GR-303 Solution For Access Gateways

GR-303 Soluton for Access Gateways GR-303 Soluton For Access Gateways Verson 1.0 October 2003 Page 1 of 18

GR-303 Soluton for Access Gateways COPYRIGHT Ths materal s the propretary property of and confdental to OpenCon Systems, Inc. Dsclosure or dstrbuton s prohbted except as per lcense or confdentalty agreement. Copyrght 2003 OpenCon Systems, Inc. All Rghts Reserved Page 2 of 18

GR-303 Soluton for Access Gateways Table of Contents 1. OVERVIEW 4 2. DIGITAL LOOP CARRIER SYSTEMS 5 3. ACCESS GATEWAYS 9 4. GR-303 OVERVIEW 13 5. OCS-303 PRODUCT OVERVIEW 15 6. REFERENCES 16 7. ABBREVIATIONS 17 Page 3 of 18

GR-303 Soluton for Access Gateways 1. Overvew Snce 1970s, Dgtal Loop Carrer (DLC) systems have been extensvely used by Servce Provders n delverng a relable, robust and hgh qualty voce servce to ther customers. DLC systems are prmarly desgned to delver narrowband servces such as voce and low bt-rate data and are not sutable as a delvery platform for hgh bandwdth servces such as data and vdeo. The deregulaton acton of 1996 and explosve growth of nternet traffc n 1990s provded the mpetus for servce provders to examne alternate technologes that can be used to delver voce, vdeo and data over the same access transport. The frst generaton ntegrated access systems served as a platform for delverng voce, data and vdeo servces over multple T1/E1 lnes and n some cases over OC-3 fber lnk. The frst generaton ntegrated systems were prmarly based on TDM technology and therefore were not so effcent n transportng packet traffc. Access gateways are desgned to not only address bandwdth neffcences nvolved n transportng packet traffc but also serve as an condut nto PSTN for voce/vdeo traffc carred over varety of access transport technologes such as xdsl, ATM over Passve Optcal Network (APON), Ethernet over PON (EPON), Wreless Local Loop (WLL) and Cable networks. Although the buzz words assocated wth such access platforms are broad-band and multmeda, however, from a servce provder pont of vew, unless the platform can be ntegrated wth the exstng network assets to delver voce servces n a cost effectve manner, t cannot be consdered for a large scale deployment. In ths whte paper, we wll examne how Telcorda s GR-303 plays an mportant role n transportng voce traffc through these type of access gateways and how GR303 enables a brand access platform to effectvely provde voce servce through the exstng swtches owned by the servce provders. Page 4 of 18

GR-303 Soluton for Access Gateways 2. Dgtal Loop Carrer Systems In the 1960s, telephony servce was provded to the subscrbers by a par of copper wres (commonly referred to as subscrber loops). These copper wres connected the subscrbers phones drectly wth a class 5 swtch located n the central offce. Analog transmsson technques were used to transmt sgnals between the phone and the swtch. Fgure 1, llustrates an analog subscrber loop network. There were number of problems assocated wth ths technology- dstance lmtaton and nterference from atmospherc nose and other sources of nose affected qualty of voce servces tremendously. As such, analog subscrber loops were dffcult to mantan and qualty of voce sgnals could not always be assured. In spte of all these problems, analog subscrber loops are stll n use, even though they have been mostly replaced by dgtal loop carrer systems and other alternate loop technologes. Classs 5 Swtch Man Dstrbuton Frame IB M Mult-Tenant Buldng Fgure 1: Analog Subscrber Loop Early attempts to address the problems assocated wth analog loop carrer systems were focused manly on ncreasng the dstance between the swtch and subscrber and to mprove the qualty of sgnals transmtted over the subscrber loops. The frst generaton dgtal loop carrer systems, also known as Unversal Dgtal Loop Carrer Systems (UDLC), were based on a network archtecture that ncluded two new network elements: Remote Termnal (RT) and Central Offce Termnal (COT). RT, also known as Remote Subscrber Termnal, was placed n the subscrber neghborhood and typcally served between 24 to 96 subscrbers. Subscrbers were connected to the RT usng a par of copper wres for each telephone connecton. COT was placed close to the swtch n a central offce and was connected to the swtch usng (analog) copper wres, one par for each subscrber s telephone lne. Dgtal transmsson lnes (T1 lnes) were used to connect the RT and COT together. By usng T1 lnes between RT and COT servce provders were able to extend the lmts of the servng area of the swtch located n the central offce wthout affectng the qualty of the sgnals transmtted between Page 5 of 18

