IPTEL Working Group J.Yu
Internet Draft Nuestar
Intended status: Standards track D. Hancock
Expires: December 2007 CableLabs
F. Andreasen
Cisco
July 4, 2007
DAI Parameter for the "tel" URI
draft-yu-tel-dai-02
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document defines a "dai" parameter for the "tel" Uniform
Resource Identifier (URI) to support the Dial Around Indicator (DAI).
The "dai" parameter is associated with the "cic" parameter, defined
in [RFC4694], and indicates how the carrier identified in the "cic"
parameter was selected. This document also expands the use of the
"cic" parameter to support pre-subscribed and dialed long-distance
carrier requirements.
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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 RFC2119 [RFC2119].
Table of Contents
1. Introduction...................................................2
2. Abbreviations..................................................3
3. Formal Syntax..................................................3
4. Normative Rules................................................4
5. Examples......................................................12
6. Security Considerations.......................................13
7. IANA Considerations...........................................13
8. References....................................................13
1. Introduction
Before equal access was supported in the United States, only AT&T's
subscribers could dial "1" to reach AT&T when they made long distance
calls. Other long distance carriers' subscribers needed to dial
extra digits to reach their long distance carriers. For the fair
competition, the Federal Communication Commission in the U.S.
mandated the support for equal access that allowed any long distance
carrier's subscriber to follow the same dialing plan to reach his/her
pre-subscribed long distance carrier. The regulatory bodies in many
other countries also have mandated equal access.
To allow a telephony subscriber to use a non-pre-subscribed long
distance carrier for some of their long distance calls, the U.S. has
implemented the dialing prefix "10XXX" that was later expanded to
"101XXXX" in the dialing plan. The prefix allows the caller to use
"XXX" or "XXXX" to specify the long distance carrier to handle that
particular call. This dialing prefix was also used to identify the
local toll carrier in the United States when equal access also
applied to the local toll calls.
One of the purposes of the DAI is to indicate to the long distance
carrier that receives a call from the local exchange carrier whether
the call came from a pre-subscribed customer or not. Due to
operator-assisted calls, where the called party or a third party may
be charged for the call in some cases, the DAI is also used to
indicate to the receiving long distance carrier if it is the primary
or alternate preferred long distance carrier of the charged party.
The long distance carrier information, the Carrier Identification
Code (CIC), can be carried in the "cic" parameter [RFC4694], a
parameter of the "tel" Uniform Resource Identifier (URI) [RFC3966].
The "cic" parameter defined in [RFC4694] identifies the freephone
service provider that serves the freephone number. As described in
[RFC4694], it can also be used to carry the CIC associated with the
carrier who is to handle a call to a geographic telephone number;
such usage is leveraged in this document. When the carrier that is
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assigned the CIC receives the call, the "dai" parameter defined in
this document indicates to that carrier how it was selected.
2. Abbreviations
ANSI American National Standards Institute
BNF Backus-Naur Form
CIC Carrier Identification Code (also cic)
DAI Dial Around Indicator (also dai)
FCC Federal Communications Commission
ENUM Telephone Number Mapping
GSTN Global Switched Telephone Network
GW Gateway
IETF Internet Engineering Task Force
IP Internet Protocol
ISUP Integrated Services Digital Network User Part
SS7 Signaling System number 7
SW Switch
URI Uniform Resource Identifier
3. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) as described in RFC 4234 [RFC4234] and defines the "dai"
parameter by extending the "parameter" production rule of the "tel"
URI defined in [RFC3966].
Parameter =/ dai
dai = ";dai="
"no-ind" /
"presub" /
"presub-da" /
"presub-daUnkwn" /
"da" /
"CIC-chrgPty" /
"altCIC-chrgPty" /
"verbal-clgPty" /
"verbal-chrgPty" /
"emergency" /
"presubUnkwn-da" /
"operator"
The "dai" parameter can appear in the "tel" URI at most once. The
"dai" parameter MUST NOT be present if the "cic" parameter is not
present. When the "cic" parameter is present due to carrier
selection, the "dai" parameter MUST be present so that its presence
in the tel URI can differentiate the carrier selection case from the
freephone case. Please see [RFC4694] for the syntax specification of
the "cic" parameter.
Below are the descriptions of the values of the "dai" parameter.
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"no-ind": indicates that it is not known how the carrier identified
in the CIC was selected.
"presub": indicates that the CIC contains the caller's presubscribed
carrier.
"presub-da": indicates that the CIC contains the caller's dialed
carrier-identification-code; the selected carrier is the caller's
presubscribed carrier.
"presub-daUnkwn": indicates that the CIC may contain either a caller
dialed carrier-identification-code or the caller's presubscribed
carrier.
"da": indicates that the CIC contains the caller's dialed carrier-
identification-code; the selected carrier is not the caller's
presubscribed carrier.
"CIC-chrgPty": indicates that the CIC contains the preferred carrier
of the charged party.
"altCIC-chrgPty": indicates that the CIC contains the alternate
carrier of the charged party.
"verbal-clgPty": indicates that the CIC contains the carrier
delivered verbally by the calling party.
"verbal-chrgPty": indicates that the CIC contains the carrier
delivered verbally by the charged party.
"emergency": indicates that the CIC is selected for emergency call
handling.
"presubUnkwn-da": indicates that the CIC contains the caller's dialed
carrier-identification-code; it is not known if the selected carrier
is the caller's presubscribed carrier.
"operator": indicates that the CIC contains a carrier selected by a
network operator.
4. Normative Rules
This section discusses how a network node adds the "dai" parameter to
the "tel" URI or handles a received "tel" URI that contains the "dai"
parameter. Since the "dai" parameter goes with the "cic" parameter,
the latter is included in some of the discussions below. The phone
numbers of the caller and called party are geographic numbers in the
discussions.
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When the call signaling message contains a "tel" URI that carries the
"cic" parameter, ENUM [RFC3761] could map the phone number in the
"tel" URI to other URI(s) such as SIP URI [RFC3261]. In that case,
the mapped URI instead of the parameters in the "tel" URI MAY be used
to route the call. In this document it is assumed that ENUM is not
involved.
4.1. Network Model
The network model in Figure 1 is used to help describing the rules
for sending and receiving the "dai" parameter. The discussion below
focuses on the handling of the "tel" URI in the signaling messages.
It is assumed that the signaling message will contain the "cic" and
"dai" parameters after it leaves "Network Node A" for a call
originated by the user or after it leaves "GSTN GW" when the call
comes from the PSTN.
+-------------------------------+
| |
+---------+ +---------+ +---------+ +---------+
| Network | | Network | | Network | | User |
| Node C |-----| Node B |-----| Node A |------| Device |
+---------+ +---------+ +---------+ +---------+
| | |
| | |
| | +---------+ +---------+
| +----------| GSTN | | GSTN |
+--------------------------| GW |------| SW |
+---------+ +---------+
Figure 1. Network Model
"User Device" generates the signaling message requesting a call
setup.
"Network Node A" represents those network nodes that receive the call
request and can analyze the type of call (e.g., local toll, long
distance or international based on the calling party number/address
and called party number) and determine or identify the carrier that
is to handle the call. The latter can be based on the information
from the caller (e.g., "101XXXX"), the presubscribed carrier
information in the service profile of the caller, or via the
involvement of an operator that interacts with the calling party,
called party (e.g., for collect call) or a third party (e.g., when
the call is charged to a third party) for an operator-assisted call.
If configured by the network operator, Node A can apply a preferred
CIC for all calls where carrier selection is needed. Note that
although Figure 1 shows Node A as a single entity, its
responsibilities can be shared amongst multiple Node As such that the
Node A that is connected to or communicates with the user device is
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separate from the Node A that determines or identifies the carrier to
handle the call.
