Multimedia Services in the Internet

1. Multimedia Services in the Internet Dorgham Sisalem / Sven Ehlert FhG Fokus sisalem@fokus.fhg.de sip:sisalem@iptel.org

2. Lecture Overview • Introduction to the Course • Goals • Administrative Stuff • Topics covered • Basic Networking Principles Refresh • PSTN • IP Networking • Routing

3. Goals • Overview of multimedia service (SIP) • Understanding of multimedia services in the Internet • Understanding of the general pictures • Transport protocols, signaling, traffic types, QoS • Practical experience with protocols and applications • Basic knowledge of the different involved protocols and concepts • We are not dealing with: • Audio and video compression • Web programming • Image processing or speech recognition • Audio and video hardware • MMS or video over GSM • Where to get the latest movies or how to copy a DVD

4. Structure • Pre-requirements • Good understanding of IP networking principles • 2-Hour credit • Written exam on 11.7 • There is no second exam date • There are no other exam means (oral …) • Office hours: After the lecture • Contact: • sisalem@fokus.fraunhofer.de • Slides • http://www.tkn.tu-berlin.de/curricula/ss06/vl-mkn/index.html • Basically still valid but will be updated soon

5. References • www.ietf.org (RFCs and drafts) • www.iptel.org (SIP tutorial) • www.cs.columbia.edu/~hgs/internet Schulzrinne Overview • Stevens, „TCP/IP Illustarted, V1“ (basic protocols) • Ferguson, Huston, „Quality of Service“ (general QoS stuff) • Henry Sinnreich and Alan B. Johnston „Internet Communication Using SIP: Delivering VoIP and Multimedia Services with Session Initiation Protocol“ • Olivier Hersent, David Gurle, Jean-Pierre Petit,“IP Telephony“ • Huitema, „IPv6“ • Wikipedia

6. Acknowledgements • Slides based on work of Henning Schulzrinne, Jim Kurose, Michael Smirnov, Georg Carle, Jiri Kuthan, Heikki Waris, Kevin Fall, Jim Chou, Thinh Nguyen, Vishal Misra, Steve Deering, Geert Heijenk, Ofer Hadar, John Floroiu, Nick McKeown, Eric D. Siegel, Ibrahim Matta, Steven Low, Vincent Roca, Nitin H. Vaidya, Charles Lang as well many other anonymous contributers.

7. Topics: Introduction • Introduction to Internet • Very brief covering • Difference between IP and PSTN • Basic concepts • Transport protocols: TCP, UDP, SCTP, RTP • Why use UDP for VoIP and TCP for signaling? • What are the benefits of SCTP • What is the difference between RTP and RTCP • You are expected to have visited the networking lecture of Prof. Wolisz

8. Topics: VoIP • What is VoIP • Signaling • Addressing • Intelligent services • Deployment problems: NAT, emergency • Integration with PSTN

9. Topics: VoIP What happens during this registration?

10. Topics: VoIP What does this address mean? How do we find the other side? How do we call a PSTN number? What happens when we press call?

11. VoIP in UMTS • What does IMS stand for? • Basic concepts of UMTS • What is the difference to normal VoIP? • How does it work? • Why a special version?

12. Problems of VoIP • Why doesn’t VoIP work over my DLS link • What are the problems of network address translators? • How to deal with firewalls • Regulatory issues • How can I call the 110? • QoS • Is it true that VoIP has bad voice quality

13. Streaming • How are resource described? • What happens when we press play? (signaling) • What does it mean when it says “buffering” or ran out of buffer • What protocols exist and how do they work?

14. Peer-To-Peer Networking • How do P-2-P solutions work? • What solutions exist? • What is Skype? • Basic concepts and approaches

15. Instant Messaging and Presence • What is presence and IM • Basic concepts and approaches • What solutions and technologies exist • What are the current standards • ICQ, Yahoo, MSN, etc is NOT a standard • Relation to VoIP

16. Group Communication • What is the difference between broadcast and multicast • How does a conference bridge work • What solution is best for which scenario?

