NETWORK PARADIGMS. Bandwidth (Mbps) ATM LANS Gigabit Ethernet ATM. Voice, Image, Video, Data. Fast Ethernet FDDI SMDS (DQDB)

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1 1. INTRODUCTION

2 NETWORK PARADIGMS Bandwidth (Mbps) 1000 ATM LANS Gigabit Ethernet ATM Fast Ethernet FDDI SMDS (DQDB) Voice, Image, Video, Data 1 Ethernet/ Token Ring/ Token Bus Frame Relay X.25 LAN MAN/WAN Distance

3 NETWORKING EVOLUTION Traditionally Disjoint Networks Voice Telephone networks Data Computer networks and LAN Video Teleconference Private corporate networks TV Broadcast radio or cable networks * These networks are engineered for a specific application and are ill-suited for other applications, e.g., the traditional telephone network is too noisy and inefficient (capacity limited) for bursty data communication. * Data networks are not suitable for voice and video traffic because they cannot satisfy the time-sensitivity of these traffic types.

4 GOAL INTEGRATION Old Fashioned Broadband ISDN WIDE AREA LOCAL PSTN PBX X.25 Internet LAN WIDE AREA LOCAL B-ISDN A Single Unifying Technology Voice Before Integration Data Video, Image, Voice and Data After Integration kbps => Narrowband Mbps => Wideband > 45 Mbps => Broadband

5 GOAL INTEGRATION (One Network Carrying Multimedia Traffic) Source Broadband Integrated Services Network (Data, Voice, Video, Still Image) Destination WHY INTEGRATION? Voice Traffic (based on AT&T data, 1993) 125 to 130 Million Calls/day x 5 min/call x 64 kbps = 28.8 Gbps = 1 / 1000 th of fiber capacity

6 GOAL INTEGRATION Updated statistics for 1998 Average calls per business day = million Average calls per day = million Average length per business call = 2.5 min. Average length per consumer call = 8.0 min. Suppose 200 Million x 24 hours/day x 64 kbps = 12.8 Tbps Bottomline: Gigantic Capacity of fiber cannot be utilized only by Voice Traffic!!! FURTHER REASONS: Convergence of computer and communications technologies Integration could offer efficiencies (lower cost) and support of new applicatons Single network management & maintenance No duplication of cables, plants (since one physical network) => Less costs

7 INTEGRATION PROBLEMS Integration is not easy because different applications have different performance requirements. Telemetry Telecontrol Telealarm Voice Telefax Low Speed Data Hifi Sound Video Telephony High Quality Video Video Library Video Education Medium Speed Data High Speed Data Very High Speed Data

8 INTEGRATION PROBLEMS Voice Video Data Still Image 64 Kbps (Bandwidth Demand) 2 min. (End-to-End Delay on the Average) (Request-Transfer Cycle) > 140 Mbps (BW Demand) 60 min. (E2E Delay on the Average) Extremely variable (BW Demand) Extremely variable (E2E Delay on the Average) e.g., long telnet sessions; short finger requests 1-50 Mbps (BW Demand) 1 Sec. (E2E Delay on the Average) (Cannot be seen as data traffic because it may have real-time nature, e.g. medical image retrieval; geographic databases)

9 ATM NETWORKS Asynchronous Transfer Mode (ATM): A new multiplexing and a new switching technique to realize the Broadband Integrated Services Digital Networks (B-ISDN) Asynchronous: Packet transmission is not synchronized to a global (network) clock!!!

10 Multiplexing Defines the means by which multiple streams of information share a common physical transmission medium. Sources N Mux. Demux. Physical Link (Channel) Shares single output between many inputs. Sinks (Destinations) Demux has one input which must be distributed among outputs.

11 Multiplexing Techniques Multiplexing Techniques Frequency Division Multiplexing Time Division Multiplexing Synchronous TDM (STM) Asynchronous TDM (Statistical Multiplexing) (ATM)

12 STM STM Circuit Switching used for Telephone Networks (also for N-ISDN) (Time Division Multiplexing) (Classical TDM) Information is transferred with a certain repetition frequency. e.g., 8 bits every 125µsec for 64kbps 1000 bits every 125µsec for 8Mbps From Nyquists Sampling Theorem 4kHz voice signal requires 8000 samples/sec One 8 bit sample every 125µsec = 64kbps (Golden Rule of Tel. Networks) (DS0 Channel) 8 bits/sample Basic unit of repetition frequency is called a TIME SLOT.

