Internet Engineering Task Force (IETF) G. Lebovitz
Request for Comments: 6518 M. Bhatia
Category: Informational Alcatel-Lucent
ISSN: 2070-1721 February 2012
Keying and Authentication for Routing Protocols (KARP)
Design Guidelines
Abstract
This document is one of a series concerned with defining a roadmap of
protocol specification work for the use of modern cryptographic
mechanisms and algorithms for message authentication in routing
protocols. In particular, it defines the framework for a key
management protocol that may be used to create and manage session
keys for message authentication and integrity.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6518.
Lebovitz & Bhatia Informational [Page 1]RFC 6518 KARP Design Guidelines February 2012
Copyright Notice
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document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
1.1. Conventions Used in This Document ..........................4
2. Categorizing Routing Protocols ..................................5
2.1. Category: Message Transaction Type .........................5
2.2. Category: Peer versus Group Keying .........................6
3. Consider the Future Existence of a Key Management Protocol ......6
3.1. Consider Asymmetric Keys ...................................7
3.2. Cryptographic Keys Life Cycle ..............................8
4. Roadmap .........................................................9
4.1. Work Phases on Any Particular Protocol .....................9
4.2. Work Items per Routing Protocol ...........................11
5. Routing Protocols in Categories ................................13
6. Supporting Incremental Deployment ..............................16
7. Denial-of-Service Attacks ......................................17
8. Gap Analysis ...................................................18
9. Security Considerations ........................................20
9.1. Use Strong Keys ...........................................21
9.2. Internal versus External Operation ........................22
9.3. Unique versus Shared Keys .................................22
9.4. Key Exchange Mechanism ....................................24
10. Acknowledgments ...............................................26
11. References ....................................................26
11.1. Normative References ....................................26
11.2. Informative References ..................................26
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1. Introduction
In March 2006, the Internet Architecture Board (IAB) held a workshop
on the topic of "Unwanted Internet Traffic". The report from that
workshop is documented in RFC 4948 [RFC4948]. Section 8.1 of that
document states that "A simple risk analysis would suggest that an
ideal attack target of minimal cost but maximal disruption is the
core routing infrastructure". Section 8.2 calls for "[t]ightening
the security of the core routing infrastructure". Four main steps
were identified for that tightening:
o Increase the security mechanisms and practices for operating
routers.
o Clean up the Internet Routing Registry [IRR] repository, and
securing both the database and the access, so that it can be used
for routing verifications.
o Create specifications for cryptographic validation of routing
message content.
o Secure the routing protocols' packets on the wire.
The first bullet is being addressed in the OPSEC working group. The
second bullet should be addressed through liaisons with those running
the IRR's globally. The third bullet is being addressed in the SIDR
working group.
This document addresses the last bullet, securing the packets on the
wire of the routing protocol exchanges. Thus, it is concerned with
guidelines for describing issues and techniques for protecting the
messages between directly communicating peers. This may overlap
with, but is strongly distinct from, protection designed to ensure
that routing information is properly authorized relative to sources
of this information. Such authorizations are provided by other
mechanisms and are outside the scope of this document and the work
that relies on it.
This document uses the terminology "on the wire" to talk about the
information used by routing systems. This term is widely used in
RFCs, but is used in several different ways. In this document, it is
used to refer both to information exchanged between routing protocol
instances and to underlying protocols that may also need to be
protected in specific circumstances. Other documents that will
analyze individual protocols will need to indicate how they use the
term "on the wire".
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The term "routing transport" is used to refer to the layer that
exchanges the routing protocols. This can be TCP, UDP, or even
direct link-level messaging in the case of some routing protocols.
The term is used here to allow a referent for discussing both common
and disparate issues that affect or interact with this dimension of
the routing systems. The term is used here to refer generally to the
set of mechanisms and exchanges underneath the routing protocol,
whatever that is in specific cases.
Keying and Authentication for Routing Protocols (KARP) will focus on
an abstraction for keying information that describes the interface
between routing protocols, operators, and automated key management.
Conceptually, when routing protocols send or receive messages, they
will look up the key to use in this abstract key table.
Conceptually, there will be an interface for a routing protocol to
make requests of automated key management when it is being used; when
keys become available, they will be made available in the key table.
There is no requirement that this abstraction be used for
implementation; the abstraction serves the needs of standardization
and management. Specifically, as part of the KARP work plan:
1) KARP will design the key table abstraction, the interface between
key management protocols and routing protocols, and possibly
security protocols at other layers.
2) For each routing protocol, KARP will define the mapping between
how the protocol represents key material and the protocol-
independent key table abstraction. When routing protocols share a
common mechanism for authentication, such as the TCP
Authentication Option, the same mapping is likely to be reused
between protocols. An implementation may be able to move much of
the keying logic into code related to this shared authentication
primitive rather than code specific to routing protocols.
3) When designing automated key management for both symmetric keys
and group keys, we will only use the abstractions designed in
point 1 above to communicate between automated key management and
routing protocols.
Readers must refer to [THTS-REQS] for a clear definition of the
scope, goals, non-goals, and the audience for the design work being
undertaken in the KARP WG.
1.1. Conventions Used in This Document
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].
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2. Categorizing Routing Protocols
This document places the routing protocols into two categories
according to their requirements for authentication. We hope these
categories will allow design teams to focus on security mechanisms
for a given category. Further, we hope that each protocol in the
group will be able to reuse the authentication mechanism. It is also
hoped that, down the road, we can create one Key Management Protocol
(KMP) per category (if not for several categories), so that the work
can be easily leveraged for use in the various routing protocol
groupings. KMPs are useful for allowing simple, automated updates of
the traffic keys used in a base protocol. KMPs replace the need for
humans, or operational support systems (OSS) routines, to
periodically replace keys on running systems. It also removes the
need for a chain of manual keys to be chosen or configured on such
systems. When configured properly, a KMP will enforce the key
freshness policy among peers by keeping track of the key's lifetime
and negotiating a new key at the defined interval.
2.1. Category: Message Transaction Type
The first category defines three types of messaging transactions used
on the wire by the base routing protocol. They are as follows:
One-to-One
One peer router directly and intentionally delivers a route
update specifically to one other peer router. Examples are BGP
[RFC4271]; LDP [RFC5036]; BFD [RFC5880]; and RSVP-TE [RFC3209],
[RFC3473], [RFC4726], and [RFC5151]. Point-to-point modes of
both IS-IS [RFC1195] and OSPF [RFC2328], when sent over both
traditional point-to-point links and when using multi-access
layers, may both also fall into this category.
