draft-ietf-rtgwg-rfc3682bis-06.txt   draft-ietf-rtgwg-rfc3682bis-07.txt 
Routing WG V. Gill Routing WG V. Gill
Internet-Draft J. Heasley Internet-Draft J. Heasley
Obsoletes: 3682 (if approved) D. Meyer Obsoletes: 3682 (if approved) D. Meyer
Intended status: Standards Track P. Savola Intended status: Standards Track P. Savola
Expires: March 1, 2007 August 28, 2006 Expires: May 26, 2007 November 22, 2006
The Generalized TTL Security Mechanism (GTSM) The Generalized TTL Security Mechanism (GTSM)
draft-ietf-rtgwg-rfc3682bis-06.txt draft-ietf-rtgwg-rfc3682bis-07.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
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skipping to change at page 1, line 35 skipping to change at page 1, line 35
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This Internet-Draft will expire on March 1, 2007. This Internet-Draft will expire on May 26, 2007.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The IETF Trust (2006).
Abstract Abstract
The use of a packet's Time to Live (TTL) (IPv4) or Hop Limit (IPv6) The use of a packet's Time to Live (TTL) (IPv4) or Hop Limit (IPv6)
to verify whether the packet originated within the same link has been to verify whether the packet originated within the same link has been
used in many recent protocols. This document generalizes this used in many recent protocols. This document generalizes this
technique. This document obsoletes RFC 3682. technique. This document obsoletes RFC 3682.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Assumptions Underlying GTSM . . . . . . . . . . . . . . . . . 3 2. Assumptions Underlying GTSM . . . . . . . . . . . . . . . . . 3
2.1. GTSM Negotiation . . . . . . . . . . . . . . . . . . . . . 4 2.1. GTSM Negotiation . . . . . . . . . . . . . . . . . . . . . 4
2.2. Assumptions on Attack Sophistication . . . . . . . . . . . 4 2.2. Assumptions on Attack Sophistication . . . . . . . . . . . 4
3. GTSM Procedure . . . . . . . . . . . . . . . . . . . . . . . . 5 3. GTSM Procedure . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5.1. TTL (Hop Limit) Spoofing . . . . . . . . . . . . . . . . . 7 5.1. TTL (Hop Limit) Spoofing . . . . . . . . . . . . . . . . . 7
5.2. Tunneled Packets . . . . . . . . . . . . . . . . . . . . . 7 5.2. Tunneled Packets . . . . . . . . . . . . . . . . . . . . . 7
5.2.1. IP in IP . . . . . . . . . . . . . . . . . . . . . . . 8 5.2.1. IP in IP . . . . . . . . . . . . . . . . . . . . . . . 7
5.2.2. IP in MPLS . . . . . . . . . . . . . . . . . . . . . . 8 5.2.2. IP in MPLS . . . . . . . . . . . . . . . . . . . . . . 8
5.3. Multi-Hop Protocol Sessions . . . . . . . . . . . . . . . 9 5.3. Multi-Hop Protocol Sessions . . . . . . . . . . . . . . . 9
6. Applicability Statement . . . . . . . . . . . . . . . . . . . 10 6. Applicability Statement . . . . . . . . . . . . . . . . . . . 9
6.1. Backwards Compatibility . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Changes between -05 and -06 . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 Appendix A. Multihop GTSM . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11 Appendix B. Changes Since RFC3682 . . . . . . . . . . . . . . . 12
Appendix A. Multihop GTSM . . . . . . . . . . . . . . . . . . . . 12 Appendix C. Draft Changelog . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Appendix C.1. Changes between -06 and -07 . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13 Appendix C.2. Changes between -05 and -06 . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 14
1. Introduction 1. Introduction
The Generalized TTL Security Mechanism (GTSM) is designed to protect The Generalized TTL Security Mechanism (GTSM) is designed to protect
a router's IP based control plane from CPU-utilization based attacks. a router's IP based control plane from CPU-utilization based attacks.
