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Versions: 00 01 02 03 04 05 06 draft-ietf-sidr-rpki-rtr

Network Working Group                                            R. Bush
Internet-Draft                                                       IIJ
Intended status: Standards Track                              R. Austein
Expires: January 7, 2011                                             ISC
                                                            July 6, 2010


                        The RPKI/Router Protocol
                    draft-ymbk-rpki-rtr-protocol-06

Abstract

   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 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].

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, and it may not be
   published except as an Internet-Draft.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 7, 2011.



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Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Deployment Structure . . . . . . . . . . . . . . . . . . . . .  4
   3.  Operational Overview . . . . . . . . . . . . . . . . . . . . .  4
   4.  Protocol Data Units (PDUs) . . . . . . . . . . . . . . . . . .  5
     4.1.  Serial Notify  . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Serial Query . . . . . . . . . . . . . . . . . . . . . . .  6
     4.3.  Reset Query  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  Cache Response . . . . . . . . . . . . . . . . . . . . . .  7
     4.5.  IPv4 Prefix  . . . . . . . . . . . . . . . . . . . . . . .  8
     4.6.  IPv6 Prefix  . . . . . . . . . . . . . . . . . . . . . . .  9
     4.7.  End of Data  . . . . . . . . . . . . . . . . . . . . . . .  9
     4.8.  Cache Reset  . . . . . . . . . . . . . . . . . . . . . . . 10
     4.9.  Error Report . . . . . . . . . . . . . . . . . . . . . . . 10
     4.10. Fields of a PDU  . . . . . . . . . . . . . . . . . . . . . 11
   5.  Protocol Sequences . . . . . . . . . . . . . . . . . . . . . . 12
     5.1.  Start or Restart . . . . . . . . . . . . . . . . . . . . . 12
     5.2.  Typical Exchange . . . . . . . . . . . . . . . . . . . . . 13
     5.3.  No Incremental Update Available  . . . . . . . . . . . . . 14
     5.4.  Cache has No Data Available  . . . . . . . . . . . . . . . 14
   6.  SSH Transport  . . . . . . . . . . . . . . . . . . . . . . . . 15
   7.  Router-Cache Set-Up  . . . . . . . . . . . . . . . . . . . . . 15
   8.  Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 16
   9.  Error Codes  . . . . . . . . . . . . . . . . . . . . . . . . . 17
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   11. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   13. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 19
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     14.2. Informative References . . . . . . . . . . . . . . . . . . 20



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   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20


















































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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.  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 a 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.

   When the cache updates its database, it sends a Notify message to
   every currently connected router.  This is a hint that now would be a
   good time for the router to poll for an update, but is only a hint.
   The protocol requires the router to poll for updates periodically in
   any case.

   Strictly speaking, a router could track a cache simply by asking for
   a complete data set every time it updates, but this would be very
   inefficient.  The serial number based incremental update mechanism
   allows an efficient transfer of just the data records which have
   changed since last update.  As with any update protocol based on
   incremental transfers, the router must be prepared to fall back to a
   full transfer if for any reason the cache is unable to provide the
   necessary incremental data.  Unlike some incremental transfer
   protocols, this protocol requires the router to make an explicit
   request to start the fallback process; this is deliberate, as the
   cache has no way of knowing whether the router has also established
   sessions with other caches that may be able to provide better
   service.


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.











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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     |                     |
   +-------------------------------------------+
   |                                           |
   |                Length=12                  |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               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.

   The cache replies to this query with a Cache Response PDU
   (Section 4.4) if the cache has a record of the changes since the
   serial number specified by the router.  If there have been no changes
   since the router last queried, the cache responds with an End Of Data
   PDU.  If the cache does not have the data needed to update the
   router, perhaps because its records do not go back to the Serial
   Number in the Serial Query, then it responds with a Cache Reset PDU
   (Section 4.8).