GR-303 Soluton for Access Gateways the swtch and subscrber s telephone. Remote Termnal (RT) Classs 5 Swtch IBM Analog lnes Remote Termnal (RT) Central Offce Termnal (COT) Remote Termnal (RT) Mult-Tenant Buldng Fgure 2: Unversal Dgtal Loop Carrer System UDLC systems have evolved nto what are now known as Integrated Dgtal Loop Carrer (IDLC) Systems. In an IDLC system, the Remote Termnals are drectly connected to the swtch through or OC-3 lnes. IDLC systems elmnated the need for COT systems n central offce and thereby provdng substantal cost and space savngs to the servce provders. IDLC systems also allowed servce provders to roll out new servces such as Dgtal Data Servce (DDS) and ISDN, provdng new sources of revenues. Telcorda s TR-008 and TR-057 standards defne the nterface specfcaton for IDLC systems. IDLC systems requred fxed tme-slots to be provsoned on the T1 lnes from RT to the swtch, for each customer. By assgnng fxed tme-slots capacty of the T1 lnes was not fully utlzed, especally when the lnes Page 6 of 18

d g t a l d g t a l * 8 # * 8 # d g t a l GR-303 Soluton for Access Gateways are dle.. The Next Generaton DLC (NGDLC) addressed ths ssue by dynamcally assgnng a tme-slot to a subscrber and reassgnng the same tme-slot to a dfferent subscrber after the frst subscrber completes hs call. The NGDLC systems also provded the capablty to remotely confgure and montor the operaton of remote termnals. Remote Dgtal Termnal Classs 5 Swtch (Integrated Dgtal Termnal) Remote Dgtal Termnal IBM OC-3 Remote Dgtal Termnal Mult-Tenant Buldng Fgure 3: NextGen Integrated Dgtal Carrer Loop Systems Next Generaton IDLC systems nclude two man elements: Remote Dgtal Termnal (RDT) and Integrated Dgtal Termnal (IDT). RDT s located closer to subscrber premse and delvers servces to subscrbers over POTS, T1/E1 or ISDN lnes. IDT s an ntegral component of the swtch and nteracts wth the RDT to support dynamc tme-slot assgnment and remote provsonng. RDT and IDT are connected together by T1 lnes or OC-3 fber connectons. Telcorda s GR-303 standard defnes nterface specfcaton (physcal layer as well as applcaton layers) between IDT and RDT. Dynamc tme-slot assgnment capablty defned by GR-303 allows up to 2048 subscrbers to be served by group of T1 trunks wth an aggregate capacty of 672 tmeslots. That s roughly about 4:1 oversubscrpton. The group of trunks servng a set of subscrbers s called an Interface Group (IG). Each IG can serve a maxmum of 2048 subscrbers. An RDT can be confgured to support multple Page 7 of 18

GR-303 Soluton for Access Gateways nterface groups (mult-ig). Each nterface group n the mult-ig collecton can be logcally connected to the same swtch or to dfferent swtches. Mult-IG feature provdes the flexblty to connect subscrbers from the same locaton to dfferent swtches. Page 8 of 18

d g t a l d g t a l d g t a l GR-303 Soluton for Access Gateways 3. Access Gateways Integrated access systems were frst developed to address the needs of large corporatons whch wanted to use leased lnes ( or OC-3) to transport voce, vdeo and data traffc between ther corporate head quarters and branch offces. Fgure 4 llustrates a network deployment usng ntegrated access systems. Frst generaton ntegrated access systems used channelzed T1/T3 lnks to transport voce, data and vdeo traffc between them and requred bandwdth (.e., tme-slots) to be assgned statcally for each type of traffc. Even though these types of systems enabled corporatons to reduce ther communcatons related expenses sgnfcantly, utlzaton of the avalable bandwdth between the corporate locatons was very poor. Increase n voce and data traffc between the offce locatons forced corporatons to lease addtonal trunk lnes and thereby slowly erasng the cost savngs acheved by deployed of ntegrated access systems. Packet-based technology was later ncorporated nto these systems to transport for voce, data and vdeo traffc over the trunk lnes and acheve better utlzaton of avalable bandwdth. Integrated Access System Classs 5 Swtch (Integrated Dgtal Termnal) DCS Integrated Access System IBM OC-3 PSTN OC-3 OC-3c Router T-3 WAN Integrated Access System DCS; Dgtal Cross-Connect System Fgure 4: Integrated Access Systems Even though the ntegrated access systems were frst developed to address the needs of busness customers, the Page 9 of 18

