GNUComm Overview: ----------------- History 08/23/01 v0.6 - bug squishing, function spec example - rsb 07/25/01 v0.5 - more terminology - rsb 07/04/01 v0.4 - added design goals:ease of use, general rewrite - rsb 06/05/01 v0.3 - TOC, typos, minor changes. - rsb 06/04/01 v0.2 - added design goals:documentation - rsb 03/13/01 v0.1 - created - Rich Bodo - firstname.lastname@example.org Contents 1.0 Intro 2.0 Functional Goals 3.0 Deployment 4.0 Design Overview 4.1 Functions 4.1.1 A walk through application space 4.1.2 Function Spec Example 4.1.3 Function List 4.2 Components 4.2.1 Component Standards 4.2.2 Core Components 4.2.3 Application Components 4.2.4 Miscellaneous Components 4.3 Design Goals 4.3.1 Power 4.3.2 Reliability 4.3.3 Security 4.3.4 Ease of Use 4.3.5 Documentation 5.0 How you can help 1.0 Intro --------- Telephony equipment is currently reliant on proprietary hardware and software to power everything from PBX's, voicemail systems, softphones, and gateways to large call-centers and carrier infrastructures. GNUComm will offer a replacement for this proprietary software and integrate the functionality of these common applications into a more flexible and broadly functional free system running on commodity hardware. Along the way, GNUComm will provide a number of applications and software components useful to other free software projects. The next section describes the functional goals of GNUComm based on the problems we would like to solve. We don't want developers to feel the need to satisfy someone else's requirements. Rather, we would like GNUComm to be the type of system that people will want to use to satisfy their own requirements. The current developers eat their own dog food and use the early prototypes of GNUComm every day. We hope that GNUComm becomes as useful and fun to work on to others as it is to us. Throughout this document, we will sometimes refer to the GNUComm subsystem of the GNU project as "GNUComm", or sometimes just "the system". GNUComm is part of a larger project, called the GNU project, which you can learn more about at www.gnu.org. If after reading this document you are still wondering what GNUComm is or how it will be designed, see the web site and the mailing lists. Whenever we refer to "the GNUComm web site" or "the web site", we are referring to: http://www.gnu.org/software/gnucomm/gnucomm.html. You can join the mailing lists on the web site. 2.0 Functional Goals -------------------- A functional spec will be completed for each individual milestone. However, a minimal initial set of overall goals based on the anticipated needs of the user-base can be described right here. Many users would like to handle messaging (voice, fax, text) and that's about it. Next on the list for multi-user installations are PBX-type applications, and more advanced call distribution and switching capabilities. Larger organizations will require sales and support automation, business software integration, softphones and requisite gateway software. On our way to implementing these basic needs, a number of more esoteric and interesting areas will get some attention, such as remote automation and control of networked computer systems. Users of the GNU system will be able to fill these needs with GNUComm applications that will interoperate with each other and the rest of the GNU system. We can further describe those functional goals with the following parameters: GNUComm is to be a working subsystem of the GNU project providing interoperable components that enable human communications. GNUComm will rely on a number of new servers, clients, supporting component libraries, and an extensive library of applications. GNUComm will be fully integrated with GNU Enterprise. GNUComm applications will eventually be composed at a high enough level to allow users with little or no special knowledge of system internals or theory to design their own telecommunications systems. GNUComm will support a wide variety of telephony resources and communications mechanisms including VoIP and PSTN communications. It will provide mechanisms for communicating with useful proprietary systems whenever possible. As a free software project, whatever is deemed useful gets supported; we are not beholden to any company or standards organization in this regard. GNUComm aims to be scalable and configurable. Several GNUComm components are designed to increase the reliability of existing three-tiered application architectures. GNUComm's component architecture will allow the system to be broken down for embedding into very tight systems. In all cases the unique flexibility of free software will be leveraged (i.e. configuration available on many levels for many users, interoperability with other free software components). In no case should the average programmer with access to a low-end PC and not much else be left with no solution. 3.0 Deployment -------------- The deployment strategy taken will be similar to other GNU meta-projects (GNOME, GNUE, etc.). In this section we will put first things first, describe our strategy for solving the right amount of the problem, and cover standard development practices. At the time of this writing, we have defined the following milestones: M1 - SAG, Interoperability Deliverable is a GNUComm System Administrator's Guide (GSAG), and a User's Guide for each application we have checked in. This will provide a working base for users and developers to get started with. (Actually, I wouldn't exclude manuals for applications that are *not* yet checked in. I tend to write the manual first, then design the application.) Many of the functions performed by proprietary telecommunications systems can be carried out with free software already. Some of this software is already part of GNUComm. Documenting this software is our first task, making M1 largely a documentation project. If new software needs to be developed to meet the minimum Functional Goals of GNUComm, then specific documentation of that fact is a requirement of M1. Although M1 will not be a complete system, it will be a working system consisting of GNUComm Components that interoperate with some other applications. In M1, although work can begin on apps and system design documents, the focus will be on Interoperability. Design documents are not required deliverables of M1; the SAG and Users guides are. The average free software user should be able to follow the M1 documentation to create a working system. GNUComm documentation should have separate sections geared for programmers and end-users. There are several reasons to do this first: 1) The documentation will help people to create useful systems while long-term solutions are being developed. 