"Network Node B" represents those network nodes that are not
associated with the carrier identified in the "cic" parameter and
need to route the signaling message that contains the "cic" and "dai"
parameters towards the carrier identified in the "cic" parameter.
"Network Node C" represents those network nodes that receive the
signaling message from "Network Node B" and belongs to the carrier
identified in the "cic" parameter.
"GSTN GW" stands for "Global Switched Telephone Network (GSTN)
Gateway (GW)". It interfaces between the Internet Protocol (IP)
domain and the GSTN domain for signaling protocols and the user
traffic. The GSTN includes the wireline network, wireless network
and other circuit-switched network. Signaling traffic and user
traffic could be handled by separate network nodes. In this
document, both types of traffic are handled by "GSTN GW" to simplify
the discussion.
"GSTN Switch (SW)" is a circuit switch in the GSTN that is connected
with the GSTN GW.
"User Device", "Network Node A", "Network Node B" and "Network Node
C" are in the IP domain. "Network Node A", "Network Node B" and
"Network Node C" can route the calls to the GSTN via the GSTN GW.
The rules for various scenarios are described below.
4.2. Adding the "dai" Parameter to the "tel" URI
This section discusses those cases where "Network Node A" receives a
call request from "User Device" and may need to add the "dai"
parameter to the "tel" URI. If the "cic" Parameter is included and
"Network Node A" does not know how the carrier is selected or does
not want to reveal how the carrier is selected (if it is allowed to
do it), "Network Node A" MUST include the "dai" Parameter and set it
to "no-ind".
4.2.1. CIC Information provided in call signaling from "User Device"
"User Device" can provide the CIC information via call signaling in
two ways.
a. Include the "cic" parameter in the "tel" URI to carry the selected
CIC. It is outside the scope of this document as to how "User
Device" adds the "cic" parameter to the "tel" URI. "User Device"
SHOULD NOT include the "dai" parameter in the "tel" URI. When
included by the "User Device", "Network Node A" SHALL ignore the
"dai" parameter.
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b. Include the selected CIC information in the dialed string (e.g.,
"101XXXX" followed by a national number). [String] specifies one way
to deliver the dialed string in the SIP protocol [RFC3261]. It is
outside the scope of this document as to how the dialed string is
carried in the signaling message and how "Network Node A" knows how
to identify the caller selected CIC information when applicable and
the called phone number from the received dialed string.
When receiving a call request containing the "cic" parameter or the
CIC information in the signaling message from "User Device" and an
operator is not involved in call handling, "Network Node A" MUST
follow the rules described below. The cases where an operator is
involved in determining/selecting a carrier to handle the call are
addressed in 4.2.3 and 4.2.4 below.
- If the call is to be handled by the carrier "Network Node A" is
associated with (that is, the carrier network is the network within
which Node A resides), "Network Node A" MUST remove the "cic"
parameter, if present in the "tel" URI, and MUST NOT include the
"dai" parameter if it needs to forward the signaling message to
another network node.
- If "Network Node A" selects a carrier other than the caller's pre-
subscribed carrier or the one specified by "User Device" to handle
the call (e.g., does not allow the caller to specify the carrier to
handle the call), "Network Node A" MUST set the "cic" parameter to
contain the CIC it selects and include the "cic" parameter, if not
yet present, in the "tel" URI. "Network Node A" MUST include the
"dai" parameter in the "tel" URI and set it to "operator".
- If the "User Device" specified carrier is the same as the caller's
pre-subscribed carrier and "Network Node A" knows that the CIC
information is provided by "User Device", "Network Node A" MUST set
the "cic" parameter to contain the caller's pre-subscribed carrier's
CIC and include the parameter, if not yet present, in the "tel" URI.
"Network Node A" MUST set the "dai" parameter to "presub-da" and
include the parameter in the "tel" URI.
