ATM

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Presentation Transcript

ATM : 

Networks: ATM 1 ATM Asynchronous Transfer Mode

Issues Driving LAN Changes : 

Networks: ATM 2 Issues Driving LAN Changes Traffic Integration Voice, video and data traffic Multimedia became the ‘buzz word’ One-way batch Web traffic Two-way batch voice messages One-way interactive Mbone broadcasts Two-way interactive video conferencing Quality of Service guarantees (e.g. limited jitter, non-blocking streams) LAN Interoperability Mobile and Wireless nodes

Slide 3: 

Networks: ATM 3 Stallings “High-Speed Networks”

Slide 4: 

Networks: ATM 4 Stallings “High-Speed Networks”

Slide 5: 

Networks: ATM 5 A/D Voice s1 , s2 … Digital voice samples A/D Video Compression compressed frames picture frames Data Bursty variable-length packets Figure 9.3 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies AAL AAL AAL

Slide 6: 

Networks: ATM 6 MUX ` Wasted bandwidth ATM TDM 4 3 2 1 4 3 2 1 4 3 2 1 4 3 1 3 2 2 1 Voice Data packets Images Figure 7.37 Asynchronous Transfer Mode (ATM) Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

ATM : 

Networks: ATM 7 ATM ATM standard (defined by CCITT) is widely accepted by common carriers as mode of operation for communication – particularly BISDN. ATM is a form of cell switching using small fixed-sized packets. Header Payload 5 Bytes 48 Bytes Figure 9.1 Basic ATM Cell Format Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

ATM Conceptual ModelFour Assumptions : 

Networks: ATM 8 ATM Conceptual ModelFour Assumptions ATM network will be organized as a hierarchy. User’s equipment connects to networks via a UNI (User-Network Interface). Connections between provided networks are made through NNI (Network-Network Interface). ATM will be connection-oriented. A connection (an ATM channel) must be established before any cells are sent.

Slide 9: 

Networks: ATM 9 X X X X X X X X X Private UNI Public UNI NNI Private NNI Private ATM network Public UNI B-ICI Public UNI Public ATM network A Public ATM network B Figure 9.5 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

ATM Connections : 

Networks: ATM 10 ATM Connections two levels of ATM connections: virtual path connections virtual channel connections indicated by two fields in the cell header: virtual path identifier VPI virtual channel identifier VCI

Slide 11: 

Networks: ATM 11 Physical Link Virtual Paths Virtual Channels Figure 7.40 ATM Virtual Connections Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

ATM Conceptual Model Assumptions (cont.) : 

Networks: ATM 12 ATM Conceptual Model Assumptions (cont.) Vast majority of ATM networks will run on optical fiber networks with extremely low error rates. ATM must supports low cost attachments This decision lead to a significant decision – to prohibit cell reordering in ATM networks. ? ATM switch design is more difficult.

Slide 13: 

Networks: ATM 13 GFC (4 bits) VPI (4 bits) VPI (4 bits) VCI (4 bits) VCI (8 bits) VCI (4 bits) PT (3 bits) CLP (1 bit) HEC (8 bits) ATM cell header Payload (48 bytes) Figure 9.7 UNI Cell Format Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 14: 

Networks: ATM 14 2 3 N 1 Switch N 1 … 5 6 video 25 video voice data 32 32 61 25 32 32 61 75 67 39 67 N 1 3 2 video 75 voice 67 data 39 video 67 Figure 7.38 … … ATM Cell Switching Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 15: 

Networks: ATM 15 c ATM Sw 1 ATM Sw 4 ATM Sw 2 ATM Sw 3 ATM DCC a b d e VP3 VP5 VP2 VP1 a b c d e Sw = switch Figure 7.39 Digital Cross Connect Only switches virtual paths Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

ATM Protocol Architecture : 

Networks: ATM 16 ATM Protocol Architecture ATM Adaptation Layer (AAL) – the protocol for packaging data into cells is collectively referred to as AAL. Must efficiently package higher level data such as voice samples, video frames and datagram packets into a series of cells. Design Issue: How many adaptation layers should there be?

