ECRIT H. Schulzrinne
Internet-Draft Columbia University
Intended status: Standards Track S. McCann
Expires: January 14, 2010 Siemens/Roke Manor Research
G. Bajko
Nokia
H. Tschofenig
Nokia Siemens Networks
July 13, 2009
Extensions to the Emergency Services Architecture for dealing with
Unauthenticated and Unauthorized Devices
draft-schulzrinne-ecrit-unauthenticated-access-05.txt
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Abstract
The IETF emergency services architecture assumes that the calling
device has acquired rights to use the access network or that no
authentication is required for the access network, such as for public
wireless access points. Subsequent protocol interactions, such as
obtaining location information, learning the address of the Public
Safety Answering Point (PSAP) and the emergency call itself are
largely decoupled from the underlying network access procedures.
In some cases, the device does not have credentials for network
access, does not have a VoIP provider, or the credentials have become
invalid, e.g., because the user has exhausted their prepaid balance
or the account has expired.
This document provides a problem statement, introduces terminology
and describes an extension for the base IETF emergency services
architecture to address these scenarios.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. No Access Authorization (NAA) . . . . . . . . . . . . . . 5
1.2. No VoIP Service Provider (NVP) . . . . . . . . . . . . . . 6
1.3. Zero-Balance VoIP Service Provider (ZBP) . . . . . . . . . 6
2. A Warning Note . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Considerations for ISPs to support Unauthenticated
Emergency Services without Architecture Extensions . . . . . . 7
5. Considerations for ISPs to support Unauthenticated
Emergency Services with Architecture Extensions . . . . . . . 8
6. Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. End Host Profile . . . . . . . . . . . . . . . . . . . . . 12
6.1.1. LoST Server Discovery . . . . . . . . . . . . . . . . 12
6.1.2. ESRP Discovery . . . . . . . . . . . . . . . . . . . . 12
6.1.3. Location Determination and Location Configuration . . 12
6.1.4. Emergency Call Identification . . . . . . . . . . . . 12
6.1.5. SIP Emergency Call Signaling . . . . . . . . . . . . . 13
6.1.6. Media . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1.7. Testing . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. IAP/ISP Profile . . . . . . . . . . . . . . . . . . . . . 13
6.2.1. ESRP Discovery . . . . . . . . . . . . . . . . . . . . 13
6.2.2. Location Determination and Location Configuration . . 13
6.3. ESRP Profile . . . . . . . . . . . . . . . . . . . . . . . 14
6.3.1. Emergency Call Routing . . . . . . . . . . . . . . . . 14
6.3.2. Emergency Call Identification . . . . . . . . . . . . 14
6.3.3. SIP Emergency Call Signaling . . . . . . . . . . . . . 14
6.3.4. Location Retrieval . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
Summoning police, the fire department or an ambulance in emergencies
is one of the fundamental and most-valued functions of the telephone.
As telephone functionality moves from circuit-switched telephony to
Internet telephony, its users rightfully expect that this core
functionality will continue to work at least as well as it has for
the older technology. New devices and services are being made
available that could be used to make a request for help, which are
not traditional telephones, and users are increasingly expecting them
to be used to place emergency calls.
Roughly speaking, the IETF emergency services architecture (see
[I-D.ietf-ecrit-phonebcp] and [I-D.ietf-ecrit-framework]) divides
responsibility for handling emergency calls between the access
network (ISP), the VoIP service provider (VSP) and the provider of
emergency signaling services, the emergency service network (ESN).
The access network may provide location information to end systems,
but does not have to provide any VoIP signaling functionality. The
emergency caller can reach the ESN either directly or through the
VoIP provider's outbound proxy. Any of the three parties can provide
the mapping from location to PSAP URI by offering LoST [RFC5222]
services.
In general, a set of automated configuration mechanisms allows a
device to function in a variety of architectures, without the user
being aware of the details on who provides location, mapping services
or call routing services. However, if emergency calling is to be
supported when the calling device lacks access network authorization
or does not have a VoIP provider, one or more of the providers may
need to provide additional services and functions.
In all cases, the end device MUST be able to perform a LoST lookup
and otherwise conduct the emergency call in the same manner as when
the three exceptional conditions discussed below do not apply.
We distinguish between three conditions:
No access authorization (NAA): The current access network requires
access authorization and the caller does not have valid user
credentials. (This includes the case where the access network
allows pay-per-use, as is common for wireless hotspots, but there
is insufficient time to pay for access.)
