ESW – May 2010
UK Architecture for VoIP 999/112s
John Medland – BT 999/112 Policy Manager
UK Emergency Service
Public Emergency numbers
- 999/112,
- 18000 (ITU v21 text over voice, ie real time text using special terminals)
Police 52%
Stage 1 PSAPs
BT (5) or C&W (2)
BT or CW
Public
Network
999/112/
18000
•31 million calls each
year to stage 1 PSAPs,
55% from mobile
phones
Fixed/Mobile
Networks
Ambulance
42%
•Around 60% are connected
to Stage 2 PSAPs (usually
within 10 seconds)
Public
networks
Fire 6%
Coastguard
<1%
(204 Local Controls)
999/112/18000
(
Location for emergency callers
• Available automatically on fixed and mobile calls at Stage 1 and
Stage 2 PSAPs
• Fixed lines : civic locations as name and address updated daily to
Stage 1 PSAP database
• Mobile networks provide cell coverage area (enhanced with timing
advance for some) over standard ETSI interface: radius ~2.2km
• Limitations for VoIP calls, calls from private networks, mobile
roamers
• Stage 1 PSAPs provide Location Servers which can be
accessed by Stage 2 PSAPs ( location retrieved instantly using
telephone number + secure TCP/IP link)
• Industry funded Stage 1 PSAPs supply location free to Stage 2
PSAPs (Stage 2 PSAPs pay for their lines, hardware and software)
• Telematics emergency calls (non-standard eCalls) growing and can
provide GPS information
Handling VoIP 999 now
•
•
•
•
•
PSAPs still TDM based so VoIP goes through PSTN / IP Gateways
Small number of VoIP 999s at present, mostly fixed users
Regulation says if PSTN access, then must allow 999
999s identified as VoIP
Registered “default” address accessed through E164 tel number
(CLI) for “fixed” users….
• ….but default address marked as needing voice confirmation
Verbal routing
• Device/CPE use PSTN/GSM for 999 if possible
• Key issues for VoIP 999 : - only default name+address data from large number of VoIP SPs
- challenge of 24 hour VSP contact point for PSAP use (tracing, alternative contact numbers)
- lack of information to PSAP for nomadic users
• Need to Automate Location provision………
NICC Task Group
•
The Network Interoperabilty Consultative Committee : NICC is a UK
telecommunications industry committee which acts as an industry
consensus group in which specifications and technical issues associated
with network competition can be discussed. It also is a source of technical
advice to the UK Regulator
• Location Task Group : Routing 999/112 for VoIP to correct local EA
supplying caller location information on all calls
• Membership : BT, C&W, Ericssons, Huawei, Andrew, Nominet,
Magrathea, Aeonvista,Vodafone, VirginMedia, Orange, and Ofcom
+….
• Approach :- VSP, ISP and Access Provider(s) all different organisations
- PSAPs are still TDM based
- Start with UK only (all parties UK-based)
- Cover DSL, Cable, Enterprise, WiFi and GSM scenarios
- Use developing standards wherever possible, eg IETF, ETSI
- Don’t rely on user
- Don’t rely on device
Overview of Architecture and Interfaces
VoIP call
VSP 1
Soft-Switch
SBC1
1
SBC2
SBC1/2
VSP 2 soft switch
(Aggregation + SS7
interconnect )
2
CLI + VSP1 id
PSTN—IP
Gateway
PIG
a
Source IP+Port,
VSP 1 ID and CLI
information
(NENA v2)
LIS URI
Access
and IP
Log-on
functions
Internet service & access
infrastructure providers
IP
b
VPC
CLI + VSP1 id
3
IAIC
c
ISP LIS
4
Emergency
Handling
Authority –
Stage 1 PSAP
Key
Voice path
Data path
Request using CLI, VSP id.
Response gives location
HELD third party request
using Source IP (+ Port no.),
in HELD ID extensions.
