[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 RFC 6092

IPv6 Operations                                         j. woodyatt, Ed.
Internet-Draft                                                     Apple
Intended status: Informational                            March 26, 2010
Expires: September 27, 2010


Recommended Simple Security Capabilities in Customer Premises Equipment
            for Providing Residential IPv6 Internet Service
                draft-ietf-v6ops-cpe-simple-security-10

Abstract

   This document makes specific recommendations to the makers of devices
   that provide "simple security" capabilities at the perimeter of
   local-area IPv6 networks in Internet-enabled homes and small offices.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   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 September 27, 2010.

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



woodyatt               Expires September 27, 2010               [Page 1]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   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
     1.1.  Special Language . . . . . . . . . . . . . . . . . . . . .  4
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Basic Sanitation . . . . . . . . . . . . . . . . . . . . .  6
     2.2.  Internet Layer Protocols . . . . . . . . . . . . . . . . .  6
     2.3.  Transport Layer Protocols  . . . . . . . . . . . . . . . .  6
   3.  Detailed Recommendations . . . . . . . . . . . . . . . . . . .  7
     3.1.  Stateless Filters  . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Connection-free Filters  . . . . . . . . . . . . . . . . .  9
       3.2.1.  Internet Control and Management  . . . . . . . . . . .  9
       3.2.2.  Upper-layer Transport Protocols  . . . . . . . . . . .  9
       3.2.3.  UDP Filters  . . . . . . . . . . . . . . . . . . . . . 10
       3.2.4.  6to4 Tunnels . . . . . . . . . . . . . . . . . . . . . 11
       3.2.5.  IPsec and Internet Key Exchange (IKE)  . . . . . . . . 11
     3.3.  Connection-oriented Filters  . . . . . . . . . . . . . . . 12
       3.3.1.  TCP Filters  . . . . . . . . . . . . . . . . . . . . . 12
       3.3.2.  SCTP Filters . . . . . . . . . . . . . . . . . . . . . 16
       3.3.3.  DCCP Filters . . . . . . . . . . . . . . . . . . . . . 19
       3.3.4.  Level 3 Multihoming Shim Protocol for IPv6 (SHIM6) . . 21
     3.4.  Passive Listeners  . . . . . . . . . . . . . . . . . . . . 21
     3.5.  Management Applications  . . . . . . . . . . . . . . . . . 22
   4.  Summary of Recommendations . . . . . . . . . . . . . . . . . . 23
   5.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 29
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 29
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 30
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 31
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 32
     A.1.  draft-ietf-v6ops-cpe-simple-security-00 to
           draft-ietf-v6ops-cpe-simple-security-01  . . . . . . . . . 33
     A.2.  draft-ietf-v6ops-cpe-simple-security-01 to
           draft-ietf-v6ops-cpe-simple-security-02  . . . . . . . . . 33
     A.3.  draft-ietf-v6ops-cpe-simple-security-02 to
           draft-ietf-v6ops-cpe-simple-security-03  . . . . . . . . . 33
     A.4.  draft-ietf-v6ops-cpe-simple-security-03 to
           draft-ietf-v6ops-cpe-simple-security-04  . . . . . . . . . 34
     A.5.  draft-ietf-v6ops-cpe-simple-security-04 to
           draft-ietf-v6ops-cpe-simple-security-05  . . . . . . . . . 34



woodyatt               Expires September 27, 2010               [Page 2]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


     A.6.  draft-ietf-v6ops-cpe-simple-security-05 to
           draft-ietf-v6ops-cpe-simple-security-06  . . . . . . . . . 35
     A.7.  draft-ietf-v6ops-cpe-simple-security-06 to
           draft-ietf-v6ops-cpe-simple-security-07  . . . . . . . . . 36
     A.8.  draft-ietf-v6ops-cpe-simple-security-07 to
           draft-ietf-v6ops-cpe-simple-security-08  . . . . . . . . . 36
     A.9.  draft-ietf-v6ops-cpe-simple-security-08 to
           draft-ietf-v6ops-cpe-simple-security-09  . . . . . . . . . 36
     A.10. draft-ietf-v6ops-cpe-simple-security-09 to
           draft-ietf-v6ops-cpe-simple-security-10  . . . . . . . . . 36
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 37








































woodyatt               Expires September 27, 2010               [Page 3]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


1.  Introduction

   Some IPv6 gateway devices that enable delivery of Internet services
   in residential and small office settings are augmented with 'simple
   security' capabilities as described in the Informational document
   "Local Network Protected for IPv6" [RFC4864].

   The principle goal of these capabilities is to improve security of
   the IPv6 Internet without increasing the perceived complexity for
   users who just want to accomplish useful work.  However, there is a
   constructive tension between the desires of users for transparent
   end-to-end connectivity on the one hand, and the need for local-area
   network administrators to detect and prevent intrusion by
   unauthorized public Internet users on the other.  The specific
   recommendations in this document are intended to promote optimal
   local-area network security while retaining full end-to-end
   transparency for users, and to highlight reasonable limitations on
   transparency where security considerations are deemed important.

   Residential and small office network administrators are expected to
   have no expertise in Internet engineering whatsoever.  Configuration
   interfaces for simple security in router/gateway appliances marketed
   toward them should be easy to understand and even easier to ignore.
   In particular, extra care should be taken in designing the baseline
   operating modes of unconfigured devices, since the security functions
   of most devices will never be changed from their factory set default.

   The mechanisms described in this document cause packets to be
   discarded by residential gateways in an attempt to make home networks
   and the Internet more secure.  However, some packets sent by
   legitimate applications may also be discarded in the process,
   affecting reliability and ease of use for these applications.

   Note well: this document is not a standard and conformance with it is
   not required in order to claim conformance with IETF standards for
   IPv6.  It uses the normative keywords defined below only for
   precision.  Particular attention is drawn to recommendation REC-41,
   which calls for an easy way for a user to set a gateway to a
   transparent mode.

1.1.  Special 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].

   The key word "DEFAULT" in this document is to be interpreted as the
   configuration of a device, as applied by its vendor, prior to the



woodyatt               Expires September 27, 2010               [Page 4]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   operator changing it for the first time.


2.  Overview

   For the purposes of this document, residential Internet gateways are
   assumed to be fairly simple devices with a limited subset of the full
   range of possible features.  They function as default routers
   [RFC4294] for a single local-area network segment, e.g. an ethernet,
   a Wi-Fi network, a bridge between two or more such segments.  They
   have a single interface by which they connect to the public Internet,
   and they can obtain service by any combination of sub-IP mechanisms,
   including tunnels and transition mechanisms.  In referring to their
   security capabilities, it is reasonable to distinguish between the
   "interior" network, i.e. the local-area network, and the "exterior"
   network, i.e. the public Internet.  This document is concerned with
   the behavior of packet filters that police the flow of traffic
   between the interior and exterior networks of residential Internet
   gateways.

   The operational goals of security capabilities in Internet gateways
   are described with more detail in "Local Network Protection for IPv6"
   [RFC4864], but they can be summarized as follows.

   o  Check all traffic to and from the public Internet for basic
      sanity, e.g. anti-spoofing and "martian" [RFC4949] filters.

   o  Allow tracking of application usage by source and destination
      transport addresses.

   o  Provide a barrier against untrusted external influences on the
      interior network by requiring filter state to be activated by
      traffic originating at interior network nodes.

   o  Allow manually configured exceptions to the stateful filtering
      rules according to network administration policy.

   o  Isolate local network DHCP and DNS proxy resolver services from
      the public Internet.

   Prior to the widespread availability of IPv6 Internet service, homes
   and small offices often used private IPv4 network address realms
   [RFC1918] with Network Address Translation (NAT) functions deployed
   to present all the hosts on the interior network as a single host to
   the Internet service provider.  The stateful packet filtering
   behavior of NAT set user expectations that persist today with
   residential IPv6 service.  "Local Network Protection for IPv6"
   [RFC4864] recommends applying stateful packet filtering at



woodyatt               Expires September 27, 2010               [Page 5]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   residential IPv6 gateways that conforms to the user expectations
   already in place.

   Conventional stateful packet filters activate new states as a side
   effect of forwarding outbound flow initiations from interior network
   nodes.  This requires applications to have advance knowledge of the
   addresses of exterior nodes with which they expect to communicate.
   Several proposals are currently under consideration for allowing
   applications to solicit inbound traffic from exterior nodes without
   advance knowledge of their addresses.  While consensus within the
   Internet engineering community has emerged that such protocols are
   necessary to implement in residential IPv6 gateways, the best current
   practice has not yet been established.

2.1.  Basic Sanitation

   In addition to the functions required of all Internet routers
   [RFC4294], residential gateways are expected to have basic stateless
   filters for prohibiting certains kinds of traffic with invalid
   headers, e.g. "martian" packets, spoofs, routing header type code
   zero, etc.  (See Section 3.1 for details.)

   Conversely, simple Internet gateways are not expected to prohibit the
   development of new applications.  In particular, packets with end-to-
   end network security and routing extension headers for mobility are
   expected to pass Internet gateways freely.

   Finally, Internet gateways that route multicast traffic are expected
   to implement appropriate filters for multicast to limit the scope of
   multicast groups that span the demarcation between residential
   networks and service provider networks.

2.2.  Internet Layer Protocols

   As virtual private networking tunnels are regarded as an unacceptably
   wide attack surface, this document recommends the DEFAULT operating
   mode for residential IPv6 simple security is to treat IP-in-IP and
   GRE tunneling protocols as opaque transport layers, i.e. inbound
   tunnel initiations are denied and outbound tunnel initiations are
   accepted.  IPsec transport and tunnel modes are explicitly secured by
   definition, so this document recommends the DEFAULT operating mode
   permit IPsec and Internet Key Exchange (IKE) flows to pass without
   filtering.

2.3.  Transport Layer Protocols

   IPv6 simple security functions are principally concerned with the
   stateful filtering of Internet Control and Management Protocol (ICMP)



woodyatt               Expires September 27, 2010               [Page 6]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   [RFC4884] and transport layers like User Datagram Protocol (UDP)
   [RFC0768] (and Lightweight User Datagram Protocol (UDP-Lite)
   [RFC3828]), Transport Control Protocol (TCP) [RFC0793], the Stream
   Control Transmission Protocol (SCTP) [RFC4960], the Datagram
   Congestion Control Protocol (DCCP) [RFC4340], and potentially any
   standards-track transport protocols to be defined in the future.

   The general operating principle is that transport layer traffic is
   not forwarded into the interior network of a residential IPv6 gateway
   unless it has been solicited explicitly by interior transport
   endpoints, e.g. by matching the reverse path for previously forwarded
   outbound traffic, or by matching manually configured exceptions set
   by the network administrator.  All other traffic is expected to be
   discarded or rejected with an ICMPv6 error message to indicate the
   traffic is administratively prohibited.


3.  Detailed Recommendations

   This section describes the specific recommendations made by this
   document in full detail.  They are summarized into a convenient list
   in Section 4.

   Some recommended filters are to be applied to all traffic that passes
   through residential Internet gateways regardless of the direction
   they are to be forwarded.  Other recommended filters are intended to
   be sensitive to the "direction" of traffic flows.  Applied to
   bidirectional transport flows, "direction" has a specific meaning in
   this document.

   Packets are said to be "outbound" if they originate from interior
   nodes to be forwarded to the Internet, and "inbound" if they
   originate from exterior nodes to be forwarded to any node or nodes on
   the interior prefix.

   Flows, as opposed to packets, are said to be "outbound" if the
   originator of the initial packet in any given transport association
   is an interior node and one or more of the participants are at
   exterior addresses.  Flows are said to be "inbound" if the originator
   of the initial packet is an exterior node and one or more of the
   participants are nodes on the interior network.

3.1.  Stateless Filters

   Certain kinds of IPv6 packets MUST NOT be forwarded in either
   direction by residential Internet gateways regardless of network
   state.  These include packets with multicast source addresses,
   packets to destinations with certain non-routable and/or reserved



woodyatt               Expires September 27, 2010               [Page 7]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   prefixes and packets with deprecated extension headers.

   Other stateless filters are recommended to implement ingress
   filtering (see [RFC2827] and [RFC3704]), to enforce multicast scope
   boundaries, and to isolate certain local network services from the
   public Internet.

   REC-1: Packets which bear in their outer IPv6 headers multicast
   source addresses MUST NOT be forwarded or transmitted on any
   interface.

   REC-2: Packets which bear in their outer IPv6 headers multicast
   destination addresses of equal or narrower scope (see IPv6 Scoped
   Address Architecture [RFC4007]) than the configured scope boundary
   level of the gateway MUST NOT be forwarded in any direction.  The
   DEFAULT scope boundary level SHOULD be organization-local scope, and
   it SHOULD be configurable by the network admininistrator.

   REC-3: Packets bearing source and/or destination addresses forbidden
   to appear in the outer headers of packets transmitted over the public
   Internet MUST NOT be forwarded.  In particular, site-local addresses
   are deprecated by [RFC3879], and [RFC5156] explicitly forbids the use
   of addresses with IPv4-Mapped, IPv4-Compatible, Documentation and
   ORCHID prefixes.

   REC-4: Packets bearing deprecated extension headers prior to their
   first upper-layer-protocol header SHOULD NOT be forwarded or
   transmitted on any interface.  In particular, all packets with
   routing extension header type 0 [RFC2460] preceding the first upper-
   layer-protocol header MUST NOT be forwarded.  (See [RFC5095] for
   additional background.)

   REC-5: Outbound packets MUST NOT be forwarded if the source address
   in their outer IPv6 header does not have a unicast prefix configured
   for use by globally reachable nodes on the interior network.

   REC-6: Inbound packets MUST NOT be forwarded if the source address in
   their outer IPv6 header has a global unicast prefix assigned for use
   by globally reachable nodes on the interior network.

   REC-7: By DEFAULT, packets with unique local source and/or
   destination addresses [RFC4193] SHOULD NOT be forwarded to or from
   the exterior network.

   REC-8: By DEFAULT, inbound non-recursive DNS queries received on
   exterior interfaces MUST NOT be processed by any integrated DNS proxy
   resolving server.




woodyatt               Expires September 27, 2010               [Page 8]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-9: Inbound DHCP discovery packets received on exterior interfaces
   MUST NOT be processed by any integrated DHCP server.

3.2.  Connection-free Filters

   Some Internet applications use connection-free transport protocols
   with no release semantics, e.g.  UDP.  These protocols pose a special
   difficulty for stateful packet filters because most of the
   application state is not carried at the transport level.  State
   records are created when communication is initiated and abandoned
   when no further communication is detected after some period of time.

3.2.1.  Internet Control and Management

   Recommendations for filtering ICMPv6 messages in firewall devices are
   described separately in [RFC4890] and apply generally to residential
   gateways as to any class of router.  No additional recommendations
   are made here, but it's important to note that Destination
   Unreachable and Packet Too Big errors corresponding to filtering
   states for all upper-layer transport protocols are important to the
   proper function of the Internet.

3.2.2.  Upper-layer Transport Protocols

   Residential IPv6 gateways are not expected to prohibit the use of
   applications to be developed using future upper-layer transport
   protocols.  In particular, transport protocols not otherwise
   discussed in subsequent sections of this document are expected to be
   treated consistently, i.e. as having connection-free semantics and no
   special requirements to inspect the transport headers.

   In general, upper-layer transport filter state records are expected
   to be created when an interior endpoint sends a packet to an exterior
   address.  The filter allocates (or reuses) a record for the duration
   of communications, with an idle timer to delete the state record when
   no further communications are detected.

   REC-10: Filter state records for generic upper-layer transport
   protocols MUST BE indexable by a 3-tuple comprising the interior node
   address, the exterior node address and the upper-layer transport
   protocol identifier.

   REC-11: Filter state records for generic upper-layer transport
   protocols MUST NOT be deleted or recycled until an idle timer not
   less than two minutes has expired without having forwarded a packet
   matching the state in some configurable amount of time.  By DEFAULT,
   the idle timer for such state records is five minutes.




woodyatt               Expires September 27, 2010               [Page 9]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-12: IPv6 gateways MUST forward ICMP Destination Unreachable and
   Packet Too Big messages containing IP headers that match generic
   upper-layer transport state 3-tuples.

3.2.3.  UDP Filters

   "Network Address Translation (NAT) Behavioral Requirements for
   Unicast UDP" [RFC4787] defines the terminology and best current
   practice for stateful filtering of UDP applications in IPv4 with NAT,
   which serves as the model for behavioral requirements for simple UDP
   security in IPv6 gateways, notwithstanding the requirements related
   specifically to network address translation.

   An interior endpoint initiates a UDP exchange through a stateful
   packet filter by sending a packet to an exterior address.  The filter
   allocates (or reuses) a filter state record for the duration of the
   exchange.  The state record defines the interior and exterior IP
   addresses and ports used between all packets in the exchange.

   State records for UDP exchanges remain active while they are in use
   and only abandoned after an idle period of some time.

   REC-13: A state record for a UDP exchange where both interior and
   exterior ports are outside the well-known port range (ports 0-1023)
   MUST NOT expire in less than two minutes of idle time.  The value of
   the UDP state record idle timer MAY be configurable.  The DEFAULT is
   five minutes.