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No VoIP provider (NVP): The caller does not have a VoIP service
provider (VSP) at the time of the call.
Zero-balance VoIP provider (ZBP): The caller has valid credentials
with a VSP, but is not allowed to place calls, e.g., because the
user has a zero balance in a prepaid account.
A user may well suffer from both NAA and NVP or ZBP at the same time.
Depending on local policy and regulations, it may not be possible to
place emergency calls in the NAA case. Unless local regulations
require user identification, it should always be possible to place
calls in the NVP case, with minimal impact on the ISP. Unless the
ESN requires that all calls traverse a known set of VSPs, a caller
should be able to place an emergency call in the ZBP case. We
discuss each case in separate sections below.
1.1. No Access Authorization (NAA)
In the NAA (No Access Authorization) case, the emergency caller does
not posses valid credentials for the access network. If local
regulations or policy allows or require, the access network may or
needs to cooperate in providing emergency calling services.
Generally, the ISP will want to ensure that devices do not pretend to
place emergency calls, but then abuse the access for obtaining more
general services fraudulently.
In particular, the ISP MUST allow emergency callers to acquire an IP
address and to reach a LoST server, either provided by the ISP or
some third party. It SHOULD also provide location information via
one of the mechanisms specified in [I-D.ietf-ecrit-phonebcp] without
requiring authorization unless it can safely assume that all nodes in
the access network can determine their own location, e.g., via GPS.
The details of how filtering is performed depends on the details of
the ISP architecture and are beyond the scope of this document. We
illustrate a possible model. If the ISP runs its own LoST server, it
would maintain an access control list including all IP addresses
contained in responses returned by the LoST server, as well as the
LoST server itself. (It may need to translate the domain names
returned to IP addresses and hope that the resolution captures all
possible DNS responses.) Since the media destination addresses are
not predictable, the ISP also has to provide a SIP outbound proxy so
that it can determine the media addresses and add those to the filter
list.
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1.2. No VoIP Service Provider (NVP)
In the second case, the emergency caller has no current VoIP service
provider (VSP). This case poses no particular difficulties unless it
is assumed that only VSPs provide LoST server or that ESNs only
accept calls that reach it through a set of known VSPs. However,
since the calling device cannot obtain configuration information from
its VSP, the ISP MUST provide the address of a LoST server via DHCP
[RFC5223] if this model is to be supported. The LoST server may be
operated either by the ISP or a third party.
1.3. Zero-Balance VoIP Service Provider (ZBP)
In the case of zero-balance VoIP service provider, the VSP can
authenticate the caller, but the caller is not authorized to place
regular VoIP calls, e.g., because the contract has expired or the
prepaid account for the customer has been depleted. Naturally, a VSP
can simply disallow access by such customers, so that all such
customers find themselves in the NVP situation described above. If
VSPs desire or are required by regulation to provide emergency
calling services to such customers, they need to provide LoST
services to such customers and may need to provide outbound SIP proxy
services. As usual, the calling device looks up the LoST server via
SIP configuration.
Unless the emergency call traverses a PSTN gateway or the VSP charges
for IP-to-IP calls, there is little potential for fraud. If the VSP
also operates the LoST server, the outbound proxy MAY restrict
outbound calls to the SIP URIs returned by the LoST server. It is
NOT RECOMMENDED to rely on a fixed list of SIP URIs, as that list may
change.
2. A Warning Note
At the time of writing there is no regulation in place that demands
the functionality described in this memo. SDOs have started their
work on this subject in a proactive fashion in the anticipation that
national regulation will demand it for a subset of network
environments.
There are also indications that the functionality of unauthenticated
emergency calls (called SIM-less calls) in today's cellular system in
certain countries leads to a fair amount of hoaks or test calls.
This causes overload situations at PSAPs with .
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As an example, Federal Office of Communications (OFCOM,
Switzerland) provided statistics about 112 calls in Switzerland
from Jan. 1997 to Nov. 2001. Switzerland did not offer SIM-less
emergency calls except for almost a month in July 2000 where a
significant increase in hoaks and test calls was reported. As a
consequence, the functionality was disabled again. More details
can be found in the panel presentations of the 3rd SDO Emergency
Services Workshop [esw07].
3. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119
[RFC2119].
