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LIS-ALE Architecture, and FLAP. Authors:. Date: 2007-11-12. Abstract.

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LIS-ALE Architecture, and FLAP

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Lis ale architecture and flap

LIS-ALE Architecture, and FLAP

Authors:

Date: 2007-11-12

Vijay Patel, Andrew Corporation


Abstract

Abstract

Emergency Services Interconnection Forum (ESIF), a division of ATIS, is working on FLAP. The purpose of FLAP (Flexible LIS-ALE Protocol) is to facilitate transfer of values of location measurement parameters from the network to the LIS (Location Information Server) enabling the latter to compute the location of an IP end-device.

LIS interacts with ALE (Access Location Entity) residing in the access network to retrieve location measurements.

ESIF/NGES plans to send a liaison shortly to many SDOs (including IEEE802, 3GPP, IETF, and ITU-T) to seek input from the industry on this work for developing a standardized location parameter conveyance framework (requirements, architecture, and protocols) following the ANSI guidelines.

Vijay Patel, Andrew Corporation


Internet location services model location information server lis

  • Location by value

  • Device obtains location from the location server in the access network

  • Device conveys location* to the service in the applicable application protocol.

Service

1

2

* Location values are encoded as a PIDF-LO per RFC4119

AccessDomain

InternetDomain

ServiceDomain

  • Location by reference

  • Device obtains reference from the location server in the access network

  • Device conveys reference to the service in the applicable application protocol.

  • Service queries location server directly for location value one or more times

Internet

Internet

3

LIS

Service

1

2

AccessDomain

InternetDomain

ServiceDomain

The protocol used for 1 & 3 is HELD (HTTP Enabled Location Delivery). Step 2, location conveyance, is application protocol dependent (e.g. SIP supports location conveyance)

Internet location services model – Location Information Server (LIS)

Vijay Patel, Andrew Corporation


Internet location services model obo requests

  • On-Behalf-Of (OBO)

  • Trusted third party application (service) queries for location of the device. A client identity which is understood by the LIS is used as a query parameter (e.g. IP address)

  • If applicable, third party provides location information to external service entities.

  • If location was requested and provided by-reference, the external entity queries back to the LIS for location value updates.

Trusted Service

Application*protocol

2

1

Service

Internet

HELD

3

LIS

HELD

AccessDomain

InternetDomain

ServiceDomain

Target device

* OBO requests are typically applicable where the target device and/or application protocol do not have native support for the communication of location information. For example a large enterprise with legacy deployment of standard form factor VoIP phones using H.323 may need to provide location-based routing for emergency and other calls from geographically diverse sites. The IP PABX in this case may perform OBO queries to the LIS using the IP address of the phone(s) as the query parameter. The PABX may use SIP conveyance externally if the location needs to sent to an external service entity. OBO implies two important characteristics of the service making the query. The service needs to be trusted by the LIS such that it is authorized, by whatever mechanism is suitable to the situation, to query for the location of devices in the LIS’ network. Where there are multiple possible LIS that the service could query, it needs to be able to ensure that it is associating the device with the correct LIS to provide the location.

Internet location services model – OBO Requests

Vijay Patel, Andrew Corporation


How does a lis know location

How does a LIS “know” Location

  • The Internet location services model describes how LIS clients request and receive location information from the LIS

  • It does not describe how a LIS determines the location associated with the device

  • The value of parameters derived from the communication network used by the device can be used by the LIS to determine location

  • In order to make use of these parameters, it is necessary for their values to be transferred from the communication network elements to the LIS

  • This is the purpose of FLAP.

Vijay Patel, Andrew Corporation


Flexible lis ale protocol flap scope

Scope of FLAP

ALE

ALE

ALE

ALE

Flexible LIS-ALE Protocol (FLAP) - Scope

Vijay Patel, Andrew Corporation


Location measurement

Location Measurement

  • Location measurement involves determining the value of a number of parameters associated with the network connection in use by the IP device.

  • Since devices will typically connect to a network using some form of link, the parameters will often be layer 2 information directly associated with the physical link in use by the device – though not always

    • e.g. Typical layer 2 pieces of information are the Ethernet switch port the device is connected to or the identity of a wireless access point the device is using.

    • e.g. The permanent virtual circuit (PVC) identifier on the ATM aggregation of a DSL network may be measured even though it is physically separate from the copper pair or DSLAM connections of the physical link.

  • Parameters taken from access networks need to be uniquely associated with the IP device in question and this association will often, if not always, be able to be done against the IP address of the device or terminating equipment.

  • A common framework for access networks to transfer parameter values from the network equipment to the LIS is desirable.

