CISC452 Telecommunications Systems. Lesson 6 Frame Relay and ATM

Transcription

1 CISC452 Telecommunications Systems Lesson 6 Frame Relay and ATM 1

2 Technology Comparison Private Line X.25 SMDS Frame Relay ATM IP Speed 56K - 622M 9.6K M 56K - 34M Dial - 45M 1.5M - 622M Dial - 45M Traffic Type Data/Vo ic e / Vide o Connection Oriented Data Data Data/On Ne t Vo ic e and Vide o Data/Vo ic e / Vide o Data Ye s Ye s No Ye s Ye s No Typical Topology Star/Multipo int/multi- Dro p Star Any-to - An y Me s h/partial Me s h/star Me s h /Partial Mes h/s tar Any-to - Any QoS Support No No No Pro prie tary Ye s No 2

3 Benefits of Frame Relay? Savings over Private Lines Reduces number of dedicated devices which reduces equipment costs Reduces complexity for network managers? Greater Bandwidth Flexibility than Private Lines? Higher Reliability and Resiliency than Private Lines? Lower Cost of Ownership and Better Bandwidth Utilization Growth of Branch Office Networks 3

4 Benefits of Frame Relay (cont d)? Consolidation of LAN, SNA, On-net Voice, and/or Packetized Video Simplifies Network Architecture Reduces Operations and Administrative Costs Improves Application Performance and Network Efficiency? Smooth migration to ATM Service and Network Interworking with ATM (FRF.5 and FRF.8) 4

5 Frame Relay Terms And Definitions (cont d)? Committed Information Rate (CIR) The bandwidth defined for a VC? Bc = Committed Burst Maximum number of committed bits to be transmitted over time interval? Be = Excess Burst Number of Excess bits that will be transmitted over time? Tc Time interval Time measurement based how much bandwidth is available for data to burst on to the network 5

6 Frame Relay Terms And Definitions (cont d)? FECN Forward Explicit Congestion Notification Bit set by the network node (FR Switch) that is experiencing congestion Sent in the direction of the receiver (destination)? BECN Backward Explicit Congestion Notification Bit set by the network node that is experiencing congestion Sent in the direction of the sender (source)? DE Discard Eligible bit Set by either the DTE (access device FRAD, router etc.) or the network nodes (switches) May be set selectively by some DTE devices May be set by network nodes in the event the user has exceeded CIR and the network is experiencing congestion 6

7 Service Comparison Private Lines (TDM) Frame Relay Engineer Network for Peak Traffic Needs CSU/DSU per Leased Line per remote site Time Division Multiplexing Resiliency is Not Inherent Engineer Network for Average Traffic Needs CSU/DSU per Leased Line that can access many remote sites Statistical Multiplexing and Burst Capability Resiliency is Inherent in Network 7

8 Frame Relay Complements Other Technologies Application Technology Speeds Technology LAN LAN & SNA Data & On-net net Voice Data, On-net net Voice & Packetized Video FR, SMDS, ATM FR, ATM FR, ATM FR, ATM < 1.5 Mbps Mbps >45 Mbps FR FR, ATM ATM FR or ATM HQ Interworking FR - ATM Agreement FRF.5 and FRF.8 FR or ATM Regional Sites FR - SMDS SIP Dedicated or Dial FR Dial Remote Access or Dial FR Remote Sites Mobile Workers & Telecommuters 8

9 Understanding Public Frame Relay Services DS-3/E-3 DS-3/E-3 ATM X-25 DS-1/E-1 DS-0 ISDN Public Frame Relay International FR Dial Access Management Reports Dial Access Internet Access IP FR Access 9

10 Characteristics of ATM Voice Data Video Cells? Uses small, fixed-sized cells? Connection-oriented? Supports multiple service types? Applicable to LAN and WAN 10

11 Creating Cells from Packets Packet Dest. Address Source Address Data Frame Check Cells Header Payload Header Payload 53 Bytes 5 Byte Header 48 Byte Payload Header Payload Header Payload ATM Cell 11

12 Campus Networking Evolution Shared Ethernet Clients Traditional Network Local Workgroup Servers Corporate WAN and Internet? Hierarchical design with broadcast control? 80/20 rule? Homogenous user communities? Moves, adds, and changes manually

13 Switched Ethernet Clients Campus Networking Evolution Contemporary Network Ethernet Switch with VLAN Support Campus ATM Network Corporate WAN and Internet ATM-Attached Station(s) Centralized High-Performance Servers? Network hierarchy maintained? Traffic patterns migrating? Client and server performance increases? Moves, adds, and changes automated 13

14 Rudimentary ATM Concepts? Physical layer? Signaling? Cell format? Connection types 14

15 ATM Transmission Media ATM SDH/SONET Rates Chart SDH SONET Rate Mbps STM-1 STM-4 STM-8 STM-16 STS-1/OC-1 STS-3/OC 3/OC-3 STS-12/OC 12/OC-12 STS-24/OC-24 STS-48/OC , ,488.32? CCITT (Consultative Committee for International Telephony and Telegraph)? ITU (International Telecommunications Union)

16 ATM Physical Interface Rates Framing DS1 E1 J2 DS3 E3 E4 ATM25 STS 1 STS3c/STM1 STS 12c/STM4 4B/5B (TAXI) 8B/10B (Fiberchannel) Data Rate (Mbps) Multi- Mode Fiber Single- Mode Fiber Coaxial Cable X Media UTP 5 UTP X STP (TP) (TP) = Standardized X = Proposed/In Progress 16

17 Rudimentary ATM Concepts? Physical layer? Signaling? Cell format? Connection types 17

18 ATM Building Blocks? ATM signaling UNI and NNI? Virtual connections VCC, VP, and VC 18

19 ATM Signaling Public UNI aka B-ICI Public ATM Network UNI NNI NNI Token Ring NNI Private ATM Network? UNI = User-to-Network Interface? NNI = Network-to-Network Interface? Cell header content varies depending on who s talking to whom 19

20 Virtual Path and Virtual Channels Virtual Channels (VC) ATM Physical Link Virtual Channel Connection (VCC) E3 OC 12 Virtual Path (VP) Virtual Path (VP) Virtual Channels (VC) Virtual Channel Connection (VCC) Contains Multiple VPs Virtual Path (VP) Contains Multiple VCs Virtual Channel (VC) Logical Path Between ATM End Points Connection Identifier = VPI/VCI

21 ATM Switches Input Port VPI/VCI Output Port VPI/VCI ? ATM switches translate VPI/VCI values? VPI/VCI value unique only per interface eg: locally significant and may be re-used elsewhere in network 21

22 VP and VC Switching VC Switch VCI 1 VCI 2 VCI 3 VCI 4 VP Switch VPI 1 VPI 3 VPI 2 Port 2 Port 1 VPI 2 VCI 1 VCI 2 VPI 1 VPI 3 VCI 1 VCI 2 VPI 4 VPI 5 Port 3

23 Virtual Channels and Virtual Paths Virtual Channel Connection (VCC) Virtual Path Connection (VPC) UNI VC Switch NNI VP Switch NNI VC Switch UNI VPI = 1 VCI = 1 VPI = 2 VCI = 44 VPI = 26 VCI = 44 VPI = 20 VCI = 30? This hop-by-hop forwarding is known as cell relay 23

24 Rudimentary ATM Concepts? Physical layer? Signaling? Cell format? Connection types 24

25 Creating Cells from Packets Packet Dest. Address Source Address Data Frame Check Cells Header Payload Header Payload SAR Segmentation and Reassembly Header Payload Segmentation Happens at Source Reassembly Happens at Destination Header Payload 25

26 ATM Cell Header 5 Byte Header 53 Bytes 48 Byte Payload ATM Cell 26

27 ATM Cell Header Details GFC (4) VCI (16) 48 Byte Payload VPI (8) PTI HEC ATM UNI Cell CLP GFC Generic Flow Control UNI Cells Only! VPI/VCI Identifies Virtual Paths and Channels PTI CLP HEC Payload Type Identifier 3 Bits: 1. User/Control Data 2. Congestion 3. Last Cell Cell Loss Priority Bit Header Error Check 8 Bit CRC VPI (12) 48 Byte Payload VCI (16) PTI HEC ATM NNI Cell CLP 27

28 Rudimentary ATM Concepts? Physical layer? Signaling? Cell format? Connection types 28

29 ATM Connection Types? PVC? SVC? Soft PVC 29

30 Connection Types S2 1 S6 S2 S6 1 1 S1 S8 S1 S3 S5 S8 S3 S5 2 2 VC S4 2 S7 S4 S7 Connectionless: Packet Routing? Path 1 = S1, S2, S6, S8? Path 2 = S1, S4, S7, S8? Data can take different path and can arrive out of order Connection Oriented: Cell Switching? VC = S1, S4, S7, S8? Data takes the same path and arrives in sequence 30

31 Permanent Virtual Circuit (PVC) A 29 Input Output Port VPI/VCI Port VPI/VCI Input Output Port VPI/VCI Port VPI/VCI B Input Output Port VPI/VCI Port VPI/VCI D Input C Output Port VPI/VCI Port VPI/VCI ? VPI/VCI tables in network equipment updated by administrator 31

32 Switched Virtual Circuit (SVC) Input Output Port VPI/VCI Port VPI/VCI Input Output Port VPI/VCI Port VPI/VCI A UNI Signaling B Input Output Port VPI/VCI Port VPI/VCI 4 1 NNI Signaling UNI Signaling C Input Output Port VPI/VCI Port VPI/VCI D ? Dynamically set up connections via signaling 32

33 Switched Virtual Circuit (SVC) Input Output Port VPI/VCI Port VPI/VCI Input Output Port VPI/VCI Port VPI/VCI A UNI Signaling B Input Output 4 1 NNI Signaling D 2 UNI Signaling C Input Output Port VPI/VCI Port VPI/VCI Port VPI/VCI Port VPI/VCI ? Transfer data over newly established link 33

34 Switched Virtual Circuit (SVC) Input Output Port VPI/VCI Port VPI/VCI Input Output Port VPI/VCI Port VPI/VCI A UNI Signaling B Input Output Port VPI/VCI Port VPI/VCI NNI Signaling D 2 UNI Signaling C Input Output Port VPI/VCI Port VPI/VCI ? Dynamically tear down connections via signaling 34

35 Soft PVC Input Output Port VPI/VCI Port VPI/VCI Input Output Port VPI/VCI Port VPI/VCI A UNI Signaling B 1 3 NNI Signaling UNI Signaling C Input Output Port VPI/VCI Port VPI/VCI D 1 Input Output Port VPI/VCI Port VPI/VCI ? PVC established manually across UNI and dynamically across NNI 35

36 ATM Reference Model? Physical layer? ATM layer? ATM adaptation layer? A day in the life of a cell 36

37 ATM Reference Model ATM Adaptation Layer (AAL) ATM Layer Physical Layer 37

38 ATM Reference Model ATM Adaptation Layer (AAL) ATM Layer Physical Layer Physical Layer Two Sublayers:? Transmission Convergence (TC) Framing HEC? Physical Media Dependent (PMD) Physical media coding 38

39 Physical Layer ATM Adaptation Layer (AAL) ATM Layer Framing DS1 E1 J2 DS3 E3 E4 Data Rate (Mbps) Multi- Mode Fiber Single- Mode Fiber Media Coaxial Cable X UTP 5 UTP 3 STP (TP) (TP) Physical Layer ATM25 STS 1 STS3c/STM1 STS 12c/STM4 4B/5B (TAXI) 8B/10B (Fiberchannel) X = Standardized X = Proposed/In Progress 39

40 ATM Reference Model ATM Adaptation Layer (AAL) ATM Layer Physical Layer ATM Layer? Cell header insertion/removal? Cell Relay? Multiplexes/demultiplexes cells of different connections 40

41 ATM Layer Virtual Channel Connection (VCC) ATM Adaptation Layer (AAL) Virtual Path Connection (VPC) UNI UNI ATM Layer NNI NNI VC Switch VP Switch VC Switch Physical Layer VPI = 0 VCI = 38 VPI = 12 VCI = 44 VPI = 26 VCI = 44 VPI = 0 VCI = 36? Provides VPI/VCI values in header? Ensures that cells stay in the correct order 41

42 ATM Reference Model ATM Adaptation Layer (AAL) ATM Layer Physical Layer ATM Adaptation Layer (AAL) Two Sublayers:? Convergence Sublayer (CS)? Segmentation and Reassembly (SAR) 42

43 ATM Adaptation Layer AAL ATM Adaptation Layer (AAL) ATM Layer PBX AAL C S S A R Physical Layer AAL = QoS + SAR? CS assigns different AAL s/qosfor different traffic types? SAR cell <-> packet 43

44 ATM Adaptation Layer Class Service Categories Bit Rate Connection Timing Mode Concern Application Examples ATM Adaptation Layer (AAL) A AAL1 CBR (Constant) Connection- Oriented Yes Bandwidth and throughput guaranteed Good for voice and video ATM Layer B AAL2 VBR (Variable) VBR-AT and VBR-NRT Connection- Oriented Yes Best effort bandwidth and throughput Good for live video, multimedia, LAN-to-LAN Physical Layer C AAL5 ABR (Available) Connection- Oriented No Best effort with congestion feedback Reliable delivery of bursty traffic if latency okay D AAL3/4 UBR (Un- specified) Connection- less No No guarantee For SMDS/LAN 44

45 ATM Reference Model? Physical layer? ATM layer? ATM adaptation layer? A day in the life of a cell 45

46 A Day in the Life of a Cell TCP ATM Payload Processing TCP Packet TCP Header App Data IP IP Datagram IP Header TCP Header App Data LLC/SNAP LLC IP Header TCP Header App Data AAL Convergence Sublayer (CS) QoS + LLC IP Header TCP Header Put in 48 Byte Cells SAT into PDU App Data SAR ATM PHY Add 5 Byte Headers with VPI/VCI and CLP Transmission Convergence (STS, STM, DS) Physical Media (MMF, SMF, STP, UDP, 46

47 A Day in the Life of a Cell Traversing the Network A A L A T M VPI 2 VCI 37 P H Y UNI ATM Switch Port 1 P H Y Port 2 P H Y A T M A T M Port ATM Layer VPI VCI NNI ATM Switch ATM Layer A A L VPI 3 VCI 39 A T M P H Y UNI Port 1 P H Y Port 2 P H Y A T M A T M Port VPI VCI

48 Agenda? Introduction? ATM Fundamentals Rudimentary ATM Concepts ATM Reference Model ATM Adaptation Layer (AAL) Traffic Management? ATM Transport Standards? Campus ATM Internetworking? Wrap Up 48

49 AAL? AAL criteria Traffic parameters QoS parameters? The AAL s AAL1 CBR AAL2 VBR AAL3/4 UBR AAL5 ABR 49

50 AAL Criteria Contract Contract Contract? Traffic Parameters Peak cell rate Sustainable cell rate Maximum burst size Minimum Cell Rate? Quality of Service Delay Cell loss ATM Network 50

51 AAL Criteria Traffic Parameters? Peak Cell Rate PCR Maximum data rate a connection can handle without losing data? Sustainable Cell Rate SCR Average ATM cell throughput the application is permitted? Maximum Burst Size MBS Size of the maximum burst of contiguous cells that can be transmitted? Minimum Cell Rate MCR MCR Rate of an application s ability to handle latency 51

52 AAL Criteria QoS Delay? Maximum Cell Transfer Delay MCTD How long the network can take to transmit a cell from one endpoint to another? Cell Delay Variation Tolerance CDVT CDVT Line distortion caused by change in interarrival times between cells aka jitter 52

53 AAL Criteria QoS Cell Loss? Cell Loss Ratio CLR CLR Acceptable percentage of cells that the network can discard due to congestion 53

54 Quality of Service QoS? AAL criteria Traffic parameters QoS parameters? The AAL s AAL1 CBR AAL2 VBR AAL3/4 UBR AAL5 ABR 54

55 The AAL s AAL1 Constant Bit Rate (CBR) Real Time Voice and Video Traffic Parameter PCR Peak Cell Rate Overhead 5 Byte Header 47 Byte Payload QoS LOW 1 Byte Tolerance Cell Loss Cell Delay HIGH 55

56 The AAL s AAL2 Variable Bit Rate (VBR-RT/VBR-NRT) Packetized Voice/Video, SNA Traffic Parameter PCR Peak Cell Rate SCR Sustainable Cell Rate MBS Maximum Burst Size Overhead 5 Byte Header 1 47 Byte Payload QoS LOW 1 48 Bytes Tolerance Cell Loss Cell Delay (RT) HIGH Cell Delay (NRT) 56

57 The AAL s AAL3/4 Unspecified Bit Rate (UBR) Public WAN SMDS Traffic Parameter No Guarantees Send and Pray Overhead 5 Byte Header 44 Byte Payload QoS LOW 4 Bytes Tolerance Cell Delay Cell Loss HIGH 57

58 The AAL s AAL5 Available Bit Rate (ABR) LAN Interconnect for Data Traffic Parameter PCR Peak Cell Rate MCR Minimum Cell Rate QoS LOW Tolerance HIGH Cell Loss Cell Delay Overhead 5 Byte Header 48 Byte Payload? No cell overhead? Uses congestion feedback instead 58

59 Traffic Management? Why traffic management?? Traffic control techniques? AAL5/ABR congestion feedback? Buffers are your friend 59

60 Why Traffic Management?? Proactively combat congestion? Provision for priority control? Maintain well-behaved traffic 60

61 Why Traffic Management? Cell Loss Data s Critical Enemy Ethernet (1500 Bytes) = 32 Cells FDDI (4470 Bytes) = 96 Cells IP over ATM 1577 (9180 Bytes) = 192 Cells TCP/IP Packet X? Lose one cell and the rest are useless? Need to re-transmit 32+ cells for one cell lost? Congestion collapse is the result 61

62 Traffic Control Techniques? Connection management Acceptance? Traffic management Policing? Traffic smoothing Shaping 62

63 Traffic Control Techniques Connection Management Contract Contract Contract? Traffic Parameters Peak cell rate Sustainable cell rate Burst tolerance Etc.? Quality of Service Delay Cell loss ATM Network 63

64 Traffic Control Techniques Connection Management Connection Admission Control (CAC) I want a VC: X Mbps Y Delay Z Cell Loss Guaranteed QoS Request CAC Can I Support this Reliably without Jeopardizing Other Contracts No or Yes, Agree to a Traffic Contract Contract ATM Network

65 Traffic Control Techniques Traffic Management Usage Parameter Control (UPC) aka Policing Contract You are Not in Conformance with the Contract. What Should the Penalty Be?? REBEL APPLICATION ATM Network?DECISION? PASS MARK CLP BIT DROP

66 Traffic Control Techniques Traffic Management UPC Marked D r o p?decision? PASS MARK CLP BIT DROP? CLP Control When congested drop marked cells? Public UNI Generic Cell Rate Algorithm (GCRA) 66

67 Traffic Control Techniques Traffic Management UPC Marked D r o p 3 2? Intelligent Packet Discard IPD? Discard cells from same bad packet? Tail packet discard? Maximize Goodput 67

68 Traffic Control Techniques Traffic Smoothing I Want to Comply With My Contract. So, I Will Smooth/Shape My Traffic Go Ahead, Make My Day Actual Data Shaper Shaped Data Private ATM Network Public ATM Network? Traffic shaper at customer site? Changes traffic characteristics? Leaky bucket algorithm 68

69 Traffic Control Techniques Buffers Are Your Friend? Absorb traffic bursts from simultaneous connections? Switches schedule traffic based on priority of traffic according to QoS? Switch must reallocate buffers as the traffic mix changes? Effective buffering maximizes throughput of usable cells as opposed to raw cells (aka goodput) 69

70 ATM Internetworking? Challenges? RFC1483? RFC1577? LANE? MPOA 70

71 ATM Internetworking Existing and New Applications Network Address MAC Address??? The Challenges API New Applications ATM Address ATM Address? MAC address to ATM address resolution? No Standard ATM API 71

72 ATM Internetworking Overlay Model Router or Switch ATM Addresses Router or Switch Ethernet ATM Network Ethernet Direct-Attached Stations Network Addresses, MAC Addresses? Multiple layers of addressing 72