   REC-14: A state record for a UDP exchange where one or both of the
   interior and exterior ports are in the well-known port range (ports
   0-1023) MAY expire after a period of idle time shorter than two
   minutes to facilitate the operation of the IANA-registered service
   assigned to the port in question.

   As [RFC4787] notes, outbound refresh is necessary for allowing the
   interior endpoint to keep the state record alive.  Inbound refresh
   may be useful for applications with no outbound UDP traffic.
   However, allowing inbound refresh can allow an attacker in the
   exterior or a misbehaving application to keep a state record alive
   indefinitely.  This could be a security risk.  Also, if the process
   is repeated with different ports, over time, it could use up all the
   state record memory and resources in the filter.

   REC-15: A state record for a UDP exchange MUST be refreshed when a
   packet is forwarded from the interior to the exterior, and it MAY be
   refreshed when a packet is forwarded in the reverse direction.

   As described in section 5.5 of [RFC4787], the connection-free



woodyatt               Expires September 27, 2010              [Page 10]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   semantics of UDP pose a difficulty for packet filters in trying to
   recognize which packets comprise an application flow and which are
   unsolicited.  Various strategies have been used in IPv4/NAT gateways
   with differing effects.

   REC-16: If application transparency is most important, then a
   stateful packet filter SHOULD have "Endpoint independent filter"
   behavior for UDP.  If a more stringent filtering behavior is most
   important, then a filter SHOULD have "Address dependent filtering"
   behavior.  The filtering behavior MAY be an option configurable by
   the network administrator, and it MAY be independent of the filtering
   behavior for TCP and other protocols.  Filtering behavior SHOULD by
   endpoint independent by DEFAULT in gateways intended for provisioning
   without service-provider management.

   Applications mechanisms may depend on the reception of ICMP error
   messages triggered by the transmission of UDP messages.  One such
   mechanism is path MTU discovery.

   REC-17: If a gateway forwards a UDP exchange, it MUST also forward
   ICMP Destination Unreachable and Packet Too Big messages containing
   UDP headers that match the exchange state record.

   REC-18: Receipt of any sort of ICMP message MUST NOT terminate the
   state record for a UDP exchange.

   REC-19: UDP-Lite exchanges [RFC3828] SHOULD be handled in the same
   way as UDP exchanges, except that the upper-layer transport protocol
   identifier for UDP-Lite is not the same as UDP, and therefore UDP
   packets MUST NOT match UDP-Lite state records, and vice versa.

3.2.4.  6to4 Tunnels

   Typical dual-stack IPv4/IPv6 residential gateways use private IPv4
   address ranges and network address/port translation on a single IPv4
   address assigned by the service provider.  The use of private
   addresses prevents interior hosts from using 6to4 [RFC3068] tunnels.

3.2.5.  IPsec and Internet Key Exchange (IKE)

   Internet protocol security (IPsec) offers greater flexibility and
   better overall security than the simple security of stateful packet
   filtering at network perimeters.  Therefore, residential IPv6
   gateways need not prohibit IPsec traffic flows.

   REC-20: In their DEFAULT operating mode, IPv6 gateways MUST NOT
   prohibit the forwarding of packets, to and from legitimate node
   addresses, with destination extension headers of type "Authenticated



woodyatt               Expires September 27, 2010              [Page 11]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   Header (AH)" [RFC4302] in their outer IP extension header chain.

   REC-21: In their DEFAULT operating mode, IPv6 gateways MUST NOT
   prohibit the forwarding of packets, to and from legitimate node
   addresses, with an upper layer protocol of type "Encapsulating
   Security Payload (ESP)" [RFC4303] in their outer IP extension header
   chain.

   REC-22: In their DEFAULT operating mode, IPv6 gateways MUST NOT
   prohibit the forwarding of any UDP packets, to and from legitimate
   node addresses, with a destination port of 500, i.e. the port
   reserved by IANA for the Internet Key Exchange Protocol [RFC4306].

   REC-23: In all operating modes, IPv6 gateways SHOULD use filter state
   records for Encapsulating Security Payload (ESP) [RFC4303] that are
   indexable by a 3-tuple comprising the interior node address, the
   exterior node address and the ESP protocol identifier.  In
   particular, the IPv4/NAT method of indexing state records also by
   security parameters index (SPI) SHOULD NOT be used.  Likewise, any
   mechanism that depends on detection of Internet Key Exchange (IKE)
   [RFC4306] initiations SHOULD NOT be used.

3.3.  Connection-oriented Filters

   Most Internet applications use connection-oriented transport
   protocols with orderly release semantics.  These protocols include
   the Transport Control Protocol (TCP) [RFC0793], the Stream Control
   Transmission Protocol (SCTP) [RFC4960], the Datagram Congestion
   Control Protocol (DCCP) [RFC4340], and potentially any future IETF
   standards-track transport protocols that use such semantics.
   Stateful packet filters track the state of individual transport
   connections and prohibit the forwarding of packets that do not match
   the state of an active connection and do not conform to a rule for
   the automatic creation of such state.

3.3.1.  TCP Filters

   An interior endpoint initiates a TCP connection through a stateful
   packet filter by sending a SYN packet.  The filter allocates (or
   reuses) a filter state record for the connection.  The state record
   defines the interior and exterior IP addresses and ports used for
   forwarding all packets for that connection.

   Some peer-to-peer applications use an alternate method of connection
   initiation termed simultaneous-open (Fig. 8, [RFC0793]) to traverse
   stateful filters.  In the simultaneous-open mode of operation, both
   peers send SYN packets for the same TCP connection.  The SYN packets
   cross in the network.  Upon receiving the other end's SYN packet,



woodyatt               Expires September 27, 2010              [Page 12]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   each end responds with a SYN-ACK packet, which also cross in the
   network.  The connection is established at each endpoint once the
   SYN-ACK packets are received.

   To provide stateful packet filtering service for TCP, it is necessary
   for a filter to receive, process and forward all packets for a
   connection that conform to valid transitions of the TCP state machine
   (Fig. 6, [RFC0793]).

   REC-24: All valid sequences of TCP packets (defined in [RFC0793])
   MUST be forwarded for outbound connections and explicitly permitted
   inbound connections.  In particular, both the normal TCP 3-way
   handshake mode of operation and the simultaneous-open modes of
   operation MUST be supported.

   It is possible to reconstruct enough of the state of a TCP connection
   to allow forwarding between an interior and exterior node even when
   the filter starts operating after TCP enters the established state.
   In this case, because the filter has not seen the TCP window-scale
   option, it is not possible for the filter to enforce the TCP window
   invariant by dropping out-of-window segments.

   REC-25: The TCP window invariant MUST NOT be enforced on connections
   for which the filter did not detect whether the window-scale option
   (see [RFC1323]) was sent in the 3-way handshake or simultaneous open.

   A stateful filter can allow an existing state record to be reused by
   an externally initiated connection if its security policy permits.
   Several different policies are possible as described in "Network
   Address Translation (NAT) Behavioral Requirements for Unicast UDP
   [RFC4787] and extended in "NAT Behavioral Requirements for TCP"
   [RFC5382].

   REC-26: If application transparency is most important, then a
   stateful packet filter SHOULD have "Endpoint independent filter"
   behavior for TCP.  If a more stringent filtering behavior is most
   important, then a filter SHOULD have "Address dependent filtering"
   behavior.  The filtering behavior MAY be an option configurable by
   the network administrator, and it MAY be independent of the filtering
   behavior for UDP and other protocols.  Filtering behavior SHOULD by
   endpoint independent by DEFAULT in gateways intended for provisioning
   without service-provider management.

   If an inbound SYN packet is filtered, either because a corresponding
   state record does not exist or because of the filter's normal
   behavior, a filter has two basic choices: to discard the packet
   silently, or to signal an error to the sender.  Signaling an error
   through ICMP messages allows the sender to detect that the SYN did



woodyatt               Expires September 27, 2010              [Page 13]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   not reach the intended destination.  Discarding the packet, on the
   other hand, allows applications to perform simultaneous-open more
   reliably.  A more detailed discussion of this issue can be found in
   [RFC5382], but the basic outcome of it is that filters need to wait
   on signaling errors until simultaneous-open will not be impaired.

   REC-27: By DEFAULT, a gateway MUST respond with an ICMP Destination
   Unreachable error (administratively prohibited) to any unsolicited
   inbound SYN packet after waiting at least 6 seconds without first
   forwarding the associated outbound SYN or SYN/ACK from the interior
   peer.

   A TCP filter maintains state associated with in-progress and
   established connections.  Because of this, a filter is susceptible to
   a resource-exhaustion attack whereby an attacker (or virus) on the
   interior attempts to cause the filter to exhaust its capacity for
   creating state records.  To defend against such attacks, a filter
   needs to abandon unused state records after a sufficiently long
   period of idleness.

   A common method used for TCP filters in IPv4/NAT gateways is to
   abandon preferentially sessions for crashed endpoints, followed by
   closed TCP connections and partially-open connections.  A gateway can
   check if an endpoint for a session has crashed by sending a TCP keep-
   alive packet on behalf of the other endpoint and receiving a TCP RST
   packet in response.  If the gateway connot determine whether the
   endpoint is active, then the associated state record needs to be
   retained until the TCP connection has been idle for some time.  Note:
   an established TCP connection can stay idle (but live) indefinitely;
   hence, there is no fixed value for an idle-timeout that accommodates
   all applications.  However, a large idle-timeout motivated by
   recommendations in [RFC1122] and [RFC4294] can reduce the chances of
   abandoning a live connection.

   TCP connections can stay in the established phase indefinitely
   without exchanging packets.  Some end-hosts can be configured to send
   keep-alive packets on such idle connections; by default, such packets
   are sent every two hours, if enabled [RFC1122].  Consequently, a
   filter that waits for slightly over two hours can detect idle
   connections with keep-alive packets being sent at the default rate.
   TCP connections in the partially-open or closing phases, on the other
   hand, can stay idle for at most four minutes while waiting for in-
   flight packets to be delivered [RFC1122].

   The "established connection idle-timeout" for a stateful packet
   filter is defined as the minimum time a TCP connection in the
   established phase must remain idle before the filter considers the
   associated state record a candidate for collection.  The "transitory



woodyatt               Expires September 27, 2010              [Page 14]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   connection idle-timeout" for a filter is defined as the minimum time
   a TCP connection in the partially-open or closing phases must remain
   idle before the filter considers the associated state record a
   candidate for collection.  TCP connections in the TIME_WAIT state are
   not affected by the "transitory connection idle-timeout" parameter.

   REC-28: If a gateway cannot determine whether the endpoints of a TCP
   connection are active, then it MAY abandon the state record if it has
   been idle for some time.  In such cases, the value of the
   "established connection idle-timeout" MUST NOT be less than two hours
   four minutes, as discussed in [RFC5382].  The value of the
   "transitory connection idle-timeout" MUST NOT be less than four
   minutes.  The value of the idle-timeouts MAY be configurable by the
   network administrator.

   Behavior for handing RST packets, or connections in the TIME_WAIT
   state is left unspecified.  A gateway MAY hold state for a connection
   in TIME_WAIT state to accommodate retransmissions of the last ACK.
   However, since the TIME_WAIT state is commonly encountered by
   interior endpoints properly closing the TCP connection, holding state
   for a closed connection can limit the throughput of connections
   through a gateway with limited resources.  [RFC1337] discusses
   hazards associated with TIME_WAIT assassination.

   The handling of non-SYN packets for which there is no active state
   record is left unspecified.  Such packets can be received if the
   gateway abandons a live connection, or abandons a connection in the
   TIME_WAIT state before the four minute TIME_WAIT period expires.  The
   decision either to discard or to respond with an ICMP Destination
   Unreachable error, code 1 (administratively prohibited) is left up to
   the implementation.

   Behavior for notifying endpoints when abandoning live connections is
   left unspecified.  When a gateway abandons a live connection, for
   example due to a timeout expiring, the filter MAY send a TCP RST
   packet to each endpoint on behalf of the other.  Sending a RST
   notification allows endpoint applications to recover more quickly,
   however, notifying endpoints might not always be possible if, for
   example, state records are lost due to power interruption.

   Several TCP mechanisms depend on the reception of ICMP error messages
   triggered by the transmission of TCP segments.  One such mechanism is
   path MTU discovery, which is required for correct operation of TCP.

   REC-29: If a gateway forwards a TCP connection, it MUST also forward
   ICMP Destination Unreachable and Packet Too Big messages containing
   TCP headers that match the connection state record.




woodyatt               Expires September 27, 2010              [Page 15]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-30: Receipt of any sort of ICMP message MUST NOT terminate the
   state record for a TCP connection.

3.3.2.  SCTP Filters

   Because Stream Control Transmission Protocol (SCTP) [RFC4960]
   connections can be terminated at multiple network addresses, IPv6
   simple security functions cannot achieve full transparency for SCTP
   applications.  In multipath traversal scenarios, full transparency
   requires coordination between all the packet filter processes in the
   various paths between the endpoint network addresses.  Such
   coordination is not "simple" and it is, therefore, beyond the scope
   of this recommendation.

   However, some SCTP applications are capable of tolerating the
   inherent unipath restriction of IPv6 simple security, even in
   multipath traversal scenarios.  They expect similar connection-
   oriented filtering behaviors as for TCP, but at the level of SCTP
   associations, not stream connections.  This section describes
   specific recommendations for SCTP filtering for such traversal
   scenarios.

   An interior endpoint initiates SCTP associations through a stateful
   packet filter by sending a packet comprising a single INIT chunk.
   The filter allocates (or reuses) a filter state record for the
   association.  The state record defines the interior and exterior IP
   addresses and the observed verification tag used for forwarding
   packets in that association.

   Peer-to-peer applications use an alternate method of association
   initiation termed simultaneous-open to traverse stateful filters.  In
   the simultaneous-open mode of operation, both peers send INIT chunks
   at the same time to establish an association.  Upon receiving the
   other end's INIT chunk, each end responds with an INIT-ACK packet,
   which is expected to traverse the same path in reverse.  Because only
   one SCTP association may exist between any two network addresses, one
   of the peers in simultaneous-open mode of operation will send an
   ERROR or ABORT chunk along with the INIT-ACK chunk.  The association
   is established at each endpoint once an INIT-ACK chunks is received
   at one end without an ERROR or ABORT chunk.

   To provide stateful packet filtering service for SCTP, it is
   necessary for a filter to receive, process and forward all packets
   for an association that conform to valid transitions of the SCTP
   state machine (Fig. 3, [RFC4960]).

   REC-31: All valid sequences of SCTP packets (defined in [RFC4960])
   MUST be forwarded for outbound associations and explicitly permitted



woodyatt               Expires September 27, 2010              [Page 16]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   inbound associations.  In particular, both the normal SCTP
   association establishment and simultaneous-open modes of operation
   MUST be supported.

   If an inbound INIT packet is filtered, either because a corresponding
   state record does not exist or because of the filter's normal
   behavior, a filter has two basic choices: to discard the packet
   silently, or to signal an error to the sender.  Signaling an error
   through ICMP messages allows the sender to detect that the INIT
   packet did not reach the intended destination.  Discarding the
   packet, on the other hand, allows applications to perform
   simultaneous-open more reliably.  Delays in signaling errors can
   prevent the impairment of simultaneous-open mode of operation.

   REC-32: By DEFAULT, a gateway MUST respond with an ICMP Destination
   Unreachable error (administratively prohibited) to any unsolicited
   inbound INIT packet after waiting at least 6 seconds without first
   forwarding the associated outbound INIT from the interior peer.

   An SCTP filter maintains state associated with in-progress and
   established associations.  Because of this, a filter is susceptible
   to a resource-exhaustion attack whereby an attacker (or virus) on the
   interior attempts to cause the filter to exhaust its capacity for
   creating state records.  To defend against such attacks, a filter
   needs to abandon unused state records after a sufficiently long
   period of idleness.

   A common method used for TCP filters in IPv4/NAT gateways is to
   abandon preferentially sessions for crashed endpoints, followed by
   closed associations and partially opened associations.  A similar
   method is an option for SCTP filters in IPv6 gateways.  A gateway can
   check if an endpoint for an association has crashed by sending
   HEARTBEAT chunks and looking for the HEARTBEAT ACK response.  If the
   gateway cannot determine whether the endpoint is active, then the
   associated state records needs to be retained until the SCTP
   association has been idle for some time.  Note: an established SCTP
   association can stay idle (but live) indefinitely, hence there is no
   fixed value of an idle-timeout that accommodates all applications.
   However, a large idle-timeout motivated by [RFC4294] can reduce the
   chances of abandoning a live association.

   SCTP associations can stay in the ESTABLISHED state indefinitely
   without exchanging packets.  Some end-hosts can be configured to send
   HEARTBEAT chunks on such idle associations, but [RFC4960] does not
   specify (or even suggest) a default time interval.  A filter that
   waits for slightly over two hours can detect idle associations with
   HEARTBEAT packets being sent at the same rate as most hosts use for
   TCP keep-alive, which is a reasonably similar system for this



woodyatt               Expires September 27, 2010              [Page 17]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   purpose.  SCTP associations in the partially-open or closing states,
   on the other hand, can stay idle for at most four minutes while
   waiting for in-flight packets to be delivered (assuming the suggested
   SCTP protocol parameter values in Section 15 of [RFC4960]).