2) In the long-term, GNUComm should interoperate with as many of these applications as possible. Experience with these applications will help us to do that. 3) Experience with these applications will help us to design our own components. 4) We may find applications that we can integrate with. We should define a few terms here: GNUComm Component - Any software entity natively hosted as an official part of GNUComm. GNUComm components can be built from code checked out from the GNU project cvs repository. For a Component to achieve release status (non-beta) within GNUComm, it must both meet the Component Standards and associate with (help implement) a Function. They support all applicable GNUComm protocols, reporting facilities, and other requisite standards for their given Function(s). GNUComm Component Standards - Coding, documentation and testing standards that are applied to all GNUComm components. What it takes to create a stable component. GNUComm Function - An interface specification contract fulfilled by GNUComm Components. Functions define how the entire GNUComm system cooperates. Outside Component - We will sometimes use this term for any software entity which is not a GNUComm Component. Maybe we should come up with a better name for these. Interoperate - When a GNUComm Component and an Outside Component interoperate, they share their underlying resources and data as necessary to carry out normal operations without interfering with one another. Integrate - When an outside application is fully integrated with the GNUComm subsystem, it is made to support all the features of a GNUComm Component. Some comments on Outside Components: Interoperability is a good thing. We are interested in free software only, so if an Outside Component does not meet the free software definition or depends on other software that does not, it will never be integrated with GNUComm. We can, of course, Interoperate via any communications protocol used by an Outside Component, whether free, proprietary, or other. For many useful functions, interoperability will have to do at first until a better solution can be found. Testing and Documentation of Outside Components may be necessary. This is not to say that we should create User's Guides for individual applications that will not be integrated with GNUComm in the long run; those should already exist and should be checked in as part of their own projects. We only need create enough documentation for these applications to give users a coherent manual for their use within our system. The more apps we can interoperate with, the better. An example of this? How about an integrated messaging system. No attempt need be made to reinvent the wheel. We will only need to write a document that describes how a large number of servers (web, mail, sms, ivr, etc., etc.) can be configured to cooperate to carry out the desired functionality. No new functionality needs to be developed. M2 - SDD, Integration Deliverable is the GNUComm System Design Document (GSDD), an overview of which is described here and in the System Overview diagram on the GNUComm web site. This overview is very general. The GSDD will quantitatively describe GNUComm Functions, Components, and Component Standards. We are designing a system that is practical, open, flexible, scalable, and interoperable. Interoperability sums up the challenge for this version; making the interfaces clean enough so that alternate versions of any given server can be hot-swapped into the system is important. Design documents detailing required and optional infrastructure components, interfaces, and protocols will be hashed out. A functional spec for M3 will be hammered out. Anything that needs to be built from scratch or re-written will be. M2 will lead to GNUComm 1.0., and will be held to the same standards of documentation that M1 was. Comments on Integration: Integration is a good thing. If there are multiple Integration options for a given function, we should, at this stage, value stability and interoperability, i.e. a 0.1 version or a version that has only a gui interface are not likely to recommend a project for integration, but support for commodity protocols will. We want to get a working system up as soon as possible. That's the extent of the milestones in the initial plan, but here are a few thoughts on where we go from there: From here, we set higher functional goals and iterate. Both a stable track and an unstable track will continually be pursued. When we refer to milestones, such as M1, we are describing deliverables. When we describe versions of the system, such as GNUComm 0.1 and GNUComm 0.2, we are describing modules, or versions of the entire system whose components are to be developed, tested, and used together. The odd modules (0.1, 0.3, 2.1) are the unstable track modules. The even modules (0.2, 1.0, 1.4) are the stable track modules. Components that achieve release-status will be packaged into GNUComm Releases. We may talk about reaching milestone