d g t a l 3C om HIT ACHI GR-303 Soluton for Access Gateways concept of delverng multple servces over the same physcal transport meda was used to buld access gateway platforms for resdental customers. Access gateways are now avalable to support wde varety of access transport technologes such as xdsl, Cable, WLL and xpon. The prmary objectve of these access gateways s to provde hgh bandwdth nternet access and delver hgh qualty voce servces. Dependng on the access transport technologes, some of these gateways also delver vdeo servces such as lve TV and vdeo-ondemand. The followng three applcatons are selected to descrbe how GR-303 s used to delver voce servces through the access gateways: Voce Over xdsl (VoxDSL) Voce over Cable (VoCable) Voce over xpon (VoxPON) An access gateway can be mplemented as a stand-alone devce or an add-on card for a gven access platform. However, for the sake of easy understandng, n the followng paragraphs, only the stand-alone access gateways (VoxDSL, VoCable, or VoxPON) are presented. Classs 5 Swtch (Integrated Dgtal Termnal) IBM IAD WAN (Data) (GR-303) VoDSL Gateway OC-3c DSLAM IAD Router IAD OC-3c WAN IAD SoftSwtch Fgure 5: Voce Over xdsl Applcaton Fgure 5 llustrates network confguraton used n a voce over xdsl applcaton. An Integrated Access Devce (IAD) located n customer premse provdes connectons to telephones for voce traffc and for data traffc. Voce and data traffc from IAD are transported over xdsl lnes to DSLAM where the voce and data traffc are separated and voce traffc s transported over an OC-3c lnk to a VoDSL gateway. The VoDSL gateway s an access platform, whch can drect the voce traffc to PSTN network or to VoIP network. Communcaton for VoxDSL gateway and PSTN swtch conforms to GR-303 standard. Page 10 of 18

d g t a l HITACH I 3Co m GR-303 Soluton for Access Gateways Classs 5 Swtch (Integrated Dgtal Termnal) IBM Vdeo Server (GR-303) VoCable Gateway 100/1000BaseT Cable Modem Headend Router OC-3c WAN (Data) WAN SoftSwtch Fgure 6: Voce Over Cable Applcaton Fgure 6, llustrates network confguraton used n a voce over cable applcaton. A Set Top Box () located n customer premse provdes connectons to TV, telephones and. It s assumed that the has bult-n modem for data communcatons. Otherwse, an external cable modem would be requred for data traffc. Voce and data traffc from are transported to cable modem termnaton headend where the voce and data traffc are separated and voce traffc s transported over a 100/1000BaseT lnk to voce over cable gateway 1. Voce traffc from subscrbers s transported n packet form s converted by VoCable gateway nto TDM stream and sent to class 5 swtch. VoCable gateway uses GR-303 for communcaton wth the PSTN swtch. Vdeo servces are typcally delvered from a vdeo server located near the cable modem termnaton headend. Fgure 7 llustrates network confguraton used n a voce over EPON/APON applcaton. In Fber to the home (FTTH) archtecture, an Optcal Network Termnaton () s used n customer premse to delver voce, data and vdeo servces. In the Fber-to-the-curb (FTTC) archtecture, an Optcal Network Unt (ONU) s located close to customer locaton and servces are delvered to customer premses over copper wre usng VDSL technology. A Set Top Box () s requred nsde customer premse to provde connectons to TV, telephones and. Voce and data traffc from or are transported to Optcal Lne Termnaton (OLT) unt where the voce and data traffc are separated and voce traffc s transported over an OC-3c lnk to voce over xpon gateway located n the central offce. Voce Over xpon gateway uses GR-303 nterface to 1 If Cable Modem Termnaton Headend and Voce over Cable Gateway are not co-located then a WAN lnk such as T1/T3 or OC-3c should be used to connect them together. Page 11 of 18

d g t HI TACHI a l 3 Co m Data General GR-303 Soluton for Access Gateways communcate wth a class 5 Swtch. Classs 5 Swtch (Integrated Dgtal Termnal) IBM Vdeo Server (GR-303) VoxPON Gateway OC-3/ Optcal Lne Termnaton Unt Router OC-3c WAN (Data) WAN OLT: Optcal Lne Termnaton Unt : Optcal Network Termnaton ONU: Optcal Network Unt : Set Top Box ONU SoftSwtch Fgure 7: Voce Over xpon Gateway Applcaton Page 12 of 18

GR-303 Soluton for Access Gateways 4. GR-303 Overvew Telcorda s GR-303 standard specfes sgnalng, performance montorng, alarm survellance, provsonng and testng requrements to ensure connectvty and consstency n operatons between IDT and RDT from dfferent equpment vendors. For each Interface Group, the number of DS1 lnes connectng RDT and IDT (whch s a logcal part of Local Dgtal Swtch) could be from 2 to 28. GR-303 specfcaton defnes two message-based channels (TMC and EOC) for exchangng sgnalng and operatonal nformaton between RDT and IDT. To protect aganst physcal or logcal lnk falures, each of these two message channels have a standby channel confgured on physcally separate T1 lne. Both TMC and EOC use LAPD protocol (CCITT Q.920/Q.921) at the data lnk layer. IDT (CMISE Manager) OAMP Applcaton RDT (CMISE Agent) MIB and Resource Mappng CMIP CMIP Convergence Convergence LAPD LAPD EOC Fgure 8: GR-303 EOC Protocol Stack EOC s used by RDT and IDT to manage GR-303 related servces and assets located n RDT. Tme-Slot Management Channel (TMC) s based on Q.931 protocol and s used for dynamc assgnment of DS1 faclty tmeslot to a subscrber crcut durng the call setup phase, and for the tmeslot release after the call s termnated. IDT Call Control Applcaton TMC (Q.931) LAPD RDT Call Control Applcaton TMC (Q.931) LAPD TMC Fgure 9: GR-303 TMC Protocol Stack Page 13 of 18