   The "established association idle-timeout" for a stateful packet
   filter is defined as the minimum time an SCTP association in the
   established phase must remain idle before the filter considers the
   corresponding state record a candidate for collection.  The
   "transitory association idle-timeout" for a filter is defined as the
   minimum time an SCTP association in the partially-open or closing
   phases must remain idle before the filter considers the corresponding
   state record a candidate for collection.

   REC-33: If a gateway cannot determine whether the endpoints of an
   SCTP association are active, then it MAY abandon the state record if
   it has been idle for some time.  In such cases, the value of the
   "established association idle-timeout" MUST NOT be less than two
   hours four minutes.  The value of the "transitory association idle-
   timeout" MUST NOT be less than four minutes.  The value of the idle-
   timeouts MAY be configurable by the network administrator.

   Behavior for handling ERROR and ABORT packets is left unspecified.  A
   gateway MAY hold state for an association after its closing phases
   have completed to accommodate retransmissions of its final SHUTDOWN
   ACK packets.  However, holding state for a closed association can
   limit the throughput of associations traversing a gateway with
   limited resources.  The discussion in [RFC1337] regarding the hazards
   of TIME_WAIT assassination are relevant.

   The handling of inbound non-INIT packets for which there is no active
   state record is left unspecified.  Such packets can be received if
   the gateway abandons a live connection, or abandons an association in
   the closing states before the transitory association idle-timeout
   expires.  The decision either to discard or to respond with an ICMP
   Destination Unreachable error, code 1 (administratively prohibited)
   is left to the implementation.

   Behavior for notifying endpoints when abandoning live associations is
   left unspecified.  When a gateway abandons a live association, for
   example due to a timeout expiring, the filter MAY send an ABORT
   packet to each endpoint on behalf of the other.  Sending an ABORT
   notification allows endpoint applications to recover more quickly,
   however, notifying endpoints might not always be possible if, for
   example, state records are lost due to power interruption.

   Several SCTP mechanisms depend on the reception of ICMP error
   messages triggered by the transmission of SCTP packets.



woodyatt               Expires September 27, 2010              [Page 18]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-34: If a gateway forwards an SCTP association, it MUST also
   forward ICMP Destination Unreachable and Packet Too Big messages
   containing SCTP headers that match the association state record.

   REC-35: Receipt of any sort of ICMP message MUST NOT terminate the
   state record for an SCTP association.

3.3.3.  DCCP Filters

   The connection semantics described in Datagram Congestion Control
   Protocol (DCCP) [RFC4340] are very similar to those of TCP.  An
   interior endpoint initiates a DCCP connection through a stateful
   packet filter by sending a DCCP-Request packet.  Simultaneous open is
   not defined for DCCP.

   In order to provide stateful packet filtering service for DCCP, it is
   necessary for a filter to receive, process and forward all packets
   for a connection that conform to valid transitions of the DCCP state
   machine (Section 8, [RFC4340]).

   REC-36: All valid sequences of DCCP packets (defined in [RFC4340])
   MUST be forwarded for all connections to exterior servers and those
   connections to interior servers with explicitly permitted service
   codes.

   It is possible to reconstruct enough of the state of a DCCP
   connection to allow forwarding between an interior and exterior node
   even when the filter starts operating after DCCP enters the OPEN
   state.  Also, a filter can allow an existing state record to be
   reused by an externally initiated connection if its security policy
   permits.  As with TCP, several different policies are possible, with
   a good discussion of the issue involved presented in Network Address
   Translation (NAT) Behavioral Requirements for Unicast UDP [RFC4787]
   and extended in NAT Behavioral Requirements for TCP [RFC5382].

   If an inbound DCCP-Request packet is filtered, either because a
   corresponding state record does not already exist for it or because
   of the filter's normal behavior of refusing connections not
   explicitly permitted, then a filter has two basic choices: to discard
   the packet silently, or to signal an error to the sender.  Signaling
   an error through ICMP messages allows the sender to detect that the
   DCCP-Request did not reach the intended destination.  Discarding the
   packet, on the other hand, only delays the failure to connect and
   provides no measurable security.

   A DCCP filter maintains state associated with in-progress and
   established connections.  Because of this, a filter is susceptible to
   a resource-exhaustion attack whereby an attacker (or virus) on the



woodyatt               Expires September 27, 2010              [Page 19]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   interior attempts to cause the filter to exhaust its capacity for
   creating state records.  To prevent such an attack, a filter needs to
   abandon unused state records after a sufficiently long period of
   idleness.

   A common method used for TCP filters in IPv4/NAT gateways is to
   abandon preferentially sessions for crashed endpoints, followed by
   closed TCP connections and partially-open connections.  No such
   method exists for DCCP, and connections can stay in the OPEN phase
   indefinitely without exchanging packets.  Hence, there is no fixed
   value for an idle-timeout that accommodates all applications.
   However, a large idle-timeout motivated by [RFC4294] can reduce the
   chances of abandoning a live connection.

   DCCP connections in the partially-open or closing phases can stay
   idle for at most eight minutes while waiting for in-flight packets to
   be delivered.

   The "open connection idle-timeout" for a stateful packet filter is
   defined as the minimum time a DCCP connection in the open state must
   remain idle before the filter considers the associated state record a
   candidate for collection.  The "transitory connection idle-timeout"
   for a filter is defined as the minimum time a DCCP connection in the
   partially-open or closing phases must remain idle before the filter
   considers the associated state record a candidate for collection.
   DCCP connections in the TIMEWAIT state are not affected by the
   "transitory connection idle-timeout" parameter.

   REC-37: A gateway MAY abandon a DCCP state record if it has been idle
   for some time.  In such cases, the value of the "established
   connection idle-timeout" MUST NOT be less than two hours four
   minutes.  The value of the "transitory connection idle-timeout" MUST
   NOT be less than eight minutes.  The value of the idle-timeouts MAY
   be configurable by the network administrator.

   Behavior for handing DCCP-Reset packets, or connections in the
   TIMEWAIT state is left unspecified.  A gateway MAY hold state for a
   connection in TIMEWAIT state to accommodate retransmissions of the
   last DCCP-Reset.  However, since the TIMEWAIT state is commonly
   encountered by interior endpoints properly closing the DCCP
   connection, holding state for a closed connection can limit the
   throughput of connections through a gateway with limited resources.
   [RFC1337] discusses hazards associated with TIME_WAIT assassination
   in TCP, and similar hazards exists for DCCP.

   The handling of non-SYN packets for which there is no active state
   record is left unspecified.  Such packets can be received if the
   gateway abandons a live connection, or abandons a connection in the



woodyatt               Expires September 27, 2010              [Page 20]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   TIMEWAIT state before the four minute 2MSL period expires.  The
   decision either to discard or to respond with an ICMP Destination
   Unreachable error, code 1 (administratively prohibited) is left up to
   the implementation.

   Behavior for notifying endpoints when abandoning live connections is
   left unspecified.  When a gateway abandons a live connection, for
   example due to a timeout expiring, the filter MAY send a DCCP-Reset
   packet to each endpoint on behalf of the other.  Sending a DCCP-Reset
   notification allows endpoint applications to recover more quickly,
   however, notifying endpoints might not always be possible if, for
   example, state records are lost due to power interruption.

   Several DCCP mechanisms depend on the reception of ICMP error
   messages triggered by the transmission of DCCP packets.  One such
   mechanism is path MTU discovery, which is required for correct
   operation.

   REC-38: If a gateway forwards a DCCP connection, it MUST also forward
   ICMP Destination Unreachable and Packet Too Big messages containing
   DCCP headers that match the connection state record.

   REC-39: Receipt of any sort of ICMP message MUST NOT terminate the
   state record for a DCCP connection.

3.3.4.  Level 3 Multihoming Shim Protocol for IPv6 (SHIM6)

   IPv6 simple security is applicable to residential networks with only
   one default router, i.e. a single residential gateway to exactly one
   Internet service provider.  The use of Level 3 Multihoming Shim
   Protocol for IPv6 (SHIM6) [RFC5533] as a site multi-homing solution
   is not generally compatible with IPv6 simple security.

   Residential gateways that are capable of site multi-homing
   simultaneously on more than one exterior network link SHOULD
   reference addresses in SHIM6 headers when comparing and creating
   filter state corresponding to interior endpoint hosts.

