MM_intro_07.ppt

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Multimedia Services in the Internet

Dr. Dorgham Sisalem

[email protected]

Tekelec Confidential

Tekelec Confidential / For Discussion Purposes Only /

Non-Binding

Goals

• Overview of multimedia service

• 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 speach recognition Audio and video hardware MMS or video over GSM Where to get the latest movies or how to copy a DVD



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Structure

• Pre-requirements Good understanding of IP networking principles

• 2-Hour credit

• Exam 10-12 10.07.07

• Office hours: After the lecture

• Contact: [email protected]

• Slides:

http://www.iptel.org/~dor/uni.htm



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References

• www.ietf.org (RFCs and drafts)

• www.iptel.org (SIP tutorial)

• www.cs.columbia.edu/~hgs/internet XXXX

• 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“



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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.



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Topics: Introduction

• Introduction to Internet Very brief covering

Difference between IP and PSTN Basic concepts Transport protocols: TCP, UDP, RTP

Why use UDP for VoIP and TCP for signaling? What is the difference between RTP and RTCP

You are expected to have visited the networking lecture of Prof. Wolisz



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Topics: VoIP

• What is VoIP

• Signaling

• Addressing

• Intelligent services

• Deployment problems: NAT, emergency

• Integration with PSTN



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Topics: VoIP

What happens during this registration?



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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?



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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?



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Problems of VoIP

• Why doesn’t VoIP work over my DSL link What are the problems of network address tarnslators? How to deal with firewalls

• Regulatory issues How can I call the 110?

• Scalability How do I build a reliable carrier-grade VoIP infrastructure

• Security What kind of attacks can we expect



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Group Communication

• What is the difference between broadcast and multicast

• How does a conference bridge work

• What solution is best fro which scenario?



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Peer-To-Peer Networking

• How do P-2-P solutions work?

• What solutions exist?

• What is Skype?

• Basic concepts and approaches



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Instant Messaging and Presence

• What is presence and IM

• Basic concepts and approaches

• What solutions and technologies exist

• What are the current standards

• Relation to VoIP



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Streaming

• How are resources 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?


Public Switched Transmission Network

PSTN



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Public Switched Transport Network (PSTN)

• Exists now for around 100 years

• 800 M Subscribers

• Optimized for 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)

InternationalIdentity2 digits

NationalIdentity2-to-5 digits

UserIdentity11 to 5 digits

SubaddressUp to 40 digits



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PSTN Architecture in Germany

AVStAuslandvermittlungsstelle

Ca. 50 HVStHauptvermittlungsstelle

Ca. 550 KVStKnotenvermittlungsstelle

Ca. 500 OVStOrtvermittlungsstelle

Ca. 40 M Teilnehmer

Fern

netz

Ort

sn

etz

Ref. Prof. Dr.-Ing. Habil. Lutz Winkler, FH Mittweida



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Routing in PSTN




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Switching in PSTN


Capacity 10099 calls

active

busy



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Resource Sharing (TDM)

• Time division multiplexing (TDM) Allocate a time slot to a each call

Resources are guaranteed

May under utilize channel with idle senders Applicable only for a fixed number of flows Requires precise timers

Multiplexer1 link, 30kb/s speed

10 kb/s10 kb/s

10 kb/s



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Intelligent Service in PSTN




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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)



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• Allow calls to a generic number: No costs for the caller, final location decided based on time of day ….

Example of Free Call



Introduction to the Internet



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General Words

• Since more than 20 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 x countries and uses the TCP/IP protocols to form a single, cooperative virtual network”. (Comer)

• intranet: connection of different LANs within an organization Private may use leased lines usually small, but possibly hundreds of routers may be connected to the Internet (or not), often by firewall



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Packet Switched Communication

End Users End Users

Data Packets (Voice, Video, Games, Signaling…)

Router



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What‘s a network?

• 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

12

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What‘s a Protocol?

• Protocol: rules by which active network elements communicate with each 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, ...)



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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



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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 (A later discovery. How many ARPAnets could the world support? A few

hundred, maybe… ?)



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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. New applications can be introduced at end systems with no need for network

upgrades.



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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

Multiplexer5 kb/s

1 link, 30kb/s speed

20 kb/s

5 kb/s



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Resource Sharing (Statistical)

• Statistical multiplexing Resources are NOT guaranteed Need Mechanisms to prevent congestion and domination

Multiplexer5 kb/s

1 links, 30kb/s speed, 50% Loss

50 kb/s

5 kb/s



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Who runs the Internet?

• “nobody”

• standards: Internet Engineering Task Force (later. . . )

• names: Internic (US), RIPE (Europe), . . .

• numbers: IANA (Internet Assigned Numbers Authority)

• network: ISPs (Internet Service Providers), NAPs (Network Access Points), DFN, . . .

• fibres: telephone companies (mostly)

• content: thousands of companies, universities, individuals, . . .



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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



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Host Count



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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



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An Example Network

USER Local Loop Carrier

Point of Presence

Backbone



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Network Access Point: Chicago NAP



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Making the Standards

• Internet Architecture Board: IAB architectural oversight elected by ISOC

• Internet Engineering Steering Group (IESG) approves standards

• Internet Society: ISOC Conferences “hosts” IANA

• Internet Assigned Number Authority: IANA keeps track of numbers delegates Internet address assignment

• Internet Engineering Task Force: IETF Define the problems and specify solutions to them Run by interested people (people should contribute in person and not as company

representatives)



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RFCs and Drafts

• “Request for Comments”, since 1969

• most RFCs are not standards!