17. Quality of Service (QoS) Control • Why is the voice communication over the Internet not understandable some times? • What can we do at the end system to improve the QoS? • What can we do in the network to improve the QoS? • Why can’t we find a network that deploys QoS concepts

18. Public Switched Transmission NetworkPSTN

19. Public Switched Transport Network (PSTN) • Exists now for around 100 years • 800 M Subscribers • Supports Voice and Data (Fax) services • Guaranteed bandwidth share • In one country only a few exist • usually a big one controlling the whole network • Cost of switching equipment high (A few millions for a carrier grade switching component • Signaling to session establishment and control based on SS7 • Hierarchical address structure (E.164) International Identity 1-3 digits National Identity 2-to-5 digits User Identity 11 to 5 digits Subaddress Up to 40 digits

20. PSTN Architecture in Germany AVSt Auslandvermittlungsstelle Fernnetz Ca. 50 HVSt Hauptvermittlungsstelle Ca. 550 KVSt Knotenvermittlungsstelle Ca. 500 OVSt Ortvermittlungsstelle Ortsnetz Ca. 40 M Teilnehmer Ref. Prof. Dr.-Ing. Habil. Lutz Winkler, FH Mittweida

21. Routing in PSTN Ref. Prof. Dr.-Ing. Habil. Lutz Winkler, FH Mittweida

22. Switching in PSTN Capacity 100 99 calls active busy Ref. Prof. Dr.-Ing. Habil. Lutz Winkler, FH Mittweida

23. Resource Sharing (TDM) • Time division multiplexing (TDM) • May under utilize channel with idle senders • Applicable only for a fixed number of flows • Requires precise timers • Resources are guaranteed 1 link, 30kb/s speed 10 kb/s Multiplexer 10 kb/s 10 kb/s

24. Intelligent Service in PSTN Ref. Prof. Dr.-Ing. Habil. Lutz Winkler, FH Mittweida

25. Intelligent Service in PSTN • Service switching point (SSP): A switch enhanced with logic for identifying IN services • Service Transfer Point (STP): Interface of the switch to the IN environment • Service Control Point (SCP): Control the execution of the service • Service Management System (SMS): Control and manage the available services and provide the interface for adding new ones • Intelligent Peripheral: Additional components for providing certain services such as announcements • Feature Node: Execute services provided by private entities (similar to SCP)

26. PSTN Summary • Guaranteed Quality of Service • Intelligence in the Network • Signaling and Media tightly coupled • Scalability and Extension difficulties

27. Introduction to the Internet

28. General Words • Since 21 Years with the same technology (TCP/IP) • Moved from 4 sites in 1968 to around 200 M hosts today • Flat addressing and routing architecture • Based on packet switching • (the) Internet: “collection of networks and routers that spans xcountries and uses the TCP/IP protocols to form a single, cooperativevirtual network”. (Comer) • intranet:connection of different LANs within anorganization • Private • may use leased lines • usually small, but possibly hundreds of routers • may be connected to the Internet (or not), often by firewall

29. Packet Switched Communication End Users End Users Router Data Packets (Voice, Video, Games, Signaling…)

30. What‘s a network? 1 2 1 2 • Host: Communication end point (PC, PDA, cell phone, coffee machine ...) • Link: carry bits from one place to another (or maybe to many other places) • Switch/gateway/router: move bits between links, forming internetwork • IP router receives a packet from one interface and sends it out over another

31. What‘s a Protocol? • Protocol: rules by which active network elements communicate witheach other • protocols = “algorithms + data structures” • formats of messages exchanged • actions taken on receipt of messages • how to handle errors • hardware/operating-system independent • real-life examples: • rules for meetings • conversational rules (interrupts, request for retransmission, ...)

32. Protocol Mechanisms(What Do Protocols Do for a Living?) • All or some of the following: • addressing/naming: manage identifiers • fragmentation: divide large message into smaller chunks to fit lower layer • resequencing: reorder out-of-sequence messages • error control: detection and correction of errors and losses • retransmission; forward error correction • flow control: avoid flooding/overwhelming of slower receiver • congestion control: avoid flooding of slower network nodes/links

33. Architectural Requirements of the Internet • Generality • Support ANY set of diverse applications, • Heterogeneity • Interconnect ANY set of network technologies • Robustness • More important than efficiency • Extensibility • More important than efficiency • Scalability

34. End-to-End Principle Foundation of the Internet architecture: • Dumb network, smart end systems • (Exact opposite of telephone network!) • Dumb networks: require only least common service • Datagram service: no connection state in routers • Best effort: all packets treated equally. • Can lose, duplicate, reorder packets. • Smart hosts: • Maintain state to enhance service for applications. • “Fate-sharing”-- If a host crashes and loses communication state, applications that are communicating share this fate.

35. Resource Sharing (Statistical) • Statistical multiplexing • Traffic is sent on demand, so channel is fully utilized if there is traffic to send • Any number of flows 1 link, 30kb/s speed 5 kb/s Multiplexer 20 kb/s 5 kb/s

36. Resource Sharing (Statistical) • Statistical multiplexing • Resources are NOT guaranteed • Need Mechanisms to prevent congestion and domination 1 links, 30kb/s speed, 50% Loss 5 kb/s Multiplexer 50 kb/s 5 kb/s

37. Who runs the Internet? • “nobody” • standards: Internet Engineering Task Force • names: Internet Corporation for Assigned Names and Numbers (ICANN) • numbers: IANA (Internet Assigned Numbers Authority) • network: ISPs (Internet Service Providers), NAPs (Network AccessPoints), DFN, . . . • fibres: telephone companies (mostly) • content: thousands of companies, universities, individuals, . . .

38. How big is the Internet? • Many measures: • networks (routed entities) • domains, host names (but: several names per host!) • directly (continuously) attached hosts (“ping’able”) • IP-connected hosts (SLIP, PPP) • firewalled hosts • e-mail reachable • As of January 2006, over 1 billion people use the Internet according to Internet World Stats

39. Host Count

40. What Networks are There? • Access (ISP): • Carry data from users • Core • Carry data from access • Network peering points • Connect networks together • Some enterprises might be connected directly to core networks

41. An Example Network Backbone USER Local Loop Carrier Point of Presence

42. RFCs and Drafts • “Request for Comments”, since 1969 • most RFCs are not standards! • Internet drafts: working documents, but often used forprototypes • edited, but not refereed • numbered sequentially (Jan 2006: more than 4000) • check the April 1 ones. . . (RFC 1149) • ftp://ds.internic.net/rfc

43. TCP/IP Stack TCP/IP Application Application VoIP Email .. Transport Transport TCP, UDP, SCTP Network Network Network IP, IPv6 Link Link Link Ethernet Cable, UMTS Host Host Router

44. Internet Protocol • Deliver an IP packet from host to host(s) • Connectionless, unreliable • No loss handling • No flow or congestion control VoIP RTP DNS SMTP HTTP FTP UDP ICMP TCP IPv4/IPv6 PPP AALx Ethernet GPRS SONET V.x ATM

45. Internet Names • Physical link address • Ethernet, Token Ring, FDDI.. • Flat • IP address • Identify an interface • Topological • IP Name • Identify the object to reach • Hierarchical

46. IP Addresses • Identify an interface not host: • A host can have more than 1 address • IP addresses are 32-bit numbers (4.3 billion of them!) • Divided into parts: (network prefix, host number) • 4 decimal numbers, called “dotted quad” • Each (decimal) number is one byte • Example: 128.32.25.12 • Can generally be used in place of names

47. Special Addresses • Private addresses: Only of meaning inside an intranet • 172.16 through 172.31 16 • 192.168.0 through 192.168.255 256 • Loopback: 127.0.0.1 (local interface) • Local broadcast: all 1 (receive by all members of link) • Multicast: • 224.0.0.0 239.255.255.255 • Do not describe a host or interface but a group of receivers • Reserved: 240.0.0.0 255.255.255.255

48. Internet Packets • A lot of headers describing the different layers Phy IP UDP/ TCP Body

49. IP Header • Version: 4 or 6 • Header length: number of 32 bit words of header • Type of Service: delay, throughput, reliability, monetary • Total length: length of packet in bytes • Identification: identify packet • Flag: • Do not fragment • More fragments • Fragmentation offset: Distance from the first bit of the original packet • Time-to-Live: Avoid loops • Protocol: Which protocol is used (TCP, UDP, ICMP ..) • Header Checksum: Calculated over IP header • Source address: Address of sender • Destination address: Address of receiver

50. IPv6: Why move to another protocol? • Lack of IP addresses • Support for nearly endless range of addresses • Better handling of options • Reduce complexity of IP header • Better support for management and administration • auto configuration and renumbering • Support plug&play • Higher Packet sizes (Jumbograms) • Need for better support for mobile and secure communication • Remove the need for network address translators • Really?