13 STM Time Slot... n... n Periodic Frame (one cycle) Start of each Frame L sec (α bits can be transmitted) Each slot is assigned to a particular call. The call is identified by the position of the slot. When the user is assigned a slot, it owns a circuit. The user uses the same slot within consecutive frames. If a user is not transmitting data in its own slot, that time slot remains reserved (nobody else can transmit there).

14 ATM ATM In ATM, the MUX takes a packet (one or more packets) & appends a header (5 Bytes) and transmits based on statistical characteristics of the sources. MUX can take according number of cells from a source & transmit. 1 Video 2 Voice Header Data MUX Physical Trunk 4 Video 5

15 ATM e.g., from a video source 10 cells can be taken, while from voice source 1 cell because of their bandwidth demands. Each packet must have a header (control information)!! No SYNCHRONIZATION!! (No network clock!)

16 STM vs. ATM Simple Example: Sources Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit STM ATM I I I I 3 I cycle 1 cycle 1 cycle

17 STM vs. ATM STM (Synchronous Transfer Mode) Channel 1 Time Slot Channel Channel N Channel 1 Channel 2 Channel N Frame Header FRAME (Cycle) FRAME (Cycle) ATM (Asynchronous Transfer Mode) Channel 1 Channel 5 Channel 1 Channel unused Channel 7 Channel 5 Channel 2... Header Data (cell)

18 STM vs ATM (STM) Users t0 t1 t2 t3 t4 A B C D (ATM) MUX (Multiplexer) To Network Synchronous time-division multiplexing Wasted Bandwidth A1 B1 C1 D1 A2 B2 C2 D2 Asynchronous Statistical time-division multiplexing First Cycle A1 B1 B2 C2 Second Cycle Extra Bandwidth Available First Cycle Data Second Cycle Address

19 STM Advantages No overhead in packetization. Constant repetition of frames low delay jitters. Easy to maintain synchronization between sender & receiver. Disadvantages Limited flexibility i) BW (bandwidth) allocation at 64kbps modularity ii) Inefficient for VBR (Variable Bit Rate) traffic Long connection set-up delays. Complex switching system.

20 ATM Advantages Flexible BW-Allocation (sources with widely different bit rates). i) Accommodate bursty sources (e.g., VBR) ii) Asymmetrical link bandwidths A wide range multimedia traffic types. High efficiency due to statistical multiplexing. Allows Quality of Service (QoS) guarantees. Simple routing (small buffers). Simple switching. High BW Low BW

21 ATM Disadvantages Overhead for cell header (bytes) 40Bits overhead 10% overhead Requests fast switching technology (need new switches). Complex scheduling algorithms needed. Connection set-up & signaling overhead. Traffic management problem. Difficult to reroute virtual circuits. Jitter problem.

22 SWITCHING TECHNIQUE Takes multiple instances of a physical transmission medium containing multiplexed info streams and rearrange the info streams between input & output. In other words, information from a particular physical link in a specific multiplex position is switched to another output physical link.

23 SWITCHING TECHNIQUE Inlets = Inputs Outlets = Outputs Switch 2 N M Ports Fabric

24 Switch Architectures Single Bus Self-Routing (Blocking) Multiple Bus Self-Routing (Non-Blocking Queueing - Internal Queueing - Input Queueing - Output Queueing (Shared Buffer Theoretically optimal Achieves maximum throughput!) Actual ATM switches have combination of input, output, and internal queueing. The way how these functions are implemented, where in the switch these functions are located, will distinguish one switching solution from another.

25 SWITCHING Question : Why could existing switch architectures (circuit-switches for voice, packet-switches for data ) NOT be used for ATM? Reasons : 1. High speed at which the switch must operate ( Mbps; now on Gigabit levels) 2. Statistical behavior of ATM streams passing through the switch 3. ATM has small fixed cell size & limited header functionality

26 ATM SWITCHING Combines Space & Time Switching Principles!! Inlets N x y z w Space (Rerouting) Switching Switch y w z x N Outlets Time Switching Inlet Switch t x y z w w y x z t Outlet

27 ATM Basic Switching Principle data Header d c a a b b I 1 I 2 Switch data O 1 O 2 p k q y y p t e b c Cell I j Incoming Headers Header / link translation table O n Outgoing Headers Routing Table r y k Translation Table Incoming Link I 1 Header a c d Outgoing Link O 1 Header p k q I j c b e O n k y r