x before releasing version y.z, which gives the project direction, but milestones are not tied to either dates or modules (too much pressure! ;-) ). With goals and deployment issues behind us, we know what we need and begin the design process. The rest of this document is a design overview, and refers to figures on the web site. 4.0 Design Overview ------------------- Even for those who have the background to know what generally works when designing telephony systems, a number of design challenges arise every time a new project is taken on. In our case these challenges are exacerbated by the both the large scope of the functional goals and the wide breadth of the platform support. This version of the GNUComm Design Overview will be an informal introduction to these challenges and our proposed solutions. How do we design in modularity? When both the application space and platform range are as large as ours, modularity is a dominant design challenge. The rest of this section will attempt to answer the modularity question while briefly describing the GNUComm Functions, Components and Component Standards. Having the ability to combine functionality into one process can be a practical necessity (this is often the case with application and media servers). However, having the ability to strip a server down into simpler stand-alone components can also be extremely useful. A simpler piece of code generally simplifies configuration, maintenance, debugging, security, performance optimization, re-use and integration. Add to this the requirement for GNUComm components to scale up and down to accommodate the broad range of machines and operating systems running GNU software, and we can justify several potential abstraction layers. A component model for GNUComm will be helpful for project management reasons alone. We definitely want to involve as many developers as possible in GNUComm at a high-level. In addition to this general predilection, GNUComm needs to interoperate with some object request architectures (i.e. GNUE:CORBA) *and* make it easy for average users (read:novices without specialized hardware) to combine components. (Yes, we will be working on this design for a while.) We will enumerate Components and Functions later, but let's solidify the relationship right now: GNUComm Component - Any software entity natively hosted as an official part of GNUComm. GNUComm components can be built from code checked out from the GNU project cvs repository. For a Component to achieve release status (non-beta) within GNUComm, it must both meet the Component Standards and associate with (help implement) a Function. They support all applicable GNUComm protocols, reporting facilities, and other requisite standards for their given Function(s). GNUComm Function - An interface specification contract fulfilled by GNUComm Components. Functions define how the entire GNUComm system cooperates. The set of all GNUComm Functions defines is the interface contract of the system. Note that components are considered beta until they fill a Function. Often this will mean that we need to write a new function and redesign GNUComm to accommodate a component. The design of the Function interface should be thorough enough to allow any vendor to rip out the GNUComm component filling that function and drop in their own. Multiple Components can fill one Function and one Component can fill multiple Functions. The set of all GNUComm Functions defines the interface contract of the system. The set of all Components that have reached release status forms the implementation of the system. We will perform a system test on released components prior to making a GNUComm stable release. So, we've probably beaten that to death. To give give you a feel for the design of the system we will contrast GNUComm telephony services with a system that you may already be familiar with. We know that telecom resources (protocol stacks, drivers, etc.) are typically state machines which should respond within some real-time constraints with signaling information and/or data payloads, and our applications need to be able to act in kind to use them. We can also assume that we have observed the working, scalable server designs used to power the internet and we see that there is much to reuse. Although HTTP is typically served in a soft real-time manner, the state machine for the protocol is not too different from a state machine used to control a telephony resource. So the interface description language is a little different, but with little modification the same three-tiered architecture can power a telephony application and a web application at the same time. The additional interface server is called Bayonne instead of Apache, the interface language is called BayonneXML instead of HTML, and we are using TGI instead of CGI, but application development is no harder to for a developer to learn. In fact, you could probably call Bayonne an Interface Server or a Voice Server instead of an Application Server. With server-side scripting the line gets a bit blurry. The development methodology is three tier, and parallels web development closely. The same comparison can be made with GNU Enterprise. In fact, the same back end logic could be used in all three systems. They all interface with humans. The same perl or python scripts used for CGI, TGI, or (EGI?). Apache, Bayonne, and GEAS are at the same level. When thinking a bit bigger, the same CORBA-based Object Web can be drawn upon to implement the business logic for all of these application servers. The objects drawn from the object web could be cgi scripts, tgi scripts, egi scripts, or perhaps Enterprise Java beans. The web comparison stops there. Gnucomm Components will interact with systems that we are already using. Not just our existing phone lines or phones but our web and business