Internet Engineering Task Force (IETF) S. Channabasappa, Ed.
Request for Comments: 6461 CableLabs
Category: Informational January 2012
ISSN: 2070-1721
Data for Reachability of Inter-/Intra-NetworK SIP (DRINKS)
Use Cases and Protocol Requirements
Abstract
This document captures the use cases and associated requirements for
interfaces that provision session establishment data into Session
Initiation Protocol (SIP) Service Provider components to assist with
session routing. Specifically, this document focuses on the
provisioning of one such element termed the "registry".
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/rfc6461.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Overview ........................................................2
2. Terminology .....................................................5
3. Registry Use Cases ..............................................6
3.1. Category: Provisioning Mechanisms ..........................6
3.2. Category: Interconnect Schemes .............................7
3.3. Category: SED Exchange and Discovery Models ................8
3.4. Category: SED Record Content ...............................9
3.5. Category: Separation and Facilitation of Data Management ...9
3.6. Category: Public Identifiers, TN Ranges, and RNs ..........10
3.7. Category: Misc ............................................11
4. Requirements ...................................................11
4.1. Provisioning Mechanisms ...................................12
4.2. Interconnect Schemes ......................................12
4.3. SED Exchange and Discovery Requirements ...................12
4.4. SED Record Content Requirements ...........................12
4.5. Data Management Requirements ..............................13
4.6. Public Identifier, TN Range, and RN Requirements ..........13
4.7. Misc. Requirements ........................................13
5. Security Considerations ........................................14
6. Acknowledgments ................................................14
7. References .....................................................15
7.1. Normative References ......................................15
7.2. Informative References ....................................15
1. Overview
[RFC5486] (Section 3.3) defines Session Establishment Data, or SED,
as the data used to route a call to the next hop associated with the
called domain's ingress point. More specifically, the SED is the set
of parameters that the outgoing signaling path border elements (SBEs)
need to establish a session. However, [RFC5486] does not specify the
protocol(s) or format(s) to provision SED. To pave the way to
specify such a protocol, this document presents the use cases and
associated requirements that have been proposed to provision SED.
SED is typically created by the terminating or next-hop SIP service
provider (SSP) and consumed by the originating SSP. To avoid a
multitude of bilateral exchanges, SED is often shared via
intermediary systems -- termed "registries" within this document.
Such registries receive data via provisioning transactions from SSPs,
and then distribute the received data into Local Data Repositories
(LDRs). These LDRs are used for call routing by outgoing SBEs. This
is depicted in Figure 1.
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*-------------*
1. Provision SED | |
-----------------------> | Registry |
| |
*-------------*
/ \
/ \
/ \
/ \
/ \
/ \
/ 2.Distribute \
/ SED \
V V
+----------+ +----------+
|Local Data| |Local Data|
|Repository| |Repository|
+----------+ +----------+
Figure 1: General Diagram
In this document, we address the use cases and requirements for
provisioning registries. Data distribution to local data
repositories is out of scope for this document. The resulting
provisioning protocol can be used to provision data into a registry
or between multiple registries operating in parallel. In Figure 2,
the case of multiple registries is depicted with dotted lines.
. . . . . . .
. . . . . . . registry . . . . . . .
. . . . . . . . .
. . .
. . .
. . provision .
+-----------+ . +-----------+
| | provision +----------+ provision | |
| SSP 1 |------------>| Registry |<-----------| SSP 2 |
| | +----------+ | |
| +-----+ | /\ | +-----+ |
| | LDR | <-------------------- ------------------>| LDR | |
| +-----+ | distribute distribute | +-----+ |
| | | |
+-----------+ +-----------+
. .
. . . . . . . . . . . . . . . . . . . . . . . .
(provision / distribute)
Figure 2: Functional Overview
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In addition, this document proposes two aggregation groups, as
follows:
o Aggregation of public Identifiers into a destination group.
o Aggregation of SED records into a route group.
The use cases in Section 3.5 provide the rationale. The data model
depicted in Figure 3 shows the various entities, aggregations, and
the relationships between them.
