Internet Engineering Task Force Ken Carlberg
INTERNET DRAFT UCL
January 20, 2003 Ran Atkinson
Extreme Networks
General Requirements for
Emergency Telecommunication Service
<draft-ietf-ieprep-ets-general-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Abstract
This document presents a list of general requirements in support of
Emergency Telecommunications Service (ETS). Solutions to these
requirements are not presented in this document. Additional
requirements pertaining to specific applications, or types of
applications, are to be specified in separate document(s).
1. Introduction
Effective telecommunications capabilities can be imperative to
facilitate immediate recovery operations for serious disaster events,
such as, hurricanes, floods, earthquakes, and terrorist attacks.
Disasters can happen any time, any place, unexpectedly. Quick
response for recovery operations requires immediate access to any
public telecommunications capabilities at hand. These capabilities
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include: conventional telephone, cellular phones, and Internet
access via online terminals, IP telephones, and wireless PDAs. The
commercial telecommunications infrastructure is rapidly evolving to
Internet-based technology. Therefore, the Internet community needs to
consider how it can best support emergency management and recovery
operations.
1.1 Existing Emergency Related Standards
The following are standards from other organizations that are
specifically aimed at supporting emergency communications. Most of
these standards specify telephony mechanisms or define telephony
related labels.
Standard / Organization
--------------------------
1) T1.631 / ANSI
2) E.106 / ITU
3) F.706 / ITU
4) H.460.4 / ITU
5) I.255.3 / ITU
The first specifies an indicator for SS7 networks that signals the
need for a High Probability of Completion (HPC) service. This
indicator is termed National Security / Emergency Preparedness
(NS/EP) The T1.631 standard [2] is the basis for the U.S. Government
Emergency Telecomunications Service (GETS) [7].
The second standard describes functional capabilities for the PSTN to
support International Emergency Preparedness System (IEPS) [3]. From
the PSTN perspective, one can view NS/EP as a standard with national
boundaries, while IEPS is extention to international boundaries for
telephony.
The third standard extends IEPS beyond the scope of telephony into
other forms that encompass multimedia [4].
The fourth and fifth standard focuses on a multi-level labeling
mechanism distinguishing emergency type traffic from that which is
not. The former case focuses on call signaling for H.323 networks
[5], while the latter has been applied for both SS7 [6] and data
networks.
1.2 Problem
One problem faced by the IEPREP working group entails how, and to
what degree, support for these standards are to be realized within
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the Internet architecture and the existing suite of IETF standards
and associated working groups.
A subsequent problem is to ensure that this support is not focused
just on IP telephony applications. The I-Am-Alive (IAA) database
system is an example of an emergency related application used in
Japan that supports both signaled and non-signaled access by
users[10]. Hence, requirements and subsequent solutions that address
these problems must not assume the existance of signaling and must be
able to support applications that only have labels in data packets.
These label(s) may be in various places, such as the application or
IP header. Further comments on labels are discussed below in section
3.
2. Scope
This document defines a set of general system requirements to achieve
support for ETS and addressing the problem space presented in Section
1.2. In defining these requirements, we consider known systems such
as GETS and IAA that represent existing manifestations of emergency
related systems. These two examples also represent a broad spectrum
of characteristics that range from signaling/interactive non-elastic
applications to non-signaled/elastic applications.
We stress that ETS, and its associated requirements, is not the only
means of supporting authorized emergency communications. It is
simply an approach influenced by by existing systems and standards.
Solutions to requirements are not defined. This document does not
specify protocol enhancements or specifications. Requirements for
specific types of applications that go beyond the general set stated
in section 3 are to be specified in other document(s). At the
current writing of this document, [9] has been written for the case
of IP telephony.
Below we present a structural relationship of documents for the
IEPREP working group. Specific solutions that are proposed in
response to the requirements are to be developed in other working
groups. We note that other specific requrements (like that of IP
telephony) may be defined as an extension of the general requirements
presented in section 3 below.
2.1 Out of Scope
While the problem space stated in section 1.2 includes standards
related to telephony, this document is meant to be broader in scope.
Hence, emulation of specific architectures, like the PSTN, or focus
on a specific application is out of scope. Further, the
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specifications of requirements that are aimed at adhering to
regulations or laws of governments is also out of scope of this
document. The focus of the IETF and its working groups is technical
positions that follow the architecture of the Internet.
Another item that is not in scope of this document is mandating
acceptance and support of the requirements presented in this
document. There is an expectation that business contracts, (e.g.,
Service Level Agreements) , will be used to satisfy those
requirements that apply to service providers. Absence of an SLA
implies best effort service is provided.
3. General Requirements
These are general requirements that apply to authorized emergency
telecommunications service. The first requirement is presented as a
conditional one since not all applications use or are reliant on
signaling.
1) Signaling
IF signaling is to be used to convey the state or existance of
emergency, then signaling mechanism(s) MUST exist to carry
applicable labels.
2) Labels
Labels may exist in various forms at different layers. They
might be carried as part of signaling, and/or as part of the
header of a data packet. Labels from different layers are NOT
required to be the same, but MAY be related to each other.
3) Policy
Policy MUST be kept separate from label(s). This topic has
generated a fair amount of debate, and so we provide additional
guidance from the following:
A set of labels may be defined as being related to each other.
Characteristics (e.g., drop precedence) may also be attributed
to these labels. [11] is an example of a related set of labels
based on a specific characteristic.
However, the mechanisms used to achieve a stated characteristic
MUST NOT be stated in the definition of a label. Local policy
determines mechanism(s) used to achieve or support a specific
characteristic. This allows for the possibility of different
mechanisms to achieve the same stated characteristic.