28 ATM Switching All cells which have header a or (c or d ) on incoming I 1 are switched to O 1 and their header is translated (switched) to value p or (k or q ). All cells with a header c (or b or e) on link I j are also switched to outlet O n, but their header gets values k (or y or r). Remark: On each incoming & outgoing link individually, the values of the header are unique, but identical headers can be found on different links, e.g., c on link I 1 and I j. Realization: Routing info is contained in the header (label), not explicit address. Explicit addressing is not possible because of short fixed size cell. A physical Inlet/Outlet, characterized by a physical port number. A logical channel on the physical port characterized by a VCI and/or VPI. Routing Tables Must be set up in advance (signaling phase) Either pre-defined or dynamically allocated

29 ATM SWITCHING Header VPI a VCI b Switch Header VPI x VCI y Input Port P Output Port Q Routing Info: Input Port VPI VCI Output Port VPI VCI P a b Q x y Basic Functions Space Switching (Routing) Header Switching Queueing Why Queueing? Suppose 2 cells from different Inlet (I 1 & I n ) arrive simultaneously at ATM switch and are destined to the same outlet O 1. Thus, they cannot be put on the output or the outlet at the same time buffering, i.e., to store the cells which cannot be served. (No pre-assigned time slots, statistical multiplexing) Remark: The way these 3 functions are implemented, where in the switch these functions are located, will distinguish one switching solution from another.

30 ATM NETWORK Host UNI Host ATM Switch NNI ATM Switch NNI UNI ATM Switch NNI ATM Switch Backbone Network

31 ATM CELL STRUCTURE Octet HEADER 2 (5 octets) PAYLOAD : (48 octets) : : 53 Octets are sent in increasing order 1,2,3 Within an octet the bits are sent in decreasing order 8,7,6,5,4... User Network Interface (UNI) Cell S tructure : : GFC VPI VCI VPI VCI Network Network Interface (NNI) Cell S tructure : : VCI PT PR VCI PT PR HEC PAYLOAD (48 octets) VPI VPI VCI HEC PAYLOAD (48 octets) VCI GFC : Generic Flow Control VPI : Virtual Path Identifier VCI : Virtual Channel Identifier PT : Payload Type PR : Priority HEC : Header Error Control

32 ATM Interfaces UNI / NNI Host UNI Host ATM Switch NNI ATM Switch NNI UNI ATM Switch NNI ATM Switch Backbone Network

33 ATM Network Interfaces (Detailed) Regional Carriers (Intra-LATA) computer computer private UNI private UNI Private Switch Private NNI Private Switch (P-NNI) public UNI Public Switch Public NNI Intersystem Switching Interface (ISSI) Long Distance Carrier Public Switch Public Switch (Local Access & Transp Area) B-ICI (Broadband Inter-Carrier Interface) computer Router DXI Digital Service Unit (Inter LATA ISSI) B-ICI Public UNI Public Switch DXI: Data Exchange Interface, between packet routers & ATM Digital S ervice Units (DS U)

34 ATM Cell Generic Flow Control (GFC) (4 Bits) (only at UNI) It provides flow control information towards the network. It allows a multiplexer to control the rate of an ATM terminal. Currently, no standard. 0 s are used for this field. Routing Field (VPI/VCI) 24 Bits (8 Bits for VPI, 16 for VCI) at UNI. 28 Bits (12 for VPI, 16 for VCI) at NNI. VPI/VCI have only local significance only; they identify the next destination. Remark: Each physical UNI to support not more than 2 8 =256 VPs. NNI 2 12 = 4096 VPs. Each VP can support 2 16 = 65,636 VC on UNI and NNI. Payload Type Field (PT) (3 Bits) PT indicates whether the cell contains users data, signaling data or maintenance information. Cell Loss Priority (CLP) (1 Bit) CLP indicates the priority of the cell. Lower priority cells are discarded before higher priority cells when congestion occurs. Remark: If CLP =1 Cell has low priority dropped in heavy load. If CLP =0 Cell has high priority not discarded. Header Error Control (HEC) (8 Bits) HEC detects and corrects errors in the header. (i.e., single Bit Error Correction or Multiple-Bit Error Detection). The info field is passed through the network intact, with no error checking or correction. ATM relies higher protocols for this purpose.