In particular, while cryptographic techniques can protect the router- In particular, while cryptographic techniques can protect the router-
based infrastructure (e.g., BGP [RFC4271], [RFC4272]) from a wide based infrastructure (e.g., BGP [RFC4271], [RFC4272]) from a wide
variety of attacks, many attacks based on CPU overload can be variety of attacks, many attacks based on CPU overload can be
prevented by the simple mechanism described in this document. Note prevented by the simple mechanism described in this document. Note
that the same technique protects against other scarce-resource that the same technique protects against other scarce-resource
attacks involving a router's CPU, such as attacks against processor- attacks involving a router's CPU, such as attacks against processor-
line card bandwidth. line card bandwidth.
GTSM is based on the fact that the vast majority of protocol peerings GTSM is based on the fact that the vast majority of protocol peerings
are established between routers that are adjacent [PEERING]. Thus are established between routers that are adjacent . Thus most
most protocol peerings are either directly between connected protocol peerings are either directly between connected interfaces or
interfaces or at the worst case, are between loopback and loopback, at the worst case, are between loopback and loopback, with static
with static routes to loopbacks. Since TTL spoofing is considered routes to loopbacks. Since TTL spoofing is considered nearly
nearly impossible, a mechanism based on an expected TTL value can impossible, a mechanism based on an expected TTL value can provide a
provide a simple and reasonably robust defense from infrastructure simple and reasonably robust defense from infrastructure attacks
attacks based on forged protocol packets from outside the network. based on forged protocol packets from outside the network. Note,
Note, however, that GTSM is not a substitute for authentication however, that GTSM is not a substitute for authentication mechanisms.
mechanisms. In particular, it does not secure against insider on- In particular, it does not secure against insider on-the-wire
the-wire attacks, such as packet spoofing or replay. attacks, such as packet spoofing or replay.
Finally, the GTSM mechanism is equally applicable to both TTL (IPv4) Finally, the GTSM mechanism is equally applicable to both TTL (IPv4)
and Hop Limit (IPv6), and from the perspective of GTSM, TTL and Hop and Hop Limit (IPv6), and from the perspective of GTSM, TTL and Hop
Limit have identical semantics. As a result, in the remainder of Limit have identical semantics. As a result, in the remainder of
this document the term "TTL" is used to refer to both TTL or Hop this document the term "TTL" is used to refer to both TTL or Hop
Limit (as appropriate). Limit (as appropriate).
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Assumptions Underlying GTSM 2. Assumptions Underlying GTSM
GTSM is predicated upon the following assumptions: GTSM is predicated upon the following assumptions:
1. The vast majority of protocol peerings are between adjacent 1. The vast majority of protocol peerings are between adjacent
routers [PEERING]. routers.
2. It is common practice for many service providers to ingress 2. It is common practice for many service providers to ingress
filter (deny) packets that have the provider's loopback addresses filter (deny) packets that have the provider's loopback addresses
as the source IP address. as the source IP address.
3. Use of GTSM is OPTIONAL, and can be configured on a per-peer 3. Use of GTSM is OPTIONAL, and can be configured on a per-peer
(group) basis. (group) basis.
4. The peer routers both implement GTSM. 4. The peer routers both implement GTSM.
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the victim protocol speaker decrements TTL properly (clearly, if the victim protocol speaker decrements TTL properly (clearly, if
either the path or the adjacent peer is compromised, then there are either the path or the adjacent peer is compromised, then there are
worse problems to worry about). worse problems to worry about).
Since the vast majority of peerings are between adjacent routers, we Since the vast majority of peerings are between adjacent routers, we
can set the TTL on the protocol packets to 255 (the maximum possible can set the TTL on the protocol packets to 255 (the maximum possible
for IP) and then reject any protocol packets that come in from for IP) and then reject any protocol packets that come in from
configured peers which do NOT have an inbound TTL of 255. configured peers which do NOT have an inbound TTL of 255.
GTSM can be disabled for applications such as route-servers and other GTSM can be disabled for applications such as route-servers and other
large diameter multi-hop peerings. In the event that an the attack multi-hop peerings. In the event that an attack comes in from a
comes in from a compromised multi-hop peering, that peering can be compromised multi-hop peering, that peering can be shut down.
shut down (a method to reduce exposure to multi-hop attacks is
outlined below).
