Network Working Group                                            R. Bush
Internet-Draft                           Internet Initiative Japan, Inc.
Intended status: Standards Track                           March 6, 2009
Expires: September 7, 2009


                        The RPKI/Router Protocol
                    draft-ymbk-rpki-rtr-protocol-01

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Abstract

   In order to formally validate the origin ASes of BGP announcements,



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   routers need a simple but reliable mechanism to receive RPKI
   [I-D.ietf-sidr-arch] or analogous prefix origin data from a trusted
   cache.  This document describes a protocol to deliver validated
   prefix origin data to routers over ssh.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Deployment Structure . . . . . . . . . . . . . . . . . . . . .  3
   3.  Operational Overview . . . . . . . . . . . . . . . . . . . . .  3
   4.  Protocol Data Units (PDUs) . . . . . . . . . . . . . . . . . .  4
     4.1.  Serial Notify  . . . . . . . . . . . . . . . . . . . . . .  4
     4.2.  Serial Query . . . . . . . . . . . . . . . . . . . . . . .  4
     4.3.  Reset Query  . . . . . . . . . . . . . . . . . . . . . . .  5
     4.4.  Cache Response . . . . . . . . . . . . . . . . . . . . . .  5
     4.5.  IPv4 Prefix  . . . . . . . . . . . . . . . . . . . . . . .  6
     4.6.  IPv6 Prefix  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.7.  End of Data  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.8.  Cache Reset  . . . . . . . . . . . . . . . . . . . . . . .  8
     4.9.  Error Report . . . . . . . . . . . . . . . . . . . . . . .  8
     4.10. Fields of a PDU  . . . . . . . . . . . . . . . . . . . . .  9
   5.  Protocol Sequences . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Start or Restart . . . . . . . . . . . . . . . . . . . . . 10
     5.2.  Typical Exchange . . . . . . . . . . . . . . . . . . . . . 10
     5.3.  Cache has Reset  . . . . . . . . . . . . . . . . . . . . . 11
   6.  SSH Transport  . . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Router-Cache Set-Up  . . . . . . . . . . . . . . . . . . . . . 12
   8.  Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   10. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 15
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     13.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16








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1.  Introduction

   In order to formally validate the origin ASes of BGP announcements,
   routers need a simple but reliable mechanism to receive RPKI
   [I-D.ietf-sidr-arch] or analogous formally validated prefix origin
   data from a trusted cache.  This document describes a protocol to
   deliver validated prefix origin data to routers over ssh.

   Section 2 describes the deployment structure and Section 3 then
   presents an operational overview.  The binary payloads of the
   protocol are formally described in Section 4, and the expected PDU
   sequences are described in Section 5.  And the transport protocol is
   described in Section 6.  Section 7 details how routers and caches are
   configured to connect and authenticate.  Section 8 describes likely
   deployment scenarios.  The traditional security and IANA
   considerations end the document.


2.  Deployment Structure

   Deployment of the RPKI to reach routers has a three level structure
   as follows:

   Global RPKI:  The authoritative data of the RPKI are published in a
      distributed set of servers, RPKI publication repositories, e.g.
      the IANA, RIRs, NIRs, and ISPs, see [I-D.ietf-sidr-repos-struct].

   Local Caches:  A local set of one or more collected and verified non-
      authoritative caches.  A relying party, e.g. router or other
      client, MUST have a formally authenticated trust relationship
      with, and a secure transport channel to, any non-authoritative
      cache(s) it uses.

   Routers:  A router fetches data from a local cache using the protocol
      described in this document.  It is said to be a client of the
      cache.  There are mechanisms for the router to assure itself of
      the authenticity of the cache and to authenticate itself to the
      cache.


3.  Operational Overview

   A router establishes and keeps open an authenticated connection to a
   cache with which it has an client/server relationship.  It is
   configured with a semi-ordered list of caches, and establishes a
   connection to the highest preference cache that accepts one.

   Periodically, the router sends to the cache the serial number of the



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   highest numbered data record it has received from that cache, i.e.
   the router's current serial number.  When a router establishes a new
   connection to a cache, or wishes to reset a current relationship, it
   sends a Reset Query.

   The Cache responds with all data records which have serial numbers
   greater than that in the router's query.  This may be the null set,
   in which case the End of Data PDU is still sent.  Note that 'greater'
   must take wrap-around into account, see [RFC1982].

   When the router has received all data records from the cache, it sets
   its current serial number to that of the serial number in the End of
   Data PDU.


4.  Protocol Data Units (PDUs)

   The exchanges between the cache and the router are sequences of
   exchanges of the following PDUs according to the rules described in
   Section 5.

4.1.  Serial Notify

   The cache notifies the router that the cache has new data.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |   reserved = zero   |
   |    0     |    0     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'

4.2.  Serial Query

   Serial Query: The router sends Serial Query to ask the cache for all
   payload PDUs which have serial numbers higher than the serial number
   in the Serial Query.






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   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |   reserved = zero   |
   |    0     |    1     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'

4.3.  Reset Query

   Reset Query: The router tells the cache that it wants to receive the
   total active, current, non-withdrawn, database.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |    reserved = zero  |
   |    0     |    2     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   `-------------------------------------------'

4.4.  Cache Response

   The cache responds with zero or more payload PDUs, the set of all
   data records it has with serial numbers greater than that sent by the
   client router, or all data records if the cache received a Reset
   Query.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |   reserved = zero   |
   |    0     |    3     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   `-------------------------------------------'



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4.5.  IPv4 Prefix

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |        Color        |
   |    0     |    4     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   | Announce |  Prefix  |   Max    |  Data    |
   | Withdraw |  Length  |  Length  |  Source  |
   |   0/1    |   0..32  |   0..32  | RPKI/IRR |
   +-------------------------------------------+
   |                                           |
   |                IPv4 prefix                |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |         Autonomous System Number          |
   |                                           |
   `-------------------------------------------'

   Due to the nature of the RPKI and the IRR, there can be multiple
   identical IPvX PDUs.  Hence the router will likely keep an internal
   ref-count on each IPvX PDU.

   In the RPKI, nothing prevents a signing certificate from issuing two
   identical ROAs, and nothing prohibits the existence of two identical
   route: or route6: objects in the IRR.  In this case there would be no
   semantic difference between the objects, merely a process redundancy.

   In the RPKI, there is also an actual need for what will appear to the
   router as identical IPvX PDUs.  This occurs when an upstream
   certificate is being reissued or a site is changing providers, often
   a 'make and break' situation.  The ROA is identical in the router
   sense, i.e. has the same {prefix, len, max-len, asn}, but has a
   different validation path in the RPKI.  This is important to the
   RPKI, but not to the router.

   It is this possibility of duplication that creates the need for a
   nonce, the Sequence Number, in the IPvX PDUs, so that an Error Report
   PDU can uniquely identify the erroneous PDU.






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4.6.  IPv6 Prefix

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |        Color        |
   |    0     |    6     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   | Announce |  Prefix  |   Max    |  Data    |
   | Withdraw |  Length  |  Length  |  Source  |
   |   0/1    |  0..128  |  0..128  | RPKI/IRR |
   +-------------------------------------------+
   |                                           |
   +---                                     ---+
   |                                           |
   +---            IPv6 prefix              ---+
   |                                           |
   +---                                     ---+
   |                                           |
   +-------------------------------------------+
   |                                           |
   |         Autonomous System Number          |
   |                                           |
   `-------------------------------------------'

4.7.  End of Data

   End of Data: Cache tells router it has no more data for the request.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |   reserved = zero   |
   |    0     |    7     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'




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4.8.  Cache Reset

   The cache may respond to a Serial Query informing the router that the
   cache's serial number is no longer commensurate with that of the
   router.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |    reserved = zero  |
   |    0     |    8     |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   `-------------------------------------------'

4.9.  Error Report

   This PDU is used by either party to report an error to the other.

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |    Error Number     |
   |    0     |    10    |                     |
   +-------------------------------------------+
   |                                           |
   |             Sequence Number               |
   |                                           |
   +-------------------------------------------+
   |                                           |
   ~           Copy of Erroneous PDU           ~
   |                                           |
   +-------------------------------------------+
   |  Length  |                                |
   |    of    |     Arbitrary Text             |
   |   Text   |                                |
   +----------'           of                   |
   |                                           |
   ~           Error Diagnostic Message        ~
   |                                           |
   `-------------------------------------------'








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4.10.  Fields of a PDU

   PDUs contain the following data elements:

   Protocol Version:  A cardinal, currently 0, denoting the version of
      this protocol.

   Sequence Number:  A 32-bit cardinal nonce, not to be confused with a
      Serial Number, constructed by the PDU sender to allow the sender
      to uniquely identify which PDU the receiver is reporting in an
      Error Report PDU.  As the only part of the protocol which is
      asynchronous is the streaming of IPvX PDUs, they are the only PDUs
      needing differentiation using a Sequence Number.  But all PDUs
      include one for simplicity and homogeneity, the additional
      transport cost is negligible.

   Serial Number:  The serial number of the RPKI Cache when this ROA was
      received from the cache's up-stream cache server or gathered from
      the global RPKI.  A cache increments its serial number when
      completing an rcynic from a parent cache.  See [RFC1982] on DNS
      Serial Number Arithmetic for too much detail on serial number
      arithmetic.

   Color:  An arbitrary 16 bit field that might be used in some way.

   Announce/Withdraw:  Whether this PDU announces a new right to
      announce the prefix or withdraws a previously announced right.
      The allowed values are 0 for withdraw and 1 for announce.  A
      withdraw effectively deletes all previously announced IPvX Prefix
      PDUs with the exact same Prefix, Length, Max-Len, ASN, Data
      Source, and Color.

   Prefix Length:  A cardinal denoting the shortest prefix allowed for
      the prefix.

   Max Length:  A cardinal denoting the longest prefix allowed by the
      prefix.  This MUST NOT be less than the Prefix Length element.

   Data Source:  A cardinal denoting the source of the data, e.g. for
      RPKI data, it is 0, for IRR data it is 1.

   Prefix:  The IPv4 or IPv6 prefix of the ROA.

   Autonomous System Number:  ASN allowed to announce this prefix, a 32
      bit cardinal.






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5.  Protocol Sequences

   The sequences of PDU transmissions fall into three conversations as
   follows:

5.1.  Start or Restart

   Cache                         Router
     ~                             ~
     | <----- Reset Query -------- | R requests data
     |                             |
     | ----- Cache Response -----> | C tells R C's serial
     | ------- IPvX Prefix ------> | C sends zero or more
     | ------- IPvX Prefix ------> |   IPv4 and IPv6 Prefix
     | ------- IPvX Prefix ------> |   Payload PDUs
     | ------  End of Data ------> | C sends End of Data
     ~                             ~

   When a transport session is first established, the router sends a
   Reset Query and the cache responds with a data sequence of all data
   it contains.

   This Reset Query sequence is also used in response to the cache
   sending a Cache Reset, the router choosing a new cache, or the router
   fearing it has otherwise lost its way.

   To limit the length of time a cache must keep withdraws, a router
   MUST send either a Serial Query or a Reset Query no less frequently
   than once an hour.  This also acts as a keep alive at the application
   layer.

5.2.  Typical Exchange

   Cache                         Router
     ~                             ~
     | -------- Notify ----------> |  (optional)
     |                             |
     | <----- Serial Query ------- | R requests data
     |                             |
     | ----- Cache Response -----> | C tells R C's serial
     | ------- IPvX Prefix ------> | C sends zero or more
     | ------- IPvX Prefix ------> |   IPv4 and IPv6 Prefix
     | ------- IPvX Prefix ------> |   Payload PDUs
     | ------  End of Data ------> | C sends End of Data

   The cache server SHOULD send a notify PDU with its current serial
   number when the cache's serial changes, with the expectation that the
   router MAY then issue a serial query earlier than it otherwise might.



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   This is analogous to DNS NOTIFY in [RFC1996].  The cache SHOULD rate
   limit Serial Notifies to no more frequently than one per minute.

   When the transport layer is up and either a timer has gone off in the
   router, or the cache has sent a Notify, the router queries for new
   data by sending a Serial Query, and the router sends all data newer
   than the serial in the Serial Query.

   To limit the length of time a cache must keep old withdraws, a router
   MUST send either a Serial Query or a Reset Query no less frequently
   than once an hour.

5.3.  Cache has Reset

   Cache                         Router
     ~                             ~
     | <-----  Serial Query ------ | R requests data
     | ------- Cache Reset ------> | C has lost serial
     |                             |
     | <------ Reset Query ------- | R requests new data
     |                             |
     | ----- Cache Response -----> | C tells R C's serial
     | ------- IPvX Prefix ------> | C sends zero or more
     | ------- IPvX Prefix ------> |   IPv4 and IPv6 Prefix
     | ------- IPvX Prefix ------> |   Payload PDUs
     | ------  End of Data ------> | C sends End of Data
     ~                             ~

   The cache may respond to a Serial Query informing the router that the
   cache's serial number is no longer commensurate with that of the
   router.  The most likely cause is that the cache was completely
   restarted when or since the transport session to the router was down.
   When a router receives this, the router SHOULD attempt to connect to
   any more preferred caches in its cache list.  If there are no more
   preferred caches it MUST issue a Reset Query and get an entire new
   load from the cache


6.  SSH Transport

   The transport layer session between a router and a cache carries the
   binary Protocol Data Units (PDUs) in a persistent SSH session.

   To run over SSH, the client router first establishes an SSH transport
   connection using the SSH transport protocol, and the client and
   server exchange keys for message integrity and encryption.  The
   client then invokes the "ssh-userauth" service to authenticate the
   application, as described in the SSH authentication protocol RFC 4252



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   [RFC4252].  Once the application has been successfully authenticated,
   the client invokes the "ssh-connection" service, also known as the
   SSH connection protocol.

   After the ssh-connection service is established, the client opens a
   channel of type "session", which results in an SSH session.

   Once the SSH session has been established, the application invokes
   the application transport as an SSH subsystem called "rpki-rtr".
   Subsystem support is a feature of SSH version 2 (SSHv2) and is not
   included in SSHv1.  Running this protocol as an SSH subsystem avoids
   the need for the application to recognize shell prompts or skip over
   extraneous information, such as a system message that is sent at
   shell start-up.

   It is assumed that the router and cache have exchanged keys out of
   band by some reasonably secured means.


7.  Router-Cache Set-Up

   A cache has the public authentication data for each router it is
   configured to support.

   A router may be configured to peer with a selection of caches, and a
   cache may be configured to support a selection of routers.  So each
   must have the name of each peer and authentication data for each.  In
   addition, in a router, this list has a non-unique preference value
   for each server in order of preference.  The client router attempts
   to establish a session with each potential serving cache in
   preference order, and then starts to load data from the highest
   preference cache to which it can connect and authenticate.  The
   router's list of caches has the following elements:

   Preference:  A cardinal denoting the router's preference to use that
      cache, the lower the value the more preferred.

   Name:  The IP Address or fully qualified domain name of the cache.

   Key:  The public ssh key of the cache.

   MyKey:  The private ssh key of this client.

   As caches can not be rigorously synchronous, a client which changes
   servers can not combine data from different parent caches.
   Therefore, when a lower preference cache becomes available, if
   resources allow, it would be prudent for the client to start a new
   buffer for that cache's data, and only switch to those data when that



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   buffer is fully up to date.


8.  Deployment Scenarios

   For illustration, we present three likely deployment scenarios.

   Small End Site:  The small multi-homed end site may wish to outsource
      the RPKI cache to one or more of their upstream ISPs.  They would
      exchange authentication material with the ISP using some out of
      band mechanism, and their router(s) would connect to one or more
      up-streams' caches.  The ISPs would likely deploy caches intended
      for customer use separately from the caches with which their own
      BGP speakers peer.

   Large End Site:  A larger multi-homed end site might run one or more
      caches, arranging them in a hierarchy of client caches, each
      fetching from a serving cache which is closer to the global RPKI.
      They might configure fall-back peerings to up-stream ISP caches.

   ISP Backbone:  A large ISP would likely have one or more redundant
      caches in each major PoP, and these caches would fetch from each
      other in an ISP-dependent topology so as not to place undue load
      on the global RPKI publication infrastructure.

   Experience with large DNS cache deployments has shown that complex
   topologies are ill-advised as it is easy to make errors in the graph,
   e.g. not maintaining a loop-free condition.

   Of course, these are illustrations and there are other possible
   deployment strategies.  It is expected that minimizing load on the
   global RPKI servers will be a major consideration.

   To keep load on global RPKI services from unnecessary peaks, it is
   recommended that primary caches which load from the distributed
   global RPKI not do so all at the same times, e.g. on the hour.
   Choose a random time, perhaps the ISP's AS number modulo 60 and
   jitter the inter-fetch timing.


9.  Security Considerations

   As this document describes a security protocol, many aspects of
   security interest are described in the relevant sections.  This
   section points out issues which may not be obvious in other sections.






