Net-Centric Computing Division Department of Computer Science Bogor Agricultural University

1. Net-Centric Computing Division Department of Computer Science Bogor Agricultural University KOM 312 Komunikasi Data danJaringanKomputer ATM and Advanced Networks Adopted from Leon-Garcia and Widjaja Sri Wahjuni my_juni04@ipb.ac.id

2. agenda • Asynchronous Transfer Mode (ATM) • Integrated Services (intserv) • RSVP • Differentiated Services (divserv) • MPLS swj/12

3. ATM Network swj/12 • Standardized by ITU-T • End-to-end information transport using cells • 53-byte (5+48) cell provide low delay and fine multiplexing granularity • Support for many services through ATM Adaptation Layer

4. Higher Layers Higher Layers ATM Adaptation Layer (AAL) ATM Adaptation Layer (AAL) ATM Network Layer ATM Network Layer ATM Network Layer Physical Layer Physical Layer Physical Layer USER NETWORK USER ATM Layered Architecture swj/12

5. Higher Layers ATM Adaptation Layer (AAL) ATM Network Layer Physical Layer ATM Layered Architecture (2) ATM Adaptation Layer • standard interface to higher layers • adaptation functions • end-to-end between end systems • segmentation into cells and reassembly ATM Layer • Transfer of Cells • Cell-Header Generation/Extraction • VPI/VCI Translation • Cell multiplexing/demultiplexing • Flow and congestion control Physical Layer • Cell stream / bit stream conversion • Digital transmission swj/12

6. Voice AAL A/D s1 , s2 … cells Digital voice samples Video Compression … AAL A/D cells compressed frames picture frames Data AAL cells Bursty variable-length packets AAL converts Info into Cells swj/12

7. Cells Cells Cells Source Cells Switches Destination Cell-Switching – Virtual Circuit swj/12 • Connection setup establishes virtual circuit by setting pointers in tables in path across network • All cells for a connection follow the same path • Abbreviated header identifies connection • Cells queue for transmission at ATM switches & multiplexers • Fixed and Variable bit rates possible, negotiated during call set-up • Delay and loss performance negotiated prior to connection setup

8. Traffic Contract • During connection setup the user and the network negotiate two sets of parameters for a connection • Traffic descriptor: the user specifies the traffic that it will expect the network to transfer on its behalf • QoS requirements: the user specifies the type of network performance that is required by its cells • Traffic Contract • The user is expected to conform to traffic descriptor • The network is expected to deliver on its QoS commitments swj/12

9. Traffic Descriptors • Peak Cell Rate: rate in cells/second that a source is never allowed to exceed • Sustainable Cell Rate: average cell rate produced by the source over a long time interval • Maximum Burst Size: maximum number of consecutive cells that may be transmitted by a source at the peak cell rate (PCR) • Minimum Cell Rate: minimum average cell rate, in cells per second, that the source is always allowed to send • Cell Delay Variation Tolerance: cell delay variation that must be tolerated for in a given connection. swj/12

10. Quality of Service Parameters • Six QoS parameters are defined • Three are intrinsic to network performance and are not negotiated during connection setup: • Cell error ratio: fraction of delivered cells that contain bit errors • Cell mis-insertion ratio: average number of cells/second that are misdelivered • Severely errored cell block ratio: M or more out of N cells are lost, in error, or misdelivered swj/12

11. probability density of cell delay  D0 Peak-to-Peak CDV Dmax Negotiable QoS Parameters • Cell Loss Ratio (CLR): fraction of cells that are lost • Determined by buffer priority • Cell Transfer Delay (CTD): negotiate “maximum delay” • Dmax: 1-a of cells have delay less than Dmax • Determined by cell scheduling • Cell Delay Variation (CDV): Peak-to-Peak variation: Dmax-D0 swj/12

12. agenda • Asynchronous Transfer Mode (ATM) • Integrated Services (intserv) • (ReSerVation Protocol) RSVP • Differentiated Services (divserv) • MPLS swj/12

13. Integrated Services (intserv) • Standardized by IETF • Provides different QoS commitments : resources (bandwidth and buffer) must be explicitly reserved for a given data flow (using RSVP) • Packet classifier : identify flows that are to receive a certain level of service • Packet scheduler : handling different packet flows in a manner that QoS commitments are met • Admission control : determine whether a router has the necessary resource swj/12

14. Intserv Router Model Accept/reject a flow Identify a packet’s flow Buffering to control loss swj/12 Transmission scheduling to control delay

15. Admission Control • Individual flow negotiates admission into the network • Flow Descriptor has two parts • Filter specification (filterspec) provides information required by classifier to identify the packets in the flow • Flow specification(flowspec) describes traffic properties of flow and QoS requirements • Traffic Specification (Tspec) describes traffic in terms of a token bucket • Request Specification (Rspec) describes QoS in terms of bandwidth, delay, or packet loss. Each node along path must decide whether a flow can be accepted swj/12

16. Call setup swj/12

17. ReSerVation Protocol (RSVP) • RSVP is an IP signaling protocol to setup and maintain flow-specific state in hosts and routers • Multicast-oriented • Performs resource reservations for multipoint-multipoint applications • Adapts changing group membership & routes • Unicast, a special case • Simplex • Requests resources from sender to receiver • Bidirectional flows require separate reservations • Receiver-oriented • Receivers initiate and maintain resource reservations • Soft-state at intermediate routers • Reservation valid for specified duration • Released after timeout, unless first refreshed swj/12

18. RSVP Architecture swj/12 • Application requests QoS from RSVP process • RSVP prepares & sends request messages to router • Policy control determines if application allowed to make request • Admission control determines if resources available; sets up classifier & packet scheduler

19. IntServ involves High Complexity • Number of (application) flows can become extremely large • Per-flow treatment involves high complexity • Traffic Management • Per-flow classifier • Per-flow queueing • Per-flow scheduling • Hugh table sizes & high hardware complexity • Admission Control • Set up & maintenance of individual flows • High processing load IntServ is not scalable swj/12

20. agenda • Asynchronous Transfer Mode (ATM) • Integrated Services (intserv) • (ReSerVation Protocol) RSVP • Differentiated Services (diffserv) • MPLS swj/12

21. Differentiated Services (diffserv) • Differentiated Services (DiffServ) model is designed to be scalable and to provide QoS • Traffic is aggregated into a limited number of classes • Service is on aggregate-flow basis, not per individual flow • Each class receives a well-defined service treatment at each DiffServ router • No per-flow signaling swj/12

22. C =Core Router A =Access Router SLA H =Host Notwithstanding … Forwarding Path Architecture TCA … Complexity at the Edge • User negotiates Service Level Agreement (SLA) with service provider • SLA includes a Traffic Conditioning Agreement (TCA) stipulating • service level, traffic profile, marking, shaping • Access Router • classifies user packets and marks them in DS field of IP header as belonging to a specific class • conditions packet stream so it conforms to profile H H DiffServ Domain A C A H C swj/12 A C A H A A H

23. agenda • Asynchronous Transfer Mode (ATM) • Integrated Services (intserv) • (ReSerVation Protocol) RSVP • Differentiated Services (divfferv) • MPLS swj/12

24. IP L1 IP L3 IP L2 What is MPLS LER LSR LSR IP LER IP • Multiprotocol Label Switching (MPLS) • Label Switching Router (LSR) : a router that supports MPLS • A set of protocols that enable MPLS networks • Packets are assigned labels by edge routers (which perform longest-prefix match) • Packets are forwarded along a Label-Switched Path (LSP) in the MPLS network using label switching • LSPs can be created over multiple layer-2 links • ATM, Ethernet, PPP, frame relay • LSPs can support multiple layer-3 protocols • IPv4, IPv6, and in others swj/12

25. references • Garcia A.L., Widjaja A. 2004. Networks Communication.: Fundamental Concepts and Key Architectures 2nd ed. – Chapter 9-10. McGraw-Hill Companies, Inc. swj/12