3. GTSM Procedure 3. GTSM Procedure
If GTSM is not built into the protocol and used as an additional If GTSM is not built into the protocol and used as an additional
feature (e.g., for BGP, LDP, or MSDP), it SHOULD NOT be enabled by feature (e.g., for BGP, LDP, or MSDP), it SHOULD NOT be enabled by
default. default.
If GTSM is enabled for a protocol session, the following steps are If GTSM is enabled for a protocol session, the following steps are
added to the IP packet sending and reception procedures: added to the IP packet sending and reception procedures:
Sending protocol packets: Sending protocol packets:
The TTL field in all IP packets used for transmission of The TTL field in all IP packets used for transmission of
messages associated with GTSM-enabled protocol sessions MUST be messages associated with GTSM-enabled protocol sessions MUST be
set to 255. This also related error handling messages such as set to 255. This also applies to related error handling
TCP RSTs or ICMP errors. messages such as TCP RSTs or ICMP errors.
On some architectures, the TTL of control plane originated On some architectures, the TTL of control plane originated
traffic is under some configurations decremented in the traffic is under some configurations decremented in the
forwarding plane. The TTL of GTSM-enabled sessions MUST NOT be forwarding plane. The TTL of GTSM-enabled sessions MUST NOT be
decremented. decremented.
Receiving protocol packets: Receiving protocol packets:
The GTSM packet identification step associates each received The GTSM packet identification step associates each received
packet addressed to the router's control plane with one of the packet addressed to the router's control plane with one of the
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+ MAY drop packets classified as Dangerous. + MAY drop packets classified as Dangerous.
4. Acknowledgments 4. Acknowledgments
The use of the TTL field to protect BGP originated with many The use of the TTL field to protect BGP originated with many
different people, including Paul Traina and Jon Stewart. Ryan different people, including Paul Traina and Jon Stewart. Ryan
McDowell also suggested a similar idea. Steve Bellovin, Jay McDowell also suggested a similar idea. Steve Bellovin, Jay
Borkenhagen, Randy Bush, Alfred Hoenes, Vern Paxon, Robert Raszuk and Borkenhagen, Randy Bush, Alfred Hoenes, Vern Paxon, Robert Raszuk and
Alex Zinin also provided useful feedback on earlier versions of this Alex Zinin also provided useful feedback on earlier versions of this
document. David Ward provided insight on the generalization of the document. David Ward provided insight on the generalization of the
original BGP-specific idea. Alex Zinin and Alia Atlas provided original BGP-specific idea. Alex Zinin, Alia Atlas, and John Scudder
significant amount of feedback for the newer versions of the provided significant amount of feedback for the newer versions of the
document. document.
5. Security Considerations 5. Security Considerations
GTSM is a simple procedure that protects single hop protocol GTSM is a simple procedure that protects single hop protocol
sessions, except in those cases in which the peer has been sessions, except in those cases in which the peer has been
compromised. In particular, it does not protect against the wide compromised. In particular, it does not protect against the wide
range of on-the-wire attacks; protection from these attacks requires range of on-the-wire attacks; protection from these attacks requires
more rigorous security mechanisms. more rigorous security mechanisms.
5.1. TTL (Hop Limit) Spoofing 5.1. TTL (Hop Limit) Spoofing
The approach described here is based on the observation that a TTL The approach described here is based on the observation that a TTL
(or Hop Limit) value of 255 is non-trivial to spoof, since as the (or Hop Limit) value of 255 is non-trivial to spoof, since as the
packet passes through routers towards the destination, the TTL is packet passes through routers towards the destination, the TTL is
decremented by one. As a result, when a router receives a packet, it decremented by one per router. As a result, when a router receives a
may not be able to determine if the packet's IP address is valid, but packet, it may not be able to determine if the packet's IP address is
it can determine how many router hops away it is (again, assuming valid, but it can determine how many router hops away it is (again,
none of the routers in the path are compromised in such a way that assuming none of the routers in the path are compromised in such a
they would reset the packet's TTL). way that they would reset the packet's TTL).
