Y, Y
   alone, or Z alone.  (I am using X, Y and Z to avoid confusion with
   Plans A to D or Stages 1 to 3.  Sorry this is complex - but I am are
   trying to anticipate a variety of usage situations.)

   X and Y are as described in draft-whittle-ivip-fpr-00 (Plan-B, 2010-



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   01-18) and msg05975 (Plan-C - 2010-02-06).  Z is newly described
   here.

3.3.1.  X

   The QSR (initially described as a QSD) could get direct feeds of
   "Replicator format" mapping update packets directly from servers
   which generate this at various (ideally) nearby DITR-Sites.  The QSR
   will need to get two feeds for each MAB, so this will involve a bunch
   of feeds for a set MABs from one DITR-Site, and a similar bunch of
   feeds for the same MABs from another DITR-Site.  This is assuming
   that the local DITR-Sites are in similar sets, each set serving the
   MABs of one or more MABOCs.  Then there will need to be pairs of
   feeds from other DITR-Sites, a pair for each other set of MABs.

3.3.2.  Y

   As per Plan-B and Plan-C, the QSR could get feeds via a system of
   Replicators which form a fully or partially meshed flooding system,
   accepting feeds from multiple DITR-Sites, and fanning the sum of the
   mapping updates they contain.  This should be the full set of updates
   for all MABs, unless all packets with a particular payload somehow
   don't make it to any of the Replicators.

   In either X or Y, the QSRs will occasionally need to query one or
   more "Lost Payload" servers to get mapping update payloads they
   somehow missed.  With larger sets of missing payloads, the QSR would
   need to re-sync its databases for one or more MABs, which involves
   downloading a snapshot file and bringing it up to date, as described
   in draft-whittle-ivip-fpr-00.

3.3.3.  Z

   The MR sets up some kind of secure, two-way, link to one or probably
   better two (ideally) nearby DITR-sites, for a given MAB or set of
   MABs.  Assuming, for the purpose of discussion, that the entire set
   of MABs is covered by five DITR-Sites, then this means the MR will
   set up ten such sessions - using two DITR-sites per subset of MABs,
   for redundant supply of mapping changes for a given subset of the
   MABs.

   Each such link should enable a suitable server at the DITR-site to
   quickly and reliably push all mapping changes to the QSR, and for the
   QSR to be sent any changes again, if it somehow didn't get some of
   them.  I guess TLS-protected SCPT might be a good protocol for this -
   RFC 3436.  TCP would be OK, but it would be blocked for a moment by
   the loss of a single packet.




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   Theoretically, the QSR needs a single two-way link from a DITR-site
   server which handles a set of MABs, but it should have two such
   links, with two such DITR-sites for each subset of MABs - for Justin
   (Just In Case).















































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4.  (continuation from the previous sub-section)

   (Due to time constraints I haven't figured out how to make this part
   be at the end of the previous sub-section 3.3.)

   Also, it would be possible for a QSR to use the Z arrangement to pass
   on the mapping information to other QSRs.

   In this way, an QSR could get real-time mapping feeds for one or more
   MABs and so be "full database" for these, while still sending queries
   to QSAs for addresses matching other MABs.

   This enables the operators to have some flexibility.  Say the QSR was
   in New Zealand, and there were some MABs G, H and I which for some
   reason it wanted to be full-database for.  Maybe these MABs are run
   by MABOCs who lease the space to SPI-using EUNs for which this ISP
   wants to respond very quickly to for each new communication session.
   There may be some other MABs J, K and L for which the ISP doesn't
   mind so much if the session establishment takes a few tens of
   milliseconds longer, by relying on some reasonably "nearby" DITR-
   Site-QSDs.  Maybe some MABs are used primarily or solely for SPI-
   using EUNs who are almost always in a distant country, and for which
   this ISP's customers hardly ever send packets.  There's no problem
   having these MABs as usual, on a query-basis, like J, K and L - but
   the ISP can still, for whatever reason, choose to have the its QSRs
   running full mapping databases for selected MABs G, H and I.

























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5.  Please refer to the RRG message for the remaining material

   Due to time constraints this ID does not yet have all the material it
   should have.  Please refer to the latter parts of this RRG message:
   http://www.ietf.org/mail-archive/web/rrg/current/msg06128.html for
   several sections, there labelled: "Stage 2 needs a DNS-based system
   so TRs (QSRs) can find DITR-Site-QSDs (QSAs)"; "4 - With TTR
   Mobility" and "5 - DTRM for LISP".

   In this RRG message "DITR-Site-QSD" means the same thing as "QSA" in
   this ID.  Likewise, in the message, "MR" means the same thing as
   "QSR" in this ID.







































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6.  Security Considerations

   TBD.
















































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7.  IANA Considerations

   TBD.
















































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8.  Informative References

   [I-D.irtf-rrg-recommendation]
              Li, T., "Recommendation for a Routing Architecture",
              draft-irtf-rrg-recommendation-03 (work in progress),
              December 2009.

   [I-D.whittle-ivip-arch]
              Whittle, R., "Ivip (Internet Vastly Improved Plumbing)
              Architecture", draft-whittle-ivip-arch-03 (work in
              progress), March 2010.

   [I-D.whittle-ivip-fpr]
              Whittle, R., "Fast Payload Replication mapping
              distribution for Ivip", draft-whittle-ivip-fpr-01 (work in
              progress), March 2010.

   [I-D.whittle-ivip-glossary]
              Whittle, R., "Glossary of some Ivip and scalable routing
              terms", draft-whittle-ivip-glossary-01 (work in progress),
              March 2010.






























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Author's Address

   Robin Whittle
   First Principles

   Email: rw@firstpr.com.au
   URI:   http://www.firstpr.com.au/ip/ivip/












































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