International Conference and Workshop on Emerging Trends in Technology (ICWET 2010) – TCET, Mumbai, India
IP Multimedia Subsystem Testbed using Open Source Elements A H Khan
M A Qadeer
M Siddiqui
Department of Computer Engg Aligarh Muslim University Aligarh 202002, India +91-9359060609
Department of Computer Engg Aligarh Muslim University Aligarh 202002, India +91-9897705269
Univ. Women’s Polytechnic Aligarh Muslim University Aligarh 202002, India +91-9027570413
[email protected]
[email protected]
[email protected]
network may not be able to provide all the error conditions, moreover, It is also expensive to rely on operator's network for unit testing requirements of an IMS Client.
ABSTRACT The IP Multimedia Subsystem (IMS), standardized by the 3GPP, is the most promising contender for replacing legacy, voicededicated mobile networks with an All-IP technology. As 3GPP IMS standards are in their embryonic state it becomes very crucial to test IMS clients during their development on a platform that simulates the IMS network. IMS client testbed also allows the developers to experiment all error circumstances which are not possible on a live network. Furthermore, it is also very costly to use an operator’s live network for testing purpose. This paper highlights challenges involved and our experience of building an IMS client test bed using open source tools like OpenIMScore.
2. CHALLENGES CONFRONTED During the development of the IMS test bed we faced two under given challenges: a. Test bed should be able to mimic various link characteristics (like LAN, Wi-Fi or GPRS/EDGE) that the IMS Client is supposed to come across. b. The test bed should be able to simulate all the policies which may be implemented by the operator on a live network. For example, an IMS client might have to work with different versions of IMS network or different algorithms (AKAv1, MD5 etc.)
Categories and Subject Descriptors C.2.1[Computer Communication Networks]: Network Architecture and Design - Packet-switching networks, Wireless communication
3. DIFFERENT CONNECTION OPTIONS
General Terms
Following are the different options that are available for clientserver connection that we used for our testbed.
Management, Performance, Design, Reliability, Experimentation, Verification.
3.1 LAN
Keywords
LAN support for the IMS Client was tested by configuring DHCP (Dynamic Host Configuration Protocol) server and DNS server. DHCP server was configured to send FQDN of SIP server and FQDN was converted to an IP address by hosting a DNS server (bind) in the network, ref. to figure 1.
IMS, NGN, 3GPP, OpenIMSCore, VoIP, Wi-Fi, WiMax, PoC.
1. INTRODUCTION IP services like VoIP (Voice-over-IP), IPTV (Television-over-IP) have already hit the market and many are in the pipeline, As a result end-users are turning more and more towards internet based technologies in their everyday lives outside the closed PC world. All these happenings create new perspectives regarding “MobileInternet”. IMS has emerged out as a big player in these circumstances which consists of an IP-based core network connected to multiple access networks to provide a converged service to wireless, wireline and cable subscribers. With the development of IMS clients, it also becomes essential to test their performance and to check compatibility issues over a platform
Figure 1. An IMS client and server connected via a LAN.
3.2 GPRS/ EDGE
which is am exact imitation of the live network. An IMS test bed serves the same requirements. Need of a testbed was felt as a live Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. ICWET’10, February 26–27, 2010, Mumbai, Maharashtra, India. Copyright 2010 ACM 978-1-60558-812-4…$10.00.
The GPRS/EDGE network does not allow traffic to reach external IP, this is major challenge in front of us and we beat this restriction by configuring the server with in the same IMS client’s radio access network [1]. This was done by using a phone having the same operator SIM card as a modem, ref to figure 2.
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International Conference and Workshop on Emerging Trends in Technology (ICWET 2010) – TCET, Mumbai, India
5. STUN SUPPORT FOR IMS CLIENT In order to support SIP signaling from behind the Network Address Translators, IMS clients are generally equipped with STUN [4]. STUN functionality of the IMS clients can be tested by using Vovida which is an open source STUN server. The client can send a STUN request to Vovida STUN server in the test bed if it wants to know its public IP and NAT [1], ref. to fig. 4. Figure 2. Interaction between IMS client and server over radio access network.
3.3 Wi-Fi Now most of the IMS devices are coming with the feature of WiFi so it becomes essential to test the device over a simulated WiFi network. For this we attached both the IMS client and the server on to a same Access Point (AP) ref. to figure 2. This helped us to realize Wi-Fi link between IMS client and server.
Figure 4. STUN server use
6. CONCLUSION Testing an IMS client is a challenging task. Development communities generally face difficulties in validating their IMS clients for the latest specifications during the development stages of the product. This proposed IMS test bed helps developers validate their product with the help of open source tools.
7. REFERENCES [1] Ahmed Hasswa, Abd-Elhamid Taha, Hossam Hassanein, “On Extending IMS Services to WLANS”, 32nd IEEE Conference on Local Computer Networks (LCN 2007), 2007 [2] OpenIMScore – Open source implementation of IMS Call Session Control Functions and Home Subscriber Service (HSS) - http://www.openimscore.org/ [3] RFC 3489 - Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs) http://www.ietf.org/rfc/rfc3489.txt [4] StrongSwan- Open-source IPsec-based VPN solution for Linux-http://www.strongswan.org. [5] T. Magedanz, D. Witaszek, K. Knuettel, Fraunhofer,“The IMS Playground @ Fokus – An Open Testbed For Next Generation Network Multimedia Services”,International Conference on Testbeds and Research Infrastructures for the DEvelopment of NeTworks and COMmunities [6] V Karthik M, Shadangi Prateek ,“Building an IMS Client Test Bed With Open Source Tools”. International Conference on IP Multimedia Subsystem Architecture and Applications(IMSAA), 2007.
Figure 3. Screenshot of HSS management console
4. IMS SERVER USED Open source OpenIMScore [2] was used to act as an IMS server while using fedora 9 as the platform. The Open IMS Core consists of three Call Session Control Functions (CSCFs), namely PCSCF, I-CSCF and S-CSCF, and a lightweight Home Subscriber Server (HSS), which together form the core elements of all IMS/NGN architectures as specified today within 3GPP, 3GPP2, ETSI TISPAN and the Packet Cable initiative. A snapshot of the HSS management console is given as fig 3. OpenIMScore supports transport mode security by being fully compliant to TS 33.203. OpenIMScore can easily simulate cases like unprovisioned SIM card registration, network initiated deregistration, and authentication failure. Security has always been an issue which has to be kept in the mind. A fully TS 33.203 compliant IMS client supports transport mode IPSec security. Cases in which a Wi-Fi enabled IMS client needs to make use of IMS services via Wi-Fi, tunnel mode IPSec security association can be used. There are many open source VPN servers that can be used e.g. Openikev2, raccoon2, ikev2 and StrongSwan. We used StrongSwan [3] in our testbed for this purpose. IMS client sets up a tunnel a VPN tunnel with the VPN server. All the SIP messages are transferred via this tunnel and then these messages are decrypted by the VPN server before forwarding them to the PCSCF server.
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