Note, however, that while engineering a packet's TTL such that it has Note, however, that while engineering a packet's TTL such that it has
a particular value when sourced from an arbitrary location is a particular value when sourced from an arbitrary location is
difficult (but not impossible), engineering a TTL value of 255 from difficult (but not impossible), engineering a TTL value of 255 from
non-directly connected locations is not possible (again, assuming non-directly connected locations is not possible (again, assuming
none of the directly connected neighbors are compromised, the packet none of the directly connected neighbors are compromised, the packet
hasn't been tunneled to the decapsulator, and the intervening routers hasn't been tunneled to the decapsulator, and the intervening routers
are operating in accordance with RFC 791 [RFC0791]). are operating in accordance with RFC 791 [RFC0791]).
5.2. Tunneled Packets 5.2. Tunneled Packets
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Peer router ---------- Tunnel endpoint router and peer Peer router ---------- Tunnel endpoint router and peer
TTL=255 [tunnel] [TTL=255 at ingress] TTL=255 [tunnel] [TTL=255 at ingress]
[TTL=255 at egress] [TTL=255 at egress]
Peer router -------- Tunnel endpoint router ----- On-link peer Peer router -------- Tunnel endpoint router ----- On-link peer
TTL=255 [tunnel] [TTL=255 at ingress] [TTL=254 at ingress] TTL=255 [tunnel] [TTL=255 at ingress] [TTL=254 at ingress]
[TTL=254 at egress] [TTL=254 at egress]
In the first case, in which the encapsulated packet is tunneled In the first case, in which the encapsulated packet is tunneled
directly to the protocol peer, the encapsulated packet's TTL can be directly to the protocol peer, the encapsulated packet's TTL can be
set arbitrary value. In the second case, in which the encapsulated set to an arbitrary value.
packet is tunneled to a decapsulator (tunnel endpoint) which then
forwards it to a directly connected protocol peer, RFC 2003 specifies In the second case, in which the encapsulated packet is tunneled to a
the following behavior: decapsulator (tunnel endpoint) which then forwards it to a directly
connected protocol peer, RFC 2003 specifies the following behavior:
When encapsulating a datagram, the TTL in the inner IP When encapsulating a datagram, the TTL in the inner IP
header is decremented by one if the tunneling is being header is decremented by one if the tunneling is being
done as part of forwarding the datagram; otherwise, the done as part of forwarding the datagram; otherwise, the
inner header TTL is not changed during encapsulation. If inner header TTL is not changed during encapsulation. If
the resulting TTL in the inner IP header is 0, the the resulting TTL in the inner IP header is 0, the
datagram is discarded and an ICMP Time Exceeded message datagram is discarded and an ICMP Time Exceeded message
SHOULD be returned to the sender. An encapsulator MUST SHOULD be returned to the sender. An encapsulator MUST
NOT encapsulate a datagram with TTL = 0. NOT encapsulate a datagram with TTL = 0.
Hence the inner IP packet header's TTL, as seen by the decapsulator, Hence the inner IP packet header's TTL, as seen by the decapsulator,
can be set to an arbitrary value (in particular, 255). As a result, can be set to an arbitrary value (in particular, 255), however as the
it may not be possible to deliver the protocol packet to the peer decapsulator forwards the protocol packet to the peer, TTL will be
with a TTL of 255. decremented.
5.2.2. IP in MPLS 5.2.2. IP in MPLS
Protocol packets may also be tunneled over MPLS to a protocol peer Protocol packets may also be tunneled over MPLS to a protocol peer
which either the penultimate hop (when the penultimate hop popping which either the penultimate hop (when the penultimate hop popping
(PHP) is employed [RFC3032]), or one hop beyond the penultimate hop. (PHP) is employed [RFC3032]) or the final hop These cases are
These cases are depicted below. depicted below.