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The interaction between unrelated labels MUST NOT be embedded
within the definition of a label. Local policy states the
actions (if any) to be taken if unrelated labeled traffic
merges at a node.
Finally, labels may have additional characteristics added to
them as a result of local policy.
4) Network Functionality
Functionality to support better than best effort SHOULD focus
on probability versus guarantees. Probability can be realized
in terms of reduced probability of packet loss, and/or minimal
jitter, and/or minimal end-to-end delay. There is NO
requirement that better than best effort functionality MUST
exist. There is NO requirement that if better-than-best effort
functionality exists then it must be ubuiquitous between end
users.
5) Authorisation
Authorisation is a method of validating that a user or some
traffic is authorized by policy to use a particular service
offering.
Mechanisms must be implemented so that only authorised users
have access to emergency telecommunications services. Any
mechanism for providing such authorisation beyond closed
private networks should meet IETF Security Area criterion
(e.g. clear-text passwords would not generally be acceptable).
Authorization protects network resources from excessive use,
from abuse, and might also support billing and accounting for
the offered service.
Such authorization mechanisms should be flexible enough to
provide various levels of restriction and authorization depending
on the expectations of a particular service or customer.
6) Integrity & Authentication
In practice, authentication and integrity for IP based
communications are generally bound within a single mechanism,
even though conceptually they are different. Authentication
ensures that the user or traffic is who it claims to be.
Integrity offers assurance that unauthorised modifications
to objects can be detected.
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Authorised emergency traffic needs to have reduced risk of
adverse impact from denial of service. This implies a need to
ensure integrity of the authorised emergency network traffic.
Users of emergency network services SHOULD consider deploying
end-to-end integrity and authentication, rather than relying on
services that might be offered by any single provider of
emergency network services. Users should also carefully
consider which application-layer security services might be
appropriate to use.
7) Confidentiality
Some emergency communications might have a requirement that they
not be susceptible to interception or viewing by others, due to
the sensitive and urgent nature of emergency response activities.
An emergency telecommunications service MAY offer options to
provide confidentiality for certain authorised user traffic.
Consistent with other IETF standards and the Internet
Architecture, this document recommends that IEprep users deploy
end-to-end security mechanisms, rather than rely on security
services that might be offered by a single network operator.
IEPREP users should carefully consider security alternatives
(e.g. PGP, TLS, IPsec transport-mode) at different layers
(e.g. Application Layer, Session Layer, Transport Layer) of the
Internet Architecture before deployment.
4. Issues
This section presents issues that arise in considering solutions for
the requirements that have been defined for ETS. This section does
not specify solutions nor is it to be confused with requirements.
Subsequent documents that articulate a more specific set of
requirements for a particular service may make a statement about the
following issues.
1) Accounting
Accounting represents a method of tracking actual usage of a
service. We assume that the usage of any service better than
best effort will be tracked and subsequently billed to the user.
Accounting is not addressed as a general requirement for ETS.
However, solutions used to realize ETS should not preclude an
accounting mechanism.
2) Admission Control
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The requirements of section 3 discuss labels and security. In
going beyond this, the ability to distinguish emergency flows
implies the need for admission control if resources become
scarce. Solutions must recognize this when trying to satisfy
the above requirements such that the simple presence of a label
does not imply admission control always exists along the
end-to-end path.
3) Digital Signatures
Verification of digital signatures is computationally expensive.
If an operator acts upon a label and hence needs to verify the
authenticity of the label, then there is a potential denial-of-
service attack on the entity performing the authentication.
The DoS attack works by flooding the entity performing the
authentication with invalid (i.e. not authentic) labelled
information, causing the victim to spend excessive amounts of
computing resources on signature validation. Even though the
invalid information might get discarded after the signature
validation fails, the adversary has already forced the victim to
expend significant amounts of computing resource. Accordingly,
any system requiring such validation SHOULD define operational
and protocol measures to reduce the vulnerability to such a DoS
attack.
5. Security
Security in terms of requirements is discussed section 3 and 4.
6. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 ANSI, "Signaling System No. 7(SS7) "High Probability of
Completion (HPC) Network Capability" , ANSI T1.631-1993 (R1999).
3 "Description of an International Emergency Preference
Scheme (IEPS)", ITU-T Recommendation E.106 March, 2000.
4 "Description for an International Emergency Multimedia Service",
ITU Draft Recommendation F.706, February, 2002.
5 "Call Priority Designation for H.323 Calls", ITU Recommendation
H.460.4, November, 2002.
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6 ITU, "Multi-Level Precedence and Preemption Service, ITU,
Recomendation, I.255.3, July, 1990.
7 U.S. National Communications System: http://www.ncs.gov
8 U.K Office of Telecommunications (Oftel): http://www.oftel.gov.uk/
9 Carlberg, K., Atkinson, R., "General Requirements for Emergency
Telecommunications Service", Internet Draft, Work In Progress,
September, 2002
10 Tada, N., et. al., "IAA System (I Am Alive): The Experiences of
the Internet Disaster Drills", Proceedings of INET-2000, June.
11 Heinanen, J., et. al., "Assured Forwarding PHB Group", RFC 2597,
June 1999
7. Author's Addresses
Ken Carlberg Ran Atkinson
University College London Extreme Networks
Department of Computer Science 3585 Monroe Street
Gower Street Santa Clara, CA
London, WC1E 6BT 95051 USA
United Kingdom
k.carlberg@cs.ucl.ac.uk rja@extremenetworks.com
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