ECE544Lec3DR08

ECE544Lec3DR08 - EC E544: C m om unication Ne tworks-I I ,...

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Unformatted text preview: EC E544: C m om unication Ne tworks-I I , S pring 2008 D. Raychaudhuri Lecture 3 Includes tutorial materials from the ATM Forum & U VA Today's Le cture Switched Networks Switched Ethernet ATM networks Concepts Learning bridge, spanning tree Overview Signaling PNNI Routing (basics) Used to connect hosts to Ethernet LAN and to connect multiple Ethernet LANs Collisions are propagated Ethernet Hub Host IP IP Ethe t Hub rne Ethernet Hub Host LLC LLC 802.3 MAC Hub Hub 802.3 MAC Bridge s/LAN switche s We will use the terms bridge and LAN switch (or Ethernet switch in the context of Ethernet) interchangeably. Interconnect multiple LAN, possibly with different type Bridges operate at the Data Link Layer (Layer 2) Tokenring Bridge IP Bridge LLC IP LLC LLC 802.3 MAC LAN 802.3 MAC 802.5 MAC LAN 802.5 MAC Ethe t Hubs vs. Ethe t S rne rne witche s An Ethernet switch is a packet switch for Ethernet frames An Ethernet Hub does not perform buffering: Hub CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD CSMA/CD Buffering of frames prevents collisions. Each port is isolated and builds its own collision domain Collisions occur if two frames arrive at the same time. Switch CSMA/CD CSMA/CD HighSpeed Backplane CSMA/CD CSMA/CD CSMA/CD CSMA/CD Input Buffers Output Buffers AS witche Ente d rpriseNe twork Internet Router Switch What do bridges do if some LANs are reachable only in multiple hops ? What do bridges do if the path between two LANs is not unique ? Ne d for Routing e LAN 2 d Bridge 3 Bridge 1 Bridge 4 LAN 5 Bridge 5 LAN 1 Bridge 2 LAN 3 LAN 4 Transpare Bridge nt s Three principal approaches can be found: Fixed Routing Source Routing Spanning Tree Routing (IEEE 802.1d) We only discuss the last one in detail. Bridges that execute the spanning tree algorithm are called transparent bridges Transpare Bridge nt s Three parts to transparent bridges: (1) Forwarding of Frames (2) Learning of Addresses (3) Spanning Tree Algorithm (1) Fram Forwarding e Each bridge maintains a forwarding database with entries < MAC address, port, age> MAC address: port: age: host name or group address port number of bridge aging time of entry with interpretation: a machine with MAC address lies in direction of the port number from the bridge. The entry is age time units old. (2) Addre Le ss arning (Le arning Bridge s) Routing tables entries are set automatically with a simple heuristic: The source field of a frame that arrives on a port tells which hosts are reachable from this port. Src=x, Dest=y Port 1 Port 2 Port 3 x is at Port 1 y is at Port 5 Port 4 Port 5 Port 6 Src=x, Dest=y Exam ple Consider the following packets: (Src=A, Dest=F), (Src=C, Dest=A), (Src=E, Dest=C) What have the bridges learned? Bridge 2 Port1 Port2 Port1 Bridge 2 Port2 LAN 1 A B C LAN 2 D E LAN 3 F Dange of Loops r Consider the two LANs that are connected by two bridges. Assume host n is transmitting a frame F with unknown destination. F What is happening? Bridges A and B flood the frame Bridge A to LAN 2. Bridge B sees F on LAN 2 (with unknown destination), and copies the frame back to LAN 1 Bridge A does the same. The copying continues LAN 2 F Bridge B F F LAN 1 F host n S panning Tre s / Transpare Bridge e nt s A solution is to prevent loops in the topology IEEE 802.1d has an algorithm that organizes the bridges as spanning tree in a dynamic environment Note: Trees don't have loops LAN 2 d Bridge 3 Bridge 1 Bridge 4 Bridges that run 802.1d are called transparent bridges Bridges exchange messages to configure the bridge (Configuration Bridge Protocol Data Unit, Configuration BPDUs) to build the tree. LAN 5 Bridge 5 LAN 1 Bridge 2 LAN 3 LAN 4 ATM Ove w rvie Introduction Physical Layers ATM Layer ATM Adaptation Layer Interfaces Management ATM Basic C pts once Negotiated Service Connection Endtoend connections, called virtual circuits Traffic contract Switched Based Dedicated capacity Cell Based Small, fixed length A Ne gotiate S rviceC ction d e onne Traffic Contract Parameters Traffic Characteristics Peak Cell Rate Sustainable Cell Rate Virtual Connection 1-QOS A Virtual Connection 1-QOS B Quality of Service Delay Cell Loss Virtual Connection 1-QOS b TheATM Ce ll Header Payload 5 Bytes 48 Bytes Small Size Fixed Size Header contains virtual circuit information Payload can be voice, video or other data types 5 Byte Header 48 Byte Payload A ATM Vision The Ultimate Integrated Services Network Voice Voice Data Voice Video ATM Network Video Data Data Video ATM network moves cells (fixed length packets) with low delay and low delay variation at high speeds Devices at ends translate (e.g., segment and reassemble) between cells and original traffic ATM S mArchite yste cture Voice Cell Data Cell Video Cell A ATM Adaptation Laye r AAL 1 2 Types Circuit Emulation -Constant Bit Rate (CBR) Low Bit Rate Voice (Real Time) -Variable Bit Rate (VBR) 48 Bytes 3/4 Time Invariant Data 5 "Simple" Data Provides Mapping Of Applications To ATM Service Of The Same Type Segments/Reassembles Into 48 Payloads Hands 48 Byte Payloads To ATM Layer A ATM Laye r 48-Byte Payloads From AAL 5-Byte Header Header Contains Virtual Path and Channel Identifiers } 53-Byte Cell To Physical Layer Adds/Removes Header To 48 Byte Payload Header Contains Connection Identifier Multiplexes 53 Byte Cells Into Virtual Connections Sequential Delivery Within A Virtual Connection A Physical Laye r Speed Matching and Framing Cable Plants Uses Existing Media Wide Range of Speeds Twisted Pair Coax Transmission Frame LAN, MAN, WAN Compatibility Fiber -Multimode -Single Mode A ATM S mArchite yste cture ATM Cell Creation Transmission Forward Cell Through Network Conversion to ATM Data Types, 48Byte Length Add 5-Byte Header Convert To Correct Electrical Or Optical Format Voice Cell Data Cell Video Cell Services Adaptation Layer ATM Layer Physical Layer A PrivateUNI PHY ATM Forum Physical Layer UNI Interfaces Frame Format Cell Stream STS-1 FDDI STS-3c, STM-1 STS-3c, STM-1 Cell Stream STS-3c, STM-1 STS-12, STM-4 STS-48, STM-16* Bit Rate/Line Rate 25.6 Mb/s / 32 Mbaud 51.84 Mb/s 100 Mb/s / 125 Mbaud 155.52 Mb/s 155.52 Mb/s 155.52 Mb/s / 194.4 Mbaud Transmission Media UTP-3 UTP-3 MMF UTP-5, STP SMF, MMF, Coax pair MMF/STP UTP-3 SMF, MMF SMF 155.52 Mb/s 622.08 Mb/s 2,488.32 Mb/s *-Under Development SMF-Single Mode Fiber MMF-Multimode Fiber UTP-Unshielded Twisted Pair STP-Shielded Twisted Pair DS1 and DS3-Also Private Speeds B Public UNI PHY ATM Forum Physical Layer UNI Interfaces Frame Format DS1 DS3 STS-3c, STM-1 E1 E3 J2 N X T1 N X E1 Bit Rate 1.544 Mb/s 44.736 Mb/s 155.520 Mb/s 2.048 Mb/s 34.368 Mb/s 6.312 Mb/s N X 1.544 Mb/s N X 2.048Mb/s Transmission Media Twisted Pair Coax Pair SMF Twisted Pair, Coax Pair Coax pair Coax pair Twisted pair Twisted pair *-Under Development SMF-Single Mode Fiber PLCP-Physical Layer Convergence Protocol B ATM PHY: Two S ublaye rs Transmission Convergence Sublayer Physical Layer Medium Dependent Sublayer PMD: TCS: Medium, line code, connectors Probably use existing standards and technology Specific to the PMD Cell delineation Cell rate decoupling (inserting empty cells during idle periods) 155 Mbps, S ONET S -3c/S TS DH S columns TM-1 270 9 R o w s Maintenance and operations ... 1 Synchronous Payload Envelope (1 column of overhead) 125 sec 9 bytes 9 260 8/125 sec = 149.76 Mbps payload A HECC ll De ation e line (For S ONET, e tc...) Peek ahead at the cell format HEC (Header Error Check) Header Payload Coverage of the 1 byte HEC Receiver locks on 5 byte blocks that Satisfy the HEC calculation Are separated by 48 bytes HEC includes coset so that empty cell (first 4 bytes of header = 0) does not make HEC = 0 A 1.5 Mbps, DS 1 125 sec ...FBB...BFB...BF... 24 bytes Framing Bit (24 bytes x 8 bits/byte)/125 sec=1.536 Mbps of payload Cell delineation by HEC detection as with SONET Cell payload=1.536 Mbps x (48/53)=1.391 Mbps Based on IEEE 802.5 physical layer with 4B/5B coding plus scrambling 32 Mbaud x 4/5 = 25.6 Mbps Cells delineated by special symbol pairs x x Cell Reset Scramble 25.6 Mbps UTP-3 or x 4 Cell No Scramble Reset A ATM UNI C ll e 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier 5 Bytes CLP Header Error Check Payload (48 bytes) 48 Bytes CLP = Cell Loss Priority