This document reuses terminology from [I-D.ietf-geopriv-l7-lcp-ps]
and [RFC5012], namely Internet Access Provider (IAP), Internet
Service Provider (ISP), Application Service Provider (ASP), Voice
Service Provider (VSP), Emergency Service Routing Proxy (ESRP),
Public Safety Answering Point (PSAP), Location Configuration Server
(LCS), (emergency) service dial string, and (emergency) service
identifier.
4. Considerations for ISPs to support Unauthenticated Emergency
Services without Architecture Extensions
On a very high-level, the steps to be performed by an end host not
being attached to the network and the user starting to make an
emergency call are the following:
o Some radio networks have added support for unauthenticated
emergency access, some other type of networks advertise these
capabilities using layer beacons. The end host learns about these
unauthenticated emergency services capabilities either from the
link layer type or from advertisement.
o The end host uses the link layer specific network attachment
procedures defined for unauthenticated network access in order to
get access to emergency services.
o When the link layer network attachment procedure is completed the
end host learns basic configuration information using DHCP from
the ISP, including the address of the LoST server.
o The end host MUST use a Location Configuration Protocol (LCP)
supported by the IAP or ISP to learn its own location.
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o The end host MUST use the LoST protocol [I-D.ietf-ecrit-lost] to
query the LoST server and ask for the PSAP URI responsible for
that location.
o After the PSAP URI has been returned to the end host, the SIP UA
in the end host directly initiates a SIP INVITE towards the PSAP
URI.
The IAP and the ISP will probably want to make sure that the claimed
emergency caller indeed performs an emergency call rather than using
the network for other purposes, and thereby acting fraudulent by
skipping any authentication, authorization and accounting procedures.
By restricting access of the unauthenticated emergency caller to the
LoST server and the PSAP URI, traffic can be restricted only to
emergency calls.
Using the above procedures, the unauthenticated emergency caller will
be successful only if:
o the ISP (or the IAP) support an LCP that the end host can use to
learn its location. A list of mandatory-to-implement LCPs can be
found in [I-D.ietf-ecrit-phonebcp]).
o the ISP configures it's firewalls appropriately to allow emergency
calls to traverse the network towards the PSAP.
Some IAPs/ISPs may not be able to fulfill the above requirements. If
those IAPs/ISPs want to support unauthenticated emergency calls, then
they can deploy an extended architecture as described in Section 5.
5. Considerations for ISPs to support Unauthenticated Emergency
Services with Architecture Extensions
For unauthenticated emergency services support it is insufficient to
provide mechanisms only at the link layer in order to bypass
authentication for the cases when:
o the IAP/ISP does not support any Location Configuration Protocol
o the IAP/ISP does not have knowledge of a LoST server (which would
assist the client to find the correct PSAP)
A modification to the emergency services architecture is necessary
since the IAP and the ISP need to make sure that the claimed
emergency caller indeed performs an emergency call rather than using
the network for other purposes, and thereby acting fraudulent by
skipping any authentication, authorization and accounting procedures.
Hence, without introducing some understanding of the specific
application the ISP (and consequently the IAP) will not be able to
detect and filter malicious activities. This leads to the
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architecture described in Figure 1 where the IAP needs to implement
extensions to link layer procedures for unauthenticated emergency
service access and the ISP needs to deploy emergency services related
entities used for call routing, such as the Emergency Services
Routing Proxy (ESRP), a Location Configuration Server (LCS) and a
mapping database.
On a very high-level, the interaction is as follows starting with the
end host not being attached to the network and the user starting to
make an emergency call.
o Some radio networks have added support for unauthenticated
emergency access, some other type of networks advertise these
capabilities using layer beacons. The end host learns about these
unauthenticated emergency services capabilities either from the
link layer type or from advertisement.
o The end host uses the link layer specific network attachment
procedures defined for unauthenticated network access in order to
get access to emergency services.
o When the link layer network attachment procedure is completed the
end host learns basic configuration information using DHCP from
the ISP, including the address of the ESRP, as shown in (2).
o When the IP address configuration is completed then the SIP UA
initiates a SIP INVITE towards the indicated ESRP, as shown in
(3). The INVITE message contains all the necessary parameters
required by Section 6.1.5.
o The ESRP receives the INVITE and processes it according to the
description in Section 6.3.3. The location of the end host may
need to be determined using a protocol interaction shown in (4).
o Potentially, an interaction between the LCS of the ISP and the LCS
of the IAP may be necessary, see (5).
o Finally, the correct PSAP for the location of the end host has to
be evaluated, see (6).
o The ESRP routes the call to the PSAP, as shown in (7).
o The PSAP evaluates the initial INVITE and aims to complete the
call setup.
o Finally, when the call setup is completed media traffic can be
exchanged between the PSAP and the emergency caller.