+---------+ +--------------+ +---------+
| Data |0..n 0..n| Route | 1 0..n| SED |
|Recipient|------------| Group | --------------| Record |
+---------+ +--------------+ +---------+
|0..n |0..n
| |
| |
| |
|0..n |
1 +--------------+ 0..1 |
---------| Destination |--------- |
| | Group | | |
| +--------------+ | |
| | | |
| 1| | |
| | | |
| | | |
0..n | 0..n | | 0..n |
+---------+ +---------+ +----------+ |
| RN | | TN | | Public |----
| | | Range | |Identifier| 1
+---------+ +---------+ +----------+
Figure 3: Data Model Diagram
The relationships are as described below:
- A public identifier object can be directly related to zero or more
SED Record objects, and a SED Record object can be related to
exactly one public identifier object.
- A destination group object can contain zero or more TN (telephone
number) Range objects, and a TN Range object can be contained in
exactly one destination group object.
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- A destination group object can contain zero or more public
identifier objects, and a public identifier object can be
contained in exactly one destination group object.
- A destination group object can contain zero or more RN (routing
number) objects, and an RN object can be contained in exactly one
destination group object.
- A route group object can contain zero or more SED Record objects,
and a SED Record object can be contained in exactly one route
group object.
- A route group object can be associated with zero or more
destination group objects, and a destination group object can be
associated with zero or more route group objects.
- A data recipient object can be associated with zero or more route
group objects, and a route group object can refer to zero or more
data recipient objects.
2. Terminology
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].
This document reuses terms from [RFC3261] (e.g., SIP), [RFC5486]
(e.g., SSP, LUF, LRF, SED) and [RFC5067] (carrier-of-record and
transit provider). In addition, this document specifies the
following additional terms.
Registry: The authoritative source for provisioned session
establishment data (SED) and related information. A registry can
be part of an SSP or be an independent entity.
Registrar: An entity that provisions and manages data into the
registry. An SSP can act as its own registrar or -- additionally
or alternatively -- delegate this function to a third party (who
acts as its registrar).
Local Data Repository (LDR): The data store component of an
addressing server that provides resolution responses.
Public Identifier: A public identifier refers to a telephone number
(TN), a SIP address, or other identity as deemed appropriate, such
as a globally routable URI of a user address (e.g.,
sip:john.doe@example.net).
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Telephone Number (TN) Range: A numerically contiguous set of
telephone numbers.
Telephone Number (TN) Prefix: A preceding portion of the digits
common across a series of E.164 numbers. A given TN prefix will
include all the valid E.164 numbers that satisfy the expansion
rules mandated by the country or the region with which the TNs
comply.
Routing Number (RN): A Routing Number. For more information, see
[RFC4694].
Destination Group: An aggregation of a set of public identifiers, TN
Ranges, or RNs that share common SED, which is exposed to a common
set of peers.
Data Recipient: An entity with visibility into a specific set of
public identifiers (or TN Ranges or RNs), the destination groups
that contain these public identifiers (or TN Ranges and RNs), and
a route group's SED records.
Route Group: An aggregation that contains a related set of SED
records and is associated with a set of destination groups. Route
groups facilitate the management of SED records for one or more
data recipients.
3. Registry Use Cases
This section documents use cases related to the provisioning of the
registry. Any request to provision, modify, or delete data is
subject to several security considerations (see Section 5). The
protocols that implement these use cases (and associated
requirements) will need to explicitly identify and address them.
3.1. Category: Provisioning Mechanisms
UC PROV #1 Real-Time Provisioning: Registrars have operational
systems that provision public identifiers (or TN Ranges
or RNs) in association with their SED. These systems
often function in a manner that expects or requires that
these provisioning activities be completed immediately,
as opposed to an out-of-band or batch provisioning scheme
that can occur at a later time. This type of
provisioning is referred to as "real-time" or "on-demand"
provisioning.
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UC PROV #2 Non-Real-Time Bulk Provisioning: Operational systems that
provision public identifiers (or TN Ranges or RNs) and
associated SED sometimes expect that these provisioning
activities be batched up into large sets. These batched
requests are then processed using a provisioning
mechanism that is out of band and occurs at a later time.
UC PROV #3 Multi-Request Provisioning: Regardless of whether or not
a provisioning action is performed in real time, SSPs
often perform several provisioning actions on several
objects in a single request or transaction. This is done
for performance and scalability reasons, and for
transactional reasons, such that the set of provisioning
actions either fail or succeed atomically, as a complete
set.
3.2. Category: Interconnect Schemes
UC INTERCONNECT #1 Inter-SSP SED: SSPs create peering relationships
with other SSPs in order to establish
interconnects. Establishing these interconnects
involves, among other things, communicating and
enabling the points of ingress and other SED used
to establish sessions.