Peer router -------- Penultimate Hop (PH) and peer Peer router -------- Penultimate Hop (PH) and peer
TTL=255 [tunnel] [TTL=255 at ingress] TTL=255 [tunnel] [TTL=255 at ingress]
[TTL<=254 at egress] [TTL<=254 at egress]
Peer router -------- Penultimate Hop -------- On-link peer Peer router -------- Penultimate Hop -------- On-link peer
TTL=255 [tunnel] [TTL=255 at ingress] [TTL <=254 at ingress] TTL=255 [tunnel] [TTL=255 at ingress] [TTL <=254 at ingress]
[TTL<=254 at egress] [TTL<=254 at egress]
TTL handling for these cases is described in RFC 3032. RFC 3032 TTL handling for these cases is described in RFC 3032. RFC 3032
states that when the IP packet is first labeled: states that when the IP packet is first labeled:
... the TTL field of the label stack entry MUST BE set to the ... the TTL field of the label stack entry MUST BE set to the
value of the IP TTL field. (If the IP TTL field needs to be value of the IP TTL field. (If the IP TTL field needs to be
decremented, as part of the IP processing, it is assumed that decremented, as part of the IP processing, it is assumed that
this has already been done.) this has already been done.)
When the label is popped: When the label is popped:
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In either of these cases, the minimum value by which the TTL could be In either of these cases, the minimum value by which the TTL could be
decremented would be one (the network operator prefers to hide its decremented would be one (the network operator prefers to hide its
infrastructure by decrementing the TTL by the minimum number of LSP infrastructure by decrementing the TTL by the minimum number of LSP
hops, one, rather than decrementing the TTL as it traverses its MPLS hops, one, rather than decrementing the TTL as it traverses its MPLS
domain). As a result, the maximum TTL value at egress from the MPLS domain). As a result, the maximum TTL value at egress from the MPLS
cloud is 254 (255-1), and as a result the check described in section cloud is 254 (255-1), and as a result the check described in section
3 will fail. 3 will fail.
5.3. Multi-Hop Protocol Sessions 5.3. Multi-Hop Protocol Sessions
While GTSM could possibly offer a slightly more limited security While GTSM could possibly offer some small though difficult to
properties also when used with multi-hop protocol sessions (see quantify degree of protection when used with multi-hop protocol
Appendix A), we do not specify GTSM for multi-hop scenarios due to sessions (see Appendix A), we do not specify GTSM for multi-hop
simplicity, lack of deployment and implementation. scenarios due to simplicity, lack of deployment and implementation.
6. Applicability Statement 6. Applicability Statement
GTSM is only applicable to environments with inherently limited GTSM is only applicable to environments with inherently limited
topologies (and is most effective in those cases where protocol peers topologies (and is most effective in those cases where protocol peers
are directly connected). In particular, its application should be are directly connected). In particular, its application should be
limited to those cases in which protocol peers are directly limited to those cases in which protocol peers are directly
connected. connected.
Experimentation on GTSM's applicability and security properties is Experimentation on GTSM's applicability and security properties is
needed in multi-hop scenarios. The multi-hop scenarios where GTSM needed in multi-hop scenarios. The multi-hop scenarios where GTSM
might be applicable is expected to have the following might be applicable is expected to have the following
characteristics: the topology between peers is fairly static and well characteristics: the topology between peers is fairly static and well
known, and in which the intervening network (between the peers) is known, and in which the intervening network (between the peers) is
trusted. trusted.
7. IANA Considerations 6.1. Backwards Compatibility
This document requires no action from IANA.
8. Changelog
NOTE to the RFC-editor: please remove this section before
publication.
8.1. Changes between -05 and -06
o Clarify the assumptions wrt. resource separation and protection
based on comments from Alex Zinin.
o Rewrite the GTSM procedure based on text from Alex Zinin. RFC 3682 did not specify how to handle "related messages" such as TCP
RSTs or ICMP errors. This specification mandates setting and
verifying TTL=255 of those as well as the main protocol packets.
o Reduce TrustRadius and multi-hop scenarios to a mention in an Setting TTL=255 in related messages does not cause issues for RFC
Appendix. 3682 implementations.
o Describe TCP-RST, ICMP error and "related messages" handling. Requiring TTL=255 in related messages may have impact with RFC 3682
implementations, depending on which default TTL the implementation
uses for originated packets; some implementations are known to use
255, while 64 or other values are also used. Related messages from
the latter category of RFC 3682 implementations would be discarded.