For editorial reasons the end-to-end SIP and media exchange between
the PSAP and SIP UA are not shown in Figure 1.
Two important aspects are worth to highlight:
o The IAP/ISP needs to understand the concept of emergency calls and
the SIP profile described in this document. No other VoIP
protocol profile, such as XMPP, Skype, etc., are supported for
emergency calls in this particular architecture. Other profiles
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may be added in the future, but the deployment effort is enormous
since they have to be universally deployed.
o The end host has no obligation to determine location information.
It may attach location information if it has location available
(e.g., from a GPS receiver).
Figure 1 shows that the ISP needs to deploy SIP-based emergency
services functionality. It is important to note that the ISP itself
may outsource the functionality by simply providing access to them
(e.g., it puts the IP address of an ESRP or a LoST server into an
allow-list). For editorial reasons this outsourcing is not shown.
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+---------------------------+
| |
| Emergency Network |
| Infrastructure |
| |
| +----------+ +----------+ |
| | PSAP | | ESRP | |
| | | | | |
| +----------+ +----------+ |
+-------------------^-------+
|
| (7)
+------------------------+-----------------------+
| ISP | |
| | |
|+----------+ v |
|| Mapping | (6) +----------+ |
|| Database |<----->| ESRP / | |
|+----------+ | SIP Proxy|<-+ |
|+----------+ +----------+ | +----------+|
|| LCS-ISP | ^ | | DHCP ||
|| |<---------+ | | Server ||
|+----------+ (4) | +----------+|
+-------^-------------------------+-----------^--+
+-------|-------------------------+-----------|--+
| IAP | (5) | | |
| V | | |
|+----------+ | | |
|| LCS-IAP | +----------+ | | |
|| | | Link | |(3) | |
|+----------+ | Layer | | | |
| | Device | | (2)| |
| +----------+ | | |
| ^ | | |
| | | | |
+------------------------+--------+-----------+--+
| | |
(1)| | |
| | |
| +----+ |
v v |
+----------+ |
| End |<-------------+
| Host |
+----------+
Figure 1: Overview
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It is important to note that a single ESRP may also offer it's
service to several ISPs.
6. Profiles
6.1. End Host Profile
6.1.1. LoST Server Discovery
The end host MAY attempt to use [I-D.ietf-ecrit-lost] to discover a
LoST server. If that attempt fails, the end host SHOULD attempt to
discover the address of an ESRP.
6.1.2. ESRP Discovery
The end host only needs an ESRP when location configuration or LoST
server discovery fails. If that is the case, then the end host MUST
use the "Dynamic Host Configuration Protocol (DHCP-for-IPv4) Option
for Session Initiation Protocol (SIP) Servers" [RFC3361] (for IPv6)
and / or the "Dynamic Host Configuration Protocol (DHCPv6) Options
for Session Initiation Protocol (SIP) Servers" [RFC3319] to discover
the address of an ESRP. This SIP proxy located in the ISP network
will be used as the ESRP for routing emergency calls. There is no
need to discovery a separate SIP proxy with specific emergency call
functionality since the internal procedure for emergency call
processing is subject of ISP internal operation.
6.1.3. Location Determination and Location Configuration
The end host SHOULD attempt to use the supported LCPs to configure
its location. If no LCP is supported in the end host or the location
configuration is not successful, then the end host MUST attempt to
discover an ESRP, which would assist the end host in providing the
location to the PSAP.
The SIP UA in the end host SHOULD attach the location information in
a PIDF-LO [RFC4119] when making an emergency call. When constructing
the PIDF-LO the guidelines in PIDF-LO profile
[I-D.ietf-geopriv-pdif-lo-profile] MUST be followed. For civic
location information the format defined in [RFC5139] MUST be
supported.
6.1.4. Emergency Call Identification
To determine which calls are emergency calls, some entity needs to
map a user entered dialstring into this URN scheme. A user may
"dial" 1-1-2, but the call would be sent to urn:service:sos. This
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mapping SHOULD be performed at the endpoint device.
End hosts MUST use the Service URN mechanism [RFC5031] to mark calls
as emergency calls for their home emergency dial string (if known).
