Where do you put your Services?

An essay by Warren Montgomery (wamontgomery@ieee.org)

 

Innovated communication services are essential both to carriers and to end customers.  For carriers, services are what differentiates them from competitors and allows them to retain customers and charge a premium rate for what is rapidly becoming commodity transport.  For end customers, services are what allow them to increase business and personal productivity and get the best value for their communication spending.  In the past, most communication services had to be implemented inside the switches and other network elements in the carrier’s network, which was difficult, slow, and expensive.  Rapid change in communication and computer technology has made it possible to position services in many different places now, and the choice of where services are positioned has a profound effect on flexibility, security, and cost for communication services

1.   Where do services go?

.  Figure 1 illustrates some of the options:

 

  1. In the user endpoints (phones, PC’s, private phone systems, etc.)
  2. In the core network components (Switches, softswitches, routers, etc.)
  3. In network based application servers (Intelligent Network SCPs, web/application servers, etc.)
  4. In network based media service nodes (Service nodes, media servers, etc.

 

 

1.1.        Endpoints

Many people looking at the internet immediately suggest the only right place for services is in individual user endpoints. 

  1. Because end users control their own endpoints, they can install new services there without without waiting for carriers to act.
  2. Entrepreneurs can market new services directly to end users, creating a mass market for innovation like that of PCs and PC applications.
  3. Many of the security, reliability, and privacy issues associated with network based service implementations are not a factor in the endpoints.
  4. Endpoints are replaced more often, creating more opportunities for innovation

 

Not all services will work in the endpoints, however,  and the limitations of endpoint based services are critical to understand

  1. Many users use more than one endpoint.  Implementing services in each endpoint leads to inconsistency and duplication of data such as personal directories and profiles. 
  2. Many endpoints are not always connected to the network, meaning that any service that needs to be available at all times, such as call coverage, can be lost if it is implemented in an endpoint.
  3. Services that require multiple media streams, such as conferencing, may be very inefficient to implement in an endpoint, as it may not be cost effective or even possible to deliver all the information.
  4. Privacy and security concerns make some services difficult, because the users associated with the endpoints may not trust each other enough to permit sensitive information (e.g. caller’s identification) required for a service to be delivered.

 

Endpoint based services will have a large role, especially for convenience features (speed calling, local directories, distinctive alerting, etc.) but will not be the only place fo innovation.

 

1.2.        Core Network Elements

Embedding services in core network elements, such as switches, gateways, routers, etc. Has been much maligned as reproducing the “mainframe” era for communications.  These network elements are nearly always under severe performance and reliability pressure, meaning that innovation here is difficult, and lead times to develop, install, and test new services are long.  Still there are many advantages to embedding services in core network elements:

  1. Performance – This is the only acceptable place for some services, especially those that process complete media streams,  or monitor every communication through the network.
  2. Security – Services that must be provided, such as legally mandated wiretapping, emergency access, or even collecting critical data for billing and network management are natural candidates for core network services.
  3. Universality – Services that must be provided consistently the same way everywhere, such interpretation of naming, numbering, and routing plans, are good candidates for the core network.

 

Still, in the past the communication industry has generally erred in the direction of putting too many, not too few services inside the core network.  When the service does not naturally go there this leads to many problems. 

  1. Limited capacity – Core network elements often have limited processing capacity and severe performance requirements.  This makes it difficult to add new services.
  2. Impact on security and reliability – Failures of any service implementation in a core network element can impact many customers, so this is no the place for rapid introduction of new services with limited testing. 
  3. Long lifecycles.  Core network elements typically have long lifetimes, making it difficult to incorporate the latest technologies in them universally.
  4. High specialized hardware and software – Meaning that few engineers have the skills to work with them and service development can be difficult.
  5. Limited numbers and markets.  The total number of switches in the US telephone network is in the thousands, not the millions, like PCs.  This means the cost of developing applications for them must be recovered over a relatively small market.  Routers and Softswitches face similar challenges.

 

In short, the core network elements are good places for services with extreme needs for performance, reliability, universal availability, or legally mandated availability, but a poor place for many others.

1.3.        Network Based Servers

Network based servers are servers such as Intelligent Network Service Control Points or Internet Application servers which are located and managed inside of a communication network, but not in the flow of every communication.  The key difference between these and the core network elements above is that user communication requiring a service provided by a network server are routed to it, while other communication does not.  This gives Network based Servers many of the advantages of core network elements without many of the disadvantages:

  1. They can provide a trusted intermediary between users and provide services requiring information that the users would not trust to another endpoint.
  2. They can be always on and available, providing services for users whose endpoints are not currently connected (essentially as a proxy for a user)
  3. They can serve a variety of different security and reliability needs.  Because users are connected to network servers only when they request a specific service, the security model is like that of web services – Errors in a website only impact users who go there for services, not other services and other users.  This enables more rapid innovation and a more open environment for introducing new services.
  4. They can be installed quickly and scaled to provide performance.
  5. They can provide the same service for all of a user’s endpoints.  A corporate directory in a network server is available to a user on all his or her endpoints.
  6. They can provide services efficiently.  Routing for media streams can be optimized inside the network, avoiding inefficient “hairpinning”

 

Not every service belongs in a network server, for many reasons.