3.4.  Passive Listeners

   Some applications expect to solicit traffic from exterior nodes
   without any advance knowledge of the exterior address.  This
   requirement is met by IPv4/NAT gateways typically by the use of
   either [I-D.cheshire-nat-pmp] or [UPnP-IGD].  On IPv4/NAT networks
   connected by gateways without such services, applications must use
   techniques like Session Traversal Utilities for NAT (STUN) [RFC5389]
   to obtain and maintain connectivity, despite the translation and
   filtering effects of NAT.



woodyatt               Expires September 27, 2010              [Page 21]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   While NAT for IPv6 is unlikely to be used in most residential
   gateways, the filtering effect of the simple security functions
   recommended by this document are derived from those in widespread use
   on the IPv4 Internet, and a similar barrier to communication at
   passive listeners is a natural outcome of its deployment.  To avoid
   the need for IPv6 applications to use techniques like STUN for
   opening and maintaining dynamic filter state, something similar to
   NAT-PMP and UPnP-IGD but without actually supporting NAT needs to be
   deployed.  Alas, no consensus has yet emerged in the Internet
   engineering community as to what is most appropriate for residential
   IPv6 usage scenarios.

   One proposal that has been offered as an Internet Draft is the
   Application Listener Discovery Protocol [I-D.woodyatt-ald].  It
   remains to be seen whether the Internet Gateway Device profile of the
   Universal Plug And Play protocol will be extended for IPv6.  Other
   proposals of note include the Middlebox Communication Protocol
   [RFC5189] and the Next Steps in Signaling framework [RFC4080].  Until
   a consensus emerges around a specific method, the following
   recommendations are the best guidance available.

   REC-40: Gateways SHOULD implement a protocol to permit applications
   to solicit inbound traffic without advance knowledge of the addresses
   of exterior nodes with which they expect to communicate.

   REC-41: Gateways MUST provide an easily selected configuration option
   that permits a "transparent mode" of operation that forwards all
   unsolicited flows regardless of forwarding direction, i.e. to disable
   the IPv6 simple security capabilities of the gateway.

   In general, "transparent mode" will enable more flexibility and
   reliability for applications which require devices to be contacted
   inside the home directly, particularly in absence of a protocol as
   described in REC-40.  Operating in transparent mode may come at the
   expense of security if there are IPv6 nodes in the home that do not
   have their own host-based firewall capability and require a firewall
   in the gateway in order not to be compromised.

3.5.  Management Applications

   Subscriber managed residential gateways are unlikely ever to be
   completely zero-configuration, but their administrators will very
   often possess no particular expertise in Internet engineering.  In
   general, the specification of management interfaces for residential
   gateways is out of scope for this document, but security of
   subscriber managed gateways merit special attention here.

   REC-42: By DEFAULT, subscriber managed residential gateways MUST NOT



woodyatt               Expires September 27, 2010              [Page 22]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   offer management application services to the exterior network.


4.  Summary of Recommendations

   This section collects all of the recommendations made in this
   document into a convenient list.

   REC-1  Packets bearing in their outer IPv6 headers multicast source
      addresses MUST NOT be forwarded or transmitted on any interface.

   REC-2  Packets which bear in their outer IPv6 headers multicast
      destination addresses of equal or narrower scope (see IPv6 Scoped
      Address Architecture [RFC4007]) than the configured scope boundary
      level of the gateway MUST NOT be forwarded in any direction.  The
      DEFAULT scope boundary level SHOULD be organization-local scope,
      and it SHOULD be configurable by the network admininistrator.

   REC-3  Packets bearing source and/or destination addresses forbidden
      to appear in the outer headers of packets transmitted over the
      public Internet MUST NOT be forwarded.  In particular, site-local
      addresses are deprecated by [RFC3879], and [RFC5156] explicitly
      forbids the use of addresses with IPv4-Mapped, IPv4-Compatible,
      Documentation and ORCHID prefixes.

   REC-4  Packets bearing deprecated extension headers prior to their
      first upper-layer-protocol header SHOULD NOT be forwarded or
      transmitted on any interface.  In particular, all packets with
      routing extension header type 0 [RFC2460] preceding the first
      upper-layer-protocol header MUST NOT be forwarded.  (See [RFC5095]
      for additional background.)

   REC-5  Outbound packets MUST NOT be forwarded if the source address
      in their outer IPv6 header does not have a unicast prefix assigned
      for use by globally reachable nodes on the interior network.

   REC-6  Inbound packets MUST NOT be forwarded if the source address in
      their outer IPv6 header has a global unicast prefix assigned for
      use by globally reachable nodes on the interior network.

   REC-7  By DEFAULT, packets with unique local source and/or
      destination addresses [RFC4193] SHOULD NOT be forwarded to or from
      the exterior network.

   REC-8  By DEFAULT, inbound non-recursive DNS queries received on
      exterior interfaces MUST NOT be processed by any integrated DNS
      proxy resolving server.




woodyatt               Expires September 27, 2010              [Page 23]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-9  Inbound DHCP discovery packets received on exterior interfaces
      MUST NOT be processed by any integrated DHCP server.

   REC-10  Filter state records for generic upper-layer transport
      protocols MUST BE indexable by a 3-tuple comprising the interior
      node address, the exterior node address and the upper-layer
      transport protocol identifier.

   REC-11  Filter state records for generic upper-layer transport
      protocols MUST NOT be deleted or recycled until an idle timer not
      less than two minutes has expired without having forwarded a
      packet matching the state in some configurable amount of time.  By
      DEFAULT, the idle timer for such state records is five minutes.

   REC-12  IPv6 gateways MUST forward ICMP Destination Unreachable and
      Packet Too Big messages containing IP headers that match generic
      upper-layer transport state 3-tuples.

   REC-13  A state record for a UDP exchange where both interior and
      exterior ports are outside the well-known port range (ports
      0-1023) MUST NOT expire in less than two minutes of idle time.
      The value of the UDP state record idle timer MAY be configurable.
      The DEFAULT is five minutes.

   REC-14  A state record for a UDP exchange where one or both of the
      interior and exterior ports are in the well-known port range
      (ports 0-1023) MAY expire after a period of idle time shorter than
      two minutes to facilitate the operation of the IANA-registered
      service assigned to the port in question.

   REC-15  A state record for a UDP exchange MUST be refreshed when a
      packet is forwarded from the interior to the exterior, and it MAY
      be refreshed when a packet is forwarded in the reverse direction.

   REC-16  If application transparency is most important, then a
      stateful packet filter SHOULD have "Endpoint independent filter"
      behavior for UDP.  If a more stringent filtering behavior is most
      important, then a filter SHOULD have "Address dependent filtering"
      behavior.  The filtering behavior MAY be an option configurable by
      the network administrator, and it MAY be independent of the
      filtering behavior for TCP and other protocols.  Filtering
      behavior SHOULD by endpoint independent by DEFAULT in gateways
      intended for provisioning without service-provider management.

   REC-17  If a gateway forwards a UDP exchange, it MUST also forward
      ICMP Destination Unreachable and Packet Too Big messages
      containing UDP headers that match the exchange state record.




woodyatt               Expires September 27, 2010              [Page 24]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-18  Receipt of any sort of ICMP message MUST NOT terminate the
      state record for a UDP exchange.

   REC-19  UDP-Lite exchanges [RFC3828] SHOULD be handled in the same
      way as UDP exchanges, except that the upper-layer transport
      protocol identifier for UDP-Lite is not the same as UDP, and
      therefore UDP packets MUST NOT match UDP-Lite state records, and
      vice versa.

   REC-20  In their DEFAULT operating mode, IPv6 gateways MUST NOT
      prohibit the forwarding of packets, to and from legitimate node
      addresses, with destination extension headers of type
      "Authenticated Header (AH)" [RFC4302] in their outer IP extension
      header chain.

   REC-21  In their DEFAULT operating mode, IPv6 gateways MUST NOT
      prohibit the forwarding of packets, to and from legitimate node
      addresses, with an upper layer protocol of type "Encapsulating
      Security Payload (ESP)" [RFC4303] in their outer IP extension
      header chain.

   REC-22  In their DEFAULT operating mode, IPv6 gateways MUST NOT
      prohibit the forwarding of any UDP packets, to and from legitimate
      node addresses, with a destination port of 500, i.e. the port
      reserved by IANA for the Internet Key Exchange Protocol [RFC4306].

   REC-23  In all operating modes, IPv6 gateways SHOULD use filter state
      records for Encapsulating Security Payload (ESP) [RFC4303] that
      are indexable by a 3-tuple comprising the interior node address,
      the exterior node address and the ESP protocol identifier.  In
      particular, the IPv4/NAT method of indexing state records also by
      security parameters index (SPI) SHOULD NOT be used.  Likewise, any
      mechanism that depends on detection of Internet Key Exchange (IKE)
      [RFC4306] initiations SHOULD NOT be used.

   REC-24  All valid sequences of TCP packets (defined in [RFC0793])
      MUST be forwarded for outbound connections and explicitly
      permitted inbound connections.  In particular, both the normal TCP
      3-way handshake mode of operation and the simultaneous-open modes
      of operation MUST be supported.