For visited emergency dial string the translation into the Service
URN mechanism is not mandatory since the ESRP in the ISPs network
knows the visited emergency dial strings.
6.1.5. SIP Emergency Call Signaling
SIP signaling capabilities [RFC3261] are mandated for end hosts.
The initial SIP signaling method is an INVITE. The SIP INVITE
request MUST be constructed according to the requirements in Section
9.2 [I-D.ietf-ecrit-phonebcp].
Regarding callback behavior SIP UAs MUST have a globally routable URI
in a Contact: header.
6.1.6. Media
End points MUST comply with the media requirements for end points
placing an emergency call found in Section 14 of
[I-D.ietf-ecrit-phonebcp].
6.1.7. Testing
The description in Section 15 of [I-D.ietf-ecrit-phonebcp] is fully
applicable to this document.
6.2. IAP/ISP Profile
6.2.1. ESRP Discovery
An ISP hosting an ESRP MUST implement the server side part of
"Dynamic Host Configuration Protocol (DHCP-for-IPv4) Option for
Session Initiation Protocol (SIP) Servers" [RFC3361] (for IPv4) and /
or the "Dynamic Host Configuration Protocol (DHCPv6) Options for
Session Initiation Protocol (SIP) Servers" [RFC3319].
6.2.2. Location Determination and Location Configuration
The ISP not hosting an ESRP MUST support at least one widely used
LCP. The ISP hosting an ESRP MUST perform the neccesary steps to
determine the location of the end host. It is not necessary to
standardize a specific mechanism.
The role of the ISP is to operate the LIS. The usage of HELD
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[I-D.ietf-geopriv-http-location-delivery] with the identity
extensions [I-D.winterbottom-geopriv-held-identity-extensions] may be
a possible choice. It might be necessary for the ISP to talk to the
IAP in order to determine the location of the end host. The work on
LIS-to-LIS communication may be relevant, see
[I-D.winterbottom-geopriv-lis2lis-req].
6.3. ESRP Profile
6.3.1. Emergency Call Routing
The ESRP must route the emergency call to the PSAP responsible for
the physical location of the end host. However, a standardized
approach for determining the correct PSAP based on a given location
is useful but not mandatory.
For cases where a standardized protocol is used LoST
[I-D.ietf-ecrit-lost] is a suitable mechanism.
6.3.2. Emergency Call Identification
The ESRP MUST understand the Service URN mechanism [RFC5031] (i.e.,
the 'urn:service:sos' tree) and additionally the national emergency
dial strings. The ESRP SHOULD perform a mapping of national
emergency dial strings to Service URNs to simplify processing at
PSAPs.
6.3.3. SIP Emergency Call Signaling
SIP signaling capabilities [RFC3261] are mandated for the ESRP. The
ESRP MUST process the messages sent by the client, according to
Section 6.1.5. Furthermore, the ESRP MUST be able to add a reference
to location information, as described in SIP Location Conveyance
[I-D.ietf-sip-location-conveyance], before forwarding the call to the
PSAP. The ISP MUST be prepared to receive incoming dereferencing
requests to resolve the reference to the location information.
6.3.4. Location Retrieval
The ESRP acts a location recipient and the usage of HELD
[I-D.ietf-geopriv-http-location-delivery] with the identity
extensions [I-D.winterbottom-geopriv-held-identity-extensions] may be
a possible choice. The ESRP would thereby act as a HELD client and
the corresponding LIS at the ISP as the HELD server.
The ESRP needs to obtain enough information to route the call. The
ESRP itself, however, does not necessarily need to process location
information obtained via HELD since it may be used as input to LoST
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to obtain the PSAP URI.
7. Security Considerations
The security threats discussed in [RFC5069] are applicable to this
document. A number of security vulnerabilities discussed in
[I-D.barnes-geopriv-lo-sec] around faked location information are
less problematic in this case since location information does not
need to be provided by the end host itself or it can be verified to
fall within a specific geographical area.
There are a couple of new vulnerabilities raised with unauthenticated
emergency services since the PSAP operator does is not in possession
of any identity information about the emergency call via the
signaling path itself. In countries where this functionality is used
for GSM networks today this has lead to a significant amount of
misuse.
The link layer mechanisms need to provide a special way of handling
unauthenticated emergency services. Although this subject is not a
topic for the IETF itself but there are at least a few high-level
assumptions that may need to be collected. This includes security
features that may be desirable.
8. Acknowledgments
Section 6 of this document is derived from [I-D.ietf-ecrit-phonebcp].
