B-ISDN AND ATM Telephone companies high-speed network service for high-bandwidth usage (155Mbps, 311Mbps, 622Mbps, 1.2Gbps) 3D real-time CAT scan up to 100 cross-sections, 16Mpixels/section, 24bits/pixel 2 36 bits, many times/s distance education real-time video from multiple locations (teacher and each class, to each class)
B-ISDN (BROADBAND INTEGRATED SERVCES DIGITAL NETWORK) single cable to consumer replacement for telephone network huge data rate digital encoding of digital (computer) and analogue (phone, video) data multiple connection ability via a single phone line addresses multiplicity of networks oriented to different data types
ATM (ASYNCHRONOUS TRANSFER MODE) connection-oriented protocol channel id divided into 12-bit VPI (Virtual Path Identifier) 16-bit VCI (Virtual Channel Identifier) early ATM switches switched paths - aggregates of circuits capable of transferring all higher forms of intelligence - voice, video, and data, from one user to another over a local or wide area David Ginsburg: ATM: solutions for enterprise networking
ATM 3-LAYER REFERENCE MODEL Physical layer responsibilities specified but not defined e.g. fibre wavelengths are physical layer s reponsibility but not specified ATM independent of transmission medium Plane management layer management upper layers control plane user plane ATM Adaptation layer ATM layer Physical layer
ATM LAYER establishment and release of virtual circuits congestion control routing loosely equivalent to OSI Network Layer often treated as a data link layer - isn t Cells 5-byte header 48-byte payload 53 bytes upper layers control plane user plane ATM Adaptation layer ATM layer Plane management layer management Physical layer
ATM layer supports (pairs of) unidirectional Virtual Channels possibly with different speeds e.g. data channel forward, control channel back acks left to higher layers retransmission not appropriate for real-time data in-order cell delivery preferentially discard cells with CLP = 1 HEC CLP PTI VCI VPI Header error check Cell Loss Priority Payload Type Identifier Virtual Channel Identifier Virtual Path Identifier
Payload types 000 user data no congestion cell type 0 001 user data no congestion cell type 1 010 user data congestion experienced cell type 0 011 user data congestion experienced cell type 1 100 point-to-point maintenance information 101 end-to end maintenance information 110 Resource management (for ABR cells) 111 RESERVED
ATM Adaptation Layer applications (voice, video, data) interface ATM cells maintains timing for real-time sources (e.g.cbr) Plane management layer management upper layers control plane user plane ATM Adaptation layer ATM layer Physical layer
Classes of service: CBR (Constant Bit Rate) - acts like TDM designed for 64kbps voice links, video-conferencing VBR (Variable Bit Rate) RT-VBR (real-time VBR) e.g. compressed video variability is in the supply of data, not the transmission NRT-VBR (non-real-time...) high priority, but not jitter-sensitive e.g. WWW video & sound
ABR (Available Bit Rate) for data traffic with roughly known bandwidth requirement data rate min rate guaranteed time quench source to stop congestion no guarantee for peak rates can thus set max CLR, though max rate is arbitrary. UBR (Unspecified Bit Rate) for delay and loss tolerant data; email, fax, ftp, telnet UBR cells are first to be discarded
IMPLEMENTING CLASSES OF SERVICE 1 buffer queue, with header, per VC CBR and VBR queues triggered regularly headers have VC data Circular list of headers for ABR and CBR buffer queues round robin server operates when no higher priority class output scheduled OR CBR/VBR trigger scheduled, but empty for ABR circuits, no of cells output min bandwidth guarantee CBR + VBR + min ABR bandwidth < o/p bandwidth
resource management inter-layer coordination PLANES User plane error correction transport flow control
Control plane connection setup, release, management Setup Setup Call proceeding Call proceeding Setup connect connect ack connect ack connect connect connect ack release release release complete release complete release release complete
Switching within network uses VPIs for host A, host B connection 1 st VC between establishes path later VCs follow same path no routing required Change 1 routing table entry to reroute whole path Routing table has 2 12 entries, not 2 28 Paths can act as organisations private networks
incoming port incoming path 0 0 1 2 ROUTING TABLE 2 12 entries outgoing port 3 1 5 outgoing path 0 1 4 1 0 1 2 4 0 2 0 3 9 1 st circuit along a path creates entry Later circuits use the same entry Paths go from end-switch to an end-switch so all circuits on a path end up at the same destination