Why 53 Byte s? 64 + 5 32 + 4 48 + 5 Compromise reached in ITUTS Study Group XVIII in June 1989 Packe tization De Advantageof lay S all C lls m e Percent Overhead and Packetization Delay for 64 Kbps Voice 100 % Overhead 80 60 40 20 0 0 20 40 Payload (Bytes) 60 Overhead Delay 10 8 6 4 2 0 80 Delay (ms) Que uing Advantageof S all C lls m e 100 byte message 100 other active connections 45 Mbps Max Delay (ms) 12 10 8 6 4 2 0 1 High overhead Wait for other cells Just fits in one cell 50 100 150 200 250 300 Payload (bytes) Delay and delay variation are small for small messages e.g., a digitized voice sample A 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Virtual Conne ctions 76 Video Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) 3 37 Video 42 Data 4 1 88 Voice 37 Video 78 Voice 5 2 6 52 Data 22 Video Connection Table Video Data Video Voice Port 1 1 2 2 VPI/VCI 0/37 0/42 0/37 0/78 Port 3 5 6 4 VPI/VCI 0/76 0/52 0/22 0/88 7 6 5 4 3 2 1 0 Virtual Paths and Virtual C hanne ls Physical Link Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) Virtual Path Virtual Channel 7 6 5 4 3 2 1 0 Virtual Paths and Virtual Channels ATM Switch or Network VPI = 1 VCI = 31 VCI = 32 VPI = 2 VCI = 31 VCI = 40 VPI = 3 VCI = 96 VCI = 97 VPI = 6 VCI = 96 VCI = 97 VPI = 5 VCI = 99 VCI = 32 VPI = 4 VCI = 55 VCI = 57 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) Bundles of Virtual Channels are switched via Virtual Paths Virtual Path service from a carrier allows reconfiguration of Virtual Channels without service orders to carrier 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Ce Loss Priority ll Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Cells with bit set should be discarded before those with bit not set Can be set by the terminal Can be set by ATM switches for internal network control Virtual channels/paths with low quality of service Cells that violate traffic management contract Header Error Check Payload (48 bytes) Key to ATM Traffic Management 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Ge ric Flow Control ne Used for UNI only Not NNI Currently undefined Set to 0000B Proposed future uses Flow control Shared media multiple access Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) B 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier He r Error C ck ade he Header error control Detection mode: Protects header only (all five bytes) Discards cell when header error Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) Correction mode (optional): Correct 1 bit errors else discard when error detected Cell delineation for SONET, SDH, etc... Recalculated linkbylink because of VPI/ VCI value changes Reduced cell loss in face of single bit errors Reduced error detection for multiple bit errors B Pe ane Virtual C rm nt ircuits VPI/VCI VPI/VCI Network Management System VPI/VCI VPI/VCI Long setup time (especially with human intervention) means that connections are left active for long periods of time e.g., days, weeks VPI/VCI tables setup in terminals and switches B S witche Virtual Circuits d Signalling Channel (VPI/VCI = 0/5) Signalling Channel (VPI/VCI = 0/5) Call Processing ATM Switch Switch and terminal exchange signalling messages using the predefined signalling channel, VPI/VCI = 0/5 B Point-to-Point Conne ction Data may flow in one or both directions (unidirectional or bidirectional) Bandwidth may be: Same in both directions (symmetric), or Different in each direction (asymmetric) Point-to-Multipoint Conne ction "Root" Data are replicated by the network Data flow only from Root to Leaves "Leaves" Why S s? VC Universal connectivity More efficient resource utilization A Call control protocol is used to establish, maintain, and clear virtual channel UNI or NNI User Network connections between a user and network Call Control Signalling Call C ontrol S ignalling UNI Call Control Signalling Virtual Channel Connections Interface UNI or NNI S ignalling 4.0 Delta from Q.2931 etc. Extensions for parameterized QoS, ABR, LIJ Some restrictions S ignalling Protocol S tack UNI 4.0 Q.931 Q.921 LAPD I.430/431 ISDN UNI Q.2931 SSCOP ATM SONET/DS3 ATM UNI S tting Up a C - 1 e all A wants to communicate with B A B Setup Call Proceeding Setup message Call proceeding message Call reference VPI/VCI Call reference Called party address Calling party address Traffic characteristics Quality of service B S tting Up a C - 2 e all Setup Call Proceeding Internal network processing Resource availability checking Virtual channel or path routing Function of the Network Node Interface (NNI) B S tting Up a C - 3 e all Setup Call Proceeding Setup Call Proceeding Setup message Call reference Called party address Calling party address Traffic characteristics Quality of service VPI/VCI Call Proceeding Call reference Called user deciding to accept call B S tting Up a C - 4 e all Setup Setup Call Proceeding Call Proceeding Connect Connect Ack Connect message Call reference Indicates call acceptance Connect Acknowledge B S tting Up a C - 5 e all Setup Setup Call Proceeding Call Proceeding Connect Connect Connect Ack Calling party informed that call is available for user information exchange B Connect Ack ATM Addre ssing Private networks 20 byte address Format modeled after OSI NSAP (Network Service Access Point) Mechanisms for administration exist Hierarchical structure will facilitate virtual connection routing in large ATM networks E.164 numbers (telephone numbers) Up to 15 digits MAC address will be encapsulated within NSAP Public networks Private networks B Addre to Endstation ss ATM End System Address Format Native E.164 or AESA Public ATM Network Private ATM Switch Private UNI Public UNI ATM End S mAddre yste ss AESA Format Based on ISO NSAP Format NetworkSupplied 39 DCC HO-DSP End SystemSupplied End System ID SEL SEL 47 IDC HO-DSP End System ID SEL SEL 45 E.164 Number HO-DSP End System ID SEL Private UNI Selector (Not used by Network for Routing) PrivateAddre Form ss ats Data Country Code 39 DCC Routing Fields End System ID SEL International Code Designator 47 ICD Routing Fields End System ID SEL E.164 Private Address 45 E.164 Number Routing Fields End System ID SEL D Addre Re ss gistration Allows automatic configuration Required at the private UNI Optional at the public UNI Network supplies the network prefix User supplies the user part Subaddress: S ubaddre Use ss Used to convey an AESA across a public network which supports only E.164 addresses Also can be used for NSAP UNI Private Address: AESA Subaddress: NSAP or Not Used Public UNI Address: E.164 Public Network Address Subaddress: AESA Subaddress IE: Only present if used for NSAP at Private UNI Private Network Private Network Public Network A Me ssage and I nform s ation Ele e m nts Type Length Type Length Value Type Length Value Type Length Message Header IE1 IE2 IE3 .... Very flexible and extensible encoding 19 message types Around 35 IEs AAL1: AdaptiveC Me lock thod Received Cells Reconstructing the bit stream Continuous Bit Stream Speed up bit clock Water Mark Slow down bit clock Substitute Cells Bit stream rate is independent of ATM network and (theoretically) can be any value Cell delay variation is critical to buffer sizing and bit clock jitter B AAL2 Small payload to reduce packetization delay User 1 User 2 User 3 User 1 User 3 ATM Cell Cell Header (5 Octets) AAL2 Header (3 Octets) AAL2 Payload (variable) B AAL3/4 0 - 65535 Bytes Data 4 Error Checking 4 or 8 Error Checking Bytes 2 M I D 44 2 C R C User Data 2 M I D 44 2 C R C 44 Bytes of Data per Cell CRC Checking per Cell Message Identifier (MID) Allows Multiple Interleaved Packets on a Virtual Connection User Data 2 M I D 44 2 C R C User Data M I D 44 Pad C R C D AAL 5 48 Bytes of Data per Cell Uses a PTI Bit to Indicate Last Cell Only One Packet at a Time on a Virtual Connection 0 - 65535 Bytes Error detection fields Data 0-47 2 2 4 Pad 0 48 0 L e n C R C Bytes ... 1 48 Last cell flag Not drawn to scale C 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Channel Identifier Quality-of-S rvice e Problem: Providing quality of service Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) Solution: Traffic Management How should ATM network resources be allocated to ensure good performance including preventing congestion, e.g., how many virtual channels should be assigned to a particular transmission link? Specify the traffic "contract" on each virtual channel/path Route (including rejecting setup request) each virtual channel/path along a path with adequate resources (Admission Control) Mark (via Cell Loss Priority bit) for loss all cells that violate the contract (Traffic Policing) CBR ATM S rviceC gorie e ate s rtVBR Constant Bit Rate Continuous flow of data with tight bounds on delay and delay variation RealTime Variable Bit Rate nrtVBR UBR ABR Variable bandwidth with tight bounds on delay and delay variation NonRealTime Variable Bit Rate Variable bandwidth with tight bound on cell loss Unspecified Bit Rate No guarantees (i.e., best effort delivery) Available Bit Rate Flow control on source with tight bound on cell loss Quality of S rviceParam te e e rs End to end transit delay Acceptable CDV (Forwards, Backwards) Cumulative CDV (Forwards, Backwards) Cell Loss Ratio (Forwards, Backwards) Encoded as two IEs QoS Classes may also be indicated for backwards compatibility 7 6 5 4 3 2 1 0 Ge ric C ll RateAlgorithm ne e I for each cell arrival Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) For a sequence of cell arrival times, {tk}, determines which cells conform to the traffic contract L+I A counter scheme based on two parameters denoted GCRA(I,L) Increment parameter: I Limit parameter: L affects cell rate One unit leak per unit of time affects cell bursts "Leaky bucket" A cell that would cause the bucket to overflow is nonconforming 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Payload TypeI de ntifie r Bit 3: Used to discriminate data cells from operation, administration, maintenance cells. Bit 2: Used to indicate congestion in data cells (Bit 3 = 0) Set by Switches Source and Destination Behavior Defined for Available Bit Rate Flow Control VCC's Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) Bit 1: Carried transparently endtoend in data cells Used by AAL5 C 7 6 5 4 3 2 1 0 Generic Flow Control Virtual Path Identifier Virtual Path Identifier Virtual Channel Identifier Virtual Channel Identifier ABR Fe dback e Forward RM* Cells Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) + Congestion Indication + + Source Rate & Congestion Indication + Rate Indication Destination + Backward RM* Cells Source sets Actual Cell Rate based on rate & congestion feedback *- Resource Management B Exam S ple ourceC ll RateProfile e Network Congestion Peak Cell Rate Actual Cell Rate Minimum Cell Rate Time C Bandwidth Ne gotiation UNI Setup (20 Mb/s) NNI UNI Setup (15 Mb/s) Setup (10 Mb/s) Connect (10 Mb/s) Connect (10 Mb/s) Connect (10 Mb/s) Othe ATM Inte r rface s Private UNI Private NNI Public NNI Metropolis Data Services Inc. ATM DXI Public UNI FUNI FUNI UNI User Network Interface NNI Network Node Interface BICI BISDN InterCarrier Interface ATM DXI Data eXchange Interface FUNI ATM Frame Based UNI Interface B-ICI Country Wide Carrier Services D Cell Format 7 6 5 4 3 2 1 Virtual Path Identifier Virtual Path Identifier Virtual Path Identifier NNI 0 Virtual Channel Identifier Virtual Channel Identifier Virtual Channel Identifier Payload Type Identifier CLP Header Error Check Payload (48 bytes) CLP = Cell Loss Priority Supports 212 Virtual Paths Supports virtual connection routing Distribution of topology information Distribution of resource availability information Public version being standardized by ITU TS Private version specified by ATM Forum Technical Working Group C For interfaces between public carriers Based on carrier digital transmission DS3, 44.736 Mbps STS3c, 155.52 Mbps STS12c, 622.08 Mbps B-I C I Supports multiple carrier services Cell Relay Service (PVC) Circuit Emulation Service (Synchronous Residual Time Stamp, PVC) Frame Relay Service (PVC) Switched Multimegabit Data Service D ATM Ne twork Manage e m nt Management System M3 Management System M5 Management System M1 M2 M4 M4 UNI ATM Device Private ATM Network UNI Public ATM Network BICI Public ATM Network ILMI: Integrated Layer Management Interface C Today's Hom work e Peterson & Davie, Chap 3 3.1 (v3) 3.5 (v3) 3.7,8 (v3) 3.13 (v3) 3.26 (v3) 3.30 (v3) Download and browse ATM UNI4.0 and PNNI1.0 specs Due next Fri (2/22) 78 ...
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