UC INTERCONNECT #2 Direct and Indirect Peering: Some inter-SSP
peering relationships are created to enable the
establishment of sessions to the public
identifiers for which an SSP is the carrier-of-
record. This is referred to as "direct peering".
Other inter-SSP peering relationships are created
to enable the establishment of sessions to public
identifiers for which an SSP is a transit
provider. This is referred to as "indirect
peering". Some SSPs take into consideration an
SSP's role as a transit or carrier-of-record
provider when selecting a route to a public
identifier.
UC INTERCONNECT #3 Intra-SSP SED: SSPs support the establishment of
sessions between their own public identifiers,
not just to other SSPs' public identifiers.
Enabling this involves, among other things,
communicating and enabling intra-SSP signaling
points and other SED that can differ from inter-
SSP signaling points and SED.
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UC INTERCONNECT #4 Selective Peering (a.k.a. per-peer policies):
SSPs create peering relationships with other SSPs
in order to establish interconnects. However,
SSP peering relationships often result in
different points of ingress or other SED for the
same set of public identifiers. This is referred
to as "selective peering" and is done on a route
group basis.
UC INTERCONNECT #5 Provisioning of a delegated hierarchy: An SSP may
decide to maintain its own infrastructure to
contain the route records that constitute the
terminal step in the LUF. In such cases, the SSP
will provision registries to direct queries for
the SSP's public identifiers to its own
infrastructure rather than provisioning the route
records directly. For example, in the case of
DNS-based route records, such a delegated
hierarchy would make use of NS and CNAME records,
while a flat structure would make use of NAPTR
resource records.
3.3. Category: SED Exchange and Discovery Models
UC SED EXCHANGE #1 SED Exchange and Discovery using unified LUF/LRF:
When establishing peering relationships, some
SSPs may wish to communicate or receive SED
(e.g., points of ingress) that constitutes the
aggregated result of both LUF and LRF.
UC SED EXCHANGE #2 SED Exchange and Discovery using LUF's Domain
Name: When establishing peering relationships,
some SSPs may not wish to communicate or receive
points of ingress and other SED using a registry.
They only wish to communicate or receive domain
names (LUF step only), and then independently
resolve those domain names via [RFC3263] to the
final points of ingress data (and other SED).
UC SED EXCHANGE #3 SED Exchange and Discovery using LUF's
Administrative Domain Identifier: When
establishing peering relationships, some SSPs may
not wish to communicate or receive points of
ingress and other SED using a registry. They
only wish to communicate or receive an
administrative domain identifier, which is not
necessarily resolvable via DNS. The subsequent
process of using that administrative domain
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identifier to select points of ingress or other
SED can be SSP specific and is out of scope for
this document.
UC SED EXCHANGE #4 Coexistent SED Exchange and Discovery Models:
When supporting multiple peering relationships,
some SSPs have the need to concurrently support
all three of the SED Exchange and Discovery
Models already described in this section
(Section 3.3) for the same set of public
identifiers.
3.4. Category: SED Record Content
UC SED RECORD #1 SED Record Content: Establishing interconnects
between SSPs involves, among other things,
communicating points of ingress, the service types
(SIP, SIPS, etc.) supported by each point of
ingress, and the relative priority of each point of
ingress for each service type.
UC SED RECORD #2 Time-To-Live (TTL): For performance reasons,
querying SSPs sometimes cache SED that had been
previously looked up for a given public identifier.
In order to accomplish this, SSPs sometimes specify
the TTL associated with a given SED record.
3.5. Category: Separation and Facilitation of Data Management
UC DATA #1 Separation of Provisioning Responsibility: An SSP's
operational practices often separate the responsibility
of provisioning the points of ingress and other SED from
the responsibility of provisioning public identifiers (or
TN Ranges or RNs). For example, a network engineer can
establish a physical interconnect with a peering SSP's
network and provision the associated domain name, host,
and IP addressing information. Separately, for each new
subscriber, the SSP's provisioning systems provision the
associated public identifiers.
UC DATA #2 Destination Groups: SSPs often provision identical SED
for large numbers of public identifiers (or TN Ranges or
RNs). For reasons of efficiency, groups of public
identifiers that have the same SED can be aggregated.
These aggregations are known as destination groups. The
SED is then indirectly associated with destination groups
rather than with each individual public identifier (or TN
Ranges or RNs).
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UC DATA #3 Route Groups: SSPs often provision identical SED for
large numbers of public identifiers (or TN Ranges or
RNs), and then expose that relationship between a group
of SED records and a group of public identifiers (or TN
Ranges or RNs) to one or more SSPs. This combined
grouping of SED records and destination groups
facilitates efficient management of relationships and the
list of peers (data recipients) that can look up public
identifiers and receive the associated SED. This dual
set of SED records and destination groups is termed a
"route group".
3.6. Category: Public Identifiers, TN Ranges, and RNs
UC PI #1 Additions and Deletions: SSPs often allocate and de-
allocate specific public identifiers to and from end-users.
This involves, among other things, activating or
deactivating specific public identifiers (TN Ranges or
RNs), and directly or indirectly associating them with the
appropriate points of ingress and other SED.
UC PI #2 Carrier-of-Record versus Transit Provisioning: Some inter-
SSP peering relationships are created to enable the
establishment of sessions to the public identifiers (or TN
Ranges or RNs) for which an SSP is the carrier-of-record.
Other inter-SSP peering relationships are created to enable
the establishment of sessions for which an SSP is a transit
provider. Some SSPs take into consideration an SSP's role
as a transit or carrier-of-record provider when selecting a
route.
UC PI #3 Multiplicity: As described in previous use cases, SSPs
provision public identifiers (or TN Ranges or RNs) and
their associated SED for multiple peering SSPs, and as both
the carrier-of-record and transit provider. As a result, a
given public identifier (or TN Range or RN) key can reside
in multiple destination groups at any given time.
UC PI #4 Destination Group Modification: SSPs often change the SED
associated with a given public identifier (or TN Range or
RN). This involves, among other things, directly or
indirectly associating them with a different point of
ingress, different services, or different SED.
UC PI #5 Carrier-of-Record versus Transit Modification: SSPs may
have the need to change their carrier-of-record versus
transit role for public identifiers (or TN Ranges or RNs)
that they previously provisioned.
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UC PI #6 Modification of Authority: An SSP indicates that it is the
carrier-of-record for an existing public identifier or TN
Range. If the public identifier or TN Range were
previously associated with a different carrier-of-record,
then there are multiple possible outcomes, such as a) the
previous carrier-of-record is disassociated, b) the
previous carrier-of-record is relegated to transit status,
or c) the new carrier-of-record is placed in inactive mode.
The choice may be dependent on the deployment scenario and
is out of scope for this document.
3.7. Category: Misc
UC MISC #1 Number Portability: The SSP wishes to provide, in query
response to public identifiers, an associated routing
number (RN). This is the case where a set of public
identifiers is no longer associated with the original SSP
but has been ported to a recipient SSP, who provides
access to these identifiers via a switch on the Signaling
System Number 7 network identified by the RN.
UC MISC #2 Data Recipient Offer and Accept: When a peering
relationship is established (or invalidated), SSPs
provision (or remove) data recipients in the registry.
However, a peer may first need to accept its role (as a
data recipient) before such a change is made effective.
Alternatively, an auto-accept feature can be configured
for a given data recipient.
UC MISC #3 Open Numbering Plans: In several countries, an open
numbering plan is used, where the carrier-of-record is
only aware of a portion of the E.164 number (i.e., the TN
prefix). The carrier-of-record may not know the complete
number or the number of digits in the number. The rest
of the digits are handled offline (e.g., by a Private
Branch Exchange, or PBX). For example, an SSP can be the
carrier-of-record for "+123456789" and be the carrier-of-
record for every possible expansion of that number, such
as "+12345678901" and "+123456789012", even though the
SSP does not know what those expansions could be. This
can be described as the carrier-of-record effectively
being authoritative for the TN prefix.
4. Requirements
This section lists the requirements extracted from the use cases in
Section 3. The objective is to make it easier for protocol designers
to understand the underlying requirements and to reference and list
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the requirements that they support (or not). The requirements listed
here, unless explicitly indicated otherwise, are expected to be
supported. Protocol proposals are also expected to indicate their
compliance with these requirements and highlight ones that they don't
meet (if any). Furthermore, the requirements listed here are not
meant to be limiting, i.e., protocol implementations and deployments
may choose to support additional requirements based on use cases that
are not listed in this document.
4.1. Provisioning Mechanisms
REQ-PROV-1: Real-time provisioning.
REQ-PROV-2: (Optional) Non-real-time bulk provisioning.
REQ-PROV-3: Multi-request provisioning.
