Multiservice Provisioning Platform (MSPP) & Resilient Packet Ring (RPR)
Multiservice Provisioning Platform (MSPP) is deployed in the boundary of Access and Metro core backbone. TEC has prepared two different platforms for catering to the needs of the inter city and intra equipment. The first platform is the STM-16 with the GFP-F, GFP-T protocols and layer-2 switching functionality and caters to the need of inter-city traffic. This platform also includes higher cross connect capability, and supports EoS as per IEEE standards. The second platform is using Multi service Provisioning Platform (MSPP), and caters to the need for the intra-city traffic requirements.
The main application of this system shall be for multi-service traffic switching and aggregation at MAC layer, traffic grooming and traffic consolidation of TDM traffic at SDH layer from access network towards core network. Another prominent application of MSPP shall be, multiple SDH ring inter connection at STM1 tributary interfaces as well as at STM4 & 16 aggregate interfaces. The equipment shall provide an integrated cross connect matrix to switch digital signals at SDH layer.
The MSPP equipment shall be capable of simultaneously interfacing the PDH streams and mapping / de-mapping into SDH payloads and vice-versa, thus enabling the co-existence of SDH & PDH on the same equipment. This is the greatest advantage for the network as SDH and PDH existing in the present network can integrate easily which in turn enables quick bandwidth provisioning to the customer.
MSPP is implemented with two different back haul transmission rates, viz. STM-16 and STM-64. TEC has also been working on the STM-64 in BSNL Metro networks. Apart from the standard interfaces on the tributary side, the revised STM-16 provides POS (packet over SDH) capability on Ethernet interface at 10Mb,100 Mb, and 1000Mb. The equipment is also envisaged to support DS-3 of SONET. The encapsulation of Ethernet on SDH capability shall be in accordance with ITU-T G.7041. the system should support Tandem Connection Monitoring (TCM) on N1 byte and N2 byte for HO path & LO path respectively.
ADMs supporting GFP and VCAT are known as Multi Service Provisioning Platform (MSPP). Service providers can now deliver packet based transport services using existing SDH infrastructure. GFP and VCAT is located at the endpoint s of the network, therefore MSPP need only be deployed at the edge of the transport network. MSPP targets all application connecting ultra-high capacity backbones to end customers at their premises. The advent of GFP has created a spur of customer located equipment and MSPP cards that function as aggregating Ethernet traffic onto SDH rings. The generic structure of a next generation MSPP is shown in (fig1). This platform consists of the integration of metro WDM with Ethernet /RPR and SDH VC-4 switching fabrics. Integration means both direct inter working, in terms of WDM wavelengths, and full NMS/control plane integration for management and path provisioning.
Features of MSPP:
The major features of MSPP are as listed below:
- Generic Framing Protocol-Frame (GFP-F)
- Generic Framing Protocol-Transparent (GFP-T)
- Link Capacity Adjustment Scheme (LCAS).
- Virtual concatenation (V-CAT)
- Layer 2 switching.
- Integrated higher cross connect capability
- Ethernet on SDH (EoS)
- PoS capability on Ethernet interface
- DS-3 tributary interface of SONET hierarchy
- Support block code oriented payload (FICON)
- ESCON (Enterprise system connection)
- FC (Fiber Channel) at gigabit Ethernet interface
- Tandem Connection Monitoring (TCM) on N1 & N2 bytes
- Multi service traffic switching
- Traffic aggregation at MAC layer
- Traffic grooming
- Traffic consolidation of TDM traffic at SDH layer from access towards core network.
- Multiple SDH rings interconnection at STM-1tributary interfaces as well as at STM-4/16 aggregate interfaces.
- Interfacing the PDH streams (2Mb, 34Mb, 140Mb) and mapping / De-mapping into SDH payloads and vice-versa.
A key set of technologies for delivering client services efficiently via MSPP are:
- Generic Framing Procedure (GFP), ITU-T G.7041
- Link Capacity Adjustment Scheme (LCAS), ITU-T G.7042
- Virtual Concatenation (VCAT), ITU-T G.707
VCAT is used to provide better data granularity, GFP is used to wrap the data in a converged TDM network, & LCAS is used to dynamically allocate& manage B/W.