   REC-25  The TCP window invariant MUST NOT be enforced on connections
      for which the filter did not detect whether the window-scale
      option (see [RFC1323]) was sent in the 3-way handshake or
      simultaneous open.






woodyatt               Expires September 27, 2010              [Page 25]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   REC-26  If application transparency is most important, then a
      stateful packet filter SHOULD have "Endpoint independent filter"
      behavior for TCP.  If a more stringent filtering behavior is most
      important, then a filter SHOULD have "Address dependent filtering"
      behavior.  The filtering behavior MAY be an option configurable by
      the network administrator, and it MAY be independent of the
      filtering behavior for UDP and other protocols.  Filtering
      behavior SHOULD by endpoint independent by DEFAULT in gateways
      intended for provisioning without service-provider management.

   REC-27  By DEFAULT, a gateway MUST respond with an ICMP Destination
      Unreachable error (administratively prohibited) to any unsolicited
      inbound SYN packet after waiting at least 6 seconds without first
      forwarding the associated outbound SYN or SYN/ACK from the
      interior peer.

   REC-28  If a gateway cannot determine whether the endpoints of a TCP
      connection are active, then it MAY abandon the state record if it
      has been idle for some time.  In such cases, the value of the
      "established connection idle-timeout" MUST NOT be less than two
      hours four minutes, as discussed in [RFC5382].  The value of the
      "transitory connection idle-timeout" MUST NOT be less than four
      minutes.  The value of the idle-timeouts MAY be configurable by
      the network administrator.

   REC-29  If a gateway forwards a TCP connection, it MUST also forward
      ICMP Destination Unreachable and Packet Too Big messages
      containing TCP headers that match the connection state record.

   REC-30  Receipt of any sort of ICMP message MUST NOT terminate the
      state record for a TCP connection.

   REC-31  All valid sequences of SCTP packets (defined in [RFC4960])
      MUST be forwarded for outbound associations and explicitly
      permitted inbound associations.  In particular, both the normal
      SCTP association establishment and simultaneous-open modes of
      operation MUST be supported.

   REC-32  By DEFAULT, a gateway MUST respond with an ICMP Destination
      Unreachable error (administratively prohibited) to any unsolicited
      inbound INIT packet after waiting at least 6 seconds without first
      forwarding the associated outbound INIT from the interior peer.

   REC-33  If a gateway cannot determine whether the endpoints of an
      SCTP association are active, then it MAY abandon the state record
      if it has been idle for some time.  In such cases, the value of
      the "established association idle-timeout" MUST NOT be less than
      two hours four minutes.  The value of the "transitory association



woodyatt               Expires September 27, 2010              [Page 26]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


      idle-timeout" MUST NOT be less than four minutes.  The value of
      the idle-timeouts MAY be configurable by the network
      administrator.

   REC-34  If a gateway forwards an SCTP association, it MUST also
      forward ICMP Destination Unreachable and Packet Too Big messages
      containing SCTP headers that match the association state record.

   REC-35  Receipt of any sort of ICMP message MUST NOT terminate the
      state record for an SCTP association.

   REC-36  All valid sequences of DCCP packets (defined in [RFC4340])
      MUST be forwarded for all connections to exterior servers and
      those connections to interior servers with explicitly permitted
      service codes.

   REC-37  A gateway MAY abandon a DCCP state record if it has been idle
      for some time.  In such cases, the value of the "established
      connection idle-timeout" MUST NOT be less than two hours four
      minutes.  The value of the "transitory connection idle-timeout"
      MUST NOT be less than eight minutes.  The value of the idle-
      timeouts MAY be configurable by the network administrator.

   REC-38  If a gateway forwards a DCCP connection, it MUST also forward
      ICMP Destination Unreachable and Packet Too Big messages
      containing DCCP headers that match the connection state record.

   REC-39  Receipt of any sort of ICMP message MUST NOT terminate the
      state record for a DCCP connection.

   REC-40  Gateways SHOULD implement a protocol to permit applications
      to solicit inbound traffic without advance knowledge of the
      addresses of exterior nodes with which they expect to communicate.

   REC-41  Gateways MUST provide an easily selected configuration option
      that permits a "transparent mode" of operation that forwards all
      unsolicited flows regardless of forwarding direction, i.e. to
      disable the IPv6 simple security capabilities of the gateway.

   REC-42  By DEFAULT, subscriber managed residential gateways MUST NOT
      offer management application services to the exterior network.


5.  Contributors

   Comments and criticisms during the development of this document were
   received from the following IETF participants:




woodyatt               Expires September 27, 2010              [Page 27]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


      Fred Baker

      Norbert Bollow

      Cameron Byrne

      Brian Carpenter

      Remi Despres

      Fabrice Fontaine

      Jun-ichiro "itojun" Hagino

      Thomas Herbst

      Christian Huitema

      Joel Jaeggli

      Cullen Jennings

      Suresh Krishnan

      Erik Kline

      Kurt Erik Lindqvist

      Keith Moore

      Robert Moskowitz

      Teemu Savolainen

      Hemant Singh

      Yaron Sheffer

      Iljitsch van Beijnum

      Dan Wing

   The editor thanks them all for their contributions.

   It must be noted that a substantial portion of the text describing
   the detailed requirements for TCP and UDP filtering is derived or
   transposed from [RFC4787] and [RFC5382].  The editors of those
   documents, Francois Audet and Saikat Guha, deserve substantial credit



woodyatt               Expires September 27, 2010              [Page 28]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   for the form of the present document, as well.


6.  IANA Considerations

   This memo includes no request to IANA.


7.  Security Considerations

   The IPv6 stateful filtering behavior described in this document is
   intended to be similar in function to the filtering behavior of
   commonly use IPv4/NAT gateways, which have been widely sold as a
   security tool for residential and small-office/home-office networks.
   As noted in the security considerations section of [RFC2993], the
   true impact of these tools may be a reduction in security.  It may be
   generally assumed that the impacts discussed in that document related
   to filtering (and not translation) are to be expected with the simple
   IPv6 security mechanisms described here.

   In particular, it's worth noting that stateful filters create the
   illusion of a security barrier, but without the managed intent of a
   firewall.  Appropriate security mechanisms implemented in the end
   nodes, in conjunction with the [RFC4864] local network protection
   methods, function without reliance on network layer hacks and
   transport filters that may change over time.  Also, defined security
   barriers assume that threats originate in the exterior, which may
   lead to practices that result in applications being fully exposed to
   interior attack and which therefore make breaches much easier.

   The security functions described in this document may be considered
   redundant in the event that all IPv6 hosts using a particular gateway
   have their own IPv6 host firewall capabilities enabled.  At the time
   of this writing, the vast majority of commercially available
   operating systems with support for IPv6 include IPv6 host firewall
   capability.

   Finally, residential gateways that implement simple security
   functions are a bastion between the interior and the exterior, and
   therefore are a target of denial of service attacks against the
   interior network itself by processes designed to consume the
   resources of the gateway, e.g. a ping or SYN flood.  Gateways should
   employ the same sorts of protection techniques as application servers
   on the Internet.

   IETF makes no statement, expressed or implied, as to whether using
   the capabilities described in this document ultimately improve
   security for any individual users or for the Internet community as a



woodyatt               Expires September 27, 2010              [Page 29]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   whole.


8.  References

8.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [RFC1323]  Jacobson, V., Braden, B., and D. Borman, "TCP Extensions
              for High Performance", RFC 1323, May 1992.

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

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC3828]  Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., and
              G. Fairhurst, "The Lightweight User Datagram Protocol
              (UDP-Lite)", RFC 3828, July 2004.

   [RFC3879]  Huitema, C. and B. Carpenter, "Deprecating Site Local
              Addresses", RFC 3879, September 2004.

   [RFC4007]  Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
              B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
              March 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              December 2005.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.




woodyatt               Expires September 27, 2010              [Page 30]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340, March 2006.

   [RFC4787]  Audet, F. and C. Jennings, "Network Address Translation
              (NAT) Behavioral Requirements for Unicast UDP", BCP 127,
              RFC 4787, January 2007.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              April 2007.

   [RFC4890]  Davies, E. and J. Mohacsi, "Recommendations for Filtering
              ICMPv6 Messages in Firewalls", RFC 4890, May 2007.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",
              RFC 4960, September 2007.

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              December 2007.

   [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
              April 2008.

8.2.  Informative References

   [I-D.cheshire-nat-pmp]
              Cheshire, S., "NAT Port Mapping Protocol (NAT-PMP)",
              draft-cheshire-nat-pmp-03 (work in progress), April 2008.