One-to-Many
A router peers with multiple other routers on a single network
segment -- i.e., on link local -- such that it creates and
sends one route update message that is intended for multiple
peers. Examples would be OSPF and IS-IS in their broadcast,
non-point-to-point mode and Routing Information Protocol (RIP)
[RFC2453].
Multicast
Multicast protocols have unique security properties because
they are inherently group-based protocols; thus, they have
group keying requirements at the routing level where link-local
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routing messages are multicasted. Also, at least in the case
of Protocol Independent Multicast - Sparse Mode (PIM-SM)
[RFC4601], some messages are sent unicast to a given peer(s),
as is the case with router-close-to-sender and the "Rendezvous
Point". Some work for application-layer message security has
been done in the Multicast Security (MSEC) working group and
may be helpful to review, but it is not directly applicable.
These categories affect both the routing protocol view of the
communication and the actual message transfer. As a result, some
message transaction types for a few routing protocols may be
mixtures, for example, using broadcast where multicast might be
expected or using unicast to deliver what looks to the routing
protocol like broadcast or multicast.
Protocol security analysis documents produced in the KARP working
group need to pay attention both to the semantics of the
communication and the techniques that are used for the message
exchanges.
2.2. Category: Peer versus Group Keying
The second category is the keying mechanism that will be used to
distribute the session keys to the routing transports. They are as
follows:
Peer Keying
One router sends the keying messages only to one other router,
such that a one-to-one, uniquely keyed security association (SA)
is established between the two routers (e.g., BGP, BFD and LDP).
Group Keying
One router creates and distributes a single keying message to
multiple peers. In this case, a group SA will be established and
used among multiple peers simultaneously. Group keying exists for
protocols like OSPF [RFC2328] and for multicast protocols like
PIM-SM [RFC4601].
3. Consider the Future Existence of a Key Management Protocol
When it comes time for the KARP WG to design a reusable model for a
Key Management Protocol (KMP), [RFC4107] should be consulted.
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When conducting the design work on a manually keyed version of a
routing protocol's authentication mechanism, consideration must be
made for the eventual use of a KMP. In particular, design teams must
consider what parameters would need to be handed to the routing
protocols by a KMP.
Examples of parameters that might need to be passed are as follows: a
security association identifier (e.g., IPsec Security Parameter Index
(SPI) or the TCP Authentication Option's (TCP-AO's) KeyID), a key
lifetime (which may be represented in either bytes or seconds), the
cryptographic algorithms being used, the keys themselves, and the
directionality of the keys (i.e., receiving versus the sending keys).
3.1. Consider Asymmetric Keys
The use of asymmetric keys can be a very powerful way to authenticate
machine peers as used in routing protocol peer exchanges. If
generated on the machine, and never moved off the machine, these keys
will not need to be changed if an administrator leaves the
organization. Since the keys are random, they are far less
susceptible to off-line dictionary and guessing attacks.
An easy and simple way to use asymmetric keys is to start by having
the router generate a public/private key pair. At the time of this
writing, the recommended key size for algorithms based on integer
factorization cryptography like RSA is 1024 bits and 2048 bits for
extremely valuable keys like the root key pair used by a
certification authority. It is believed that a 1024-bit RSA key is
equivalent in strength to 80-bit symmetric keys and 2048-bit RSA keys
to 112-bit symmetric keys [RFC3766]. Elliptic Curve Cryptography
(ECC) [RFC4492] appears to be secure with shorter keys than those
needed by other asymmetric key algorithms. National Institute of
Standards and Technology (NIST) guidelines [NIST-800-57] state that
ECC keys should be twice the length of equivalent strength symmetric
key algorithms. Thus, a 224-bit ECC key would roughly have the same
strength as a 112-bit symmetric key.
Many routers have the ability to be remotely managed using Secure
Shell (SSH) Protocol [RFC4252] and [RFC4253]. As such, routers will
also have the ability to generate and store an asymmetric key pair,
because this is the common authentication method employed by SSH when
an administrator connects to a router for management sessions.
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Once an asymmetric key pair is generated, the KMP generating security
association parameters and keys for routing protocol may use the
machine's asymmetric keys for the authentication mechanism. The form
of the identity proof could be raw keys, the more easily
administrable self-signed certificate format, or a PKI-issued
[RFC5280] certificate credential.
Regardless of which credential is standardized, the authentication
mechanism can be as simple as a strong hash over a string of human-
readable and transferable form of ASCII characters. More complex,
but also more secure, the identity proof could be verified through
the use of a PKI system's revocation checking mechanism, (e.g.,
Certificate Revocation List (CRL) or Online Certificate Status
Protocol (OCSP) responder). If the SHA-1 fingerprint is used, the
solution could be as simple as loading a set of neighbor routers'
peer ID strings into a table and listing the associated fingerprint
string for each ID string. In most organizations or peering points,
this list will not be longer than a thousand or so routers, and often
the list will be much shorter. In other words, the entire list for a
given organization's router ID and hash could be held in a router's
configuration file, uploaded, downloaded, and moved about at will.
Additionally, it doesn't matter who sees or gains access to these
fingerprints, because they can be distributed publicly as it needn't
be kept secret.
3.2. Cryptographic Keys Life Cycle
Cryptographic keys should have a limited lifetime and may need to be
changed when an operator who had access to them leaves. Using a key
chain, a set of keys derived from the same keying material and used
one after the other, also does not help as one still has to change
all the keys in the key chain when an operator having access to all
those keys leaves the company. Additionally, key chains will not
help if the routing transport subsystem does not support rolling over
to the new keys without bouncing the routing sessions and
adjacencies. So the first step is to fix the routing stack so that
routing protocols can change keys without breaking or bouncing the
adjacencies.
An often cited reason for limiting the lifetime of a key is to
minimize the damage from a compromised key. It could be argued that
it is likely a user will not discover an attacker has compromised the
key if the attacker remains "passive"; thus, relatively frequent key
changes will limit any potential damage from compromised keys.
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Another threat against the long-lived key is that one of the systems
storing the key, or one of the users entrusted with the key, will be
subverted. So, while there may not be cryptographic motivations of
changing the keys, there could be system security motivations for
rolling the key.