    • The XML based flexible LIS-ALE protocol (FLAP) is proposed for this purpose

Vijay Patel, Andrew Corporation


Lis ale architecture

HELD

HELD

LIS

ALE messages

ALE

ALE

ALE

HELD

LIS-ALE Architecture

Vijay Patel, Andrew Corporation


Location determination lis ale ntwk model

Location Determination: LIS-ALE Ntwk Model

Vijay Patel, Andrew Corporation


Flap message structure and content

FLAP - message structure and content

  • The LIS is responsible for establishing connections to each of the ALE instances in its service area.

  • FLAP messaging is XML based

    • XML objects are sent as part of a continuous stream on a reliable secure link – recommended to be TLS.

    • The XML schema defines the messages supported by the FLAP protocol and includes the meta-objects of terminal and access.

    • The base definition of terminal includes the IP address of the terminal. This will generally apply to IP devices that measurements are being provided for.

    • FLAP also supports sending measurements for access parameters not immediately associated with an IP device, particularly where the LIS may subsequently be able to make the association. In this case, the ALE may exclude the IP address.

  • The base XML schema supports technology and vendor extensions

    • Standard technology schema extensions define the detail of what defines a terminal in a given technology as well as the standard subset of access parameters that apply to that technology

      • E.g. A layer 2 Ethernet switch extension defines a terminal by MAC address. Access parameters include switch identity, connected port, and vlan ID.

    • Vendor extensions permit new terminal and access parameters to be defined.

      • This permits a vendor to provide additional measurement information which may contribute to improved location measurement performance.

      • A LIS may recognize, and utilize, vendor extensions or it may ignore them.

Vijay Patel, Andrew Corporation


Flap hierarchical definitions technology specific ale capabilities

FLAPBase XML Schema

Etc.

Ethernet switch

WiFi AccessPoint

WiMAXBase Station

DSL Aggregator

CableHead End

Vendor Extensions

Vendor Extensions

Vendor Extensions

Vendor Extensions

Vendor Extensions

FLAP – Hierarchical definitionsTechnology specific ALE capabilities

Vijay Patel, Andrew Corporation


Flap xml structure base definitions

FLAP - XML Structure, Base definitions

Type definitions

Header definition

Terminal definition

[vendor]

ipaddress

Access definition

Time

ExpiryTime

Messaging definitions

Message component definitions

Transaction ID

Technology

Vendor ID

Message definitions

AccessQuery

AccessQueryResponse

Notify

Synch

SynchResponse

Parameter definitions

Error codes

Result codes

Vendor

…e.g. Alcatel_LiteSpanDSL_definitions

Extensions

#include EthernetSwitchExtension

#Include DHCPRelayExtension

#Include DSLAggregatorExtension

Base definitions define semantic objects and messages

Base definitions augmented by including vendor and technology specific extensions

Vijay Patel, Andrew Corporation


Flap messaging

FLAP - messaging

To avoid unnecessary polling in the network, FLAP also supports the ability of the ALE to provide asynchronous indications of client location measurement changes. This is done via a “Notification” message from the ALE to the LIS.

Notification may also occur downstream from the LIS to the ALE, where the LIS has learnt of a change in client connectivity, in order that the ALE may also refresh its state information in a timely manner.

Vijay Patel, Andrew Corporation


Example flap message

Example FLAP message

The following message uses the Ethernet extension with additional vendor extension parameters to do a notification message:

<ntfy xsi:type=”enet:ntfy”

xmlns:vnd1=”http://www.example.com/flap/terminal/hw”

xmlns:vnd2=”http://www.example.com/flap/access/skew”>

<enet:terminal

<ip>192.168.0.1</ip>

<enet:hwaddr>12:34:56:78:90:ab</enet:hwaddr>

<vnd1:hw revision="1.2"/>

</enet:terminal>

<enet:access time="2005-04-14T10:51:23.000+10:00">

<enet:switch><ip>192.168.0.1</ip></enet:switch>

<enet:port>4</enet:port>

<vnd2:skew>0.5127</vnd2:skew>

</enet:access>

</ntfy>

Vijay Patel, Andrew Corporation


Flap messaging contd

FLAP - messaging (contd)

A LIS will typically be configured with information about the access networks that it provides location services for. This will include the definitive list of ALE instances that it can obtain location measurements from.

The LIS may poll the serving ALE set with a “Query Access” message. Each ALE will provide a response for each connected device and the measurement set applicable to it.

The LIS may request a refresh of information from the ALE set using a “Resynchronization” message in the event of, for example, coming back on line after an outage. Each ALE will provide a response covering the state of all currently connected devices or, alternatively, a response covering all changes since a given specific time.