- If "Network Node A" is not sure whether the CIC information is
provided by "User Device" (e.g., a proxy server between "User Device"
and "Network Node A" is involved), it MUST set the "dai" parameter to
"presub-daUnkwn" in the process described above.
- If the "User Device" specified carrier is different from the
caller's pre-subscribed carrier, "Network Node A" MUST set the "cic"
parameter to contain the "User Device" specified carrier and include
the parameter, if not yet present, in the "tel" URI. "Network Node
A" MUST set the "dai" parameter to "da" and include the parameter in
the "tel" URI.
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- If the "User Device" specifies a carrier and "Network Node A"
cannot determine if the selected carrier is the caller's
presubscribed carrier, "Network Node A" MUST set the "cic" parameter
to contain the "User Device" specified carrier and include the
parameter, if not yet present, in the "tel" URI. "Network Node A"
MUST set the "dai" parameter to "presubUnkwn-da" and include the
parameter in the "tel" URI.
4.2.2. CIC Information not provided in call signaling from "User
Device"
In this scenario, "User Device" did not provide any CIC information
in call signaling and an operator is not involved in call handling.
"Network Node A" MUST follow the rules described below. The cases
where an operator is involved in determining/selecting a carrier to
handle the call are addressed in 4.2.3 and 4.2.4 below.
- If the call is to be handled by the carrier "Network Node A" is
associated with, "Network Node A" MUST NOT include the "cic" and
"dai" parameters in the "tel" URI if it needs to forward the
signaling message to another network node.
- If "Network Node A" selects a carrier that is different from the
caller's pre-subscribed carrier to handle the call, it MUST set the
"cic" parameter to contain the CIC it selects and include the
parameter in the "tel" URI. "Network Node A" MUST include the "dai"
parameter in the "tel" URI and set it to "operator".
- If the caller has a pre-subscribed carrier that can handle the
call, "Network Node A" MUST set the "cic" parameter to contain the
caller's pre-subscribed carrier's CIC and include the parameter in
the "tel" URI. "Network Node A" MUST set the "dai" parameter to
"presub" and include the parameter in the "tel" URI.
4.2.3. Operator-assisted call handling, caller pays for the call
When an operator is involved in handling the call request from the
caller, "Network Node A" may or may not have the CIC information
available from the signaling message. If the caller is to pay for
the call, the operator may interact with the caller to determine the
carrier to handle the call when applicable. If the CIC information
is available from call signaling and the operator also interacts with
the caller to get the CIC information, the CIC provided by the
operator MUST be used. How the caller indicates an operator-assisted
call and passes the CIC information in call signaling is outside the
scope of this document.
"Network Node A" through the assistance of an operator MUST follow
the rules described below.
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- If the call is to be handled by the carrier "Network Node A" is
associated with, "Network Node A" MUST remove the "cic" parameter, if
present in the "tel" URI, and MUST NOT include the "dai" parameter if
it needs to forward the signaling message to another network node.
- If "Network Node A" selects a carrier other than the caller's pre-
subscribed carrier or the one specified by "User Device" or indicated
by the caller during the interaction with the operator to handle the
call, "Network Node A" MUST set the "cic" parameter to contain the
CIC it selects and include the parameter, if not yet present, in the
"tel" URI. "Network Node A" MUST include the "dai" parameter in the
"tel" URI and set it to "operator".
- If the carrier specified by "User Device" in call signaling or by
the caller via the interaction with the operator or selected by
"Network Node A" is the same as the caller's pre-subscribed carrier,
"Network Node A" MUST set the "cic" parameter to contain the caller's
pre-subscribed carrier's CIC and include the parameter, if not yet
present, in the "tel" URI. "Network Node A" MUST set the "dai"
parameter to "presub-da" and include the parameter in the "tel" URI.