software, our network monitors, our PDA's, our office applications, and the rest of the GNU system. We will need to add a few components to our infrastructure to correct the typically lax web transaction environment and to interface to business logic systems like GNUe. These business and server components are described in the next section. The web environment comparison may also be misleading in terms of scope. One place GNUComm differs from a web application platform is in the variety and sheer number of communications resources we have to consider. Replace an HTTP protocol stack with drivers from a dozen hardware vendors and a dozen or so more protocol stacks for various VoIP and signaling functions. Then we have routing, directory services, applications, etc. To see where we might draw the lines in a modular system, let's consider for a moment how we might abstract the above mentioned telephony resources. It's easy to get out of hand with multiple layers of abstraction and protocol overhead when exposing these. A thin Resource API directly encapsulating several common driver interfaces may be the simplest and most widely useful abstraction we can create. The actual implementation would be a small library with a mid-sized API. In cases where processing power and execution size is at an absolute premium, the library could be gutted and only the necessary functions compiled into an application. The Resource Library is a useful concept and a GNUComm Function. If you wanted to encapsulate a high-level protocol such as H.323, you would have to encapsulate an H323 implementation API. Most hardware driver APIs do not employ the concepts of sessions, white-boards, or talking heads, so adding this to our Resource Library would be a radical complexity increase. Effectively, an H323 implementation API is a superset of the Resource Library API. Protocol stacks like H323 require several network resources that most driver libraries do not. If we are using H323, we can safely bet that the applications can reasonably access resources in real-time across the network. In these cases, a Resource Protocol might be a useful out of band interface to both the H323 implementation's API and the Resource Library API. By Resource Protocol I mean a protocol that is a feature-replacement for the API. So a Resource Protocol library that encapsulates both VoIP protocols such as H.323 and Driver Resource Libraries could be developed for use on such a system. This might simplify life for the developer who has access to the Resource Protocol Library, but it is no picnic to develop and maintain. We also now have a network and three of our own libraries in-between our app and the driver. We can keep going. Say we want to manage our resources. We can come up with a management daemon that registers apps as users of resources, handles some security issues, and implements it's own protocol for resource sessions. In most cases a resource manager is a very complex piece of software that is going to drive performance down unacceptably. I'm not entirely opposed to implementing a resource manager, but there is a point where programmers need to think for themselves. In the world of modularity trade-offs, the functions of overbearing modules either get omitted, in-lined more efficiently into other components, or otherwise integrated in a non-intrusive way. A similar issue is the CORBA controversy. Are we seriously considering forcing an ORB down the throat of a cell phone? No. We have added an optional CORBA gateway server, called EWOK, instead of a CORBA requirement. Anything that EWOK can speak to can hit an ORB. The general problem is that there are lots of places we are tempted to put intermediate or additional protocols. Although convenient in some cases, these break many other uses of the system. The general solution is to make the intermediate protocols optional. We are not obligated to decompose our gateways or add abstraction layers to our drivers, but we may allow for it for compatibility purposes. We have discussed the component definition and have seen that a GNUComm Component is free software known to work with the rest of the GNUComm system for it's intended function. Basically, it's any module we maintain. Implicitly, the Component fulfills a GNUComm Function, and the Function has applicable protocols, reporting facilities, and other requisite standards. The Component needs to meet the GNUComm Component Standards for coding, documentation, and testing before the component can reaching release, or 1.0, status. A control server, compression library, or application could be a GNUComm component. An application component might have a certain structure, such as a flat xml file. As a component, it might be stored in a database, passed from one server to another, modified, and interpreted in one or more environments. We are planning to use CORBA for this type of object brokering. Some nice features of CORBA such as polymorphic messaging and method invocation will come in handy later on. GNUComm application designers are currently (v0.0) utilizing lightweight, homegrown alternatives to a CORBA component infrastructure (read:hacks). Nothing is stopping people from continuing to do this, but if you are putting together a large system and want to avoid a lot of work, you will eventually adopt the CORBA-based GNUComm Component Infrastructure as it develops. However, we have also stated that we would not force an object request broker into a situation to which it is unsuited. To that end, we have introduced a Function called EWOK. An EWOK server is a specialized CORBA gateway. It translates lightweight communications into CORBA communications. This is handy for both tight application environments where an ORB is unreasonable or for any server that for whatever reason has not or cannot add CORBA support. 