ESMI-032-R1

TF-34 and Web ServicesTF-34 and Web Services

Presented at ESIF-11

Task Force 34

October 26, 2004

John Sines

[email protected]

© HBF Group, Inc. 2004 For ESIF Task Force 34 Use Only Page 2

What is a Web Service?

A Web Service is“A web service is a software application identified by a URI, whose interface and bindings

are capable of being identified, described and discovered by XML artifacts and supports direct interactions with other software application using XML based messages via

Internet-based protocols.”

(World Wide Web Consortium)


Intent of Web Services

A language and platform independent method to implement Service Oriented Architecture (SOA) using standard internet technologies

For application-to-application communication Has little to do with HTML Not limited to someone adding a hook into their web site. A web

service can live anywhere on the network (Inter or Intra). Entities choose to use web services for ease of implementation,

conciseness of the standard, and low cost


Examples of Web Services

Southwest Airlines accesses Budget Rent-a-Car to make car reservations after making airline reservations

Amazon allows other companies to search and purchase items via Web Services. If you are a nutritionist you can purchase nutrition books from Amazon without leaving your nutrition web site

There are stock-quote services, traffic-report services, and a weather services available

Ideal for any Service Oriented Architecture (SOA) deployment


What makes up a Web Service

All components are based on the XML standard– SOAP: Simple Object Access Protocol

– WSDL: Web Service Description Language

– UDDI: Universal Description, Discovery, Integration


SOAP

SOAP is the service messaging layer of a web service. The messages are XML based.

The protocol consists of three parts:

An envelope that defines a framework for describing what is in a message and how to process it

A set of encoding rules for expressing instances of application-defined datatypes

A convention for representing remote procedure calls and responses A transport or protocol binding


WSDL

A WSDL is an XML document that describes the functional characteristics of the services offered.

The WSDL describes:

The operations the service has available The messages the service will accept The protocol of the service


Where Web Services exist in the Standards World

W3C– XML Specifications

– WSDL Definition Specifications

– SOAP Specifications

– UDDI Specifications

– Web Services Architecture and Interoperability (WS-I) Profiles Maturity of Standard

– Introduced in 2000, and gaining momentum. Many companies are in 2nd and 3rd generation deployments

– De-facto Standard for SOA over XML

– Who uses them?• Anyone who needs interoperability between applications

Software and Hardware industry giants such as IBM, Sun, Dell, Microsoft, Intel are behind the standard


Why Web Services for ESNet?

Can be done in a faster and cheaper manner– WSDL gives widely recognized definition language to define the service

messages between the GWs and the CSCEs Platform and Technology neutral Insulates TF-34 from the intricate underlying details of defining a

protocol Ease of adding new services ComCARE messages are being defined as web services NENA 4 Generation 1 has already developed schemas for the ALI

Type Lib. The schemas are 2 weeks away from final approval http://www.nena.org/xml%5Fschemas/Current%20Release/Version%2

04.X.X.list.html


Reliability

Reliability is a concern Leverage existing technologies such Clustering and Load Balancing to

transparently manage reliability Techniques have been established to ensure that the messages get to

their endpoints Heartbeat mechanism can still be implemented


Security

Security concerns are the same as connection oriented architecture Web Service over HTTP or HTTPS – can be as secure as any website

– SSL, Basic Auth, NTLM, Passport, custom… Relies on security capabilities of the transport layer Security best practices are being recommended. People who

specialize have put an a great amount of effort in developing the best practices documents.


Pros and Cons of Web services for ESNet

Pros– Faster definition and deployment. Reduced deployment cost for PSAPs, service providers, and

ESMI intergrades– Clarity of the Standard– Ease of implementation with off the shelf technologies

• Can use Microsoft’s .NET or Java’s J2EE (IBM Web Spear, BEA Web Logic, etc.)• Leverage Application Server Technology• Leverage Load Balancer Technology

– A number of runtime management and support tools available– A number of production/development tools available (many more than SIP). In the .NET

development environment, development of web services is completely wizard driven– Allows for extensibility in protocol– Allows for a more scalable architecture– Seamless fail-over with the use of Load Balancers and Clustering- Connections are

acquiesced on every call to a service – Leverage existing NENA XML schemas – Ease of integration of ComCARE work– Allows for easy market entry for new data service providers– Affords PSAPs highest degree of flexibility for adding new services– Supports distributed Service Registry's which dynamically show which services are available

for use


Pros and Cons of Web services for ESNet (Continued)

