RFC 3136
The SPIRITS Architecture
RFC 3136: The SPIRITS Architecture 🦋
okay bestie, this one is from June 2001 and it's an Informational doc, so it's sharing info with the Internet community, not setting a standard 💅. The editor is L. Slutsman from AT&T Labs, with co-authors I. Faynberg, H. Lu, and M. Weissman, all from Lucent Technologies. The title block doesn't list anything it obsoletes or updates. 🌸
Status of This Memo ✨
this memo is just here to provide information for the Internet community. it does not specify an Internet standard of any kind, and distribution of it is unlimited 🫶
Copyright Notice
copyright (C) The Internet Society (2001). All Rights Reserved. 💜
Abstract
okay so this doc describes the architecture for supporting SPIRITS services 🔥. these are the ones that start in the PSTN (Public Switched Telephone Network) and need interactions between the PSTN and the Internet. Internet Call Waiting, Internet Caller-ID Delivery, and Internet Call Forwarding are examples of SPIRIT services ✨. Specifically, it defines the components that make up the architecture and the interfaces between those components 🧚
1. Introduction ✨
so the intro basically repeats the abstract, lol 🙈. This document describes the architecture for supporting SPIRITS services, which are those originating in the PSTN (Public Switched Telephone Network) and necessitating the interactions between the PSTN and the Internet. (Internet Call Waiting, Internet Caller-ID Delivery, and Internet Call Forwarding are examples of SPIRIT services.) Specifically, it defines the components constituting the architecture and the interfaces between the components.
here's how the rest of the doc is laid out:
- Section 2 describes example SPIRITS services from the end-user point of view;
- Section 3 describes the SPIRITS architecture;
- Section 4 contains security considerations;
- Section 5 contains acknowledgments;
- Section 6 contains references; and
- Appendix contains the figure.
2. Brief Description of Example SPIRITS Services 💖
to show why the overall SPIRIT architecture matters, this section gives a quick rundown of the example SPIRITS services 🎀:
- Internet Call Waiting (ICW),
- Internet Caller-ID Delivery, and
- Internet Call Forwarding.
we're looking at these from the end-user point of view, under these assumptions:
- Service subscription (or cancellation) is a separate process and may be done over the telephone, via postal mail, or over the Web.
- The subscriber's IP host (e.g., a PC) is loaded with the necessary software [including a Personal Identification Number (PIN) and the IP addresses of the SPIRITS servers] for realizing the SPIRITS services. The software may be sent by postal mail or downloaded from the Web.
- The subscriber activates a SPIRITS service by an act of service session registration, which can take place anytime after he (or she) is connected to the Internet. The subscriber may specify the life span of the session. As soon as the session ends, the SPIRITS service is deactivated. Naturally, the subscriber should also be able to deactivate a SPIRITS service anytime during the service session. 🦋
for certain services (like ICW or Caller-ID Delivery), the assumption is that the subscriber has a single telephone line and a PC, which is connected to the Internet via this telephone. (only under this assumption do these services make sense 💀.) other services, though, like a Web-based Call Center where a call center assistant could re-direct or reject a call presented in a pop-up window, this assumption may be unnecessary or even inapplicable 👑.
2.1 Internet Call Waiting (ICW)
the Internet call waiting service lets a subscriber who's in an Internet dial-up session:
- be notified of an incoming call to the very same telephone line that is being used for the Internet connection;
- specify the desirable treatment of the call; and
- have the call handled as specified.
the details of the ICW service are all about the ways a waiting call can be treated [1] 🔥. Typical ways to handle a call include:
- Accept the incoming call over the PSTN by terminating the Internet connection. (As switching cannot be done immediately, the caller may hear an opening announcement followed by the "ringing" tone.)
- Forward the incoming call to another telephone number. The subscriber will remain connected to the Internet, while the caller will hear an announcement indicating the call is being forwarded and eventually be connected to the new destination number.
- Accept the incoming call by voice over IP. The subscriber will answer the incoming call via the already established Internet connection. (The proposed SPIRITS architecture, however, does not reflect this feature.) 🙈
- Redirect the incoming call to voice mail. The subscriber will remain connected to the Internet, while the caller will hear an announcement inviting him (or her) to leave a message.
- Play a pre-recorded message to the calling party and disconnect the call. The subscriber will remain connected to the Internet.