This is not believed to be a significant problem because protocols do
not depend on related messages (e.g., typically having a protocol
exchange for closing the session instead of doing a TCP-RST), and
indeed the delivery of related messages is not reliable. As such,
related messages typically provide an optimization to shorten a
protocol keepalive timeout. Regardless of these issues, given that
related messages provide a significant attack vector to e.g., reset
protocol sessions, making this further restriction seems sensible.
o Update the tunneling security considerations text. 7. IANA Considerations
o Editorial updates (e.g., shortening the abstract). This document requires no action from IANA.
9. References 8. References
9.1. Normative References 8.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981. September 1981.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996. October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
skipping to change at page 11, line 40 skipping to change at page 11, line 32
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005. for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, January 2006. RFC 4272, January 2006.
9.2. Informative References 8.2. Informative References
[BITW] "Thread: 'IP-in-IP, TTL decrementing when forwarding and [BITW] "Thread: 'IP-in-IP, TTL decrementing when forwarding and
BITW' on int-area list, Message-ID: BITW' on int-area list, Message-ID:
<Pine.LNX.4.64.0606020830220.12705@netcore.fi>", <Pine.LNX.4.64.0606020830220.12705@netcore.fi>",
June 2006, <http://www1.ietf.org/mail-archive/web/ June 2006, <http://www1.ietf.org/mail-archive/web/
int-area/current/msg00267.html>. int-area/current/msg00267.html>.
[PEERING] "Empirical data gathered from the Sprint and AOL
backbones", October 2002.
Appendix A. Multihop GTSM Appendix A. Multihop GTSM
NOTE: This is a non-normative part of the specification. NOTE: This is a non-normative part of the specification.
The main applicability of GTSM is for directly connected peers. GTSM The main applicability of GTSM is for directly connected peers. GTSM
could be used for non-directly connected sessions as well, where the could be used for non-directly connected sessions as well, where the
recipient would check that the TTL is within "TrustRadius" (e.g., 1) recipient would check that the TTL is within "TrustRadius" (e.g., 1)
of 255 instead of 255. As such deployment is expected to have a more of 255 instead of 255. As such deployment is expected to have a more
limited applicability and different security implications, it is not limited applicability and different security implications, it is not
specified in this document. specified in this document.
Appendix B. Changes Since RFC3682
o New text on GTSM applicability and use in new and existing
protocols.
o Explicitly require that related messages (e.g., TCP RSTs, ICMP
errors) must also be sent and checked to have TTL=255. See
Section 6.1 for discussion on backwards compatibility.
o Clarifications relating to security with tunneling.
o A significant number of editorial improvements and clarifications.
Appendix C. Draft Changelog
NOTE to the RFC-editor: please remove this section before
publication.
Appendix C.1. Changes between -06 and -07
o Be more reserved about multi-hop security properties in section
'Multi-Hop Protocol Sessions'.
o Clarify IP-in-IP tunnel decapsulation/forwarding as decrementing
TTL.
o Add text on related messages backwards compatibility.
o Editorial updates.
Appendix C.2. Changes between -05 and -06
o Clarify the assumptions wrt. resource separation and protection
based on comments from Alex Zinin.
o Rewrite the GTSM procedure based on text from Alex Zinin.
o Reduce TrustRadius and multi-hop scenarios to a mention in an
Appendix.
o Describe TCP-RST, ICMP error and "related messages" handling.
o Update the tunneling security considerations text.
o Editorial updates (e.g., shortening the abstract).
Authors' Addresses Authors' Addresses
Vijay Gill Vijay Gill
Email: vijay@umbc.edu Email: vijay@umbc.edu
John Heasley John Heasley
Email: heas@shrubbery.net Email: heas@shrubbery.net
skipping to change at page 13, line 7 skipping to change at page 14, line 7
Email: dmm@1-4-5.net Email: dmm@1-4-5.net
Pekka Savola Pekka Savola
Espoo Espoo
Finland Finland
Email: psavola@funet.fi Email: psavola@funet.fi
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