35 ATM CELL PAYLOAD TYPE (PT) First Bit 0 User Information First Bit 1 Network Management or Maintenance Function Second Bit Whether CONGESTION has been experienced or not. Third Bit known as AAU (ATM-User-to-ATM-User) used in AAL5 to convey information between end users. Contents: [EFCI (Explicit Forward Congestion Indication)] User Data Cell; Congestion No (EFCI=0); AAU= User Data Cell; Congestion No (EFCI=0); AAU= User Data Cell; Congestion Yes (EFCI=1); AAU= User Data Cell; Congestion Yes (EFCI=1); AAU= Segment Operation and Maintenance (OAM) (F5) Cell End-to-End (OAM) Flow F5 Cell Resource Management Cell Reserved for Future Function

36 Pre-Assigned (Pre-Defined) (Reserved) Header Values

37 Cell Types Idle Cell: Inserted and extracted by PHY in order to adapt the cell flow rate at the boundary between ATM layer & PHY layer to the available payload capacity of the transmission system. Valid Cell: has a header with no error or which has been corrected by the HEC verification process. Invalid Cell: has a header that has errors that have not been modified by the HEC verification process (discarded at PHY layer). Assigned Cell: provides service to an application using ATM layer service. Unassigned Cell: Not an assigned cell. Does not contain any useful information.

38 Cell Types (Cont.) Source Destination Upper Layers Assigned Cell Assigned Cell Upper Layers Unassigned Cell Unassigned Cell ATM Layer PHY Layer Idle Cell SAP SAP Valid Cell ATM Layer PHY Layer Invalid Cell Network Idle Cell Trash

39 Cell Types (Cont.) Difference Idle Cells vs. Unassigned Cells Unassigned Cells Visible to ATM & PHY layer. Idle Cells Visible only to PHY layer not to ATM layer. Unassigned Cells are sent whenever there is no information available at the sender. It allows full asynchronous operation of sender/receiver. Idle Cells are inserted by the PHY layer in order to match the transmission rate to the transmission system or for other PHY layer purposes. Octet 1 Octet 2 Octet 3 Octet 4 Octet Each octet of Info. field of an idle cell is filled with

40 The Size of the ATM Cell (WHY = 53 BYTES?) 1. Transmission Efficiency 2. Delays 3. Implementation Complexity

41 1) Transmission Efficiency L η µ = L +µ where L is the information size of the packet in bytes and µ is the header size of the packet in bytes. η µ 100 Transmission Efficiency x x x x x x x x L The longer the info. field, the higher is the efficiency for the same header size. A header of 4 or 5 Bytes is typical value for ATM cell. x (Assumption: All packets are completely filled.)

42 2. DELAYS Packetization Delay (Segmentation) Transmission Delay (depends on the distance between both endpoints). (Range 4-5µsec per km; depends on the transmission medium). Switching Delay Queueing (Buffering) Delay Depacketization Delay (Reassembly) Queues are necessary to avoid massive loss of cells. Delay varies with the load of the network and is determined by the behavior of queues. Conclusions: * The queueing delays increase with the size of information field. * The end-to-end delay must be below 24 ms to avoid ECHO problems for voice traffic!!!

43 EXAMPLE: [Packetization Delay (Segmentation)] Transmission of 64 kbps voice traffic over ATM. Voice signal is sampled 8000 times per second, which gives rise to 8000 bytes/sec or 1 byte every 125 usec. * If the packet size is 16 bytes, then it will take (16*125) usec or 2ms to fill up a packet. * If the packet size is 64 bytes, then it will take (64*125) usec or 8ms to fill up a packet. So the smaller the packet size, the less the delay to fill up a packet. The packetization delay could be kept small if a packet is partially filled; however, this will lead to under-utilization of the network capacity.

44 EXAMPLE: [Time for Header Conversion] The longer the packet, the more time the switch has to do the header conversion. Consider an ATM switch with OC-3 capacity, i.e., 155 Mbps. If the cell size is 53 bytes, then a maximum of about cells can arrive per second. This translates to 2.7 usec per cell, i.e., assuming that cells arrive back-to-back, a new cell arrives approximately every 2.7 usec. This means that the switch has 2.7 usec available to carry out the header conversion. Suppose a cell size of 10 bytes. A maximum of about cells can arrive per second, i.e., if cells arrive back-to-back, a new cell arrives approximately every 0.5 usec. The switch has then only 0.5 usec for the header conversion.

45 3) Implementation Complexity Two parameters play a role in determining the complexity of a system: The speed [Transmission (Processing) Time (P) = (Cell Size/Data Rate) ] The number of required bits (MEMORY: M)) = The number of cells (BUFFER SIZE IN CELLS) multiplied by the (CELL SIZE). Tradeoff Memory Size and Processing Speed To guarantee a certain limit on the cell loss ratio, a number of cells must be provided per queue. This number is independent of the cell size. So the larger the cell size, the larger the queue in bits will be (e.g., doubling the cell size will also double the memory requirements).

46 IMPLEMENTATION COMPLEXITY On the other hand, for every cell, the header must be processed. This processing must be performed in one cell time, so the longer the cell size, the larger the available time and the lower the speed requirements of the system. In Figure we show the speed and memory size in function of the cell size, if the system operates at 150 Mbps and if the queue is dimensioned for 50 cells (the header is 4 Bytes). P (processing time per cell in µs) P M M (memory size in bits) cell size

47 Explanation of the FIGURE: Assume 50 Cells; Cell Size: 16 + Header: 4 = 20 Bytes (Low) Cell Size: Header: 4 = 260 Bytes (High) Memory (M) = = Cell Size * Buffer Size in Cells = 20*50 = 1000 Bytes = 8000 Bits (Low) = 260*50=13000 Bytes= Bits (High) Processing Speed (P) = Transmission Time = {Cell Size}/{Data Rate}=160 Bits/{150*10^6 bps} ~ 1 musec (L) =2080/{150*10^6 bps} ~ 13.8 musec (H)

48 1. We see that for a cell of 16 bytes, we need only about 8000 bits for the memory, but the header processing of each cell must be performed in less than 1 µsec. 2. For a cell of 256 bytes, we need already more than 64,000 bits for a single queue. But we have about 15 µsec for the header processing of a single cell. 3. However, as seen in Figure, the speed is not the most critical issue, since in 1 µsec (in case of 16 Bytes) HIGH processing can be achieved; so the limiting factor is the memory space requirement.

49 FINALLY THE RESULT: Contradicting factors are contributing to the choice of the cell size. However, a value between 32 and 64 bytes is preferable. Europe was in favor of 32 bytes (because of the requirement for echo cancellers for voice) where US and Japan were in favor of 64 bytes because of higher transmission efficiency. Finally ==> a compromise of 48 Bytes reached at CCITT meeting in June 1989.

50 Variable vs. Fixed Length Packets Facts to consider in decision Transmission Bandwidth Efficiency Achievable Switching Performance (i.e., the switching speed vs. complexity) The Delay

51 Transmission Bandwidth Efficiency The number of Information Bytes ( L) η= L + The number of Overhead Bytes Fixed Packet Length, η F = X L X ( L+ H ) η F X L H z where Number of useful information in bytes Information Size of the Packet in bytes Header size of the packet in bytes represents the smallest integer larger than or equal to z

52 This efficiency is optimal for all information units which are multiples of the packet information size, i.e., X L L = X Optimal Case (Substitute the above value into the prev. one) η F OPT = L L + H

53 % Transmission Efficiency η V η F η FOPT Fixed Length Variable Length X[number of useful information bytes] η F has a sawtooth shape (Opt. L=48;H=5)

54 The efficiency depends very much on the useful information bytes to be transmitted If the number of useful information bytes is large, the optimal achievable efficiency is approached Only if the number of useful information bytes is small, this efficiency is rather low. So, the distribution of the number of useful information bytes to be transmitted largely determines the efficiency.

55 Different Applications Voice: Since voice is a CBR (Constant Bit Rate) service, we can take the option at the sending terminal only to transmit a packet when it is completely filled (therefore, introducing a packetization delay). So, the efficiency can reach the optimal achievable value, if packets are completely filled which then puts limitation on the packet size in order to limit the packetization delay.

56 Different Applications Video: Where fixed bit rate video coding techniques are used, this service can be considered as a CBR service, again reaching the optimal efficiency Where variable bit rate video coding techniques are used, it may occasionally happen that packets are not completely filled. However, a typical video image contains thousands of bytes, so the optimal achievable efficiency will be very closely approached.