• Internet drafts: working documents, but often used for prototypes

• edited, but not refereed

• numbered sequentially (Spetember 2002: more than 3600)

• check the April 1 ones. . . (RFC 1149)

• ftp://ds.internic.net/rfc



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TCP/IP Stack

Link Link Link

Network

Transport

Application Application

Transport

Network Network

TCP/IP

HostHost Router

EthernetCable,UMTS

IP, IPv6

TCP, UDP,SCTP

VoIPEmail ..



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Internet Protocol

• Deliver an IP packet from host to host(s)

• Connectionless, unreliable No loss handling No flow or congestion control

UDPTCP

RTP

VoIP

AALx

GPRS V.xSONETEthernet ATM

PPP

IPv4/IPv6

DNSFTPHTTPSMTP

ICMP



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Internet Names

• Physical link address Ethernet, ATM ... Flat

• IP address Identify an interface Topological

• IP Name Identify the object to reach Hierarchical



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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



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Internet Packets

• A lot of headers describing the different layers

Phy IP UDP/TCP

Body



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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: MBZ: 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



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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



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IPv6: Why move to another protocol?

• Lack of IP addresses Support for nearly endless range of addresses

• Explosion of routing tables Allow for better aggregation and routing hierarchies

• Better handling of options Reduce complexity of IP header

• Better support for management and administration auto configuration and renumbering Support plug&play

• Need for better support for mobile and secure communication Remove the need for network address translators

Really?

• Better support for QoS (which is not correct)



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• 14 fields, at least 20 octets

• 32 bit addresses

• fragmented packet processing at every hop

• header checksum recalculation at every hop

• variable Options field for extra processing information

• 8 fields, fixed 40 octet size

• 128 bit addresses

• fragmentation only in endpoints, or lower layer Usage of Path MTU discovery

• no checksums Already in lower layers

• new 20 bit flow label field

• options in Extension Headers

IPv4 vs. IPv6 Header



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IP Names

Oxany.fokus.fhg.de

host name (has IP address)

organization type or country

Organization administering

subnames to left

organization administering

host


Getting From A to B



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Getting from A to B

• Know name: need to know IP address Domain Name System (DNS)

• Know IP address: need to know the way


Getting From A to BName to IP Address



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Domain Name System

• The Domain Name System (DNS) is a distributed database that is used by TCP/IP applications to… map between hostnames and IP addresses, and to provide application routing information.

• Distributed database: No single site on the Internet “knows it all.” Each site maintains its own database and runs a server that other

systems on the Internet can query.

• DNS is the client/server protocol.



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Domains

• Top level domains arpa domain

Special domain for address-to-name mappings

generic (organizational) domains 3-character domains (e.g. edu, com, org, …)

Country (geographical) domains 2-character domains Found in ISO 3166 Some countries form second-level domains

e.g.: .ac.uk is for academic institutions in the United Kingdom.

New generic top level domains (gTLD) .biz, .tv, .name, .aero ...

• Note: No single entity manages every node.



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DNS hierarchical name space

arpa

com edu gov int mil net org

de us

unnamed root

wsu

eecs math

gazoo

top level domains

•Node labels up to 63 characters.•Root node has null label.•Comparisons are case insensitive.•Domain name formed as follows:

•start at node and work toward root•use a “dot” to separate labels

Maintained by DeNIC



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Resolvers and Name Servers

• Applications (clients and servers) contact a DNS server by calling functions in a library known as a resolver. The resolver is accessed through the functions gethostbyname() and

gethostbyaddr(). The resolver code is in a system library and is linked into the application.



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DNS Operation

• What does a server do when it does not have the requested information? Every name server must know how to contact the root name servers (via

IP address). Name server contacts a root server Root servers know the name and IP address of all the second-level

domains Each names server caches information from recent queries.



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Practical

• nslookup

• http://www.internic.org


Routing Packets from A to B



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Hierarchical PSTN Routing

030 040 050 060



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Distributed IP Routing

Enterprise

AccessAccess

AccessCore

Core

PictureTel

193.175.135.21

195.37.78.225



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IP Routing

• How to get from A to B? Different paths are possible!! Neither A nor B know the best path in advance!!

• Goal: set routing tables for packet forwarding in hosts and routers, typically based on some optimality criterion.

• Questions: who determines entries? based on what information (hops, delay, cost, ...) ? how often does it change (hop vs. delay)? where is routing information stored? algorithm used to compute routes?



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IP Routing: Goals

• scalability

• “safe” interconnection of different organizations

• adopt quickly to changes in topology

• avoid routing loops or at least terminate them quickly

• self-healing, robust

• Distributed: No central component to determine the path

• efficient: can’t use 90% of bandwidth for routing info

• multiple metrics (QOS, price, politics, ...) not yet

• routes should be (near) “optimal”

• can’t have all hosts/networks in single table hierarchical



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IP Routing

• Every router needs to determine the next hop to which to send the data

• Routing database: one entry for every possible destination in the system: Destination address: the IP address of the host or network; Next hop: the first router along the route to the destination; Interface: the physical network which must be used to reach the first hop Metric: a number, indicating the distance to the destination; Timer: the amount of time since the entry was last updated; Flags and other internal information.

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IP Routing

• DB initialization: description of the entities that are directly connected;

• DB update: messages from neighboring gateways.

• Decision taken based on topology and updated continously No gurantee that two packets will follow the same path

• ifconfig (ipconfig)

• Netstat

• http://www.traceroute.org/



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Intra-Domain Routing

• Set the routes inside an autonomous system (AS) AS: a a collection of routers

and system administered by one entity

Has a AS number assigned by IANA

• Different ASs might use different intra-domain routing schemes

• Changes in one AS do not effect other domains

• AS connects to another AS through one or more border routers

Enterprise

Access Access

AccessCore

Core



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Dr. Dorgham SisalemDirector, Strategic ArchitectureTekelec Network Signaling GroupTel.:+49 30 32 51 32 14E-mail: [email protected]

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