Converged Networks. Objectives. References

Transcription

1 Converged Networks Professor Richard Harris Objectives You will be able to: Discuss what is meant by convergence in the context of current telecommunications terminology Provide a network architecture perspective of a converged network Describe the protocols that are likely to underpin NGN Discuss methods of providing QoS in NGNs Semester Advanced Telecommunications Slide 2 References IFIP Conference papers on Converged Networking Semester Advanced Telecommunications Slide 3 1

2 Presentation Outline What do we mean by converged networks? How will they evolve? Competing protocols. Challenges for: network planners, network managers and teletraffic engineers Conclusions Semester Advanced Telecommunications Slide 4 What is a converged network? In a converged network environment, the user s voice network should work in an identical way to their data network and vice versa. This means that the way in which a user performs actions should be completely transparent irrespective of whether they are operating in the data (IP or ATM) or the voice world. The challenge is to improve on the traditional POTS network for subscribers and provide a new and more powerful environment PANS!. Semester Advanced Telecommunications Slide 5 How will converged networks evolve? Existing networks are set up with xdsl and this enables PC traffic to enter a data network and voice traffic to enter the PSTN in a manner where each is oblivious to the other. This will change as convergence occurs. In a truly converged network, all traffic will be carried on a IP-based voice/data network in a unified and powerful manner. Intelligent user phones, terminals and IP based gateways are coming to market with specially designed protocols such as SIP and MGCP (Mega Gateway Control Protocol) Semester Advanced Telecommunications Slide 6 2

3 Network Scenario 1 Semester Advanced Telecommunications Slide 7 Network Scenario - 2 Semester Advanced Telecommunications Slide 8 New features unavailable in current PSTN New features include: Unified messaging Voice, fax, integration on a unified system IP-enhanced services Feature mobility, CD-quality voice, PC phone calls Enhanced class features Selective call waiting, group ring, find-me and follow-me services Subscriber Control tools Web and Palm based applications and plugins for self provisioning and management of call and messaging features, usage and billing information. All of this will be enabled through a new concept known as a soft-switch. Semester Advanced Telecommunications Slide 9 3

4 Challenges: Network managers The PSTN has set high standards for quality and reliability. These standards have to be achieved and exceeded for this to succeed. Reliability Active calls preserved in the event of failure % availability of the service No single point of failure Software and hardware reliability and fault tolerance Semester Advanced Telecommunications Slide 10 Challenges: Network planners Scalability of the solutions Ability to handle more service instances New features and services for subscribers Affordability of the solutions for subscribers Reliability and scalability must be met simultaneously Can the above be achieved in a distributed environment? Semester Advanced Telecommunications Slide 11 Challenges: Teletraffic engineers Multiple classes of traffic Self similar or very bursty traffic to be modelled. Separation of class of service QoS requirements. How can this be achieved and managed? How to measure the data? Where to measure the data? How to translate the measured data into useful models for performance and dimensioning? Semester Advanced Telecommunications Slide 12 4

5 Which protocols? A major problem is that there are many competing protocols, which ones will win out in the end? SIP = Session Initiated Protocol MGCP = Mega Gateway Control Protocol MEGACO = Media Gateway Controller H.323 How to communicate to existing systems like SS7, ISDN in the period where the PSTN and converged networks should co-exist? Semester Advanced Telecommunications Slide 13 About the protocols - 1 H.323 First of the new generation protocols. Is actually a multimedia protocol that has a wide following and installed base as it is currently used for VoIP applications. Developed by the ITU not the IETF! SIP Intended to be more flexible than H.323 it is an application layer protocol that can establish, modify and terminate sessions or calls. It is text based and lightweight. Developed by the IETF Scalable, faster than H.323 and carrier grade Semester Advanced Telecommunications Slide 14 About the protocols - 2 MGCP Merger of the IETF protocol device control IPDC and Bellcore s simple gateway control protocol SGCP. Used currently for media gateways, ATM routers, cable modems and set-top boxes. Differs from SIP in that it believes intelligence resides in the core of the network not at the edges. Might be another candidate for telephony services? MEGACO Also known as H.248 MEGACO is being developed by the ITU. In its early stages of development. Semester Advanced Telecommunications Slide 15 5

6 Conclusions Clearly, the main challenges are to determine appropriate methods for ensuring QoS is transferred from the PSTN to the new converged network in a manner that is transparent to the user. Many problems to be overcome before the true dream of converged networks is realised. Semester Advanced Telecommunications Slide 16 Achieving QoS in IP Networks By Richard Harris Presentation Outline Comparison of ATM and IP QoS definitions Integrated Services architectures DiffServ architectures Queueing models for QoS access Introduction to MPLS Semester Advanced Telecommunications Slide 18 6

7 What is QoS Service Quality Bandwidth Delay Jitter - Loss / Errors Quality Service = Good Service Quality Class of Service Prioritisation Best Effort Service Better than Best Effort Better than Better than Best Effort Quality of Service Guarantee of Service Quality Semester Advanced Telecommunications Slide 19 ATM QoS Definitions QoS Parameters Cell Delay Variation Max Cell Transfer Delay Cell Loss Ratio Traffic Parameters Peak Cell Rate Sustainable Cell Rate Maximum Burst Size Cell Delay Variation Tolerance CBR n/a n/a Service Category rt_vbr nrt-vbr Not specified Not specified Source: Table 2.1, ATM Forum Traffic Management Specification v4.1 Semester Advanced Telecommunications Slide 20 IP QoS Definitions? QoS Parameters Packet Delay Variation (Jitter) Packet Transfer Delay (Latency) Packet Loss Ratio Traffic Parameters Peak Throughput Guaranteed Throughput Maximum Burst Size Max Packet Delay Variation Gold n/a n/a Service Category Silver Bronze Not specified Not specified Semester Advanced Telecommunications Slide 21 7

8 Integrated Services Architecture (IntServ) Based on RFC June 94 Combines Best Effort Service (Elastic) Guaranteed (real time) service Controlled Load service Extension to IP model Resources Reserved within Routers Provides CAC uses RSVP Semester Advanced Telecommunications Slide 22 IntServ Network Semester Advanced Telecommunications Slide 23 IntServ Reference Model Reservation Agent Management Agent Routing Agent Admission Control Traffic Control Database Routing Database Scheduler Input Classifier Forwarder Output Scheduler Semester Advanced Telecommunications Slide 24 8

9 IntServ Disadvantages All routers must maintain per state flow High overhead for low rate connections All routers must perform CAC Poor scalability Semester Advanced Telecommunications Slide 25 Differentiated Services Architecture (DiffServ) Scalable architecture (RFC2475) Packets classified into aggregated traffic classes at the edge of the network Packets Marked at DSCP (RFC2474) Different Per Hop behaviours are applied Semester Advanced Telecommunications Slide 26 DiffServ Domain Semester Advanced Telecommunications Slide 27 9

10 DiffServ Ingress Router DiffServ Policy Manager Routing Agent Admission Control Marker Control Meter Routing Database Marker Scheduler Input Classifier Forwarder DSCP Output Classifier Scheduler Semester Advanced Telecommunications Slide 28 DiffServ Interior Router Routing Agent Routing Database Scheduler Input Forwarder DSCP Output Classifier Scheduler Semester Advanced Telecommunications Slide 29 DiffServ Advantages No hop by hop signalling No per flow or per customer state Aggregate classification state only Small set of forwarding behaviours Complex classification/conditioning functions at boundary routers only Simple packet classification at interior routers Semester Advanced Telecommunications Slide 30 10

11 QoS Mechanisms The following list of options describe possible approaches to providing QoS in the Internet Bandwidth Queueing Admission Control MPLS Others have been tried, we ll discuss the mechanisms presented in the list above. Semester Advanced Telecommunications Slide 31 Bandwidth Solution Provide more bandwidth! This is a brute force solution Optical fibre WDM Capacity is the fastest growing Not very sensible as a solution growth years WDM Internet Moore POTS Semester Advanced Telecommunications Slide 32 Queueing Packet networks are networks of queues -based Queue manipulation is a simple extension to the basic Internet architecture Many styles of queueing have been proposed: µ Semester Advanced Telecommunications Slide 33 11

12 Priority Queueing Separate traffic according to priority Simple to implement no state Requires careful engineering µ Semester Advanced Telecommunications Slide 34 Random Early Discard (RED) Discard packets randomly once queue threshold exceeded Triggers TCP congestion avoidance to slow flows No effect on UDP traffic This method targets the biggest flows Many variations have been developed in recent years, including Blue, Green, etc! Prob(drop) Queue size Semester Advanced Telecommunications Slide 35 Fair Queueing Flows serviced fairly on packet by packet basis Prevents flows interfering State information per queues Variations: weighted FQ, stochastic FQ µ Semester Advanced Telecommunications Slide 36 12

13 Class Based Queueing Round robin servicing of classes Flexible pre-assigned allocation to traffic classes Rotation time trade off between jitter and fairness µ Semester Advanced Telecommunications Slide 37 Admission Control Required for hard QoS Per connection (RSVP) Traffic Policing delay load Semester Advanced Telecommunications Slide 38 Resource ReserVation Protocol - RSVP Signalling protocol to request specific QoS service from the network Admission control Policy control Filter spec / Flow spec Semester Advanced Telecommunications Slide 39 13

14 Token Bucket Tokens Token Bucket Data Queue Regulator Semester Advanced Telecommunications Slide 40 Multi-Protocol Label Switching (MPLS) Add label to packet with link specific significance Arbitrary mappping of IP flows to Forwarding Equivalence Classes (FEC) Separate Forwarding (label based) from Routing (address based) Multiprotocol Label Switching Architecture (RFC 3031) Semester Advanced Telecommunications Slide 41 Labels ATM / Frame Relay L2 Header L3Header L4 Header and Data PPP / Ethernet etc L2 Header Label L3Header L4 Header and Data Semester Advanced Telecommunications Slide 42 14

15 MPLS Network LSR LER Label Edge Router (LER) LSR LSR Label Switch Router (LSR) Semester Advanced Telecommunications Slide 43 MPLS Protocols OSPF/ ISIS Routing LDP TCP CR LDP/ RSVP-TE UDP IP Forwarding Link State Information MPLS Forwarding Physical Semester Advanced Telecommunications Slide 44 MPLS Advantages Explicit Control of Routing on a per Flow basis Traffic Engineering - efficiency Complex mapping of IP attributes to FECs VPNs services End to end signalling along Label Switched Paths Protection / Recovery Semester Advanced Telecommunications Slide 45 15

16 Conclusions A wide variety of different techniques have been proposed for QoS in the Internet. Experimentation and new proposals are emerging on a daily basis. MPLS is the current favourite, but others are waiting to be considered. MPLS has been generalised to wavelength networks. It is called GMPLS. Semester Advanced Telecommunications Slide 46 16