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |   reserved = zero   |
   |    0     |    1     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=12                 |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'



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4.3.  Reset Query

   Reset Query: The router tells the cache that it wants to receive the
   total active, current, non-withdrawn, database.  The cache responds
   with a Cache Response PDU (Section 4.4).

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

4.4.  Cache Response

   Cache Response: The cache responds with zero or more payload PDUs.
   When replying to a Serial Query request (Section 4.2), the cache
   sends the set of all data records it has with serial numbers greater
   than that sent by the client router.  When replying to a Reset Query,
   the cache sends the set of all data records it has; in this case the
   withdraw/announce field in the payload PDUs MUST have the value 1
   (announce).

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














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4.5.  IPv4 Prefix

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |        Color        |
   |    0     |    4     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=20                 |
   |                                           |
   +-------------------------------------------+
   |          |  Prefix  |   Max    |  Data    |
   |  Flags   |  Length  |  Length  |  Source  |
   |          |   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.  A router MUST be prepared to receive multiple
   identical record announcements and MUST NOT consider a record to have
   been deleted until it has received a corresponding number of
   withdrawals or a reset is performed Hence the router will likely keep
   an internal reference 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.

   The lowest order bit of the Flags field is 1 for an announcement and
   0 for a withdrawal.




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4.6.  IPv6 Prefix

   0          8          16         24        31
   .-------------------------------------------.
   | Protocol |   PDU    |                     |
   | Version  |   Type   |        Color        |
   |    0     |    6     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=32                 |
   |                                           |
   +-------------------------------------------+
   |          |  Prefix  |   Max    |  Data    |
   |  Flags   |  Length  |  Length  |  Source  |
   |          |  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     |                     |
   +-------------------------------------------+
   |                                           |
   |                 Length=12                 |
   |                                           |
   +-------------------------------------------+
   |                                           |
   |               Serial Number               |
   |                                           |
   `-------------------------------------------'




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4.8.  Cache Reset

   The cache may respond to a Serial Query informing the router that the
   cache cannot provide an incremental update starting from the serial
   number specified by the router.  The router must decide whether to
   issue a Reset Query or switch to a different cache.

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

4.9.  Error Report

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

   The Error Number is described in Section 9.

   If the error is not associated with any particular PDU, the Erroneous
   PDU field should be empty and the Length of Encapsulated PDU field
   should be zero.

   The diagnostic text is optional, if not present the Length of Error
   Text field should be zero.  If error text is present, it SHOULD be a
   string in US-ASCII, for maximum portability; if non-US-ASCII
   characters are absolutely required, the error text MUST use UTF-8
   encoding.


















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

4.10.  Fields of a PDU

   PDUs contain the following data elements:

   Protocol Version:  An ordinal, currently 0, denoting the version of
      this protocol.

   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.

   Length:  A 32 bit ordinal which has as its value the count of the
      bytes in the entire PDU, including the eight bytes of header which
      end with the length field.





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

   Flags:  The lowest order bit of the Flags field is 1 for an
      announcement and 0 for a withdrawal, whether this PDU announces a
      new right to announce the prefix or withdraws a previously
      announced right.  A withdraw effectively deletes one previously
      announced IPvX Prefix PDU with the exact same Prefix, Length, Max-
      Len, ASN, Data Source, and Color.

   Prefix Length:  An ordinal denoting the shortest prefix allowed for
      the prefix.

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

   Data Source:  An ordinal 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 ordinal.


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 confirms request
     | ------- 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
     |                             |   and sends new serial
     ~                             ~

   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 when the router receives a



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   Cache Reset, chooses a new cache, or fears that it has otherwise lost
   its way.

   To limit the length of time a cache must keep the data necessary to
   generate incremental updates, 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 confirms request
     | ------- 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
     |                             |   and sends new serial
     ~                             ~

   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.
   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 cache 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.