Resilient Packet Ring (RPR)
Ethernet can be transported over SDH using one of the two possible mechanism or a combination of both:-
Shared Protection Ring MSPPs supports SPRs to provide Ethernet and packet transport over SDH infrastructure. The implementation of this technology varies from vendors to vendors. It allows the provisioning of bandwidth on the SDH ring for packet transport by statistical multiplexing Ethernet traffic on to a shared packet ring (Circuit) that each MSPP node can access.
SPR technology is a precursor to true RPR. SPR processes inherent deficiencies that limit the scalability of the SPR solution. At every node on the SPR ring, a router or switch will process each packet which can be time consuming for a large network rings. As a result Ethernet will have trouble meeting the jitter and latency requirement for voice and video. Conventional SDH has implemented improvements, such as VCAT and LCAS, to suite data application. However, SDH transport creates point to point circuits that are not particularly suited for data applications. SDH also reserves bandwidth for every source on the ring and prevents nodes from claiming unused bandwidth.
Over few years demand for Internet protocol is growing at a fast pace while voice demand is remaining more or less stable. Circuit switched voice traffic has to be converted into packet switched data traffic. This does not match with the present SDH technology. Protocols like Frame relay, ATM &PPP are inefficient, costly and complex to scale the increasing demand for data services.
One of major advantages of RPR is that it protects existing investments in fibre and other transmission infrastructure. Most of the metro area fibre is ring based; therefore RPR will best utilising existing fibre facilities. Moreover, apart from dark fibre, RPR can also operate over SDH or DWDM equipment, allowing smooth and efficient migration.
RPR is a MAC layer, ring based protocol that combines intelligence of IP routing and statistical multiplexing with the bandwidth efficiencies and resiliency of optical rings. RPR network consist of two counter rotating fibre rings that are fully utilized for transport at all times for superior fibre utilisation. RPR permits more efficient use of bandwidth using statistical multiplexing. It also eliminates the need for manual provisioning, because the architecture lends itself to the implementation of automated provisioning.
Moreover, there is no need for channel provisioning as each ring member can communicate with every other member based on MAC address. RPR also provides two priority queues at the transmission level, which allow the delivery of delay and jitter sensitive application, such as voice and video.
RPR is fibre based ring network architecture. Data is carried in packets rather than over TDM circuits. RPR networks retain many of the performance characteristics, such as protection, low latency and low jitter on SDH. RPR architecture is highly scalable, very reliable and easy to manage in comparison to legacy point to point topologies. RPR achieves a loop free topology across the rings with rapid re-convergence on ring break. RPR supports auto discovery of other RPR network elements on the ring. New RPR nodes announce themselves to their direct neighbours with control messages and distribute changes in their settings or topologies.
The emerging solution for metros data transport applications is Resilient Packet Ring (RPR). RPR is a newly proposed standard of Ethernet transport. The goal of RPR is to increase the manageability and resiliency of Ethernet services while providing maximum capacity and usage over an established SDH ring. It has two features:
- Efficient Ring Topology
- Less than 50 ms recovery time from fibre cut i.e. resilience.
RPR is originated from a protocol called dynamic packet transport (DPT). RPR can be seen as a way towards simpler n/w architecture for packet transport because management is centralized and controls both switching and transport. Protection and restoration in transport layer (SDH or WDM) can be switched off reducing cost and complexity. Next-generation SDH devices such as MSPPs (multi-service provisioning platforms) are evolving to support RPR.
RPR is a dual ring network:
- packet based
- data and control traffic flow on both ringlets
- spatial re-use through destination stripping
- RPR is intended for use in MAN & WAN
- RPR is standardized as IEEE 802.17
- Defines a MAC protocol, introducing the concept of a transit path.
- physical layer agnostic
RPR effectively transforms a chain of point-to-point SDH paths between nodes to a single virtual shared medium. The shared transport ring created by RPR can then be used over multiple SDH nodes to carry connection-oriented transport services, and enable optimal and fair use of bandwidth for busty services through highly efficient statistical multiplexing, overbooking and spatial reuse transport mechanisms. RPR has many virtues of Ethernet like data efficiency, simplicity and cost advantage. SDH & Ring topology is perfect match for each other, but they are best suited for TDM n/w with circuit switched applications like voice traffic. Each circuit is allocated fixed bandwidth that is wasted when not in use.
RPR is a MAC protocol supporting dual counter-rotating rings that can potentially replace traditional SDH rings. RPR MAC introduces the concept of a transit path. At each node on an RPR ring, traffic is not destined for the node, simply passes through, avoiding the queuing and scheduling on a hop-by-hop basis.