57 Different Applications Data: Distinguish low speed and high speed data. Low speed applications, e.g., keyboard input: small information units must be considered, so the efficiency is rather small (around 10%) High speed applications, e.g., file transfer, image transfer for CAD, etc: the very long information field (e.g., file, image, etc) can be sent into fixed packets giving rise to an efficiency very close to the optimal efficiency, e.g., for 1000 bytes, the efficiency is 89%, instead of an η FOPT = 90.5% in the figure)

58 Remark: Since traffic in a broadband network will largely be composed of video, high speed data, and voice, the overall transmission efficiency approaches the optimal, even if fixed length packets are used.

59 Variable Length Packets Here the overhead is determined by the header and the flags to delimit the packets, e.g., 6 bits in HDLC, plus in addition, some stuffing bits to ensure proper flag recognition. Also, add to the header, a length indicator, determining the length of the packet η v h v = X X + H+ h v where is the specific packet header overhead mentioned above

60 In Figure, we assume 5 bytes H and 2 bytes of h v. We see the transmission efficiency can be very high (close to 100%) for very long packets Remark: For practical reasons such as buffer dimensioning, delay, the max variable length packets must be limited to a certain threshold.

61 CONCLUSIONS The transmission efficiency of variable length packets is better than that of fixed length packets However, in broadband networks, this gain of transmission efficiency is rather limited since the main traffic constituting broadband services will consist of a combination of voice, video, bulk data transfer.

62 SWITCHING SPEED AND COMPLEXITY Two factors for complexity of ATM switch implementation Speed of Operation Queue Memory Size Requirements A) Speed of Operation Header processing Let us assume that header functions are the same for fixed and variable length case. For fixed length packets, available time to perform all functions is fixed, (e.g., 2.8 µsec in the bytes solution at 150 Mbps.) For variable length packets, the available time depends on the worst case (i.e., the smallest packet), so the speed requirements are much higher (e.g., to perform same functions for a byte packet at 150 Mbps only 553 ns are available.).

63 SWITCHING SPEED AND COMPLEXITY B) (Queue) Memory Management Fixed Length Packets Memory management system can assign memory stocks with the same size, namely, the same size of the packets. This operation is simple and management of free memory list is easy. Variable Length Packets Memory management system must be able to assign memory stocks in multiples of bytes so that algorithms like find best fit, find first fit,, can be used. Memory management is complex. CONCLUSION: Regarding speed of operation and queue memory size Fixed Length Packet Size is preferred!!!! In 1988, fixed packet size has been accepted for ATM.

64 FACTS on ATM TECHNOLOGY * Provides a way of linking a wide range of devices (from telephones to computers) using the seamless network * Also removes the distinctions between LAN, MAN and WAN) * Combines packet and circuit switching * It can be sent on any physical media (copper, fiber). Wide range of transmission speed. * Scalable * Allows QoS parameters (voice, video, still image, etc.) * Supports any type of traffic * Allows sources of different bit rates * Uses fixed size packets called CELLS.

65 FACTS on ATM TECHNOLOGY * No error protection or flow control on hop base * Header functionality is reduced * Information field is very small. * Operates in Connection-Oriented Mode * Supports Connectionless Mode

66 HISTORY of ATM 1980 Narrowband ISDN adopted Early 80 s Research on fast switches 1985 B-ISDN Study Group formed 1986 ATM approach chosen for B-ISDN 1987 ATM is standardized by ITU-T June 1989 Cell Size (48+5) chosen Oct ATM Forum formed July 1992 UNI V2 released by ATM Forum October 1999 AAL Layers finalized 1993 First Gen. ATM Switches October 1995 Traffic Management Finalized 1996 Second Gen. ATM Switches 1999 Third Gen. ATM Switches Currently: Heavily used in Backbone Networks (ISP: Internet Service Providers); ADSL (Residential Access Networks) Passive Optical Networks (PONs) deployed in Residential Access Networks

67 ATM FORUM TECHNICAL COMMITTEES * Traffic Management * Signaling * Physical Layer * Testing * B-ICI * LAN Emulation * SAA (Service Aspects & Applications) (VTOA) * Network Management * P-NNI * Multiprotocol over ATM (MPOA) * Residential Broadband

68 ATM NETWORKS End Sources ATM Switch ATM Switch ATM Switch End Destinations (Native ATM ) End Sources PSTN LAN/MAN ATM Switch ATM Switch ATM Switch Internet End Destinations (Non-native ATM )