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5.3.  No Incremental Update Available

   Cache                         Router
     ~                             ~
     | <-----  Serial Query ------ | R requests data
     | ------- Cache Reset ------> | C cannot supply update
     |                             |   from specified serial
     | <------ Reset Query ------- | R requests new data
     | ----- Cache Response -----> | C confirms request
     | ------- 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
     |                             |   and sends new serial
     ~                             ~

   The cache may respond to a Serial Query with a Cache Reset, informing
   the router that the cache cannot supply an incremental update from
   the serial number specified by the router.  This might be because the
   cache has lost state, or because the router has waited too long
   between polls and the cache has cleaned up old data that it no longer
   believes it needs, or because the cache has run out of storage space
   and had to expire some old data early.  Regardless of how this state
   arose, the cache replies with a Cache Reset to tell the router that
   it cannot honor the request.  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.

5.4.  Cache has No Data Available

   Cache                         Router
     ~                             ~
     | <-----  Serial Query ------ | R requests data
     | ---- Error Report PDU ----> | C cannot supply update
     ~                             ~

   Cache                         Router
     ~                             ~
     | <-----  Reset Query ------- | R requests data
     | ---- Error Report PDU ----> | C cannot supply update
     ~                             ~

   The cache may respond to either a Serial Query or a Reset Query
   informing the router that the cache cannot supply any update at all.
   The most likely cause is that the cache has lost state, perhaps due
   to a restart, and has not yet recovered.  While it is possible that a
   cache might go into such a state without dropping any of its active



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   sessions, a router is more likely to see this behavior when it
   initially connects and issues a Reset Query while the cache is still
   rebuilding its database.

   When a router receives this kind of error, the router SHOULD attempt
   to connect to any other caches in its cache list, in preference
   order.  If no other caches are available, the router MUST issue
   periodic Reset Queries until it gets a new usable 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
   [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.  Each must
   have the name of, and authentication data for, each each peer.  In



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   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:  An ordinal 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
   buffer is fully up to date.

   When a client loses connectivity to the cache it is currently using,
   or otherwise decides to switch to a new cache, it SHOULD retain the
   data from the previous cache and only switch to using the data from
   the new cache once it has fully synchronized with it.  It should do
   this regardless of whether it has chosen a different cache or
   established a new connection to the previous cache.  However, a
   configurable timer MUST be provided to bound how long it will retain
   the "stale" data.


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.







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   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.  Error Codes

   This section contains a preliminary list of error codes.  The authors
   expect additions to this section during development of the initial
   implementations.  Eventually, these error codes will probably need to
   reside in an IANA registry.

   0: Reserved.

   1: Internal Error:  The party reporting the error experienced some
      kind of internal error unrelated to protocol operation (ran out of
      memory, a coding assertion failed, et cetera).

   2: No Data Available:  The cache believes itself to be in good
      working order, but is unable to answer either a Serial Query or a
      Reset Query because it has no useful data available at this time.
      This is likely to be a temporary error, and most likely indicates
      that the cache has not yet completed pulling down an initial
      current data set from the global RPKI system after some kind of
      event that invalidated whatever data it might have previously held
      (reboot, network partition, etcetera).





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10.  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.

   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:  The router initiates an ssh transport
      session to a cache, which it identifies by either IP address or
      fully qualified domain name.  Be aware that 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.






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11.  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].

   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 ordinal 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.


12.  IANA Considerations

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

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

   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.


13.  Acknowledgments

   The authors wish to thank Steve Bellovin, Rex Fernando, Russ Housley,
   Pradosh Mohapatra, Keyur Patel, Sandy Murphy, Megumi Ninomiya, Robert



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   Raszuk, John Scudder, Ruediger Volk, David Ward, and Bert Wijnen.


14.  References

14.1.  Normative References

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

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

14.2.  Informative References

   [I-D.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-06 (work in
              progress), March 2009.

   [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.


Authors' Addresses

   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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   Rob Austein
   Internet Systems Consortium
   950 Charter Street
   Redwood City, CA  94063
   USA

   Email: sra@isc.org












































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