   [I-D.woodyatt-ald]
              Woodyatt, J., "Application Listener Discovery (ALD) for
              IPv6", draft-woodyatt-ald-03 (work in progress),
              July 2008.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1337]  Braden, B., "TIME-WAIT Assassination Hazards in TCP",
              RFC 1337, May 1992.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.



woodyatt               Expires September 27, 2010              [Page 31]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   [RFC2993]  Hain, T., "Architectural Implications of NAT", RFC 2993,
              November 2000.

   [RFC3068]  Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
              RFC 3068, June 2001.

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [RFC4080]  Hancock, R., Karagiannis, G., Loughney, J., and S. Van den
              Bosch, "Next Steps in Signaling (NSIS): Framework",
              RFC 4080, June 2005.

   [RFC4294]  Loughney, J., "IPv6 Node Requirements", RFC 4294,
              April 2006.

   [RFC4864]  Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
              E. Klein, "Local Network Protection for IPv6", RFC 4864,
              May 2007.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              RFC 4949, August 2007.

   [RFC5189]  Stiemerling, M., Quittek, J., and T. Taylor, "Middlebox
              Communication (MIDCOM) Protocol Semantics", RFC 5189,
              March 2008.

   [RFC5382]  Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P.
              Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
              RFC 5382, October 2008.

   [RFC5389]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", RFC 5389,
              October 2008.

   [RFC5533]  Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
              Shim Protocol for IPv6", RFC 5533, June 2009.

   [UPnP-IGD]
              UPnP Forum, "Universal Plug and Play Internet Gateway
              Device Standardized Gateway Device Protocol",
              September 2006,
              <http://www.upnp.org/standardizeddcps/igd.asp>.


Appendix A.  Change Log





woodyatt               Expires September 27, 2010              [Page 32]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


A.1.  draft-ietf-v6ops-cpe-simple-security-00 to
      draft-ietf-v6ops-cpe-simple-security-01

   o  Added requirements for sequestering DHCP and DNS proxy resolver
      services to the local network.

   o  Fixed numbering of recommendations.

   o  Local Network Protection is now [RFC4864].

   o  SCTP is now [RFC4960].

   o  Moved some references to informative.

   o  Corrected the reference for
      draft-hoagland-v6ops-teredosecconcerns.

A.2.  draft-ietf-v6ops-cpe-simple-security-01 to
      draft-ietf-v6ops-cpe-simple-security-02

   o  Inserted REC-20, i.e. do not enforce TCP window invariant unless
      the TCP window-scale is known for the state.

   o  Filled out Section 4.

   o  Added reference to [RFC1323].

   o  Updated the reference for draft-hoagland-v6ops-teredosecconcerns.

   o  Expanded list of contributers and commenters.

   o  Mention that UDP-Lite should be handled just like UDP.

   o  Added section for generic upper layer transport protocols.

   o  Expanded on recommendations for IPsec ESP filtering.

   o  Expanded overview of recommendations with discussion about IP
      mobility and IPsec interactions.

   o  Added a security considerations section.

A.3.  draft-ietf-v6ops-cpe-simple-security-02 to
      draft-ietf-v6ops-cpe-simple-security-03

   o  Fixed some spelling errors.





woodyatt               Expires September 27, 2010              [Page 33]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   o  Replace "prevent such attacks" with "defend against such attacks"
      everywhere.

   o  Replace "mapping" with "state record" in the TCP filters section.

   o  Added recommendations for SCTP and DCCP.

A.4.  draft-ietf-v6ops-cpe-simple-security-03 to
      draft-ietf-v6ops-cpe-simple-security-04

   o  Removed references to draft-hoagland-v6ops-teredosecconcerns.

   o  Updated reference to [RFC5382].

   o  Add reference to RFC 4879.  (Removed in -08).

   o  Use SYSTEM resources for referencing Internet Drafts.

   o  Updated IPR boilerplate.

A.5.  draft-ietf-v6ops-cpe-simple-security-04 to
      draft-ietf-v6ops-cpe-simple-security-05

   o  Changed category from BCP to Informational.

   o  Change text in section 3 to read "activate new states as a side
      effect of forwarding outbound flow initiations" to improve
      clarity.

   o  Qualified an informative insertion by inserting the phrase "on
      such networks" appropriately and relaxed the MUST to a SHOULD in
      the text about impeding Teredo.

   o  Changed MUST to SHOULD in REC-18 about impeding Teredo.

   o  Replace "that" with "than" in REC-2.

   o  Removed an unnecessary and incorrect paragraph about IPv6/NAT from
      the overview.

   o  Changed the first MUST NOT to a SHOULD NOT in REC-3.

   o  Renumbered the recommendations in section 3.1 to increase
      monotonically and match the same recommendations in the summary.

   o  Rewrote REC-6, REC-27 and REC-32 for clarity.





woodyatt               Expires September 27, 2010              [Page 34]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   o  Added normative reference to [RFC4193].

   o  Removed REC-8 from the summary, which did not appear in section
      3.1, and was redundant with REC-27.

   o  Added a reference to [RFC5382] in REC-28.

   o  Inserted REC-32 into the summary, which had been skipped.

   o  Removed "alongside an IPv4 private address" and inserted "globally
      routed" before the first use of the word "prefix" in REC-18.

   o  Qualify an assertion with "some" in the informative section about
      TCP filters.

   o  Updated obsolete references to RFC 3989 and RFC 4748.

A.6.  draft-ietf-v6ops-cpe-simple-security-05 to
      draft-ietf-v6ops-cpe-simple-security-06

   o  Corrected some typographical spelling errors.

   o  Added more names to the contributors section and attempted to
      provide better attribution for the editors of previous RFCs.

   o  Add normative reference to [RFC5095].

   o  Editorial improvement to Section 2.3.

   o  Added DEFAULT recommendation for REC-14 and REC-26 to use
      Endpoint-independent filtering in gateways intended for
      provisioning without service-provider management.

   o  Added informative reference to [RFC4949].

   o  Added normative references for ICMP6 [RFC4884] and [RFC4890].

   o  Added normative references to [RFC3879] and [RFC5156] and inserted
      new REC-3 to forbid forwarding packets for addresses forbidden on
      the public Internet.

   o  Removed erroneous recommendation about SCTP INIT from summary
      list, which had already been removed from the detailed section in
      an earlier revision.

   o  Added a section describing the irrelevance of 6to4 and an
      informative reference to [RFC3068].




woodyatt               Expires September 27, 2010              [Page 35]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   o  Added normative reference to [RFC4291], and word-smithed REC-2 to
      add a brief discussion about multicast scope boundaries.

   o  Added a section and an information reference for SHIM6 explaining
      why it's incompatible with IPv6 simple security.

A.7.  draft-ietf-v6ops-cpe-simple-security-06 to
      draft-ietf-v6ops-cpe-simple-security-07

   o  Improve the language describing directionality of traffic flows.

   o  Explicitly recommend a less restrictive configuration option.

   o  Don't use Latin-1 characters not present in 7-bit ASCII.

A.8.  draft-ietf-v6ops-cpe-simple-security-07 to
      draft-ietf-v6ops-cpe-simple-security-08

   o  Use REC- instead of R for prefixing recommendations.

   o  Remove second sentence of REC-41, dropping the somewhat squirrely
      language about documentation standards.

   o  Remove section 3.2.7 Other Virtual Private Network Protocols,
      including REC-24.

   o  Improve section 3.4, Passive Listeners, with a reference to
      [RFC5389] and further explanation of motivation for
      recommendations.

   o  Correct order of recommendations in summary section.

   o  Update reference to [RFC5533].

A.9.  draft-ietf-v6ops-cpe-simple-security-08 to
      draft-ietf-v6ops-cpe-simple-security-09

   o  Add references to [RFC2827] and [RFC3704] for uRPF spoofing.

   o  Add REC-42 to discourage use of the WAN interface for management.

   o  Updated contributors.

A.10.  draft-ietf-v6ops-cpe-simple-security-09 to
       draft-ietf-v6ops-cpe-simple-security-10






woodyatt               Expires September 27, 2010              [Page 36]

Internet-Draft     Simple Security in IPv6 Gateway CPE        March 2010


   o  Cite [RFC4007] in REC-2.

   o  Insert REC-12 to complete consistency of recommendations with
      those in [RFC4890] and renumber subsequent recommendations.

   o  Completely remove recommendation to block Teredo.

   o  Soften the language recommending implementation of simple
      security.  Insert explicit note about intent of the document to
      inform and not to prescribe.

   o  Editorial revision in section 2.2 to match the removal of section
      3.2.7 in the -08 revision.

   o  Editorial improvements to promote the phrase "transparent mode" to
      describe the alternative operating mode recommended in REC-41.

   o  Fix some minor spelling and grammar errors.


Author's Address

   james woodyatt (editor)
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   US

   Email: jhw@apple.com






















woodyatt               Expires September 27, 2010              [Page 37]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/