  1. Network servers often have limited access to control of communications and no access to actual media streams, limiting the services that can be provided to those supported by the enabling protocols used to communicate with the core network elements.  Intelligent Networking, SIP, H.323, and other communication interfaces all provide for network servers with this kind of limited access, but each have limitations  that make some services difficult to provide.
  2. Coordination between network servers, endpoints, and core network elements can lead to service interaction issues.  The web is a good example.  Each e-commerce website establishes it’s own user interface and user profile.   Users often must enter redundant information, and implementers cannot necessarily make use of other services.
  3. An open networking model can make it difficult to guarantee service availability and performance.  With the telephone network, users have become accustom to a network operator being able to guarantee a full suite of services.  With services implemented in application servers owned by different providers, no single party may be able to do this.  Regulation and legislation may need to catch up with implementation.

 

I believe that Network based Servers represent an important opportunity, and the implementation best suited to a large number of innovative services.  Getting the protocols and interfaces right, and making the regulation and legislation fit this implementation model is critical.

 

1.4.        Media Servers and Service Nodes

I make a distinction between an application server, which deals with signaling and control for establishing communication, and a media server or a service node, which deals with the actual communication streams.  Some analysts lump all of these under the term application server, but I feel the distinction is important because application servers as I have defined them can provide many useful services without needing to deal with the capacity and interface issues created by intervening in the communication media.  In general a media server processes only the media under direction from another network element (core network element such as a softswitch, or a network server such as an application server or SCP), while a service node is self  processes both media and signaling associated with communication.   Service nodes look to the network and end users like just another user, while media servers operate like a part of the network infrastructure.  They offer advantages in implementing services

  1. Both provide a good platform for media intensive services that are not needed in every communication.  These include translation, storage, and many others.  Many of the interesting service opportunities, such as unified messaging, music and video rental and purchase, advertising, etc. require media processing and are only really effectively implemented using media servers or service nodes.
  2. Service nodes provide a way to rapidly introduce new services without requiring new network infrastructure.  Because they look like any other endpoint, they can be deployed rapidly to meet a new opportunity without updating network elements to either install a service on them or insure calls are routed to an appropriate application server.
  3. Media servers are provide high capacity and performance.  An endpoint can implement some media based services, but a true media server does it more cost effectively at a large scale.

 

Media servers and service nodes do, however, have many limitations.

  1. Hairpinning.  Because a service node looks like an endpoint, it may be difficult to get efficient routing for services that use them.  This ties up extra interfaces on the server and the network elements it connects to as well as sending additional information through the network.  The cost of bandwidth may be low, but the cost of interfaces often isn’t.  This is a particular problem for networks and services in transition, where different technologies are used.  Making services such as card based calling efficient in a circuit network with established standards and a limited number of vendors and operators has been difficult.  Don’t expect them to be efficient in a hybrid circuit/packet network with much more fluid standards and more operators and vendors.
  2. Interface density.  Bringing lots of bandwidth into a server is always a challenge.  This is especially true in circuit networks, but is an issue everywhere.
  3. Scaling and operational efficiency.  Service nodes and media servers are great places to trial services, but as the trial service becomes universal the number of servers required and consistently administering them often gets to be burdensome.  Many network services such as calling card, voice mail, and others have gone through an evolution, starting out as provided via service nodes but reaching a point where the number of service nodes and the complexity of administrating the network drove operators to seek other alternatives.

 

Media servers and service nodes are an essential part of any network strategy, but it is important to keep the limitations in mind.

 

2.   So what are the implications?

All of these locations are places for innovative services, the key is really understanding the relative strengths and limitations each offers, and understanding how to use these elements together in innovative ways.  Some implications for carriers, equipment manufacturers, and service innovators include:

  1. Insuring interface and signaling standards will support the requirements of service implementations.  The key standards include but are not limited to Intelligent Network, PINT/Spirits, SIP and H.323 proxy services, Megaco /H.248 for gateway and media server control, VoiceXML, and emerging standards for presence.
  2. For carriers, deploying the latest interface and signaling standards to support open network models for network based services.
  3. Network based servers (Application servers, SCPs, and others) in my view represent a real opportunity, provided the required interfaces are deployed.  They offer many advantages over endpoint or core network element based services.
  4. For everyone, be aware of the strengths and limitations of different alternatives, and be aware that the real issue is often coordinating multiple platforms to deliver a valuable service.