Vijay Patel, Andrew Corporation


Example wimax network controller ale

Example – WiMax Network Controller ALE

NetworkController

IP

ALE

FLAP

WiMax extension schema

Terminal definition

MAC address

IP address

Access definition extension

BTS ID

Vendor X extension schema

Vendor X

Product WAP-FamilyY-ModelZ

Access definition extensions

Channel info

RoundTripTime

RxLevel

LIS

WiMax BTS

Generic LIS record

Vendor X proprietary support LIS recordlocation is determined by an algorithm which is a function of RF signal strength and timing measurements supported by the WiMax manufacturer

Vijay Patel, Andrew Corporation


Example a dsl aggregator ale

Example – A DSL Aggregator ALE

Copper

PVC

IP

DSLAggregator

ALE

ISP/Enterprise

FLAP

ATM

LIS

Device

ATU-R

DSLAM

DSL Aggregator extension schema

Terminal definition

IP address

Access definition extension

Aggregation device ID

ATM port ID

PVC ID

Vijay Patel, Andrew Corporation


Example ethernet switch ale

Example – Ethernet Switch ALE

Switch

IP

ALE

ALE

FLAP

ALE

Ethernet

LIS

Switches

Ethernet switch extension schema

Terminal definition

MAC address

IP address

Access definition extension

Switch ID

Switch address

Port ID

VLAN ID

Vijay Patel, Andrew Corporation


Example 802 11x access point ale

Example – 802.11x Access Point ALE

Switch

WAP

IP

ALE

ALE

802.11x AP extension schema

Terminal definition

MAC address

IP address

Access definition extension

WAP ID

Channel No

Vendor X extension schema

Vendor X

Product WAP-FamilyY-ModelZ

Access definition extensions

RoundTripTime

RxLevel

FLAP

LIS

Generic LIS record

Vendor X proprietary support LIS recordlocation is determined by an algorithm which is a function of RF signal strength and timing measurements supported by the AP manufacturer

Vijay Patel, Andrew Corporation


Lis ale procedures

Access device

ALE

LIS

Device data

Update queries

Device

Device

Device

Device

LIS-ALE Procedures

  • LIS starts up

  • LIS establishes FLAP sessions* with ALEs in area of coverage

  • LIS optionally requests synchronization information from ALEs

  • ALEs report measurements as device-related events occur

  • LIS optionally informs ALEs if devices detected elsewhere

  • LIS optionally polls ALEs for measurements as HELD requests occur

  • FLAP supports the transmission, including periodic updates, of location measurement information to the LIS as it applies to connected devices.

  • FLAP messaging is based on streamed XML and a secure and reliable transport is required. * BEEP with TLS is the recommended transport and session protocol.

Vijay Patel, Andrew Corporation


Incorporating device measurements

Incorporating device measurements

As a generic constraint, a LIS cannot assume specific measurement capabilities or protocols supported by visiting devices. However, these capabilities should not be ignored.

Device measured location parameters

Vijay Patel, Andrew Corporation


Device based measurements

AppProtocol(LocationURI)

Application

GPSsatellites

3

AccessNetwork

4

IPdevice

LocReq(signed)

6

HELD

LIS

LocReq( Type(locationURI), LocCap(TechList(…))

1

LocReqResp(LocCap(SubTechList(…))

2

Selected Location Technology protocol

LocResp

Protocol specific message exchange

5

FLAP

ALE

5

Device based measurements

  • In addition to the device being able to make measurements and perform location determination independently, it may be able to:

  • - Provide the raw measurements to the LIS and leave the location determination process up to the LIS - e.g. the device takes wireless RF measurements but the LIS applies these measurements to base station data to calculate location

    • - Perform the location determination itself but need the assistance of the LIS as part of taking the necessary measurements - e.g. the device can perform GPS but needs GPS assistance data. The LIS calculates approximate location and delivers assistance data.

  • The specific protocols used to perform such co-operative location determination can be outside the scope of HELD

  • - E.g. SUPL for AGPS operations or SNMP for LLDP related measurement transfer.

  • HELD supports the exchange of a “client capability” parameter set between the device and the LIS

    • - The device volunteers its capabilities and the LIS responds with an indication of which may be supported

    • - Extension types are used in the HELD protocol to identify the specifics of these protocols.

Vijay Patel, Andrew Corporation


Summary

Summary

  • FLAP:

    • Does not convey location

    • Facilitates location parameter conveyance to LIS, from ALE

    • Being worked in ESIF (a division of ATIS).

  • HELD:

    • Location dereferencing/conveyance protocol

    • A standards track specification from IETF/Geopriv

  • ESIF/NGES plan to shortly send a liaison to IEEE requesting input on this development effort to create location parameter conveyance framework, in support of next generation emergency services.

Vijay Patel, Andrew Corporation


References

References

  • Technical Report: Location Acquisition and Location Parameter Conveyance for Internet Access Networks in Support of Emergency Services (Draft); Doc#: ATIS-xxxxxx; Source - ESIF

Vijay Patel, Andrew Corporation


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