Software Design

HA-Dispatcher’s components at a glance.

Scalability Test

ev-i’s HA‑dispatcher builds on over 2 years of practical experience with several EFC client protocols in various customer projects. The codebase of HA‑dispatcher was designed from scratch, and permits the integration of customer-specified protocols in a minimal amount of time.
In its latest revision the code was subject to a series of scalability test on a 3‑node dual‑core JBOSS‑cluster to prove the basic design principals.

Result of the Scalability Test showing linear growth of session time

The illustration shows the results of the scalability test utilizing a test client inserting 10 fee transactions per device in each session, while establishing a uniquely associated TCP/IP connection for each session.

The test shows that the average number of fee transactions inserted into the database is nearly constant for up to 7000 concurrent TCP/IP connections. As a consequence the session time for each client shows a linear growth with the number of concurrent clients.

Additional Modules

The modular design of ha-dispatcher enables project-specific plugins to provide additional features such as dynamic pricing schemes or map-matching.

Map Matching


ha-dispatcher features a pluggable security layer, with the following highlights:

  • state of the art TLS-1.2 implementation
  • preshared key (RFC4279) or X.509 certificate key agreement
  • GCM modes (NIST SP800-38D, RFC5288) for symmetric encryption

This set of algorithms allows the implementation of a lightweight TLS stack on the client side, which minimizes power consumption and software complexity on embedded devices as outlined in the schematic TLS handshake below compared to the full certificate based handshake from a standard TLS handshake.

A TLS handshake making use of preshared keys.
(Licensed under the FDL, based on material from

A TLS handshake using X509 certificates.
(Licensed under the FDL, material from


HA-Dispatcher was developed with experience gained in more than four years of work in the field of road pricing systems.

Being involved in a wide variety of aspects concerning road pricing in different countries gave us expertise which we are happy to share with our customers. As a project partner we offer you our experience in the following fields:

  • Protocol Design
  • Infrastructure Planning (Server Sizing, Bandwidth estimations)
  • Integration & Robustness Testing
  • Deployment of load balancers
  • Firewall Setup
  • Change Management (Software Updates, deployment of Future Protocol Versions)

We believe that a robust and long-lived DataCenter infrastructure is the sum of many small and interacting parts. Therefore we are committed to an integrated view on the infrastructure — from protocol design to real-world performance tests.

This approach empowers our customers to achieve a maximum of reliability and sustainability for minimum infrastructure costs.


  • Dutch National Roadpricing Research Trial
  • TFL – Traffic for London Phase I
  • Electronic Tolling Back Office – Demonstrator (EFKON / IBM)
  • Spitsmijden Brabant – Mobility Project in The Netherlands with 5000 OBUs deployed.