Although manual key distribution methods are subject to human error
and frailty, more frequent manual key changes might actually increase
the risk of exposure, as it is during the time that the keys are
being changed that they are likely to be disclosed. In these cases,
especially when very strong cryptography is employed, it may be more
prudent to have fewer, well-controlled manual key distributions
rather than more frequent, poorly controlled manual key
distributions. In general, where strong cryptography is employed,
physical, procedural, and logical access protection considerations
often have more impact on the key life than do algorithm and key size
factors.
For incremental deployments, we could start by associating life times
with the send and the receive keys in the key chain for the long-
lived keys. This is an incremental approach that we could use until
the cryptographic keying material for individual sessions is derived
from the keying material stored in a database of long-lived
cryptographic keys as described in [CRPT-TAB]. A key derivation
function (KDF) and its inputs are also specified in the database of
long-lived cryptographic keys; session-specific values based on the
routing protocol are input to the KDF. Protocol-specific key
identifiers may be assigned to the cryptographic keying material for
individual sessions if needed.
The long-lived cryptographic keys used by the routing protocols can
either be inserted manually in a database or make use of an automated
key management protocol to do this.
4. Roadmap
4.1. Work Phases on Any Particular Protocol
It is believed that improving security for any routing protocol will
be a two-phase process. The first phase would be to modify routing
protocols to support modern cryptography algorithms and key agility.
The second phase would be to design and move to an automated key
management mechanism. This is like a crawl, walk, and run process.
In order for operators to accept these phases, we believe that the
key management protocol should be clearly separated from the routing
transport. This would mean that the routing transport subsystem is
oblivious to how the keys are derived, exchanged, and downloaded as
long as there is something that it can use. It is like having a
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routing-protocol-configuration switch that requests the security
module for the "KARP security parameters" so that it can refer to
some module written, maintained, and operated by security experts and
insert those parameters in the routing exchange.
The desired end state for the KARP work contains several items.
First, the people desiring to deploy securely authenticated and
integrity validated packets between routing peers have the tools
specified, implemented, and shipped in order to deploy. These tools
should be fairly simple to implement and not more complex than the
security mechanisms to which the operators are already accustomed.
(Examples of security mechanisms to which router operators are
accustomed include: the use of asymmetric keys for authentication in
SSH for router configuration, the use of pre-shared keys (PSKs) in
TCP MD5 for BGP protection, the use of self-signed certificates for
HTTP Secure (HTTPS) access to device Web-based user interfaces, the
use of strongly constructed passwords and/or identity tokens for user
identification when logging into routers and management systems.)
While the tools that we intend to specify may not be able to stop a
deployment from using "foobar" as an input key for every device
across their entire routing domain, we intend to make a solid, modern
security system that is not too much more difficult than that. In
other words, simplicity and deployability are keys to success. The
routing protocols will specify modern cryptographic algorithms and
security mechanisms. Routing peers will be able to employ unique,
pair-wise keys per peering instance, with reasonable key lifetimes,
and updating those keys on a regular basis will be operationally
easy, causing no service interruption.
Achieving the above described end state using manual keys may be
pragmatic only in very small deployments. However, manual keying in
larger deployments will be too burdensome for operators. Thus, the
second goal is to support key life cycle management with a KMP. We
expect that both manual and automated key management will coexist in
the real world.
In accordance with the desired end state just described, we define
two main work phases for each routing protocol:
1. Enhance the routing protocol's current authentication
mechanism(s). This work involves enhancing a routing protocol's
current security mechanisms in order to achieve a consistent,
modern level of security functionality within its existing key
management framework. It is understood and accepted that the
existing key management frameworks are largely based on manual
keys. Since many operators have already built operational
support systems (OSS) around these manual key implementations,
there is some automation available for an operator to leverage in
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that way, if the underlying mechanisms are themselves secure. In
this phase, we explicitly exclude embedding or creating a KMP.
Refer to [THTS-REQS] for the list of the requirements for Phase 1
work.
2. Develop an automated key management framework. The second phase
will focus on the development of an automated keying framework to
facilitate unique pair-wise (group-wise, where applicable) keys
per peering instance. This involves the use of a KMP. The use
of automatic key management mechanisms offers a number of
benefits over manual keying. Most important, it provides fresh
traffic keying material for each session, thus helping to prevent
inter-connection replay attacks. In an inter-connection replay
attack, protocol packets from the earlier protocol session are
replayed affecting the current execution of the protocol. A KMP
is also helpful because it negotiates unique, pair-wise, random
keys, without administrator involvement. It negotiates several
SA parameters like algorithms, modes, and parameters required for
the secure connection, thus providing interoperability between
endpoints with disparate capabilities and configurations. In
addition it could also include negotiating the key lifetimes.
The KMP can thus keep track of those lifetimes using counters and
can negotiate new keys and parameters before they expire, again,
without administrator interaction. Additionally, in the event of
a breach, changing the KMP key will immediately cause a rekey to
occur for the traffic key, and those new traffic keys will be
installed and used in the current connection. In summary, a KMP
provides a protected channel between the peers through which they
can negotiate and pass important data required to exchange proof
of identities, derive traffic keys, determine rekeying,
synchronize their keying state, signal various keying events,
notify with error messages, etc.
4.2. Work Items per Routing Protocol
Each routing protocol will have a team (the Routing_Protocol-KARP
team, e.g., the OSPF-KARP team) working on incrementally improving
the security of a routing protocol. These teams will have the
following main work items:
PHASE 1:
Characterize the Routing Protocol
Assess the routing protocol to see what authentication and
integrity mechanisms it has today. Does it need significant
improvement to its existing mechanisms or not? This will
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include determining if modern, strong security algorithms and
parameters are present and if the protocol supports key agility
without bouncing adjacencies.
Define Optimal State
List the requirements for the routing protocol's session key
usage and format to contain modern, strong security algorithms
and mechanisms, per the Requirements document [THTS-REQS]. The
goal here is to determine what is needed for the routing
protocol to be used securely with at least manual key
management.
Gap Analysis
Enumerate the requirements for this protocol to move from its
current security state, the first bullet, to its optimal state,
as listed just above.
Transition and Deployment Considerations
Document the operational transition plan for moving from the
old to the new security mechanism. Will adjacencies need to
bounce? What new elements/servers/services in the
infrastructure will be required? What is an example work flow
that an operator will take? The best possible case is if the
adjacency does not break, but this may not always be possible.
Define, Assign, Design
Create a deliverables list of the design and specification
work, with milestones. Define owners. Release one or more
documents.
