OVERVIEW OF ALL VOIP SOLUTIONS

Transcription

1 OVERVIEW OF ALL VOIP SOLUTIONS Kovács Gábor Parnaki Zsolt Gergı 13/03/2009

2 TABLE OF CONTENTS Introduction Overview of VoIP protocols Standard based implementations: H.323 SIP Proprietary solutions: Skype Cisco SCCP Deployment statistics 2

3 INTRODUCTION VoIP (Voice over Internet Protocol) is a general term for a family of transmission technologies for delivery of voice communications over packet-switched networks (eg. Internet). Why VoIP? Cost reducing, network convergence How? IP PBX, hosted VoIP or Skype? Functions of VoIP solutions: Signaling (e.g. SIP) Streaming (e.g. RTP/RTCP) Audio and video codecs (e.g. G.711 PCM) Supplementary services (e.g. H.450) AAA (Authentication, Authorization, Accounting) 3

4 INTRODUCTION: VOIP PROTOCOLS [1] Image source: Javvin Press 4

5 H.323: OVERVIEW Umbrella recommendation from the ITU-T [2] H.225.0: Call signaling, synchronization H.245: Control protocol for multimedia communication H.235: Security in H.323 network H.246: H.323/PSTN interworking H.450: Supplementary services (call waiting, forwarding, etc.) H.341: Network management H.510: Mobility for H.323 multimedia systems Uses RTP/RTCP for delivery of real-time data from one endpoint to another endpoint (or multiple endpoints in the case of multicast) H.323v1: 1996, H.323v2: 1998,, H323v6:

6 H.323: ARCHITECTURE Zones Administrative domains Gatekeeper (1/zone): manages the zone (e.g. admission control) Gateway: interoperability (e.g. IP/PSTN) MCU (Multipoint Control Unit): supports conference calls (MC+MP) Terminals IP phones, voic systems Softphones (e.g. NetMeeting) 6

7 H.323: PROS AND CONS Advantages: Precisely standardized (ASN.1) Flexible addressing (e.g. URI, E.164 numbers) Reliabile, scalable (alternate gatekeepers) Compact binary format (low bandwidth usage) Drawbacks: Complex signaling system Old (PSTN) Philosophy 7

8 SIP: OVERVIEW SIP (Session Initiation Protocol) by IETF, 1996 Application layer in the TCP/IP model Transport-independent (can run on TCP, UDP or SCTP) Text-based (like HTTP) Uses SDP to describe streaming media Latest version: RFC 3261, GPP signaling protocol (IMS) 8

9 SIP: ARCHITECTURE, SIGNALING 9 Image source: Erıs Levente SIP presentation (TMIT)

10 SIP: PROS AND CONS [4] Advantages: Simple, easy to implement Internet philosophy (vertical, open) Human readable message format Has future in IMS :) Drawbacks: Has no means to detect network failures Interoperability problems Large messages (sometimes exceeds the MTU size when going over WAN links delay, packet loss) Doesn t define a NAT/FW transversal mechanism (but you can still use STUN [8]) 10

11 SKYPE: OVERVIEW Baltic Success Story : Zennström, Friis, 2003 Acquired by ebay in September 2005 for $2.6 billion [5] The closed source client uses an undocumented, proprietary, encrypted protocol Issues in China TOM-Skype (censoring, logging) Lack of lawful interception (CALEA) Peer-to-peer overlay network (based on Kazaa) instead of the classic client-server model Decentralized (apart from the Login Server) Free pc-to-pc, cheap PSTN and PLMN calls RSA for key negotiation, AES to encrypt conversations TCP signaling, UDP/TCP transfer 11

12 SKYPE: ARCHITECTURE Login session [7] Connecting to a supernode Authentication with login server Presence advertisement to other peers (alternate table) NAT/FW determination Discovery of online Skype nodes with public IP List of supernodes and their IP addresses are stored in the Host Cache (HC) User data in GI Global Index There is also a centralized DB Results cached in intermediate nodes Signaling and media transfer (direct or forwarded) ordinary hosts Skype login servers login supernodes 12

13 SKYPE: PROS AND CONS Advantages: Easy to use Distributed (p2p), worldwide system Large user base (market leader) Very good scalability BUT no interop with SIP Secure (encrypted) communication STUN and TURN protocols to bypass NAT/FW [8] ilbc, isac, SVOPC, SILK audio codecs (low latency) Drawbacks: Proprietary, closed solution Legal problems (FCC E911, CALEA) Client cannot prevent itself from becoming a supernode (unwanted traffic), NO SLA! 13

14 CISCO SCCP: OVERVIEW Cisco Skinny Call Control Protocol Originally developed by Selsius Corporation (1997) Signaling between a Skinny Client (e.g. Cisco 79xx IP phone or Cisco IP Communicator softphone) and the Cisco Call Manager (CCM) Current version: Cisco Unified Communications Manager 7.0 (September 2008) CCM acts as a signaling proxy for call events initiated over other common protocols (mostly H.323) H.323 is too resource demanding for embedded devices Easier enterprise deployment 14

15 CISCO SCCP: ARCHITECTURE Image source: Cisco Systems, Inc. CallManager typically installed on a Cisco Media Convergence Server (MCS) H.323 and MGCP interoperability 15

16 CISCO SCCP: PROS AND CONS Advantages: Lightweight Scalable Easy to deploy and upgrade Easy to add PBX features (e.g. IVR function) Ideal for enterpise users Drawbacks: Actually it is not a VoIP solution by itself SCs cannot communicate directly Proprietary 16

17 DEPLOYMENT STATS Enterprise solutions in the U.S.: 2005: VoIP revenues reach $1 billion 2007: PSTN PBX market shrinks to $1 billion 50% of global telecom traffic is handled over IP Consumer VoIP: December 2007, Ipoque (3TB data sample): 1% VoIP traffic, 30% of users using VoIP, Skype accounts for 95% of all VoIP data 2009, Ipoque Internet Study (figure) SIP generates over 50% of all VoIP traffic in most regions Skype is #1 in Eastern Europe and the Middle-East Vonage (SIP) subscribers: Sept 2005: 1M Feb 2006: 1,4M 17

18 DEPLOYMENT STATS: SKYPE 18

19 DEPLOYMENT STATS: SKYPE 19

20 REFERENCES [1] VOIP Technology Quick Guide.: Javvin Press, 2008 [2] ITU-T Rec. H.323, "Packet-Based Multimedia Communications Systems," Geneva, Switzerland, Jan [3] T. Velte, A. Velte, Cisco: A Beginner's Guide.: McGraw-Hill, [4] J. Davidson, J. Peters, B. Gracely, Voice Over IP Fundamentals: A Systematic Approach to Understanding the Basics of Voice Over IP.: Cisco Press, 2000 [5] ebay to Acquire Skype press release [Online].: [6] M. Gough, B. Campbell, Skype Me!: From Single User to Small Enterprise and Beyond.: Syngress, 2006 [7] S. A. Baset, H. Schulzrinne, An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol.: Columbia University, 2004 [8] J. Rosenberg, J. Weinberger, C. Huitema, and R. Mahy, STUN: Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs). RFC 3489, IETF, Mar