The WiMax Forum contributed parts of the terminology. Participants
of the 2nd and 3rd SDO Emergency Services Workshop provided helpful
input.
9. IANA Considerations
This document does not require actions by IANA.
10. References
10.1. Normative References
[I-D.ietf-sip-location-conveyance]
Polk, J. and B. Rosen, "Location Conveyance for the
Session Initiation Protocol",
draft-ietf-sip-location-conveyance-13 (work in progress),
March 2009.
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[RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
January 2008.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[I-D.ietf-geopriv-pdif-lo-profile]
Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV
PIDF-LO Usage Clarification, Considerations and
Recommendations", draft-ietf-geopriv-pdif-lo-profile-14
(work in progress), November 2008.
[RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location
Format for Presence Information Data Format Location
Object (PIDF-LO)", RFC 5139, February 2008.
[RFC3361] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCP-for-IPv4) Option for Session Initiation Protocol
(SIP) Servers", RFC 3361, August 2002.
[RFC3319] Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
Protocol (DHCPv6) Options for Session Initiation Protocol
(SIP) Servers", RFC 3319, July 2003.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-ecrit-phonebcp]
Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in support of Emergency Calling",
draft-ietf-ecrit-phonebcp-12 (work in progress),
July 2009.
[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", RFC 5222, August 2008.
[RFC5223] Schulzrinne, H., Polk, J., and H. Tschofenig, "Discovering
Location-to-Service Translation (LoST) Servers Using the
Dynamic Host Configuration Protocol (DHCP)", RFC 5223,
August 2008.
Schulzrinne, et al. Expires January 14, 2010 [Page 16]
Internet-Draft Unauthenticated Emergency Service July 2009
10.2. Informative References
[I-D.ietf-ecrit-lost]
Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", draft-ietf-ecrit-lost-10 (work in progress),
May 2008.
[I-D.ietf-geopriv-l7-lcp-ps]
Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
Location Configuration Protocol; Problem Statement and
Requirements", draft-ietf-geopriv-l7-lcp-ps-09 (work in
progress), February 2009.
[I-D.ietf-ecrit-framework]
Rosen, B., Schulzrinne, H., Polk, J., and A. Newton,
"Framework for Emergency Calling using Internet
Multimedia", draft-ietf-ecrit-framework-09 (work in
progress), March 2009.
[I-D.ietf-geopriv-http-location-delivery]
Barnes, M., Winterbottom, J., Thomson, M., and B. Stark,
"HTTP Enabled Location Delivery (HELD)",
draft-ietf-geopriv-http-location-delivery-15 (work in
progress), June 2009.
[RFC5012] Schulzrinne, H. and R. Marshall, "Requirements for
Emergency Context Resolution with Internet Technologies",
RFC 5012, January 2008.
[I-D.winterbottom-geopriv-held-identity-extensions]
Thomson, M., Tschofenig, H., Barnes, R., and J.
Winterbottom, "Use of Target Identity in HTTP-Enabled
Location Delivery (HELD)",
draft-winterbottom-geopriv-held-identity-extensions-09
(work in progress), February 2009.
[I-D.winterbottom-geopriv-lis2lis-req]
Winterbottom, J. and S. Norreys, "LIS to LIS Protocol
Requirements", draft-winterbottom-geopriv-lis2lis-req-01
(work in progress), November 2007.
[RFC5069] Taylor, T., Tschofenig, H., Schulzrinne, H., and M.
Shanmugam, "Security Threats and Requirements for
Emergency Call Marking and Mapping", RFC 5069,
January 2008.
[I-D.barnes-geopriv-lo-sec]
Schulzrinne, et al. Expires January 14, 2010 [Page 17]
Internet-Draft Unauthenticated Emergency Service July 2009
Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
Tschofenig, H., and H. Schulzrinne, "An Architecture for
Location and Location Privacy in Internet Applications",
draft-barnes-geopriv-lo-sec-05 (work in progress),
March 2009.
[esw07] "3rd SDO Emergency Services Workshop,
http://www.emergency-services-coordination.info/2007Nov/",
October 30th - November 1st 2007.
Authors' Addresses
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu
Stephen McCann
Siemens/Roke Manor Research
Email: stephen.mccann@roke.co.uk
Gabor Bajko
Nokia
Email: Gabor.Bajko@nokia.com
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Schulzrinne, et al. Expires January 14, 2010 [Page 18]