SONET (US) & SDH(CCITT) SYNCHRONOUS OPTICAL NETWORK & SYNCHRONOUS DIGITAL HIERARCHY fibre optic infrastructure for worldwide telecomms for next 2-3 decades supports internetworking between commercial and national carriers multiplexes multiple digital channels up to Gbps physical layer protocol 51.8Mbps 2.48Gbps plesiosynchronous clocks in adjacent nodes nearly synchronised makes it easy to keep synchronised using data signal dummy frames sent to maintain synchronisation
SONET paths may include intermediate MUXes and repeaters Source MUX repeater MUX repeater Destin ation MUX Section Section Section Section Line Line Path
SONET s multiplexed signals are byte-interleaved maps onto optical hieararchy (optical fibres with different capacities) signals also have different capacities byte-interleaving simplifies multiplexing and enables end-to-end network management. base signal (synchronous transport signal level 1, or simply STS 1) STS-1 operates at 51.84 Mbps (aka OC-1, Optical Carrier-1). An STS-N signals comprises N directly interleaved STS 1 signals N is commonly 1, 3, 12, 48, 192
SONET s 4-layer protocol stack only concerns the SONET frame. Path layer; end-to-end end-to-end transport and mapping of services, including: DS1 (T1, 1.544 Mbps) & DS3 (T3, 44.736 Mps) circuits and video. mapping these services into an STS frame (see below). Line layer; MUX to MUX 28 T1 circuits 24 64Kbps channels point-to-point transport of path layer payload and its overhead provides synchronization and multiplexing for the path layer. Section layer; point-to point connections generates & transports STS-N frames across the physical medium. framing, scrambling, section-error monitoring and communicating and adding the section layer overhead.
Photonic layer converts electrical signals to optical ones. Frames transmitted continuously Diagram shows 2 frames sent back-to-back SONET S 810-BYTE FRAME 87 columns 125 µs Line and section overhead in standard location within frame
Payload starts when payload data arrives; hence payload pointer Path overhead relates to payload, not frame section overhead repeater to repeater information for section to section communication data for framing, performance monitoring voice channel for maintenance personnel channel for OAMP (Operations, Administration, Maintenance and Provisioning) line overhead information required for line termination equipment communication such as an Add/Drop terminal.
payload pointer and has data for OAMP, line performance monitoring and another voice channel for maintenance personnel. synchronous payload the actual information being transmitted. path overhead monitors the payload makes sure that the correct connection was made identifies the payload type provides a user channel for the service provider s information is carried within the payload because the only time it is created or looked at is when the payload enters or exits the SONET network.
IPATM (IP OVER ATM) RFC 1577 Considers deployment of ATM within "classical" IP networks as a direct replacement for local area networks (ethernets) and for IP links which interconnect routers RFC deals with transmitting IP datagrams and ATM Address Resolution Protocol (ATMARP) requests and replies over ATM
End-to-end IP routing architecture stays the same. IP addresses are resolved to ATM addresses by use of an ATMARP service within the IP Subnetwork One IP subnet is used for many hosts and routers. Each VC directly connects two IP members within the same IP Subnetwork
LIS (LOGICAL IP SUBNET) Hosts and routers are configured within a logical IP subnetwork. Hosts of differing IP subnets MUST communicate via an intermediate IP router even though it may be possible to open a direct VC between the two IP members over the ATM network. Hosts within the same LIS may communicate directly via ATM
In a LIS, all members: have the same IP network/subnet no and address mask are directly connected to the ATM network. MUST be able to communicate via ATM with all other members in the same LIS MUST have a mechanism for resolving IP addresses to ATM addresses via ATMARP and vice versa via InATMARP when using SVCs. MUST have a mechanism for resolving VCs to IP addresses via InATMARP when using PVCs. permanent Virtual Circuits switched Virtual Circuits
ATMARP & INATMARP (ATM ARP AND INVERSE ATM ARP) ATMARP server gets requests for the resolution of target IP addresses to target ATM addresses. If the LIS is operating with PVCs only, IP stations are not required to send requests to the ATMARP server.
IPATM does not support broadcast or multicast messages, as ATM does not support these facilities.
MTU (Maximum Transfer Unit IP fragment size in the ATM network) 9180 octets These PDUs are segmented into 53 octet ATM cells