PHASE 2:
KMP Analysis
Review requirements for KMPs. Identify any nuances for this
particular routing protocol's needs and its use cases for a
KMP. List the requirements that this routing protocol has for
being able to be used in conjunction with a KMP. Define the
optimal state and check how easily it can be decoupled from the
KMP.
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Gap Analysis
Enumerate the requirements for this protocol to move from its
current security state to its optimal state, with respect to
the key management.
Define, Assign, Design
Create a deliverables list of the design and specification
work, with milestones. Define owners. Generate the design and
document work for a KMP to be able to generate the routing
protocol's session keys for the packets on the wire. These
will be the arguments passed in the API to the KMP in order to
bootstrap the session keys for the routing protocol.
There will also be a team formed to work on the base framework
mechanisms for each of the main categories.
5. Routing Protocols in Categories
This section groups the routing protocols into categories according
to attributes set forth in the Categories' Section (Section 2). Each
group will have a design team tasked with improving the security of
the routing protocol mechanisms and defining the KMP requirements for
their group, then rolling both into a roadmap document upon which
they will execute.
BGP, LDP, PCEP, and MSDP
These routing protocols fall into the category of the one-to-one
peering messages and will use peer keying protocols. Border
Gateway Protocol (BGP) [RFC4271], Path Computation Element
Communication Protocol (PCEP) [RFC5440], and Multicast Source
Discovery Protocol (MSDP) [RFC3618] messages are transmitted over
TCP, while Label Distribution Protocol (LDP) [RFC5036] uses both
UDP and TCP. A team will work on one mechanism to cover these TCP
unicast protocols. Much of the work on the routing protocol
update for its existing authentication mechanism has already
occurred in the TCPM working group, on the TCP-AO [RFC5925]
document, as well as its cryptography-helper document, TCP-AO-
CRYPTO [RFC5926]. However, TCP-AO cannot be used for discovery
exchanges carried in LDP as those are carried over UDP. A
separate team might want to look at LDP. Another exception is the
mode where LDP is used directly on the LAN. The work for this may
go into the group keying category (along with OSPF) as mentioned
below.
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OSPF, IS-IS, and RIP
The routing protocols that fall into the category group keying
(with one-to-many peering) includes OSPF [RFC2328], IS-IS
[RFC1195] and RIP [RFC2453]. Not surprisingly, all these routing
protocols have two other things in common. First, they are run on
a combination of the OSI datalink Layer 2, and the OSI network
Layer 3. By this we mean that they have a component of how the
routing protocol works, which is specified in Layer 2 as well as
in Layer 3. Second, they are all internal gateway protocols
(IGPs). The keying mechanisms will be much more complicated to
define for these than for a one-to-one messaging protocol.
BFD
Because it is less of a routing protocol, per se, and more of a
peer liveness detection mechanism, Bidirectional Forwarding
Detection (BFD) [RFC5880] will have its own team. BFD is also
different from the other protocols covered here as it works on
millisecond timers and would need separate considerations to
mitigate the potential for Denial-of-Service (DoS) attacks. It
also raises interesting issues [RFC6039] with respect to the
sequence number scheme that is generally deployed to protect
against replay attacks as this space can roll over quite
frequently because of the rate at which BFD packets are generated.
RSVP and RSVP-TE
The Resource reSerVation Protocol (RSVP) [RFC2205] allows hop-by-
hop authentication of RSVP neighbors, as specified in [RFC2747].
In this mode, an integrity object is attached to each RSVP message
to transmit a keyed message digest. This message digest allows
the recipient to verify the identity of the RSVP node that sent
the message and to validate the integrity of the message. Through
the inclusion of a sequence number in the scope of the digest, the
digest also offers replay protection.
[RFC2747] does not dictate how the key for the integrity operation
is derived. Currently, most implementations of RSVP use a
statically configured key, on a per-interface or per-neighbor
basis.
RSVP relies on a per-peer authentication mechanism where each hop
authenticates its neighbor using a shared key or a certificate.
Trust in this model is transitive. Each RSVP node trusts,
explicitly, only its RSVP next-hop peers through the message
digest contained in the INTEGRITY object [RFC2747]. The next-hop
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RSVP speaker, in turn, trusts its own peers, and so on. See also
the document "RSVP Security Properties" [RFC4230] for more
background.
The keys used for protecting the RSVP messages can be group keys
(for example, distributed via the Group Domain of Interpretation
(GDOI) [RFC6407], as discussed in [GDOI-MAC]).
The trust an RSVP node has with another RSVP node has an explicit
and implicit component. Explicitly, the node trusts the other
node to maintain the integrity (and, optionally, the
confidentiality) of RSVP messages depending on whether
authentication or encryption (or both) are used. This means that
the message has not been altered or its contents seen by another,
non-trusted node. Implicitly, each node trusts the other node to
maintain the level of protection specified within that security
domain. Note that in any group key management scheme, like GDOI,
each node trusts all the other members of the group with regard to
data origin authentication.
RSVP-TE [RFC3209], [RFC3473], [RFC4726], and [RFC5151] is an
extension of the RSVP protocol for traffic engineering. It
supports the reservation of resources across an IP network and is
used for establishing MPLS label switch paths (LSPs), taking into
consideration network constraint parameters such as available
bandwidth and explicit hops. RSVP-TE signaling is used to
establish both intra- and inter-domain TE LSPs.
When signaling an inter-domain RSVP-TE LSP, operators may make use
of the security features already defined for RSVP-TE [RFC3209].
This may require some coordination between domains to share keys
([RFC2747][RFC3097]), and care is required to ensure that the keys
are changed sufficiently frequently. Note that this may involve
additional synchronization, should the domain border nodes be
protected with Fast Reroute, since the merge point (MP) and point
of local repair (PLR) should also share the key.
For inter-domain signaling for MPLS-TE, the administrators of
neighboring domains must satisfy themselves as to the existence of
a suitable trust relationship between the domains. In the absence
of such a relationship, the administrators should decide not to
deploy inter-domain signaling and should disable RSVP-TE on any
inter-domain interfaces.
KARP will currently be working only on RSVP-TE, as the native RSVP
lies outside the scope of the WG charter.
Lebovitz & Bhatia Informational [Page 15]RFC 6518 KARP Design Guidelines February 2012
PIM-SM and PIM-DM
Finally, the multicast protocols Protocol Independent Multicast -
Sparse Mode (PIM-SM) [RFC4601] and Protocol Independent Multicast
- Dense Mode (PIM-DM) [RFC3973] will be grouped together. PIM-SM
multicasts routing information (Hello, Join/Prune, Assert) on a
link-local basis, using a defined multicast address. In addition,
it specifies unicast communication for exchange of information
(Register, Register-Stop) between the router closest to a group
sender and the "Rendezvous Point". The Rendezvous Point is
typically not "on-link" for a particular router. While much work
has been done on multicast security for application-layer groups,
little has been done to address the problem of managing hundreds
or thousands of small one-to-many groups with link-local scope.
Such an authentication mechanism should be considered along with
the router-to-Rendezvous Point authentication mechanism. The most
important issue is ensuring that only the "authorized neighbors"
get the keys for source/group (S,G), so that rogue routers cannot
participate in the exchanges. Another issue is that some of the
communication may occur intra-domain, e.g., the link-local
messages in an enterprise, while others for the same (*,G) may
occur inter-domain, e.g., the router-to-Rendezvous Point messages
may be from one enterprise's router to another.
One possible solution proposes a region-wide "master" key server
(possibly replicated), and one "local" key server per speaking
router. There is no issue with propagating the messages outside
the link, because link-local messages, by definition, are not
forwarded. This solution is offered only as an example of how
work may progress; further discussion should occur in this work
team. Specification of a link-local protection mechanism for PIM-
SM is defined in [RFC4601], and this mechanism has been updated in
PIM-SM-LINKLOCAL [RFC5796]. However, the KMP part is completely
unspecified and will require work outside the expertise of the PIM
working group to accomplish, another example of why this roadmap
is being created.
6. Supporting Incremental Deployment
It is imperative that the new authentication and security mechanisms
defined support incremental deployment, as it is not feasible to
deploy a new routing protocol authentication mechanism throughout the
network instantaneously. One of the goals of the KARP WG is to add
incremental security to existing mechanisms rather than replacing
them. Delivering better deployable solutions to which vendors and
operators can migrate is more important than getting a perfect
security solution. It may also not be possible to deploy such a
mechanism to all routers in a large Autonomous System (AS) at one
Lebovitz & Bhatia Informational [Page 16]RFC 6518 KARP Design Guidelines February 2012
time. This means that the designers must work on this aspect of the
authentication mechanism for the routing protocol on which they are
working. The mechanisms must provide backward compatibility in the
message formatting, transmission, and processing of routing
information carried through a mixed security environment.
7. Denial-of-Service Attacks
DoS attacks must be kept in mind when designing KARP solutions.
[THTS-REQS] describes DoS attacks that are in scope for the KARP
work. Protocol designers should ensure that the new cryptographic
validation mechanisms must not provide an attacker with an
opportunity for DoS attacks. Cryptographic validation, while
typically cheaper than signing, is still an incremental cost. If an
attacker can force a system to validate many packets multiple times,
then this could be a potential DoS attack vector. On the other hand,
if the authentication procedure is itself quite CPU intensive, then
overwhelming the CPU with multiple bogus packets can bring down the
system. In this case, the authentication procedure itself aids the
DoS attack.
There are some known techniques to reduce the cryptographic
computation load. Packets can include non-cryptographic consistency
checks. For example, [RFC5082] provides a mechanism that uses the IP
header to limit the attackers that can inject packets that will be
subject to cryptographic validation. In the design, Phase 2, once an
automated key management protocol is developed, it may be possible to
determine the peer IP addresses that are valid participants. Only
the packets from the verified sources could be subject to
cryptographic validation.
Protocol designers must ensure that a device never needs to check
incoming protocol packets using multiple keys, as this can overwhelm
the CPU, leading to a DoS attack. KARP solutions should indicate the
checks that are appropriate prior to performing cryptographic
validation. KARP solutions should indicate where information about
valid neighbors can be used to limit the scope of the attacks.
Particular care needs to be paid to the design of automated key
management schemes. It is often desirable to force a party
attempting to authenticate to do work and to maintain state until
that work is done. That is, the initiator of the authentication
should maintain the cost of any state required by the authentication
for as long as possible. This also helps when an attacker sends an
overwhelming load of keying protocol initiations from bogus sources.
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Another important class of attack is denial of service against the
routing protocol where an attacker can manipulate either the routing
protocol or the cryptographic authentication mechanism to disrupt
routing adjacencies.
Without KARP solutions, many routing protocols are subject to
disruption simply by injecting an invalid packet or a packet for the
wrong state. Even with cryptographic validation, replay attacks are
often a vector where a previously valid packet can be injected to
create a denial of service. KARP solutions should prevent all cases
where packet replays or other packet injections by an outsider can
disrupt routing sessions.
Some residual denial-of-service risk is always likely. If an
attacker can generate a large enough number of packets, the routing
protocol can get disrupted. Even if the routing protocol is not
disrupted, the loss rate on a link may rise to a point where claiming
that traffic can successfully be routed across the link will be
inaccurate.
8. Gap Analysis
The [THTS-REQS] document lists the generic requirements for the
security mechanisms that must exist for the various routing protocols
that come under the purview of KARP. There will be different design
teams working for each of the categories of routing protocols
defined.
To start, design teams must review the "Threats and Requirements for
Authentication of routing protocols" document [THTS-REQS]. This
document contains detailed descriptions of the threat analysis for
routing protocol authentication and integrity in general. Note that
it does not contain all the authentication-related threats for any
one routing protocol, or category of routing protocols. The design
team must conduct a protocol-specific threat analysis to determine if
threats beyond those in the [THTS-REQS] document arise in the context
of the protocol (group) and to describe those threats.
The [THTS-REQS] document also contains many security requirements.
Each routing protocol design team must walk through each section of
the requirements and determine one by one how its protocol either
does or does not relate to each requirement.
Examples include modern, strong, cryptographic algorithms, with at
least one such algorithm listed as a MUST, algorithm agility, secure
use of simple PSKs, intra-connection replay protection, inter-
connection replay protection, etc.
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When doing the gap analysis, we must first identify the elements of
each routing protocol that we wish to protect. In case of protocols
riding on top of IP, we might want to protect the IP header and the
protocol headers, while for those that work on top of TCP, it will be
the TCP header and the protocol payload. There is patently value in
protecting the IP header and the TCP header if the routing protocols
rely on these headers for some information (for example, identifying
the neighbor that originated the packet).