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   Cache Validation:  In order for a collection of caches as described
      in Section 8 to guarantee a consistent view, they need to be given
      consistent trust anchors to use in their internal validation
      process.  Distribution of a consistent trust anchor is assumed to
      be out of band.

   Cache Peer Identification:  As the router initiates an ssh transport
      session to a cache which it identifies by either IP address or
      fully qualified domain name, a DNS or address spoofing attack
      could make the correct cache unreachable.  No session would be
      established, as the authorization keys would not match.

   Transport Security:  The RPKI relies on object, not server or
      transport, trust.  I.e. the IANA root trust anchor is distributed
      to all caches through some out of band means, and can then be used
      by each cache to validate certificates and ROAs all the way down
      the tree.  The inter-cache relationships are based on this object
      security model, hence the inter-cache transport can be lightly
      protected.

      But this protocol document assumes that the routers can not do the
      validation cryptography.  Hence the last link, from cache to
      router, is secured by server authentication and transport level
      security.  This is dangerous, as server authentication and
      transport have very different threat models than object security.

      So the strength of the trust relationship and the transport
      between the router(s) and the cache(s) are critical.  You're
      betting your routing on this.

      While we can not say the cache must be on the same LAN, if only
      due to the issue of an enterprise wanting to off-load the cache
      task to their upstream ISP(s), locality, trust, and control are
      very critical issues here.  The cache(s) really SHOULD be as
      close, in the sense of controlled and protected (against DDoS,
      MITM) transport, to the router(s) as possible.  It also SHOULD be
      topologically close so that a minimum of validated routing data
      are needed to bootstrap a router's access to a cache.


10.  Glossary

   The following terms are used with special meaning:

   Global RPKI:  The authoritative data of the RPKI are published in a
      distributed set of servers at the IANA, RIRs, NIRs, and ISPs, see
      [I-D.ietf-sidr-repos-struct].




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   Non-authorative Cache:  A coalesced copy of the RPKI which is
      periodically fetched/refreshed directly or indirectly from the
      global RPKI using the [rcynic] protocol/tools

   Cache:  The rcynic system is used to gather the distributed data of
      the RPKI into a validated cache.  Trusting this cache further is a
      matter between the provider of the cache and a relying party.

   Serial Number:  A 32-bit monotonically increasing, cardinal which
      wraps from 2^32-1 to 0.  It denotes the logical version of a
      cache.  A cache increments the value by one when it successfully
      updates its data from a parent cache or from primary RPKI data.
      As a cache is rcynicing, new incoming data, and implicit deletes,
      are marked with the new serial but MUST not be sent until the
      fetch is complete.  A serial number is not commensurate between
      caches, nor need it be maintained across resets of the cache
      server.  See [RFC1982] on DNS Serial Number Arithmetic for too
      much detail on serial number arithmetic.


11.  IANA Considerations

   This document requests the IANA to create a registry for PDU types.

   This document requests the IANA to create a registry for Error Codes.

   In addition, a registry for Version Numbers would be needed if new
   Version Number is defined in a new RFC.

   Note to RFC Editor: this section may be replaced on publication as an
   RFC.


12.  Acknowledgments

   The author wishes to thank Rob Austein, Steve Bellovin, Rex Fernando,
   Russ Housley, Pradosh Mohapatra, Sandy Murphy, Megumi Ninomiya,
   Robert Raszuk, John Scudder, Ruediger Volk, David Ward, and Bert
   Wijnen.


13.  References

13.1.  Normative References

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              August 1996.




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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4252]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, January 2006.

   [rcynic]   Austein, R., "rcynic protocol",
              <https://subvert-rpki.hactrn.net/rcynic/>.

13.2.  Informative References

   [I-D.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-04 (work in
              progress), November 2008.

   [I-D.ietf-sidr-repos-struct]
              Huston, G., Loomans, R., and G. Michaelson, "A Profile for
              Resource Certificate Repository Structure",
              draft-ietf-sidr-repos-struct-01 (work in progress),
              October 2008.

   [RFC1996]  Vixie, P., "A Mechanism for Prompt Notification of Zone
              Changes (DNS NOTIFY)", RFC 1996, August 1996.


Author's Address

   Randy Bush
   Internet Initiative Japan, Inc.
   5147 Crystal Springs
   Bainbridge Island, Washington  98110
   US

   Phone: +1 206 780 0431 x1
   Email: randy@psg.com















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