4.2. Interconnect Schemes
REQ-INTERCONNECT-1: Inter-SSP peering.
REQ-INTERCONNECT-2: Direct and Indirect peering.
REQ-INTERCONNECT-3: Intra-SSP SED.
REQ-INTERCONNECT-4: Selective peering.
REQ-INTERCONNECT-5: Provisioning of a delegated hierarchy.
4.3. SED Exchange and Discovery Requirements
REQ-SED-1: SED containing unified LUF and LRF content.
REQ-SED-2: SED containing LUF-only data using domain names.
REQ-SED-3: SED containing LUF-only data using administrative
domains.
REQ-SED-4: Support for all the other REQ-SED requirements (listed in
this section), concurrently, for the same public
identifier (or TN Range or RN).
4.4. SED Record Content Requirements
REQ-SED-RECORD-1: Ability to provision SED record content.
REQ-SED-RECORD-2: (Optional) Communication of an associated TTL for
a SED Record.
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4.5. Data Management Requirements
REQ-DATA-MGMT-1: Separation of responsibility for the provisioning
the points of ingress and other SED, from the
responsibility of provisioning public identifiers.
REQ-DATA-MGMT-2: Ability to aggregate a set of public identifiers as
destination groups.
REQ-DATA-MGMT-3: Ability to create the aggregation termed route
group.
4.6. Public Identifier, TN Range, and RN Requirements
REQ-PI-TNR-RN-1: Provisioning of, and modifications to, the
following aggregations: destination group and route
groups.
REQ-PI-TNR-RN-2: Ability to distinguish an SSP as either the
carrier-of-record provider or the transit provider.
REQ-PI-TNR-RN-3: A given public identifier (or TN Range or RN) can
reside in multiple destination groups at the same
time.
REQ-PI-TNR-RN-4: Modification of public identifier (or TN Range or
RN) by allowing them to be moved to a different
destination group via an atomic operation.
REQ-PI-TNR-RN-5: SSPs can indicate a change to their role from
carrier-of-record provider to transit, or vice
versa.
REQ-PI-TNR-RN-6: Support for modification of authority with the
conditions described in UC PI #6.
4.7. Misc. Requirements
REQ-MISC-1: Number portability support.
REQ-MISC-2: Ability for the SSP to be offered a peering relationship
and for the SSP to accept (explicitly or implicitly) or
reject such an offer.
REQ-MISC-3: Support for open numbering plans.
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5. Security Considerations
Session establishment data allows for the routing of SIP sessions
within, and between, SIP Service Providers. Access to this data can
compromise the routing of sessions and expose a SIP Service Provider
to attacks such as service hijacking and denial of service. The data
can be compromised by vulnerable functional components and interfaces
identified within the use cases.
A provisioning framework or protocol that implements the described
use cases MUST, therefore, provide data confidentiality and message
integrity. Such frameworks and protocols MUST specify mechanisms to
authenticate and authorize any entity that provisions data into the
registry, i.e., that the entity is who it says it is and is allowed
to use the provisioning interface. The determination of whether such
an entity is authorized to provision specific data elements (e.g., a
certain public identifier or TN Range) -- while REQUIRED -- may be
left to local policy.
6. Acknowledgments
This document is a result of various contributions from (and
discussions within) the IETF DRINKS Working Group; specifically, in
alphabetical order: Alexander Mayrhofer, Deborah A Guyton, Gregory
Schumacher, Jean-Francois Mule, Kenneth Cartwright, Manjul Maharishi,
Penn Pfautz, Ray Bellis, Richard Shockey, and Syed Ali.
The editor also wishes to thank the following for their comments and
suggestions: Otmar Lendl, Sohel Khan, Peter Koch, Brian Rosen, Jon
Peterson, Gonzalo Camarillo, and Stephen Farrell.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5486] Malas, D. and D. Meyer, "Session Peering for Multimedia
Interconnect (SPEERMINT) Terminology", RFC 5486,
March 2009.
7.2. Informative References
[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.
[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263,
June 2002.
[RFC4694] Yu, J., "Number Portability Parameters for the "tel" URI",
RFC 4694, October 2006.
[RFC5067] Lind, S. and P. Pfautz, "Infrastructure ENUM
Requirements", RFC 5067, November 2007.
Author's Address
Sumanth Channabasappa (editor)
CableLabs
858 Coal Creek Circle
Louisville, CO 80027
USA
EMail: sumanth@cablelabs.com
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