Then, there will be a set of cryptography requirements that we might
want to look at. For example, there must be at least one set of
cryptographic algorithms (MD5, SHA, etc.) or constructions (Hashed
MAC (HMAC), etc.) whose use is supported by all implementations and
can be safely assumed to be supported by any implementation of the
authentication option. The design teams should look for the protocol
on which they are working. If such algorithms or constructions are
not available, then some should be defined to support
interoperability by having a single default.
Design teams must ensure that the default cryptographic algorithms
and constructions supported by the routing protocols are accepted by
the community. This means that the protocols must not rely on non-
standard or ad hoc hash functions, keyed-hash constructions,
signature schemes, or other functions, and they must use published
and standard schemes.
Care should also be taken to ensure that the routing protocol
authentication scheme has algorithm agility (i.e., it is capable of
supporting algorithms other than its defaults). Ideally, the
authentication mechanism should not be affected by packet loss and
reordering.
Design teams should ensure that their protocol's authentication
mechanism is able to accommodate rekeying. This is essential since
it is well known that keys must periodically be changed. Also, what
the designers must ensure is that this rekeying event should not
affect the functioning of the routing protocol. For example, OSPF
rekeying requires coordination among the adjacent routers, while IS-
IS requires coordination among routers in the entire domain.
If new authentication and security mechanisms are needed, then the
design teams must design in such a manner that the routing protocol
authentication mechanism remains oblivious to how the keying material
is derived. This decouples the authentication mechanism from the key
management system that is employed.
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Design teams should also note that many routing protocols require
prioritized treatment of certain protocol packets and authentication
mechanisms should honor this.
Not all routing protocol authentication mechanisms provide support
for replay attacks, and the design teams should identify such
authentication mechanisms and work on them so that this can get
fixed. The design teams must look at the protocols that they are
working on and see if packets captured from the previous/stale
sessions can be replayed.
What might also influence the design is the rate at which the
protocol packets are originated. In case of protocols like BFD,
where packets are originated at millisecond intervals, there are some
special considerations that must be kept in mind when defining the
new authentication and security mechanisms.
The designers should also consider whether the current authentication
mechanisms impose considerable processing overhead on a router that's
doing authentication. Most currently deployed routers do not have
hardware accelerators for cryptographic processing and these
operations can impose a significant processing burden under some
circumstances. The proposed solutions should be evaluated carefully
with regard to the processing burden that they will impose, since
deployment may be impeded if network operators perceive that a
solution will impose a processing burden which either entails
substantial capital expenses or threatens to destabilize the routers.
9. Security Considerations
As mentioned in the Introduction, RFC 4948 [RFC4948] identifies
additional steps needed to achieve the overall goal of improving the
security of the core routing infrastructure. Those include
validation of route origin announcements, path validation, cleaning
up the IRR databases for accuracy, and operational security practices
that prevent routers from becoming compromised devices. The KARP
work is but one step needed to improve core routing infrastructure.
The security of cryptographic-based systems depends on both the
strength of the cryptographic algorithms chosen and the strength of
the keys used with those algorithms. The security also depends on
the engineering of the protocol used by the system to ensure that
there are no non-cryptographic ways to bypass the security of the
overall system.
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9.1. Use Strong Keys
Care should be taken to ensure that the selected key is
unpredictable, avoiding any keys known to be weak for the algorithm
in use. [RFC4086] contains helpful information on both key
generation techniques and cryptographic randomness.
Care should also be taken when choosing the length of the key.
[RFC3766] provides some additional information on asymmetric and
symmetric key sizes and how they relate to system requirements for
attack resistance.
In addition to using a key of appropriate length and randomness,
deployers of KARP should use different keys between different routing
peers whenever operationally possible. This is especially true when
the routing protocol takes a static traffic key as opposed to a
traffic key derived on a per-connection basis using a KDF. The
burden for doing so is understandably much higher than using the same
static traffic key across all peering routers. Depending upon the
specific KMP, it can be argued that generally using a KMP network-
wide increases peer-wise security. Consider an attacker that learns
or guesses the traffic key used by two peer routers: if the traffic
key is only used between those two routers, then the attacker has
only compromised that one connection not the entire network.
However whenever using manual keys, it is best to design a system
where a given pre-shared key (PSK) will be used in a KDF mixed with
connection-specific material, in order to generate session unique --
and therefore peer-wise -- traffic keys. Doing so has the following
advantages: the traffic keys used in the per-message authentication
mechanism are peer-wise unique, it provides inter-connection replay
protection, and if the per-message authentication mechanism covers
some connection counter, intra-connection replay protection.
Note that certain key derivation functions (e.g., KDF_AES_128_CMAC)
as used in TCP-AO [RFC5926], the pseudorandom function (PRF) used in
the KDF may require a key of a certain fixed size as an input.
For example, AES_128_CMAC requires a 128-bit (16-byte) key as the
seed. However, for the convenience of the administrators, a
specification may not want to require the entry of a PSK be of
exactly 16 bytes. Instead, a specification may call for a key prep
routine that could handle a variable-length PSK, one that might be
less or more than 16 bytes (see [RFC4615], Section 3, as an example).
That key prep routine would derive a key of exactly the required
length, thus, be suitable as a seed to the PRF. This does NOT mean
that administrators are safe to use weak keys. Administrators are
encouraged to follow [RFC4086] [NIST-800-118]. We simply attempted
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to "put a fence around stupidity", as much as possible as it's hard
to imagine administrators putting in a password that is, say 16 bytes
in length.
A better option, from a security perspective, is to use some
representation of a device-specific asymmetric key pair as the
identity proof, as described in section "Unique versus Shared Keys"
section.
9.2. Internal versus External Operation
Design teams must consider whether the protocol is an internal
routing protocol or an external one, i.e., does it primarily run
between peers within a single domain of control or between two
different domains of control? Some protocols may be used in both
cases, internally and externally, and as such, various modes of
authentication operation may be required for the same protocol.
While it is preferred that all routing exchanges run with the best
security mechanisms enabled in all deployment contexts, this
exhortation is greater for those protocols running on inter-domain
point-to-point links. It is greatest for those on shared access link
layers with several different domains interchanging together, because
the volume of attackers are greater from the outside. Note however,
that the consequences of internal attacks maybe no less severe -- in
fact, they may be quite a bit more severe -- than an external attack.