- If "Network Node A" is not sure whether the CIC information is
provided by "User Device" or the operator did not indicate if the CIC
information came from the caller, it MUST set the "dai" parameter to
"presub-daUnkwn" in the process described above.
- If the carrier specified by "User Device" in call signaling or by
caller via the interaction with the operator is different from the
caller's pre-subscribed carrier, "Network Node A" MUST set the "cic"
parameter to contain the CIC of the selected carrier and include the
parameter, if not yet present, in the "tel" URI. "Network Node A"
MUST set the "dai" parameter to "da" and include the parameter in the
"tel" URI.
- If the operator receives verbal instructions from the caller to
use a specific carrier and it is not unknown if that carrier is the
caller's presubscribed carrier, "Network Node A" MUST set the "cic"
parameter to contain the CIC of the specified carrier and include the
parameter, if not yet present, in the "tel" URI. "Network Node A"
MUST set the "dai" parameter to "verbal-clgPty" and include the
parameter in the "tel" URI.
4.2.4. Operator-assisted call handling, caller does not pay for the
call
There are cases where the call is charged to the called party or a
third party. How the caller indicates an operator-assisted call and
passes the CIC information in call signaling is outside the scope of
this document. The caller will indicate to the operator that either
the called party or a third party is to pay for the call. The
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operator then checks with the charged party if he/she agrees to pay
for the call and may verbally get the CIC information from the
charged party or retrieve the primary and alternate preferred carrier
information from some databases. It is assumed that the "tel" URI in
the call signaling from "User Device" does not contain the "cic"
parameter and/or "dai" parameter. They are ignored if they are
present.
"Network Node A" through the assistance of an operator MUST follow
the rules described below.
- If the call is to be handled by the carrier "Network Node A" is
associated with, "Network Node A" MUST remove the "cic" parameter, if
present, and MUST NOT include the "dai" parameter in the "tel" URI.
- If "Network Node A" selects the carrier to handle the call, it MUST
set the "cic" parameter to contain the CIC it selects and include the
parameter in the "tel" URI. "Network Node A" MUST include the "dai"
parameter in the "tel" URI and set it to "operator".
- If the charged party's primary preferred carrier is used for the
call handling, "Network Node A" MUST set the "cic" parameter to
contain that carrier's CIC and include the parameter in the "tel"
URI. "Network Node A" MUST set the "dai" parameter to "CIC-chrgPty"
and include the parameter in the "tel" URI. How "Network Node A"
knows that the selected carrier is the charged party's primary
preferred carrier is outside the scope of this document.
- If the charged party's alternate preferred carrier is used for the
call handling, "Network Node A" MUST set the "cic" parameter to
contain that carrier's CIC and include the parameter in the "tel"
URI. "Network Node A" MUST set the "dai" parameter to "altCIC-
chrgPty" and include the parameter in the "tel" URI. How "Network
Node A" knows that the selected carrier is the charged party's
alternate preferred carrier is outside the scope of this document.
- If the operator receives verbal instructions from the charged party
to use a specific carrier and it is not unknown if that carrier is
the charged party's primary or alternate preferred carrier, "Network
Node A" MUST set the "cic" parameter to contain the CIC of the
specified carrier and include the parameter in the "tel" URI.
"Network Node A" MUST set the "dai" parameter to "verbal-chrgPty" and
include the parameter in the "tel" URI.
- If the caller contacts an operator for an emergency situation and a
carrier that "Network Node A" is not associated with needs to handle
the call, "Network Node A" MUST set the "cic" parameter to the CIC of
that carrier and include the parameter in the "tel" URI. "Network
Node A" MUST set the "dai" parameter to "emergency" and include the
parameter in the "tel" URI.
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4.2.5. Call signaling received from the GSTN SW by GSTN GW
The GSTN GW may receive the Signaling System number 7 (SS7)
Integrated Services Digital Network User Part (ISUP) signaling
message from the GSTN SW that contains the CIC information. For
example, American National Standards Institute (ANSI) ISUP carries
the CIC information in the "Carrier Selection Information" parameter.