Pros (Cont’d)– SOA supports the creation of Security Services which incorporates authentication, certification,

and encryption through std. PKI and other security practices– Supports 'Virtual Security Gateways' which model a physical security gateway, but are more

flexible to extend, consolidate, and upgrade – Each endpoint can be both a 'Client' and a 'Server' - this allows PSAPs to not only ask for

information, but to also provide information easily– Web-Services can be added as extensions to existing hub-and-spoke system design to enable

service-enabled applications to interoperate– Connectionless model only connects when data is needed - allows for messaging efficiency – Overall message overhead is reduced– Presence services can be implemented to ensure the application is available when needed

(Heartbeats can still be implemented)– Web-based connections are fast - since these are no different than any other IP-based

connection (on the order of milliseconds) Cons

– The web services standards may evolve– Overhead in initiating a connection– Matching requirements - individual customer requirements are possible but need to be

carefully managed among all customers– Availability - no architecture is perfect - many of the same dedicated 'guaranteed' data delivery

infrastructure can be leveraged to assure increased availability in a Web-Services model


Pros and Cons of Hub and Spoke/Connection Oriented Architecture

Pros– Few connection establishments means less overhead– Software exception is thrown if there is a problem with a TCP/IP socket– Hub-and-spoke Enterprise Integration Architecture (EAI) is the most popular of

traditional EAI models - been around for a while– Hub-and-spoke EAI's provide physical congestion control points to the PSAPs– Hub-and-spoke EAI's provide physical congestion control points to the PSAPs– Affords CESE client a certain amount of autonomy by virtue of RG hiding remote

data services– Allows for more responsibility to be placed on the hub provider for message

content, integrity, and performance Cons

– Complexity involved in defining the message set– Complexity involved in implementing the message set– Hub-and-spoke EAI's are built using proprietary 'middleware', as opposed to 'open'

s/w standards and protocols – Message hub is centrally located by design, rather than distributed by nature – Introduces risk due to potential for central point of failure for a large number of

automated processes (consider several hundred CESE's to one RG)


Pros and Cons of Hub and Spoke/Connection Oriented Architecture (Continued)

Cons (Cont’d)– Uses persistent TCP/IP connections which would require frequent teardown and

re-establishment (ref. TML initiative from T1 & OBF ATIS committees) – Dedicated circuits required - since Internet is a 'non-production' (inherently

unreliable) for persistent connections – Number of dedicated circuits between each CESE and RG endpoint (~7,000

PSAPs = lot of circuits) – PSAPs must then support two circuit types for IP connectivity, dedicated and

Internet-routed– A CESE is defined as a 'Client' only - though messages are defined to be intiated

both directions, this complicates the connection methodology – Requirements for persistent connections and continuous heartbeats, puts greater

load on systems and networks over that of a system that messages when it needs to

– Proprietary message exchange implementations, such as TF34 is proposing, requires specialized programming knowledge and effort to develop, maintain, and upgrade

– Introduces a TF34 'specific' messaging product between all available integrated applications


Problems with doing Connection Oriented Protocol in Parallel

Longer standards development time The technologies are very different No good migration path from one to the other

– Hardware as well as software required would be much different


Bi-directional Web Service

Connection-Oriented Web Services

ESNetRG

CESE

ESNetRG

CESE

Web Services

Web Services

Persistent Socket Does Not Persist


Possible Network Implementation

NETWORK

PSAP

PSAP

Load Balancer

DB ClusterApplication Server

Cluster


What a Solution Could Look Like

3

PSAP PSAP PSAP

IP WAN

PSAP PSAP PSAP

Reference: Optimizing Application Availability, Cisco Systems, Inc, Packet magazine (Volume 15, No. 2), 2003http://www.cisco.com/warp/public/784/packet/apr03/pdfs/ent_optimize.pdf

Load Balancer

Redundant AccessRouters and Links

Redundant WAN AccessRouters and Links

FirewallApp Server

ClusterDB Cluster

Data Center 1

Data Center 2 4

. . . .

. . . .


How to move Forward

Define a WSDL that includes all of the messages– Map messages to WSDL


Taken a step further, the entire ESNET could be a Web Service based peer network

PSAP1

(CESE1)

PSAP1

(CESE1)PSAPn

(CESEn)

PSAPn

(CESEn)

Service1Service1 Servicen

Servicen

This would allow CPE vendors to supply services as PSAP demand dictates – all using the same mechanism of discovery and invocation. ALI, ACN, VoIP, etc. all become an accessible service.

PSAPs share information on a peer basis.

Documents

ESMI-032-R1