An example of this internal versus external consideration is BGP,
which has both EBGP and IBGP modes. Another example is a multicast
protocol where the neighbors are sometimes within a domain of control
and sometimes at an inter-domain exchange point. In the case of PIM-
SM running on an internal multi-access link, it would be acceptable
to give up some security to get some convenience by using a group key
among the peers on the link. On the other hand, in the case of PIM-
SM running over a multi-access link at a public exchange point,
operators may favor security over convenience by using unique pair-
wise keys for every peer. Designers must consider both modes of
operation and ensure the authentication mechanisms fit both.
Operators are encouraged to run cryptographic authentication on all
their adjacencies, but to work from the outside in, i.e., External
BGP (EBGP) links are a higher priority than the Internal BGP (IBGP)
links because they are externally facing, and, as a result, more
likely to be targeted in an attack.
9.3. Unique versus Shared Keys
This section discusses security considerations regarding when it is
appropriate to use the same authentication key inputs for multiple
peers and when it is not. This is largely a debate of convenience
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versus security. It is often the case that the best secured
mechanism is also the least convenient mechanism. For example, an
air gap between a host and the network absolutely prevents remote
attacks on the host, but having to copy and carry files using the
"sneaker net" is quite inconvenient and does not scale.
Operators have erred on the side of convenience when it comes to
securing routing protocols with cryptographic authentication. Many
do not use it at all. Some use it only on external links, but not on
internal links. Those that do use it often use the same key for all
peers in a network. It is common to see the same key in use for
years, e.g., the key was entered when authentication mechanisms were
originally configured or when the routing gear was deployed.
One goal for designers is to create authentication and integrity
mechanisms that are easy for operators to deploy and manage, and
still use unique keys between peers (or small groups on multi-access
links) and for different sessions among the same peers. Operators
have the impression that they NEED one key shared across the network,
when, in fact, they do not. What they need is the relative
convenience they experience from deploying cryptographic
authentication with one key (or a few keys) compared to the
inconvenience they would experience if they deployed the same
authentication mechanism using unique pair-wise keys. An example is
BGP route reflectors. Here, operators often use the same
authentication key between each client and the route reflector. The
roadmaps defined from this guidance document should allow for unique
keys to be used between each client and the peer, without sacrificing
much convenience. Designers should strive to deliver peer-wise
unique keying mechanisms with similar ease-of-deployment properties
as today's one-key method.
Operators must understand the consequences of using the same key
across many peers. One argument against using the same key is that
if the same key that is used in multiple devices, then a compromise
of any one of the devices will expose the key. Also, since the same
key is supported on many devices, this is known by many people, which
affects its distribution to all of the devices.
Consider also the attack consequence size, the amount of routing
adjacencies that can be negatively affected once a breach has
occurred, i.e., once the keys have been acquired by the attacker.
Again, if a shared key is used across the internal domain, then the
consequence size is the whole network. Ideally, unique key pairs
would be used for each adjacency.
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In some cases, use of shared keys is needed because of the problem
space. For example, a multicast packet is sent once but then
consumed by several routing neighbors. If unique keys were used per
neighbor, the benefit of multicast would be erased because the sender
would have to create a different announcement packet for each
receiver. Though this may be desired and acceptable in some small
number of use cases, it is not the norm. Shared (i.e., group) keys
are an acceptable solution here, and much work has been done already
in this area (by the MSEC working group).
9.4. Key Exchange Mechanism
This section discusses the security and use case considerations for
key exchange for routing protocols. Two options exist: an out-of-
band mechanism or a KMP. An out-of-band mechanism involves operators
configuring keys in the device through a configuration tool or
management method (e.g., Simple Network Management Protocol (SNMP),
Network Configuration Protocol (NETCONF)). A KMP is an automated
protocol that exchanges keys without operator intervention. KMPs can
occur either in-band to the routing protocol or out-of-band to the
routing protocol (i.e., a different protocol).
An example of an out-of-band configuration mechanism could be an
administrator who makes a remote management connection (e.g., using
SSH) to a router and manually enters the keying information, e.g.,
the algorithm, the key(s), the key lifetimes, etc. Another example
could be an OSS system that inputs the same information by using a
script over an SSH connection or by pushing configuration through
some other management connection, standard (NETCONF-based) or
proprietary.
The drawbacks of an out-of-band configuration mechanism include lack
of scalability, complexity, and speed of changing if a security
breach is suspected. For example, if an employee who had access to
keys was terminated, or if a machine holding those keys was believed
to be compromised, then the system would be considered insecure and
vulnerable until new keys were generated and distributed. Those keys
then need to be placed into the OSS system, and the OSS system then
needs to push the new keys -- often during a very limited change
window -- into the relevant devices. If there are multiple
organizations involved in these connections, because the protected
connections are inter-domain, this process is very complicated.
The principle benefit of out-of-band configuration mechanism is that
once the new keys/parameters are set in OSS system, they can be
pushed automatically to all devices within the OSS's domain.
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Operators have mechanisms in place for this already for managing
other router configuration data. In small environments with few
routers, a manual system is not difficult to employ.
We further define a peer-to-peer KMP as using cryptographically
protected identity verification, session key negotiation, and
security association parameter negotiation between the two routing
peers. The KMP among peers may also include the negotiation of
parameters, like cryptographic algorithms, cryptographic inputs
(e.g., initialization vectors), key lifetimes, etc.
There are several benefits of a peer-to-peer KMP versus centrally
managed and distributing keys. It results in key(s) that are
privately generated, and it need not be recorded permanently
anywhere. Since the traffic keys used in a particular connection are
not a fixed part of a device configuration, no security sensitive
data exists anywhere else in the operator's systems that can be
stolen, e.g., in the case of a terminated or turned employee. If a
server or other data store is stolen or compromised, the thieves gain
limited or no access to current traffic keys. They may gain access
to key derivation material, like a PSK, but may not be able to access
the current traffic keys in use. In this example, these PSKs can be
updated in the device configurations (either manually or through an
OSS) without bouncing or impacting the existing session at all. In
the case of using raw asymmetric keys or certificates, instead of
PSKs, the data theft (from the data store) would likely not result in
any compromise, as the key pairs would have been generated on the
routers and never leave those routers. In such a case, no changes
are needed on the routers; the connections will continue to be
secure, uncompromised. Additionally, with a KMP, regular rekey
operations occur without any operator involvement or oversight. This
keeps keys fresh.
There are a few drawbacks to using a KMP. First, a KMP requires more
cryptographic processing for the router at the beginning of a
connection. This will add some minor start-up time to connection
establishment versus a purely manual key management approach. Once a
connection with traffic keys has been established via a KMP, the
performance is the same in the KMP and the out-of-band configuration
case. KMPs also add another layer of protocol and configuration
complexity, which can fail or be misconfigured. This was more of an
issue when these KMPs were first deployed, but less so as these
implementations and operational experience with them have matured.
One of the goals for KARP is to develop a KMP; an out-of-band
configuration protocol for key exchange is out of scope.
Lebovitz & Bhatia Informational [Page 25]
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Within this constraint, there are two approaches for a KMP:
The first is to use a KMP that runs independent of the routing and
the signaling protocols. It would run on its own port and use its
own transport (to avoid interfering with the routing protocol that it
is serving). When a routing protocol needs a key, it would contact
the local instance of this key management protocol and request a key.
The KMP generates a key that is delivered to the routing protocol for
it to use for authenticating and integrity verification of the
routing protocol packets. This KMP could either be an existing key
management protocol such as ISAKMP/IKE, GKMP, etc., extended for the
routing protocols, or it could be a new KMP, designed for the routing
protocol context.
The second approach is to define an in-band KMP extension for
existing routing protocols putting the key management mechanisms
inside the protocol itself. In this case, the key management
messages would be carried within the routing protocol packets,
resulting in very tight coupling between the routing protocols and
the key management protocol.
10. Acknowledgments
Much of the text for this document came originally from "Roadmap for
Cryptographic Authentication of Routing Protocol Packets on the
Wire", authored by Gregory M. Lebovitz.
We would like to thank Sam Hartman, Eric Rescorla, Russ White, Sean
Turner, Stephen Kent, Stephen Farrell, Adrian Farrel, Russ Housley,
Michael Barnes, and Vishwas Manral for their comments on the
document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4948] Andersson, L., Davies, E., and L. Zhang, "Report from
the IAB workshop on Unwanted Traffic March 9-10,
2006", RFC 4948, August 2007.
11.2. Informative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP
and dual environments", RFC 1195, December 1990.
Lebovitz & Bhatia Informational [Page 26]RFC 6518 KARP Design Guidelines February 2012
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
and S. Jamin, "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April
1998.
[RFC2453] Malkin, G., "RIP Version 2", STD 56, RFC 2453,
November 1998.
[RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP
Cryptographic Authentication", RFC 2747, January 2000.
[RFC3097] Braden, R. and L. Zhang, "RSVP Cryptographic
Authentication -- Updated Message Type Value", RFC
3097, April 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
LSP Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, January 2003.
[RFC3618] Fenner, B., Ed., and D. Meyer, Ed., "Multicast Source
Discovery Protocol (MSDP)", RFC 3618, October 2003.
[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys", BCP
86, RFC 3766, April 2004.
[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol
Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)", RFC 3973, January 2005.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC
4086, June 2005.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for
Cryptographic Key Management", BCP 107, RFC 4107, June
2005.
[RFC4230] Tschofenig, H. and R. Graveman, "RSVP Security
Properties", RFC 4230, December 2005.
Lebovitz & Bhatia Informational [Page 27]RFC 6518 KARP Design Guidelines February 2012
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Authentication Protocol", RFC 4252, January
2006.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
(SSH) Transport Layer Protocol", RFC 4253, January
2006.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
2006.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C.,
and B. Moeller, "Elliptic Curve Cryptography (ECC)
Cipher Suites for Transport Layer Security (TLS)", RFC
4492, May 2006.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I.
Kouvelas, "Protocol Independent Multicast - Sparse
Mode (PIM-SM): Protocol Specification (Revised)", RFC
4601, August 2006.
[RFC4615] Song, J., Poovendran, R., Lee, J., and T. Iwata, "The
Advanced Encryption Standard-Cipher-based Message
Authentication Code-Pseudo-Random Function-128 (-
AES-CMAC-PRF-128) Algorithm for the Internet Key
Exchange Protocol (IKE)", RFC 4615, August 2006.
[RFC4726] Farrel, A., Vasseur, J.-P., and A. Ayyangar, "A
Framework for Inter-Domain Multiprotocol Label
Switching Traffic Engineering", RFC 4726, November
2006.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas,
Ed., "LDP Specification", RFC 5036, October 2007.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and
C. Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5151] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur,
"Inter-Domain MPLS and GMPLS Traffic Engineering --
Resource Reservation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 5151, February 2008.
Lebovitz & Bhatia Informational [Page 28]RFC 6518 KARP Design Guidelines February 2012
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation
List (CRL) Profile", RFC 5280, May 2008.
[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol
(PCEP)", RFC 5440, March 2009.
[RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication
and Confidentiality in Protocol Independent Multicast
Sparse Mode (PIM-SM) Link-Local Messages", RFC 5796,
March 2010.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding
Detection (BFD)", RFC 5880, June 2010.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
[RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic
Algorithms for the TCP Authentication Option (TCP-
AO)", RFC 5926, June 2010.
[RFC6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White,
"Issues with Existing Cryptographic Protection Methods
for Routing Protocols", RFC 6039, October 2010.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group
Domain of Interpretation", RFC 6407, October 2011.
[THTS-REQS] Lebovitz, G., "The Threat Analysis and Requirements
for Cryptographic Authentication of Routing Protocols'
Transports", Work in Progress, June 2011.
[CRPT-TAB] Housley, R. and Polk, T., "Database of Long-Lived
Symmetric Cryptographic Keys", Work in Progress,
October 2011
[GDOI-MAC] Weis, B. and S. Rowles, "GDOI Generic Message
Authentication Code Policy", Work in Progress,
September 2011.
[IRR] Merit Network Inc , "Internet Routing Registry Routing
Assets Database", 2006, http://www.irr.net/.
Lebovitz & Bhatia Informational [Page 29]RFC 6518 KARP Design Guidelines February 2012
[NIST-800-57] US National Institute of Standards & Technology,
"Recommendation for Key Management Part 1: General
(Revised)", March 2007
[NIST-800-118] US National Institute of Standards & Technology,
"Guide to Enterprise Password Management (Draft)",
April 2009
Authors' Addresses
Gregory M. Lebovitz
Aptos, California
USA 95003
EMail: gregory.ietf@gmail.com
Manav Bhatia
Alcatel-Lucent
Bangalore
India
EMail: manav.bhatia@alcatel-lucent.com
Lebovitz & Bhatia Informational [Page 30]