There is a one-to-one mapping between the ANSI ISUP "Carrier
Selection Information" parameter and the "dai" parameter.
4.3. Handling the "tel" URI with the "cic", or "cic" and "dai"
This section discusses how "Network Node A", "Network Node B",
"Network Node C" or "GSTN GW" handles the signaling messages that
contain the "dai" and "cic" parameters in the "tel" URI. Scenarios
that do not involve the "dai" parameter in the "tel" URI are outside
the scope of this document.
A. Network Node A
After "Network Node A" has added the "dai" parameter and/or "cic"
parameter to the "tel" URI and is ready to route the call, it MUST
route the call based on the rules described in [RFC4694] to "Network
Node B", "Network Node C" or "GSTN GW". "Network Node A" MAY record
the "dai" value in the call detail record. If the carrier that
Network A is associated with is the one to handle the call, Network
Node A removes the "cic" and/or "dai" if they are present before
routing the call.
B. Network Node B
Since "Network Node B" is not associated with the carrier identified
by the CIC in the "cic" parameter, it MUST route the call based on
the "cic" parameter as stated in [RFC4694] to another "Network Node
B", "Network Node C" or "GSTN GW". "Network Node B" MAY record the
"dai" value in the call detail record.
C. Network Node C
Since "Network Node C" is associated with the carrier identified by
the CIC in the "cic" parameter, it removes the "cic" parameter and
the "dai" parameter, if present, before it determines how to handle
the call. "Network Node C" MAY record the "dai" value in the call
detail record. How "Network Node C" continues the call
routing/handling is outside the scope of this document.
D. GSTN GW
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If "GSTN GW" determines that the call is to be routed from the IP
domain to "GSTN SW", and SS7 ISUP is used in the GSTN, then the "GSTN
GW" MUST map the "dai" parameter to the corresponding ISUP parameter.
Note that when interworking with ANSI ISUP, the "dai" parameter is
mapped to the ISUP "Carrier Selection Information" parameter. There
is a one-to-one mapping between the ANSI ISUP "Carrier Selection
Information" parameter and the "dai" parameter. When "GSTN GW"
receives a signaling message from "GSTN SW" that contains the carrier
selection information, it MUST set the "dai" parameter based on the
received carrier selection information. The mapping between the
"dai" parameter and ISUP is outside the scope of this document.
"GSTN GW" MUST route the call based on the "cic" parameter as stated
in [RFC4694] to "Network Node A", "Network Node B" or "Network Node
C". "GSTN GW" MAY record the "dai" value in the call detail record.
E. User Device
"User Device" is not expected to receive signaling messages that
contain the "dai" and/or "cic" parameters. If the received signaling
messages contain the "tel" URI with the "dai" and/or "cic"
parameters, "User device" SHALL ignore the parameter(s).
5. Examples
A. A caller whose pre-subscribed carrier has a CIC of "+1-6789" makes
an outbound call with the following "tel" URI:
tel:+1-202-533-1234
"Network Node A" adds the "dai" and "cic" parameters to the "tel" URI
as shown below.
tel:+1-202-533-1234;cic=+1-6789;dai=presub
B. A caller whose pre-subscribed carrier has a CIC of "+1-6789" makes
an outbound call to +1-202-533-1234 and specifies to use the CIC of
"+1-2345" in call signaling with the following "tel" URI:
tel:+1-202-533-1234;cic=+1-2345
"Network Node A" recognizes that the caller has selected a non-
presubscribed carrier to handle the call. "Network Node A" adds the
"dai" parameter to the "tel" URI as shown below.
tel:+1-202-533-1234;cic=+1-2345;dai=da
C. A caller makes a collect call to +1-202-533-1234 through an
operator. The operator at "Network Node A" interacts with the called
party and gets a verbal approval to use the CIC of "+1-3456".
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"Network Node A" adds the "dai" and "cic" parameters to the "tel" URI
as shown below.
tel:+1-202-533-1234;cic=+1-3456;dai=verbal-chrgPty
6. Security Considerations
In addition to those security implications discussed in [RFC3966],
there may be new security implications associated with the "dai"
parameter depending on the carrier who uses the information.
Changing the content of the "dai" parameter may cause a call to be
rejected by or cause some problems (e.g., collecting call charge) to
the carrier who handles the call. For example, changing from
"presub" to "da" may cause the call to be rejected if the carrier
that is to handle the call only handles calls from its pre-subscribed
subscribers. Changing "da" to "presub" may cause a call that would
be rejected to be processed by a carrier who later finds out it
cannot collect the call charge from the caller or has to pay more
than the call charge to collect the call charge from the caller via a
third party (e.g., local exchange carrier).
It is RECOMMENDED that protocols carrying the "tel" URI provide hop
by hop integrity for the URI including the parameters. This allows
detection of any unauthorized changes to the contents of the "tel"
URI.
Please note that the information in the "dai" parameter may not be
authenticated; therefore, the use of the information by the recipient
of the "tel" URI is done at its own risk.
7. IANA Considerations
The "dai" parameter defined in this document needs to be registered
with IANA as a new parameter for the "tel" URI [RFC3966].
1. Parameter name - dai
Applicability - used to indicate how a carrier was chosen for
handling a call
Mandatory or optional - optional
Restrictions on syntax - see Section 5
Reference to a specification - defined in this document
8. References
8.1. Normative References
[RFC2119] S. Bradner, RFC 2119, "Key words for use in RFCs to
Indicate Requirement Levels", March 1997.
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[RFC3966] H. Schulzrinne, RFC 3966, "The tel URI for Telephone
Numbers", December 2004.
[RFC4234] D. Crocker and P. Overell, RFC 4234, "Augmented BNF for
Syntax Specifications: ABNF", October 2005.
[RFC4694] J. Yu, RFC 4694, "NP Parameters for the "tel" URI", October
2006.
8.2. Informative References
[RFC3261] J. Rosenberg, et al., RFC 3261, "SIP: Session Initiation
Protocol", June 2002.
[RFC3761] P. Faltstrom and M. Mealling, RFC 3761, "The E.164 to
Uniform Resource Identifiers (URI) - Dynamic Delegation Discovery
System (DDDS) Application (ENUM)", April 2004.
[String] B. Rosen, draft-rosen-iptel-dialstring-05.txt, "Dialstring
parameter for the Session Initiation Protocol Uniform Resource
Identifier", June 2006 (Work in Progress).
9. Change History
(Note to editor - please remove this section in final version.)
9.1. Changes from version 01->02
- Section 3: clarified descriptions of "dai" parameter values
- Section 4.2.5, plus various other places: removed text that said
the "dai" parameter was not included in certain cases, since we
now use "no-ind" these cases.
- Section 4.3,
o Item A: added text specifying that if Node-A is the carrier
then it removes "cic"
o Item D: added procedures for inbound calls from GSTN
Acknowledgments
The authors would like to thank Martin Dolly and Penn Pfautz for
their assistances in providing the relevant information on the DAI.
Authors' Addresses
James Yu
NeuStar, Inc.
46000 Center Oak Plaza
Sterling, VA 20166
U.S.A.
Phone: +1-571-434-5572
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Internet-Draft DAI Parameter for the "tel" URI June 2007
Email: james.yu@neustar.biz
David Hancock
CableLabs
858 Coal Creek Circle
Louisville, CO 80027-9750
U.S.A.
Phone: +1-303-661-3381
Email: d.hancock@cablelabs.com
Flemming Andreasen
Cisco Systems, Inc.
499 Thornall Street, 8th Floor
Edison, NJ 08837
U.S.A.
Email: fandreas@cisco.com
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