As service providers transition their networks to an all-IP Ethernet-centric infrastructure, they are struggling with the challenges of Class-5 switch migration. Class-5 switches have reliably delivered POTS, Special Services and Business Services for many decades, but now the operation of these legacy network elements presents tough challenges:
Migrating to a packet-based regional softswitch addresses most of these challenges, but fails to provide a complete solution. Softswitches do not support all of the special services and business services that the Class-5 switch provides. Many of these services represent meaningful revenue streams, and some are mandated by regulation. This means that service providers cannot simply remove all of the Class-5 switches from their network; a small number of Class-5 switches will need to be retained in order to offer Class-5 services until alternative solutions are developed.
The Tellabs 1000 MSAP was specifically created to cost-effectively distribute 100 percent of the Class 5 services over TDM or IP/Ethernet transport networks. This capability will allow rehoming of services to a reduced number of Class-5 switches so that most can be removed from the network. The Tellabs 1000 MSAP also delivers IP DSL and Ethernet services, allowing for continuing network and service evolution long after the last Class-5 switch is finally retired. With the Tellabs 1000 MSAP, service providers can begin rehoming and removing Universal TR-57, TR-008 and GR-303 Class-5 switches today without giving up the services and revenue associated with them. Moving forward with Tellabs 1000 MSAP, and a softswitch migration, will reduce a service provider’s operational expenses, improve service reliability and permanently improve their cost structures.
Tellabs 1000 can be used for TR-057 or Universal application, although service providers also can deploy the Tellabs 1000 as an integrated digital loop carrier (IDLC) with TR-008 or GR-303 interfaces. Service providers also can deploy the Tellabs 1000 as a line aggregation gateway (LAG), placing the LET and RST function in the same bay. In that case the LAG function can be located in the collapsing CO and will be transported to the host CO via ADMs and IDLC interfaces (either TR-008 or GR-303). The Tellabs 1000 also supports the collapse of a remote switch into a Class-5 switch, with the Tellabs 1000 taking over the function of the collapsed switch. The NNX code, which is derived from the host office, remains unchanged. All emergency stand-alone features remain within the host switch.
This is used if there are no digital switch interfaces available at the receiving Class-5 switch because the objective of any Class-5 switch replacement project is to remove cost, so the addition of digital interfaces would be counterproductive. This application extends the Class-5 switch’s analog line unit termination to the outside plant, thereby eliminating direct copper pairs and moving closer to the customer’s premises. The Class-5 switch replacement application calls for the deployment of a Tellabs 1000 LET in the receiving CO and the Tellabs 1000 RST in the collapsing CO. If the objective is to eliminate the collapsing building, the service provider can deploy the RST in a controlled environmental vault (CEV), hut or cabinet separate from the CO building. The LET to RST transport can be copper or fiber fed.
The Telcordia TR-008 technical specification defines the overall system functions and performance levels required when integrating a DLC system into a Class-5 switch to emulate the SLC-96 system. The TR-008 compliant integrated access interface allows the Tellabs 1000 system to consolidate T1 spans coming from a local digital switch. For TR-008, the Tellabs 1000 system supports POTS, Pay/Coin, and universal voice grade (UVG) circuits. After creating a TR-008 interface group (IG), the service provider maps individual DSO circuits to specific TR-008 channels.
The two TR-008 deployment modes are:
The Tellabs 1000 supports up to 24 TR-008 IGs in one system The LET to RST transport can be copper or fiber fed.
The Telcordia GR-303 technical specification defines the overall system functions and performance levels required when integrating a DLC system into a Class-5 switch. Within this application, the LET bay requires two Tellabs 1000 Data Link Processor (DLP) cards. These provide a redundant Embedded Operations Channel (EOC) and Time slot Management Channel (TMC) for a 64 Kbps datalink to the Tellabs 1000 system. The DLP cards operate in conjunction with a minimum of two T1X-XCVR modules to terminate the GR-303 switch Virtual Interface Group (VIG) up to a maximum of 28 T1X-XCVR modules. The service provider assigns Call Reference Values (CRVs) from the Class-5 switch to POTS lines at the RST. A GR-303 virtual interface group can support up to 2048 CRVs or POTS lines with 2–28 T1s, depending on the desired concentration ratio. The Tellabs 1000 supports up to 3 GR-303 VIGs in one system. The LET to RST transport can be copper or fiber fed.
Up to this point, we have addressed the Class-5 switch replacement of remote switches into receiving switches. On occasion, however, service providers may need to collapse a stand-alone Class-5 switch into another stand-alone Class-5 switch or host softswitch. In these situations, service providers must decide whether to:
Tellabs 1000 MSAP can be used for Class-5 switch replacement. Customers in the collapsing CO receive their dial tone and services from that Class-5 switch; the interoffice facilities (IOF) trunks between the COs route their calls to other end offices. The local Class-5 switch handles call processing within this CO serving area.
Tellabs 1000 can be used collapsing a Class-5 switch into another Class-5 switch. The new receiving switch now processes all calls, and local copper pairs and cables as well as additional DLCs are consolidated in the Tellabs 1000 LAG bays. If the existing local DLCs are Tellabs 1000s, the service provider can consolidate existing Tellabs 1000 LET bays into the Tellabs 1000 LAG bays to reuse the “now spare” equipment at other locations. If the existing local DLCs are not Tellabs 1000s, the service provider can reterminate those central office terminals into the Tellabs 1000 LAG bays. The Tellabs 1000 LAG now handles call processing within the CO serving area.
Tellabs 1000 can also be used when collapsing a Class-5 switch into a softswitch. This collapse scenario requires the addition of a softswitch with a SIP Mediation gateway. The softswitch functions as an IP gateway, converting the TDM-based GR303 DS1 links from the Tellabs 1000 and transporting them to the softswitch.