- Reject the incoming call. The subscriber will remain connected to the Internet, while the caller will hear an announcement rejecting the call.
the subscriber can pick the call treatment on the fly when they get notified of an incoming call. Or they can set a general treatment ahead of time for all calls (e.g., re-directed to voice mail), or call treatments tailored to the origination numbers 🍓. So when a call comes in, the subscriber won't be presented with the call, but can look back at the treatment and outcome of the call in the log that's kept for all the calls processed during the ICW service 📋. Typical info recorded in the log includes the incoming call date and time, calling party number, calling party name, and call disposition.
2.2 Internet Caller-ID Delivery
this service lets the subscriber see the caller's number or name or both while they're connected to the Internet 🌈. If the subscriber has only one telephone line and is using that very line for the Internet connection, the service is a subset of the ICW service and follows the relevant description in Section 2.1. Otherwise, the subscriber's IP host serves as an auxiliary device of the telephone that the call is first sent to.
2.3 Internet Call Forwarding
the Internet call forwarding service lets a service subscriber forward an incoming call to another telephone number while they're connected to the Internet 🦋. If the subscriber has only one telephone line and is using that very line for the Internet connection, the service is a subset of the ICW service and follows the relevant description in Section 2.1. Otherwise, the subscriber's IP host serves as an auxiliary device of the telephone that the call is first sent to.
3. SPIRITS Architecture 🧚
Figure 1 of the Appendix shows the SPIRITS architecture, which includes the following entities 👑:
- Service Control Function (SCF) [2], which executes service logic, interacts with the entities in the IP domain (e.g., the SPIRITS Gateway and PINT Server) through the SPIRITS Client, and instructs the switches on how to complete a call. Physically, the SCF may be located in either stand-alone general-purpose computers called Service Control Points (SCPs) or specialized pieces of equipment called Service Nodes (SNs) [2].
- Service Switching Function (SSF) [2], which normally resides in a switch and is responsible for the recognition of Intelligent Network (IN) triggers and interactions with the SCF.
- SPIRITS Client, which is responsible for receiving PSTN requests from the SCF as well as sending responses back. It may be co-located with the SCF. If not, it communicates with the SCF over the D interface.
- PINT Server, which receives PINT requests from the PINT Client and relays them to the PSTN for execution over the E interface.
- SPIRITS Gateway, which is co-located with the PINT Server or PINT Gateway (or both when they are co-located, as assumed here for simplicity) and serves as an intermediary between the SPIRITS Server and SPRITS Client via the B and C interfaces, respectively.
- PINT Client, which resides in the subscriber's IP host and is responsible for initiating PINT requests, which are sent to the PINT server over the A interface.
- SPIRITS Server, which terminates PSTN requests and is responsible for all interactions (e.g., incoming call notification and relaying the call treatment) between the subscriber and the SPIRITS Gateway.
the rest of the Section describes the interfaces between the entities in detail 🎀.
3.1 Interface A
this interface is used for sending PINT requests to the PINT Server. Its main job is service session registration, and as a result, activating a SPIRITS service (see Section 2). On top of that, this interface may be used for service subscription 💅.
3.2 Interface B
this interface has two main jobs: 1) notifying the subscriber of incoming calls together with the calling number and name, if available; and 2) sending the subscriber's choice of call disposition, specified on the fly, to the SPRITS Gateway 🔥.
3.3 Interface C
this interface is for communications between the SPIRITS Client and the SPIRITS Gateway. The SPIRITS Gateway may in turn communicate with the SPIRITS Server, or it may act as a virtual server, terminating the requests without sending them down to the SPIRITS Server 🌸.
3.4 Interface D
this interface handles communications between the SPIRITS Client and the SCF. From the SCF to the SPIRITS Client, the parameters associated with the applicable IN triggers are sent. From the SPIRITS Client to the SCF, the subscriber's call disposition is sent 📞.
the SCF "transforms" the user's disposition into appropriate actions, like playing an announcement to the caller, and resuming the suspended call processing in the SSP ✨.
3.5 Interface E
this interface is for sending PINT requests to the SCF for execution 🧚.
4. Security Considerations 🔐
okay bestie, this section is SERIOUS, so read it carefully 😭.
as Figure 1 shows, there are two distinct communications interfaces, B and C. The B interface is, in general, across the public Internet, so it's the most vulnerable to security attacks that result in theft or denial of service 💀. The C interface, on the other hand, is likely to be implemented across a service provider's intranet, where the security measures should be applied at the discretion of the service provider. Even then, because at least one IP host (the PINT gateway) is connected to the Internet, special measures (e.g., installation of firewalls, although this particular measure alone may be insufficient) need to be taken to protect the interface C and the rest of the network from security attacks 🛡️.
the assumption that the PINT Client and SPIRITS Server are co-located means the security considerations for the A and B interfaces are exactly the same. Detailed security requirements and solutions for interface A (and, consequently, B) can be found in RFC 2848 [3] 📚. In addition, security requirements are listed in the companion SPIRITS Protocol Requirements RFC 🫶.
5. Acknowledgments ✨
okay bestie, big thank-you energy 🫶 to these legends who gave comments and input: Alec Brusilovsky, Jorgen Bjorkner, Scott Bradner, Jim Buller, Lawrence Conroy, Jorge Gato, Dave Hewins, Naoto Makinae, and Dave Shrader 💖
6. References 📚
[1] Lu, H., Editor, Faynberg, I., Voelker, J., Weissman, M., Zhang, W., Rhim, S., Hwang, J., Ago, S., Moeenuddin, S., Hadvani, S., Nyckelgard, S., Yoakum, J. and L. Robart, "Pre-SPIRITS Implementations of PSTN-Initiated Services", RFC 2995, November 2000. 🌸
[2] Faynberg, I., L. Gabuzda, M. Kaplan, and N.Shah, "The Intelligent Network Standards: Their Application to Services", McGraw-Hill, 1997. 📖
[3] Petrack, S. and L. Conroy, "The PINT Service Protocol: Extensions to SIP and SDP for IP Access to Telephone Call Services", RFC 2848, June 2000. 🦋
Appendix 🧚
Okay so here's the big picture, and it's giving diagram realness 💅 Figure 1 shows the whole SPIRITS setup, with the PINT Client, the PINT Server/Gateway, the SPIRITS Gateway, the SPIRITS Server, the SPIRITS Client, and the Service Control Function, all wired up with interfaces A through E 🔥
......................
+----------------+ . .
| +------------+ | . +------------+ .
| | | | A . | | .
| | PINT Client|********************|PINT Server/|********
| | | | . Gateway | *
| +------------+ | . +------------+ . *
| | . . *
| Subscriber's | . . *
| | . . *
| IP Host | . . *
| | . +------------+ . *
| +------------+ | . | SPIRITS | . *
| | SPIRITS | | B . | Gateway | . *
| | Server |********************| | . * E
| | | | . +------------+ . *
| +------------+ | . * . *
+----------------+ . * . *
...........*.......... *
//-------\\ * *
/// \\\ * *
| Subscriber's | * C *
| Telephone | * *
\\\ /// * *
\\ -------// * *
* * *
* * *
++++++++++++++++++++++++++ PSTN ++++++++++++++++++++++++++
* * *
* * *
* +------------------+ *
* Line | SPIRITS Client | *
* | | *
+--------------------+ +---+----- D ---------+-*+
| | INAP/SS7 | |
|Service Switching ************Service Control Function |
| Function | | |
| | +-------------------------+
| |
| |
+--------------------+
Figure 1: SPIRITS ArchitectureAuthors' Addresses 🎀
Igor Faynberg Lucent Technologies Room 4D-601A 101 Crawfords Corner Road Holmdel, NJ 07733-3030 US
Phone: +1 732 949 0137 EMail: faynberg@lucent.com
Hui-Lan Lu Lucent Technologies Room 4C-607A 101 Crawfords Corner Road Holmdel, NJ 07733-3030 US
Phone: +1 732 949 0321 EMail: huilanlu@lucent.com
Mark Weissman Lucent Technologies Room NE406B 200 Lucent Lane Cary, NC 27511
Phone: +1 919 463 3258 EMail: maw1@lucent.com
Lev Slutsman AT&T Labs Room D5-3D26 200 Laurel Avenue Middletown, NJ 07748
Phone: 732-420-3756 EMail: lslutsman@att.com
Full Copyright Statement ⭐
This part is legal stuff, so I'm keeping the wording exactly as it is, no vibes edits 🙈
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement 🌈
Funding for the RFC Editor function is currently provided by the Internet Society. 💜
📦 where this page comes from
- ietf: rfc3136 2001-06
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms