DRINKS Use cases and Protocol Requirements
draft-ietf-drinks-usecases-requirements-04

Abstract

This document captures the use cases and associated requirements for interfaces that provision session establishment data into SIP Service Provider components, to assist with session routing. Specifically, the current version of this document focuses on the provisioning of one such element, termed the registry.

Status of this Memo

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Table of Contents

1.  Terminology
2.  Overview
3.  Registry Use Cases
    3.1.  Category: Provisioning Mechanisms
    3.2.  Category: Interconnect Schemes
    3.3.  Category: SED Exchange and Discovery Models
    3.4.  Category: SED Record Content
    3.5.  Category: Separation and Facilitation of Data Management
    3.6.  Category: Lookup Keys
    3.7.  Category: Misc
4.  Requirements
    4.1.  Provisioning Mechanisms
    4.2.  Interconnect Schemes
    4.3.  SED Exchange and Discovery Requirements
    4.4.  SED Record Content Requirements
    4.5.  Data Management Requirements
    4.6.  Lookup Key Requirements
    4.7.  Misc. Requirements
5.  Security Considerations
6.  IANA Considerations
7.  Acknowledgments
8.  References
    8.1.  Normative References
    8.2.  Informative References
§  Author's Address

1.  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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

This document reuses terms from [RFC3261] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.) (e.g., SIP, SSP), [RFC5486] (Malas, D. and D. Meyer, “Session Peering for Multimedia Interconnect (SPEERMINT) Terminology,” March 2009.) (e.g., LUF, LRF, SED) and [RFC5067] (Lind, S. and P. Pfautz, “Infrastructure ENUM Requirements,” November 2007.) (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 as well as 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:

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).

TN Range:

A numerically contiguous set (or, in the case of an open numbering plan, a prefix) of telephone numbers whose SED can be looked up (resolved).

RN:

A Routing Number. See [RFC4694] (Yu, J., “Number Portability Parameters for the "tel" URI,” October 2006.) for details

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, the destination groups that contain these public identifiers, 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.

2.  Overview

The SPEERMINT WG specifies 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. See Section 3.3 of [RFC5486] (Malas, D. and D. Meyer, “Session Peering for Multimedia Interconnect (SPEERMINT) Terminology,” March 2009.) for more details.

The specification of the format and protocols to provision SED is a task taken up by the DRINKS WG. This document contains the use cases and requirements that have been proposed in this regard.

SED is typically created by the terminating or next-hop 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. These local data repositories are used for call routing by outgoing SBEs. This is depicted in Figure 1 (General Diagram).

                                    *-------------*
             1. Provision SED       |             |
           -----------------------> |  Registry   |
                                    |             |
                                    *-------------*
                                         /  \
                                        /    \
                                       /      \
                                      /        \
                                     /          \
                                    /            \
                                   / 2.Distribute \
                                  /      SED       \
                                 V                  V
                           +----------+       +----------+
                           |Local Data|       |Local Data|
                           |Repository|       |Repository|
                           +----------+       +----------+

                               . . . . . . .
               . . . .  . . .   registry    . . . . . . .
             .                 . . . . . . .              .
           .                        .                      .
          .                         .                       .
         .                          . provision             .
    +-----------+                   .                 +-----------+
    |           |  provision  +----------+  provision |           |
    |   SSP 1   |------------>| Registry |<-----------|   SSP 2   |
    |           |             +----------+            |           |
    |  +-----+  |                   /\                |  +-----+  |
    |  | LDR | <--------------------  ------------------>| LDR |  |
    |  +-----+  |   distribute           distribute   |  +-----+  |
    |           |                                     |           |
    +-----------+                                     +-----------+
           .                                                .
            . . . . . . . . . . . . . . . . . . . . . . . .
                           (provision / distribute)


          Where, LDR = Local Data Repository

• Aggregation of public Identifiers into a destination group.
  
  
• Aggregation of SED records into a Route Group.
  
  

The data model depicted in Figure 3 (Data Model Diagram) shows the various entities, aggregations and the relationships between them.

       +---------+            +--------------+               +---------+
       |  Data   |0..n    0..n|     ROUTE    | 1         0..n|   SED   |
       |Recepient|------------|     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
               +---------+      +---------+       +----------+

-

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 Range objects, and a TN Range object can be contained in exactly one Destination Group object.

-

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 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.

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 authorization. However, the act of authorization is considered to be out of scope of this document.

3.1.  Category: Provisioning Mechanisms

UC PROV #1

Real-Time Provisioning: Registrars have operational systems that provision public identifiers, in association with their SED. These systems often function in a manner that expect or require that these provisioning activities be completed immediately, as apposed 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.

UC PROV #2

Non-Real-Time Bulk Provisioning: Operational systems that provision public identifiers 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 a provisioning action is performed in real-time or not, 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 to a set of public identifiers.

UC INTERCONNECT #2

Direct vs 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.

UC INTERCONNECT #4

Selective Peering (a.k.a. per peer policies): SSPs create peering relationships with other SSPs in order to establish interconnects. However, SSPs peering relationships often result in different points of ingress or other SED for the same set of public identifiers.

UC INTERCONNECT #5

Provisioning of a delegated hierarchy: An SSP may decide to maintain its own infrastructure to contain the route records that constitue 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 wish to only communicate or receive domain names (LUF step only), and then independently resolvable 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 wish to only communicate or receive an administrative domain identifier, which is not necessarily resolvable via DNS. The subsequent process of using that administrative domain identifier to select points of ingress or other SED can be SSP specific and occurs outside the context of this protocol.

UC SED EXCHANGE #4

Co-existent 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 described above, 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 identity. 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. 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 identity.

UC DATA #3

Route Groups: SSPs often provision identical SED for large numbers of public identifiers, and then expose that relationship between a group of SED records and a group of public identifiers to one or more SSPs. This combined grouping of SED records and Destination Groups facilitates management of public identity SED relationships and the list of peers (data recipients) that can lookup those public identifiers and receive that SED. This dual set of SED Records and Destination Groups is termed as a Route Group.

3.6.  Category: Lookup Keys

UC LOOKUP #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 (or TN ranges or RNs), and directly (or indirectly) associating them with the appropriate points of ingress and other SED.

UC LOOKUP #2

Carrier-of-Record vs Transit Lookup Key Provisioning: Some inter-SSP peering relationships are created to enable the establishment of sessions to the lookup keys for which an SSP is the carrier-of-record. Other inter-SSP peering relationships are created to enable the establishment of sessions to lookup keys 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 to a public identifier.

UC LOOKUP #3

Multiplicity of Identical Lookup Keys: As described in previous use cases, SSPs provision lookup keys and their associated SED for multiple peering SSPs, and as both the carrier-of-record and transit provider. As a result, a given lookup key can reside in multiple destination groups at any given time.

UC LOOKUP #4

Lookup Key Destination Group Modification: SSPs often change the SED associated with a given lookup key. This involves, among other things, directly or indirectly associating them with a different point of ingress, different services, and/or different other SED.

UC LOOKUP #5

Lookup Key Carrier-Of-Record vs Transit Modification: SSPs may have the need to change their Carrier-Of-Record vs Transit role for lookup keys they previously provisioned.

UC LOOKUP #6

Modification of authority: An SSP indicates that it is the carrier-of-record for an existing public identity or TN Range. If the public identity or TN Range was 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

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 original SSP but have been ported to a recipient SSP, who provides access to these identifiers via a switch on the SS7 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 it's 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, which is where the carrier-of-record is only aware of a portion of the E.164 number (i.e., the 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 PBX). For example, an SSP can be the carrier-of-record for "+123456789", and is also 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 prefix.

4.  Requirements

This Section lists the requirements based on the use cases in Section 3 (Registry Use Cases). Unless explicitly stated as optional, the registry provisioning interface must support these requirements.

4.1.  Provisioning Mechanisms

REQ-PROV-1:

Real-time provisioning.

REQ-PROV-2:

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, concurrently, for the same public identifier.

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.

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.  Lookup Key Requirements

REQ-LOOKUP-1:

Provisioning of, and modifications to, the following aggregations: destination group and route groups.

REQ-LOOKUP-2:

Ability to distinguish an SSP as either the carrier-of-record provider or transit provider.

REQ-LOOKUP-3:

A given lookup key (e.g., public identity, RN, TN Range) can reside in multiple destination groups at the same time.

REQ-LOOKUP-4:

Modification of lookup keys by allowing them to be moved to a different destination group via an atomic operation.

REQ-LOOKUP-5:

SSPs can indicate a change to their role from carrier-of-record provider to transit, or vice-versa.

REQ-LOOKUP-6:

Support for modification of authority with the conditions described in UC LOOKUP #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.

5.  Security Considerations

Session establishment data allows for the routing of SIP sesions 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 protocol or interface that implements the described use cases MUST therefore provide data confidentiality, and MUST ensure message integrity for the provisioning flow. Authentication and authorization of the provisioning entities are REQUIRED features of the protocol and interfaces.

6.  IANA Considerations

This document does not register any values in IANA registries, nor request the creation of a registry.

7.  Acknowledgments

This document is a result of various discussions held within the DRINKS WG; 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.

This specific version of the document is a result of contributions from the following individuals: Alexander Mayrhofer, Otmar Lendl, Sohel Khan, and Peter Koch. In addition, we also thank Brian Rose and Jon Peterson for suggestions we incorporated.

8.  References

8.1. Normative References

8.2. Informative References

Author's Address