4.1 Functions: -------------- Since we have already covered the relationship between GNUComm Functions and Components, we will start this section by walking through the application space and uncovering each GNUComm core Function in turn. We will then provide an example of a Function definition and a list of the Functions we have in the design overview thus far. 4.1.1 A walk through application space... ----------------------------------------- What follows is a pseudo-tutorial introduction to the GNUComm Functions we are working on, with specific examples of existing and planned components: To make large-scale telephony applications work, we suspect we'll need quite a few daemons running on the server side. For some tasks we can get by with a powerful Application Server: Application Server - This server handles user interaction over the phone system. An early version of an application server, ACS, was contributed at the inception of the project. ACS has since evolved into Bayonne. Bayonne is the default app server today, but PreViking or any other server could plug in if it was compatible with the GNUCOMM interfaces. In order to do this we need to define all the interfaces to this server type. The Application Server is a very useful program stand-alone. The first few applications (which exist today) are fairly common examples of what an application server can do: Integrated Messaging - voice messaging system that integrates with other data messaging systems, such as web-based mail or maybe just an MTA through the Post Office Protocol. Support Automation - Automated voice response with ACD to allow callers to get to the information or people they need. Sales Automation - Integration of voice and web applications for automated order processing. Once we start talking about implementing entire call centers, we are looking at doing some switching between disparate media streams while sending callers to agents, app servers, or queue servers. Let's look at some of the necessary ingredients: Switch - The most common application of a telephony switch is called a Keyterm, or PBX. Among other things, a PBX "expands" a small number of "trunks" connected to the telephone network into a larger number of "station lines". An example of this might be a few linmodems providing PSTN access to a dozen or more softphone applications running on LAN-based workstations. Our first switch will be called "Ipswich". Ipswich can be used as a "dumb" programmable switch or a "smart" switch. In it's dumb mode Ipswich informs a controller of every change of state and takes no call control action without direct instruction. We will decide on a protocol for controlling the "dumb" Ipswich later. In various smarter modes Ipswich will act as a registrar for terminals, a proxy server, and even an MCU. In a manner similar to that of Bayonne, Ipswich will accomplish smart behavior through scripting. Applications such as a PBX will be largely developed in that way. The difference between the Bayonne scripting language and Ipswich's scripting language, is that Ipswich is dealing with protocols, programs, machines. Bayonne is dealing with people, particularly people with a keypad, mic, and speaker in front of them. So the scripting languages have some differences. Queue Server - The first queue server will be called Advanced Queue Server (AQS). As with the rest of the servers, there are advantages to having the option of embedding intelligence here. For instance, when an important task enters or drops from a queue, it can be treated differently based on it's importance. When a program pulls a task from a queue, it could be issued an appropriate task based on a comparison of the available tasks and the program's profile. An example of this kind of intelligent, non-queue-like behavior would be when a call of great importance comes in; it might and get shoved to the front of the queue, and an appropriate agent might get a request to drop what he is doing and take the call out of the queue. If we want to integrate with other large telecommunications systems, particularly legacy (read:proprietary) systems, we will likely need: Device Monitor - Communicating with existing proprietary systems is a fact of life for many. The Device Monitor, Babylon, will help us carry out this function. Babylon maps various call control protocols used by Proprietary switches into a protocol usable by the GNUComm system. As of this writing, Babylon speaks SMDI and a few control protocols of the more popular PBX's. The more interesting GNUComm side of Babylon has yet to be developed. Gatekeeper - In most cases the gatekeeper will be a scripted application of Ipswich. A separate gatekeeper could be developed, but we'll see what we can do with Ipswich first. Unlike Bayonne, which deals with user interaction, Ipswich's scripting language is optimized to deal with devices and call control. So we're talking to the systems we need to talk to, but who is in control? GNUComm generally imposes fairly minimal restrictions on it's components. Some systems specify that all control servers be controlled by a Media Gateway Controller, which is a separate entity from the control server or "Media Gateway". There is no generic Media Gateway Controller in GNUComm, although any server could implement a protocol to talk to a Media Gateway or Control Server (such as MGCP). Likewise, there is no Media Server requirement (or even a specific Transcoding Server), although such a media server could be integrated. There is no requirement that media resources (telephony cards, VoIP protocol stacks, etc.) be abstracted with yet another specific protocol. As explained earlier, there is more danger in adding some requirements than there is benefit. There is more than one way to do it with GNUComm. There is more to integration of telecom systems than