Slide 17: 

Networks: ATM 17 Plane management Management plane Control plane User plane Physical layer ATM layer ATM adaptation layer Higher layers Higher layers Layer management Figure 9.2 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 18: 

Networks: ATM 18 AAL ATM User information User information AAL ATM PHY PHY ATM PHY ATM PHY … End system End system Network Figure 9.4 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Original ATM Architecture : 

Networks: ATM 19 Original ATM Architecture CCITT envisioned four classes of applications (A-D) requiring four distinct adaptation layers (1-4) which would be optimized for an application class: Constant bit-rate applications CBR Variable bit-rate applications VBR Connection-oriented data applications Connectionless data application

ATM Architecture : 

Networks: ATM 20 ATM Architecture An AAL is further divided into: The Convergence Sublayer (CS) manages the flow of data to and from SAR sublayer. The Segmentation and Reassembly Sublayer (SAR) breaks data into cells at the sender and reassembles cells into larger data units at the receiver.

Slide 21: 

Networks: ATM 21 Original ATM Architecture

Slide 22: 

Networks: ATM 22 Transmission convergence sublayer Physical medium dependent sublayer Physical medium ATM layer Physical layer Figure 9.6 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Original ATM Architecture : 

Networks: ATM 23 The AAL interface was initially defined as classes A-D with SAP (service access points) for AAL1-4. AAL3 and AAL4 were so similar that they were merged into AAL3/4. The data communications community concluded that AAL3/4 was not suitable for data communications applications. They pushed for standardization of AAL5 (also referred to as SEAL – the Simple and Efficient Adaptation Layer). AAL2 was not initially deployed. Original ATM Architecture

Slide 24: 

Networks: ATM 24 Revised ATM Architecture

Revised ATM Service Categories : 

Networks: ATM 25 Revised ATM Service Categories

QoS, PVC, and SVC : 

Networks: ATM 26 QoS, PVC, and SVC Quality of Service (QoS) requirements are handled at connection time and viewed as part of signaling. ATM provides permanent virtual connections and switched virtual connections. Permanent Virtual Connections (PVC) permanent connections set up manually by network manager. Switched Virtual Connections (SVC) set up and released on demand by the end user via signaling procedures.

Slide 27: 

Networks: ATM 27 (b) CS PDU with pointer in structured data transfer AAL 1 Pointer 1 Byte 46 Bytes 47 Bytes Figure 9.11 AAL 1 Payload Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies optional (a) SAR PDU header CSI SNP Seq. Count 1 bit 3 bits 4 bits

Slide 28: 

Networks: ATM 28 … Higher layer User data stream Convergence sublayer SAR sublayer ATM layer CS PDUs SAR PDUs ATM Cells H H H b1 b2 b3 Figure 9.10 AAL 1 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 29: 

Networks: ATM 29 (a) CPCS-PDU format (b) SAR PDU format CPI Btag BASize CPCS - PDU Payload 1 1 2 1 - 65,535 0-3 1 1 2 (bytes) (bytes) (bytes) AL Etag Length Pad Header Trailer ST SN MID SAR - PDU Payload 2 4 10 44 6 10 (bits) (bytes) (bits) LI CRC Header (2 bytes) Trailer (2 bytes) Figure 9.16 AAL 3/4 CS and SAR PDUs Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 30: 

Networks: ATM 30 Higher layer Common part convergence sublayer SAR sublayer ATM layer Service specific convergence sublayer Information Assume null T PAD User message Pad message to multiple of 4 bytes. Add header and trailer. Each SAR-PDU consists of 2-byte header, 2-byte trailer, and 44-byte payload. H 4 4 … … Information Figure 9.15 AAL 3/4 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 31: 

Networks: ATM 31 Information 0 - 65,535 0-47 1 1 2 4 (bytes) (bytes) UU CPI Length CRC Pad Figure 9.19 AAL 5 Convergent Sublayer Format SAR Format 48 bytes of Data ATM Header 1-bit end-of-datagram field (PTI) Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

Slide 32: 

Networks: ATM 32 Higher layer Common part convergence sublayer SAR sublayer ATM layer PTI = 0 Service specific convergence sublayer Assume null 48 (1) Information T PAD … … Information 48 (0) 48 (0) PTI = 0 PTI = 1 Figure 9.18 AAL 5 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies