* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download G805 Introduction
Survey
Document related concepts
Remote Desktop Services wikipedia , lookup
Wake-on-LAN wikipedia , lookup
Distributed firewall wikipedia , lookup
Zero-configuration networking wikipedia , lookup
Deep packet inspection wikipedia , lookup
Computer network wikipedia , lookup
Asynchronous Transfer Mode wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
Piggybacking (Internet access) wikipedia , lookup
Airborne Networking wikipedia , lookup
Network tap wikipedia , lookup
List of wireless community networks by region wikipedia , lookup
Multiprotocol Label Switching wikipedia , lookup
Internet protocol suite wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Transcript
Introduction to G.805 Yaakov (J) Stein Chief Scientist RAD Data Communications The classical model (OSI, X.200) once upon a time networks were exclusively described by the OSI model however few networks actually work only that way highly inflexible (always need more layers!) some features only in one place (security, mux) missing features (OAM) doesn’t help to design transport networks APPLICATION PRESENTATION SESSION TRANSPORT NETWORK LINK PHYSICAL LayerNet Slide 2 Simple telephony counter-example voice channel voice channel E1 (TDM) E1 (TDM) E3 (PDH) E3 (PDH) VC3 (SDH) there are actually 2 STM layers here: • multiplex section • regenerator section OSI application layer ? STM1 (SDH) OC3 (OTN) VC3 (SDH) STM1 (SDH) OSI physical layer OC3 (OTN) this type of scenario important to carriers, and thus to ITU-T not captured by ISO layering model there can be an arbitrary large number of intervening layers all intermediate layers fulfill the same function -- transport LayerNet Slide 3 Packet network counter-example application OSI application layer application TCP TCP IP IP MPLS MPLS Ethernet ? Ethernet MPLS MPLS SDH SDH OTN OSI physical layer OTN here as well, there may be multiple layers many of the layers are equivalent in functionality LayerNet Slide 4 The new model (G.805) a more generally applicable model for transport (infrastructure) networks a transport network is solely responsible for transfer of information from place to place (no “value added” services) a transport network is usually operated by a service provider for a client unlimited client/server layering (recursion) partitioning decomposes network into atomic functions treatment of OAM support for interworking convenient diagrammatic technique References: G.805 CO networks G.705 PDH I.326 ATM G.806 equipment G.781 timing G.8010 Ethernet G.809 CL networks G.783 SDH G.8110 MPLS G.800 Unified functional architecture G.872 OTN G.8110.1 T-MPLS LayerNet Slide 5 Network Modes Circuit Switched Packet Switched (CS) (PSN) Connection Oriented Connectionless (CO) (CL) many native network types (technologies) for each mode – CS: TDM, PDH, SDH, OTN – CO: ATM, FR, MPLS, TCP/IP, SCTP/IP – CL: UDP/IP, IPX, Ethernet, CLNP can layer any mode over any mode – but some layerings may involve performance loss – CL over CO over CS is easy – CO over CL, or CS over CO is harder – CS over CL is very hard LayerNet Slide 6 G.805 we will focus here on CO networks these are described by G.805 CO networks transfer information over connections CL networks do not have connections but may have flows CL networks are described in G.809 CS networks are described in G.705 (PDH) and G.783 (SDH) New unified approach described in G.800 LayerNet Slide 7 Characteristic Information the purpose of communications is to move information each application and network has its own information format examples: E1 with CAS HDLC SYNC TS1 TS2 flag(7E) address control IP packet in Ethernet frame Ethernet header IP header TCP header payload Ethernet CRC TS3 … signaling bits data … CRC TSn flag(7E) <HTML> <BODY> web page html </BODY> </HTML> this is called characteristic information (CI) LayerNet Slide 8 Layer Networks in the new framework, each layer is an independent network we call such a network a layer network because it exists at one layer because it is a network unto itself we will first describe features of a layer network afterwards we discuss the relationships of neighboring layers LayerNet Slide 9 Layer Networks (cont.) network inputs outputs a layer network has inputs and outputs CI is input to the network at an input and is transported to an output with no (or minimal) degradation the association of an input with an output is called a connection in CO networks connections are changed by setup and tear-down procedures in CL networks connections are transient (for a single packet) or longer lived (for a flow) LayerNet Slide 10 Network Connection a network connection matches one output to one input often we want to have a bidirectional connection + like a transceiver or a modem, = is a colocated with a LayerNet Slide 11 Network Connection Types a link connection (LC) is a fixed connection between 2 “ports” unidirectional link connection ports the LC is the smallest unit of manageable capacity bidirectional link connection a subnetwork connection (SNC) is a flexible connection for CO networks SNCs are changed by network management functions unidirectional subnetwork connection bidirectional subnetwork connection the simplest subnetwork is a network element (NE) such as a matrix, switch, or crossconnect LayerNet Slide 12 Transport and Topology a transport entity transfers information from point to point and a transport processing function performs some information processing but at a high level of abstraction only the possible connections between inputs and outputs is important the geographical location of the endpoints the data rate the type of physical connection etc. are ignored G.805 defines a topological component that relates inputs to outputs layer networks and subnetworks are topological components SNCs and LCs are transport entities we will see processing functions later, e.g. to adapt format from layer to layer LayerNet Slide 13 Reference Points unidirectional input or output point = bidirectional input/output point we concatenate connections by binding the output of one connection to the input of the next connection we can do the same thing with bidirectional connections we thus create reference points called connection points (CP) unidirectional connection point bidirectional connection point LayerNet Slide 14 Connection Points we can concatenate link connections CP CP LC LC CP similarly, we use link connections to connect subnetwork connections SNC CP LC CP SNC CP LC CP SNC we will mostly focus on bidirectional connections but remember this merely hides the functionality LayerNet Slide 15 Partitioning if we can zoom in on an SNC we discover that it too is made up of SNCs connected by LCs SNC LC SNC LC SNC LC SNC SNC we can continue recursively zooming in until we are left with LCs and flexible connections internal to NEs different degrees of detail are useful for different purposes partitioning may be used to delineate: routing domains administrative boundaries between different operators service provider/customer networks LayerNet Slide 16 Layer Network Partitioning the whole layer network can be recursively decomposed into connections internal to NEs and link connections network NE NE NE NE NE NE NE NE NE LayerNet Slide 17 OAM analog channels and 64 kbps digital channels did not have mechanisms to check signal validity and quality thus major faults could go undetected for long periods of time hard to characterize and localize faults when reported minor defects might be unnoticed indefinitely as PDH networks evolved, more and more overhead was dedicated to Operations, Administration and Maintenance (OAM) functions including: monitoring for valid signal defect reporting alarm indication/inhibition when SONET/SDH was designed overhead was reserved for OAM functions today service providers require complete OAM solutions LayerNet Slide 18 Trails since OAM is critical to proper network functioning OAM must be added to the concept of a connection a trail is defined as a connection along with integrity supervision clients gain access to the trail at access points (AP) trail terminations are denoted by triangles a trail termination (TT) source accepts CI and adds trail overhead information a trail termination (TT) sink supervises integrity of trail and removes trail overhead the triangle always points towards the supervised connection reference points where trail terminations binds to connections are called termination connecting points (TCP) LayerNet Slide 19 Trails (cont.) for bidirectional trails there is a shorthand notation for colocated termination source and sinks = bidirectional trail termination a trail is considered to run from the input to the trail termination source to the output of the trail termination sink so the access points are trail AP AP before the trail termination source after the trail termination sink TCP A TCP sometimes we specify the network inside the triangle LayerNet Slide 20 Trail Termination Functions what precise functionality does the trail add to the connection itself? continuity check (e.g. LOS, periodic CC packets) connectivity check (detect misrouting) signal quality monitoring (e.g. error detection coding) alarm indication/inhibition (e.g. AIS, RDI) source termination function: generates error check code (FEC, CRC, etc) returns remote indications (REI, RDI) inserts trail trace identification information sink termination function: detects misconnections detects loss of signal, loss of framing, AIS instead of signal, etc. detects code violations and/or bit errors monitors performance LayerNet Slide 21 Defects, Faults, etc. G.806 defines: anomaly (n): smallest observable discrepancy between desired and actual characteristics defect (d): density of anomalies that interrupts some required function fault cause (c): root cause behind multiple defects failure (f): persistent fault cause - ability to perform function is terminated action (a): action requested due to fault cause performance parameter (p): calculatable value representing ability to function for example: dLOS = loss of signal defect cPLM = payload mismatch cause aAIS = insertion of AIS action equipment specifications define relationships e.g. aAIS <= dAIS or dLOS or dLOF alarms are human observable failure indications LayerNet Slide 22 Supervision Flowchart performance monitoring anomaly pX statistics gathering nX defect correlation defect filter N.B. this is a greatly simplified picture cX persistence monitoring fX dX consequent action aX more generally there are external signals, time constants, etc. LayerNet Slide 23 Layering another lesson learned as the PSTN evolved was the importance of layering each layer network is an independent network in its own right all layer networks are described using the same tools each layer network is independently designed and maintained one should be able to add/modify layer networks without changing neighboring layer networks there is a client/server relationship between neighboring layers in order for layering to be clean server layer should transparently carry the client layer’s CI each layer network needs its own OAM mechanisms in order to guarantee QoS for its client LayerNet Slide 24 Some Layer Network Types PDH (G.705) P0 P11 P12 P21 P22 P31 P32 = = = = = = = DS0 DS1 E1 DS2 E2 DS3 E3 P1 = P11 or P12 Eq is electric level equivalent e.g. E11 is T1 P2 = P21 or P22 P3 = P31 or P32 SDH (G.783) ESn STM-N Electrical Section (n = 1) OSn STM-N Optical Section (n = 1, 4, 16, 64, 256) RSn STM-N Regenerator Section (n = 1, 4, 16, 64, 256) MSn STM-N Multiplex Section (n = 1, 4, 16, 64, 256) Sn LO (n=11, 12, 2, 3) or HO (n=3,4) VC-n LayerNet Slide 25 Some Layer Network Types ATM VP and VC layer networks Ethernet ETH (MAC) and ETY (PHY) layer networks ETY1: 10BASE-T (twisted pair electrical; full-duplex only) ETY2.1: 100BASE-TX (twisted pair electrical; full-duplex only; for further study) ETY2.2: 100BASE-FX (optical; full-duplex only; for further study) ETY3.1: 1000BASE-T (copper; for further study) ETY3.2: 1000BASE-LX/SX (long- and short-haul optical; full duplex only) ETY3.3: 1000BASE-CX (short-haul copper; full duplex only; for further study) ETY4: 10GBASE-S/L/E (optical; for further study) ETH-m VLAN multiplexed MPLS stack of multiple MPLS layer networks LayerNet Slide 26 Some client/server Relationships telephony ISDN IP DS0 ATM VC E1/T1 ATM VP E3/T3 LOP SDH HOP SDH STM-N OTN LayerNet Slide 27 Adaptation unfortunately, although all layer networks are created equal the format of their CI is different so in order to put the client information into a server format we have to adapt it this is done by an adaptation function CI an adaptation source accepts client CI and encapsulates it for transfer over the server trail creating adapted information (AI) CI an adaptation sink accepts the AI AI adaptations are denoted by trapezoids and recovers the client layer CI AI the trapezoid always points towards the server layer LayerNet Slide 28 Adaptation (cont.) for bidirectional trails there is a shorthand notation for colocated adaptation source and sinks = client CI CP adaptation function server trail AP trail termination function A B/A B server layer connection TCP sometimes we specify the layer networks inside the trapezoid order - server/client LayerNet Slide 29 Adaptation Functions what precise functionality does the adaptation perform? source adaptation may include: bit scrambling encoding framing encapsulation bit-rate adaptation multiplexing, inverse multiplexing etc. sink adaptation: descrambling decoding deframing decapsulation bit-rate adaptation demultiplexing timing recovery monitoring for AIS etc. LayerNet Slide 30 Muxing and Inverse Muxing there may be a many-to-one relationship between clients and server one server layer trail simultaneously multiplexing many client layer networks the client layer networks could be of the same or of different types there may be a one-to-many relationship between a client and servers multiple server layer trails simultaneously inverse multiplex a client layer network the server layer networks could be of the same or of different types. LayerNet Slide 31 The BIG Picture a link connection in the client layer is supported by a trail in the server layer CP client LC CP AP server trail AP TCP TCP N.B. the flexibility of the server layer connections is unavailable to the client layer LayerNet Slide 32 Shorthand notation it is often convenient to combine adaptation and trail terminations = AP and we obtain the simpler diagram: CP CP trail but AP is hidden TCP TCP LayerNet Slide 33 More and more layers .. . trail each layer has its own OAM each client/server pair has its own adaptation trail TCP TCP LayerNet Slide 34 Simple Example: SAToP-MPLS TDM trail TDM AP TDM TDM CP CP MPLS/TDM MPLS/TDM MPLS trail MPLS AP TDM AP MPLS MPLS AP MPLS MPLS network MPLS TCP MPLS TCP LayerNet Slide 35 More Complex Example PDH over SDH E1 SDH MUX VC12 ADM VC4 CC SDH MUX low order path sections G.703 interface E1 G.703 interface high order path sections multiplex sections regenerator sections LayerNet Slide 36 Layering vs. Partitioning each layer network may be separately partitioned reflecting its management requirements layering and partitioning are thus orthogonal analyses layering is vertical – client layer network is “above” the server layer network partitioning is horizontal – subnetworks and links belong to same layer network a trail in a server layer network supports a LC in its client layer network LayerNet Slide 37 Layering vs. Partitioning (cont.) layer network layer network links layer network AGs AGs layering subnetworks layer network partitioning Access Groups (AG) are colocated APs that belong to the same client LayerNet Slide 38 Service Interworking A>B we have seen how to carry traffic from network A over network B client/server relationship = A<>B A<B layer network interworking (service interworking - SI) there is a special symbol when we need to terminate network A and carry its client over network B peer to peer relationship Example: SI of ATM with MPLS N.B. SI is usually limited to a specific client type client trail ATM layer network MPLS layer network LayerNet Slide 39 Permissible Bindings inputs and outputs may be bound together iff share CI or adapted information connection points (CP) connection - adaptation adaptation - adaptation SI - adaptation termination connection points (TCP) TT - connection TT - TT access points (AP) TT - adaptation TT - SI the difference between a LNC and a SNC: network connections are delineated by TCPs SNCs are delineated by CPs adaptation - TT LayerNet Slide 40 Expansions new functionality is formally introduced by inserting a new layer network to do this one can expand a CP or a TT CP expansion TT expansion CP TCP CP TCP we will show one example of each of these expansions: CP expansion to monitor SNC TT expansion for trail protection LayerNet Slide 41 Example - tandem monitoring if we need to separately monitor subnetworks for example, in order to provide defect localization we can expand a CP to make them into full layer networks CP CP CP CP SNC CP CP CP CP adaptation adds overhead room TT adds supervision information SNC LayerNet Slide 42 Example - trail protection to add 1+1 protection for a trail, we can expand a TT we use a special transport processing function - the protection switch unprotected trail protected trail the unprotected TTs report status to the protection switch LayerNet Slide 43 G.809 CL networks can be partitioned and layered just like CO ones but in CL networks there are no connections instead we have a new concept - a flow (there are link flows, flow domain flows, and network flows) once monitored, adapted CI is transported on a connectionless trail G.809 diagrams are similar to G.805 ones but shading indicates CL components LayerNet Slide 44 CL client / CO server connectionless trail flow TFP TFP trail TCP TCP LayerNet Slide 45 CL traffic conditioning CL networks have some unique requirements For example, G.8010 defines a traffic conditioning function This transport processing function classifies packets and then meters / polices within each class You can add the TC function by expanding a FP FP expansion FP FP FP LayerNet Slide 46