dial-tone. Transaction-oriented information must be handled in a timely, secure, fault-tolerant manner. We should develop a formal method for accomplishing this: Transaction Server (TRiP) - The Transaction Redundancy Protocol Daemon (tripd) stores the state and transaction data of all transactions that are registered with it. The TRiP is a set of redundant servers that not only share the TRiP data bus, but handle any failures occurring on the servers that generate transaction data via TRiP scripting, including the TRiP itself. This is just too cool an idea to not work on. So tripd's scripting language reacts to failure events. For instance, it might respond to the untimely demise of bayonne_1 by launching various scripts on bayonne_2 based on the last known state of all bayonne_1's registered transactions. Real Time Database Server - RTDB is a MLSRTDBMS? We can't use a database that doesn't respond, and it would be nice to have an ACL manager. Examples: When a request to a database times out, RTDBS will respond with the time-out and inform the TRiP. If a foreign bayonne server wants an application component out of the database, maybe it should be disallowed. That's the kind of stuff we could use. Hopefully we can find some intrepid programmer to take charge of this. So Real Time Database server is a Multi-Level Secure Real Time Database Management System. It would be nice to find a new name for this and perhaps even nicer to avoid implementing this at all. Although I suppose the implementation could be a lot of fun. So we have a lot of functionality already, but if we stopped the design here, we would not be able to communicate with a large portion of the GNU project. Let's address these shortcomings: CORBA Interface Server - EWOK. Described earlier, this provides a gateway to CORBA services. That's the basic description of the core servers. Let's cover some of final the burning questions you might have: What do the supporting Libraries look like? All of the communications protocols and stacks can be made into libraries. In cases where a hardware interface is not required, it makes sense to have the option to encapsulate some libraries in a specialized server (like maybe a transcoding server). This gives us the ability to compile in with the core server for embedded or turnkey systems, or to create specialized servers communicating via commodity protocols. The obviously useful driver, codec, and client call control libraries are being pursued, as well as several specialized libraries and servers for interfacing to switches of various types, business logic servers, etc. In the interest of configurability and rapid application development, each server should be completely programmable, so we will likely split off libraries where distinct server-side scripting languages are created. With all this common code, why not a monolithic control server? After all, what's the difference between the control servers: Ipswich, Bayonne, and Troll? They will likely all use the same trunk class libraries for interfacing to drivers and protocol stacks. They are all scriptable and capable of some call control. It is possible to devise one server to do the work of all three. However, they are functionally and structurally quite separate. Bayonne speaks to people, Ipswich speaks to programs. The scripting language is totally different for Ipswich and Bayonne. In fact, the Troll Function is a script! The Troll Function is handled by a component that is just a scripted application of Ipswich. Therefore, the control servers should use each other as a set of cooperating processes. Bayonne and Troll will ask Ipswich to perform call control. Ipswich and Troll will ask Bayonne to present interfaces. Bayonne and Ipswich will ask Troll to gateway traffic across nets. To a large extent, the separation of control servers is driven by the desire to support large, highly optimized, distributed systems. 4.1.2 Function Example ---------------------- Functions will be defined in the SDD (M2). Here's a sample to show the format: GNUComm Function Entry ---------------------- Function: Application Server Version: 0.1 Description: The GNUComm Application Server interfaces phone users to software applications in real-time. Interfaces Supported: SIP: IETF RFC 2543 SNMPv3: IETF RFC 2572 ccscript: GNUComm Spec 1 BayonneXML: GNUComm Spec 2 Telephony Gateway Interface v2.0: GNUComm Spec 3 GNUComm Resource Library API: GNUComm Spec 4 TOSI v0.1: GNUComm Spec 5 Interfaces Required: ccscript Required Documentation: SAG: http://www.gnu.org/software/gnucomm/SAG/AppServer.html Test Spec: http://www.gnu.org/software/gnucomm/test/testas.html Optional Documentation: User's Guide: N/A Application Server Implementers Guide: N/A GNU Software Map Entry: GNUComm Application Server 4.1.3 Function List ------------------- With that much out of the way, we can check out the overview diagram (Fig 1.) and compare it with the Function List below. Keep in mind that although we list functions and components here, the System Design Document (in M2) is the place to find the canonical Function Definitions and Component Standards. GNUComm Functions: Core Functions Control Servers App Server Switch Device Monitor Business Servers Real Time Database Management Server Queue Server Matrix Servers Transaction Matrix Server CORBA Gateway Server Base Libraries Client Call Control Resource Driver Library Audio Tools Library Switch Control Protocol Library VoIP Protocol Abstraction Library Server-Side Telephony Scripting Language Library ASR Abstraction Library Application Functions Applications Voice Messaging Support Automation Sales Automation Integrated Messaging Customer Relationship Management Device Control Gatekeeper PBX Application Libraries Core TGI GNUe Integration Misc Configurator Development Tools 4.2 Gnucomm Components ---------------------- In this section we will introduce Component Standards and provide brief coverage of the components that either exist or we envision will aid in the implementation of the design. We're actually designing the system before we finish coding it ;). Again, Keep in mind that although we list functions and components here, the System Design Document (in M2) is the place to find the canonical Function Definitions and Component Standards. The following component lists correspond roughly to the Function list. 4.2.1 Component Standards ------------------------- Primarily in order to avoid "undocumented features", GNUComm will add a few standards to the very reasonable GNU coding standards. That means documented code, an administrator's guide, and a test spec before a Component can get out of beta. Not that we're control freaks or anything, but when you dial 911, it's got to work. 4.2.2 Gnucomm Core Components ----------------------------- *-> Control Servers: Bayonne - application server Ipswich - switch Babylon - device monitor *-> Business Servers: AQS - Advanced Queue Server RTDB - Real Time Database Server *-> Matrix Servers: TRiP - Transaction Redundancy Protocol Server EWOK - CORBA interface server *-> Base Libraries: +Driver Library - mostly interfaces, we may need to write some drivers. +Audio Tools Library - ccaudio +Client Call Control Protocol Library - TOSI +Switch Control Protocol Library - a babylon plugin +VoIP Protocol Abstraction Library - this really springs from a desire to port a SIP stack API interface to H.323. There are gateways that can make this coding unnecessary, but we'll see where it goes. +Server-Side Telephony Scripting Language Library - ccscript +ASR Abstraction Library - as with the VoIP Protocol Library above, we probably won't need to implement these engines because we expect that excellent free software for this purpose will exist by the time we get here. This is basically a wrapper for use primarily with the application server. We can only use a minimal set of ASR with this method, so this portion of the design is destined to be completely revamped. 4.2.3 Application Components ---------------------------- *-> Application Libraries: Core TGI GNUe Integration *-> Applications: Troll - Scripted gatekeeper on top of Ipswich. Integrated Messaging - Just a document. Voicemail - Multi-user voicemail, Bayonne application. PBX - Ipswich Application Support Automation - Sales Automation - CRM - Device Control *-> Configurator Menu-Driven application for enumeration, interrogation, and configuration of GNUCOMM components on a network. Text or GUI driven. *-> Development Tools: Web-based visual scripting environment - All servers will be will be scriptable in one or more languages. Bayonne is scriptable in ccscript. TRiP will be scriptable to handle system failures. AQS will be scriptable to act on important changes in the status of queue objects. You get the idea. The ideal environment would allow at least the boilerplate and simple scripting to be done in a drag and drop manner. A full debugging environment would be ideal. A set of test harnesses will be a requirement, although we should probably split that out into another topic. 4.2.4 Miscellaneous Components ------------------------------ These are somewhat speculative at this time. *-> Other Specialized servers and libraries: Transcoder - could encapsulate the Codec Library S.100 - Telephony resource daemon ... *-> Client Applications: A GNU softphone: * M1 - first get a simple SIP phone communicating with at least one server (most likely bayonne). Write the simplest command-line app possible, putting as much into libraries as possible. * M2 - Abstract SIP layer so that H.323 can plug in. TOSI-enable this application. * M3 - Orion - The Phone Parts Project - a gui phone with plugable skins and codecs ala xmms. 4.3 Design Goals ---------------- By way of design exercise, we will now discuss some issues that will influence the SDD. 4.5.1 Power: ------------ An application that does a lot of work with little effort and is very flexible can be said to be powerful. Placing server logic in a high-level scripting language is a means to develop a powerful server. Script passing between servers is a fairly powerful way to move intelligence around. The gateway to CORBA services enables another level of this. The concept of GNUComm Functions greatly increases the flexibility of the system as well. The ability to drop in an alternative server is key. Consider the standard, well-understood HTTP/CGI interface of web servers. 4.5.2 Reliability: ------------------ One means to achieving 5 minutes per year downtime is to have both hot failover and hot replace. This means that any component of your system, if it fails, should not dump calls. Instead, a backup system kicks in, takes over calls real-time, and notifies you that the primary system must be swapped out. In practice, this is rarely implemented. However, various forms of redundancy are implemented. There is Application redundancy, which requires two or more systems to execute in lockstep (possibly at the kernel level) so that, at best, application failures are recoverable. Application redundancy doesn't do anything for you when your kernel locks up. There is routing redundancy, which the phone company typically provides, such that if you have a hunt group spread across several systems and one system goes down, the calls active to that system are dropped and subsequent calls route to the next available port on another system. Routing redundancy is arguably the most important type, since it allows you to perform a graceful shutdown and system replacement by accepting no new calls on a given node. As a first step applications need to be designed with an awareness of this type of feature. Then there are the pair of redundancies that we are attempting to implement to give us the ability to provide hot swap and hot replace on any scale: Data Redundancy and Stream Redundancy. The foundation for these two we already have in the form of a data redundancy bus. The idea is this: First we implement a Transaction Redundancy Protocol Daemon (the TRiP), which is informed of important state changes and out-of-band data transmissions on every call. If a system goes down, the TRiP notices and requests that another system take appropriate action based on the last data it had for each active call. So if a credit card transaction needs to be rolled back or something else needs to be done, like hang up a phone or call someone back, or tell someone how much usage a caller made on his calling card, or something, then it gets done. Stream Redundancy requires that a network of cooperating systems place multicast data on a Media bus, typically a separate, high-bandwidth network between the cooperating nodes. Stream redundancy can potentially be very expensive, but it allows a system to go down at any time without the caller being dropped, and sometimes without the call being interrupted at all. There are certain situations that you just can't easily help, such as: Your T1 card or the cable running into it gets destroyed. Your service provider goes down. Nuclear Holocaust. Locusts! Etc. However, if you have very good connectivity, your reliability should be very good with such a redundant system. So that's the general idea. Hand in hand with redundancy goes the question of how nodes monitor one another. The function of the Matrix Servers require some voting logic to be carried out prior to a proclamation of process death. Voting logic does not need to be so simplistic as to 4.3.3 Security: --------------- The author refuses to pretend to be a security expert. We can't force anyone to run a program in a secure manner, but we can: 1) Try to design secure programs. 2) Have a mechanism in place for timely response to bugs, particularly security holes. A lot of projects rely on having a group of security minded people audit programs and respond to reports. To these people, discovering and fixing a race-condition attack is really neat. We definitely need some of these people. With 1) in mind, GNUComm programs should: 1) Minimize privileges. The designers should document any assumptions they make about the privileges of their software (and attempt to be more specific than "We assume here that the kernel is: linux-2.2.x"). The administrator should know what ID each app is running under. This information should be available to certain users as well. In reality, the good admin will just change all the privileges to suit his/her purposes. The bad admin will just leave things insecure. 2) Minimize trust. Designers should trust as few resources as possible and document what resources their programs will interact with. The administrator should know this information. A security audit of a GNUComm program should reveal any undocumented resource usage or misplaced trust. and, 3) Minimize bad data. Sometimes even trustworthy resources spew bad data. Assume all data is bad unless you actually figure out that it's good. At least do bounds checking. If you refuse to write code to verify data and do bounds checking, you had better document your reasons. To meet GNUComm Component Standards, documentation of these issues should be made available, possibly through a recurring security audit mechanism. Note to self: build a security audit team! 4.3.4. Ease of Use: ------------------- This has not received nearly enough mention. Individual applications require only user guides, but nothing guarantees ease of use of an application. There is a world of difference between an application with a consistent, simple user interface and the typical IVR or Dialog-based application. If we do one thing, we should rid the world of poorly designed speech applications. There has been ample research done to develop a GNUComm application user interface guide to help this happen. As far as the developers are concerned, tools are their forte. One usually doesn't have to try to hard to find developers willing to write development tools. The back-end logic is relatively benign, but there is a learning curve to the specialized scripting that makes GNUComm applications run. Tools to make these languages simpler to code are always helpful for beginners. 4.3.5 Documentation: -------------------- By this point, the focus on documentation should be apparent. Every section in this document embeds a documentation requirement of some kind. System Administrator's Guides are requirements for Components, as well as code documentation and test specs. There are a large number of optional docs that we would, of course, like to see written. We'll watch closely to see if the absence of something like the Application User Interface Guide becomes problematic. 5.0 How you can help: --------------------- Examples of things we need: Writers to help with documentation, and translations of documentation. A complete international prompt library. Lend us your voice. A library of voice applications to work with our components; we can never get enough of these. Itching to control your home, set up a meeting, or get a wake up call? GNUComm will take your breakfast order and scramble your eggs if you have the coding itch. Take a look at the web site to see who is working on what. There are probably several Functions unfilled by components and several components with no owner or too few owners. Examples of things you can do: Write one of the things we need. Document one of the things we have. Test or add features. Use GNUComm commercially. Join in the developers discussion. Copyright 2001 - The Free Software FoundationReturn to GNU's home page.
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