Response gives PIDF-LO
VPC Functions
VSP Soft Switch
Interface (a)
Key Parameters (CLI,
Source Public IP Address, source port number)
Interface ( b)
Parameter (Source
Public IP Address)
IAIC (IP Address to ISP
Converter)
VoIP Positioning
Centre
Interface ( c )
Parameter (Source
Public IP Address)
Inteface(b)
Parameter (ISP LIS
URI)
Interface (4)
Parameter
(CLI)
Emergency Handling
Agency
Interface (4)
Parameter
(Location)
Interface( c )
Parameter (PIDF-LO
Location)
ISP LIS
VPC - Mapping Source IP address to ISP
IAIC
BGP4 Route
Collector
IP Address
IP / AS
mapping
Interface (b)
LIS URI
AS / LIS
mapping
BGP Route Updates
BGP
Peers
Generic LIS Functions
Interface (c)
LIS
HELD Server
iM1
iB1
LIS
IP@
translation;
Border
Functions NAPT/SBC/AL
G
OSS
Systems
iC1
iL2
Network
Other
LIS
elements
Broadband and ADSL Access
User
Environment
Local Loop
Provider
Backhaul &
Aggregation
Provider
Internet Service
Provider
OSSLLP
OSSBAP
OSSISP
Emergency
Handling
Centre
Management
Control
RADIUS
Server
(RADIUS)
VPC
LIS
(RADIUS)
RADIUS
Server
(RADIUS)
(RADIUS)
Figure E1: xDSL Architecture for PPP Tunnelled via L2TP to ISP
L2TP Network
Server
L2TP Access
Concentrator
DSLAM
Residential
G/W
Voice
Terminal
Media
SIP
IP N/W
RTP/RTCP
Internet
Telephony
Service
Provider
BB
Customer
OSSLLP
OSSBAP
OSSISP
LIS
Provision
BB Service Req (Billing Adrs, Inst Adrs)
BB Service Req (RefISP,MPF,Inst Adrs)
BB Service Req (RefBAP, MPF, Inst Adrs)
BB Service Resp (RefBAP,SIDLLP)
BB Service Resp (RefISP,SIDBAP)
LIS Add Info (SIDBAP, Inst Adrs)
Audit
BB Inst Adrs Audit Req
(List[SIDLLP])
BB Inst Adrs Audit Req
(List[SIDBAP])
BB Inst Adrs Audit Resp
(List[SIDLLP,Inst Adrs])
BB Inst Adrs Audit Resp
(List[SIDLLP,Inst Adrs])
LIS Add/Remove/Modify Info
(SIDBAP, Inst Adrs)
Figure E5: BB Provision and Audit on a MPF Line For Binding of Service Identifier (SID) to Installation Address (Inst Adrs)
L2TP
Network
Server
L2TP
Aggregation
Concentrator
DSLAM
Residential
G/W
BAP
RADIUS
Server
ISP
RADIUS
Server
L2TP Tunnel Establishment
PPP Link Est Req
PPP Challenge(Token)
PPP Resp (UID,#PW#)
PPP Link Est Req
PPP Challenge(Token)
PPP Response
(UID,#PW#, IA=SIDBAP)
RADIUS Auth Req
(UID,Token,#PW#,IA=SIDBAP)
Auth Accept
(L2TP Tunnel End Pt, Tunnel Id)
L2TP Tunnel Est Req
(Tunnel Id,UID,Token,#PW#)
PPP Link Est Resp
L2TP Tunnel Est Resp
PPP Link Est Resp
RADIUS Auth Req
(UID,Token,#PW#,IA=SIDBAP)
Auth Accept
PPP IPCP Config Req (IP Adrs)
PPP IPCP Config Resp
RADIUS Accounting Req
(IP Adrs,SIDBAP)
RADIUS Accounting Resp
RADIUS Accounting Req
(IP Adrs,SIDBAP)
NB This example shows the case of an Intermediate
Agent at the DSLAM signalling the SIDBAP and the
ISP’s LNS allocating IP Addresses.
Figure E2: Network Attachment for PPP Tunnelled via L2TP to ISP
RADIUS Accounting Resp
LIS
Way Forward for UK
• NICC Standard published Jan 2010
http://www.niccstandards.org.uk/files/current/ND1638%20V1.1.2.pdf?type=pdf
• New requirements on all organisations (systems development)
•
Many more organisations involved to deliver 999 (not just traditional telcos
but VSPs and ISPs)
• New operational components : LIS and VPC
• New interfaces for all organisations: based on international
standards as far as possible (eg IETF HELD)
• Increased co-op and trust relationships between PSAP and VSP,
ISP and Access networks
• NICC Work to continue : other use cases, IP PSAPs (IP end to end)