Welcome SMS

Welcome SMS in Erlang. Experiences of Rapid Deployment in a GSM network

The Requirement

Send out SMS messages to One 2 One customers when they arrive in a foreign network.

Don’t send them any more messages for at least two weeks.

Different messages depending on destination Country. “Marketing” usable GUI configuration. Option to send messages to roaming customers when

they arrive in the UK. Ultra reliability not a hard requirement

Except NOT sending multiple messages

The Timescale

8 (yes, 8) weeks from start of design to launch of service.

Access to Customer Behaviour?

Monitor all international c7 signalling links. Extract contents of MAP messages:

Where is the customer? (VLR Address) Whose customer is it (IMSI) Who should receive the SMS? (MSISDN)

VLR address and IMSI are in Location Update, MSISDN is in Insert Subscriber Data. These messages can even take different physical routes...

Business Logic

Decide which message to send Different depending on class of customer (prepay,

postpay, wholesale) Different depending on destination Country Different for inbound roamers

Have we sent them one already in this country? Have they elected not to receive these messages

Operational Requirements

Integrated with existing alarm management system (SNMP Traps)

Generate statistic reports of system activity into existing stats database.

Load balancing between SMS service centres Ability to on the fly reconfigure which SMS service

centres are active and the load balancing between them.

Design Options

Commercial c7 probes to do automatic correlation of all messages for a particular activity. Best supplier delivery time longer than entire project

duration. Time taken to integrate.. Who knows.

Option to exercise Synergy across T-Mobile International group. Several useful design ideas shared. Again,

timescales not lined up Standard commercial systems - expensive, don’t meet

all requirements, integration time huge

Design Options 2

Use Erlang? But what about c7 probes?

Possibility to use standard test set (MPA 7400) to extract all c7 messages as raw data and send out as UDP

Two spare (but old) 4 CPU Sun machines about to be de-commissioned

Lead times of all elements OK. Now to work...

Design Overview

Erlang - A Erlang - B

C7 Probe C7 Probe

UDP c7UDP c7

SMS ServiceCentres

TCP (GIP Protocol)

Customer DatabaseAlso Erlang!

TCP (Internal Protocol)

Erlang Nodes

Bruce

C7 decode

gn_agent1@bruce

C7 decode

gn_agent2@bruce

correlator

correlator@bruce

logic

wsms_logic@bruce sms

Burns

C7 decode

gn_agent1@burns

C7 decode

gn_agent2@burns

correlator

correlator@burns

logic

wsms_logic@burns sms

db_read inetsmnesia

statssnmp Failover

Failover

db_readinets

mnesiastatssnmp

Standby

Customer dB

UDP c7 messages

SMS Service Centre

Active

Some screenshots

Some screenshots

Some screenshots

Problems encountered

Bug with restart of one process starting up too many sms sending processes.

LAN Latency - both for UDP and dB reads. Fixed by tuning concurrency and timeouts.

One module not permanently loaded in the customer Database.

Scanning an Mnesia table to delete some rows is pretty heavy..

What else have we been up to?

Oracle Call Interface Binding to Erlang Multithreaded Driver Pools of Sessions Decent Performance (> 1000 selects per second) 1500 lines of C (so far!) Garbage collection of stale handles

What else have we been up to?

Oracle Call Interface Binding to Erlang

N = “447956123456”,

F=fun() ->

case oci:exec(“select name, balance from cust where telno = :e”, [N]) of

[{Name, Amount}] ->

A1 = Amount - 10.0,

oci:exec(“update cust set balance = :e where telno = :e”,[A1, N])

[] ->

oci:abort(“Customer not found”)

end,

oci:transaction(Connection, F).

What else have we been up to?

Generic “behaviour” for tcp/ip clients link management (using heartbeats) simple callbacks for protocol implementation model is all transactions multiplexed down 1 socket time taken to implement new protocol down to a few days

Call Data Record - record and playback

What else have we been up to?

The Original Project used to justify the use of Erlang never got into service. All hardware has been re-deployed for other Erlang applications!