GR-303 Soluton for Access Gateways Fgure 8 and Fgure 9 llustrate the GR-303 EOC and TMC protocol stack components respectvely. To protect aganst servce dsruptons due to EOC or TMC lnk falures, GR-303 defnes a Path Protecton Swtchng (PPS) protocol whch s supported by both RDT and IDT systems. PPS protocol messages are exchanged between IDT and RDT to swtch over from a faled actve EOC (or TMC) lnk to standby EOC (or TMC) lnk. Snce call control nformaton s carred over TMC lnk, GR-303 standards requres the swtchng from actve to standby lnk to be completed n a very short perod of tme. GR-303 also requres RDTs to support a card level redundancy to preserve the state of the calls that are n-progress when card level falure occurs n RDT or IDT. Ths requrement mples that the actve TMC card s protected by a standby TMC card.the standby TMC card must synchronze the state of ts call control protocol engne wth the actve card and be n a ready state to take over the call control functons when the actve TMC card fals. Accordng to GR-303 specfcaton, the maxmum number of subscrber lnes wthn an Interface Group (IG) s lmted to 2048. To enable a class 5 swtch to support large number of subscrbers, GR-303 defnes a concept called mult-ig. The mult-ig concept can be used by RDT to support large number of subscrbers or t can be used by RDT to connect to multple swtches at the same tme. Each IG wthn a mult-ig group has ts own EOC and TMC channels and therefore can operate ndependently wth only one restrcton-.e., a subscrber lne cannot be attached to more than 1 IG. Page 14 of 18

GR-303 Soluton for Access Gateways 5. OCS-303 Product Overvew The OCS-303 product s a software package that can be used to quckly mplement GR-303 nterface on an access gateway. The OCS-303 software package conforms to all EOC and TMC requrements of the GR-303 standards. OCS-303 package enables customers to focus manly on equpment specfc applcaton software development and not spend ther tme and effort n developng GR-303 protocol software. The followng s a lst of features OCS-303 product provdes: Support for EOC management nterface and TMC call processng requrements - complant wth GR-303, ATT 5ESS, Nortel DMS SuperNode and Semens EWSD swtch specfcatons LAPD, Convergence, ROSE, CMIS and TMC protocols EOC and TMC Path Protecton Swtch Card level redundancy for TMC and EOC modules Performance Montorng Alarms and Event Reports Implements MIB for POTS, ISDN and DS1 Lne provsonng, DS1 and Path Protecton Swtch, PM and Channel Testng The OCS-303 product conssts of two major components: 303 Kernel and 303 Interface lbrary. The 303 kernel mplements essental functonalty of EOC and TMC protocols of GR-303 nterface, whereas the 303 lbrary provdes a generc development framework that mnmzes the effort nvolved n portng of the OCS-303 software package nto vendor-specfc envronment. The 303 Interface lbrary serves as an API between the user code and the 303 Kernel and conssts of a set of functons and data structures grouped by the functonalty they provde. Each such group of API functons/data structures s called Portal. For further detals about the OCS-303 package, please refer to the data sheet, the user manual or access OCS WEB page: www.opencon.com. Page 15 of 18

GR-303 Soluton for Access Gateways 6. References 1. GR-303-CORE, Integrated Dgtal Loop Carrer Systems Generc Requrements, Objectves and Interface, Issue 4.0- Telcorda December 2000. 2. GR-8-CORE, Dgtal Interface between the SLC-96 and a Local Dgtal Swtch (formerly known as TR- 008 standard)-telcorda October 2001. 3. GR-57-CORE, Functonal Crtera for Dgtal Loop Carrer (DLC) Systems (formerly known as TR-57)- Telcorda October 2001. 4. AF-VMOA-00145, Broadband Loop Emulaton Servces, ATM Forum. 5. G.983.1, Broadband Optcal Access Systems based on Passve Optcal Networks, ITU October 1998. 6. DOCSIS-2.0 Interface Specfcatons, Cable Labs. Page 16 of 18

GR-303 Soluton for Access Gateways 7. Abbrevatons APON ATM CMISE CMIP CO COT DLC DS0 DS1 DSL DSLAM EOC EPON FTTB FTTC FTTH HDLC IAD IDLC IDT IG IP ISDN LAN LAPB LAPD MDF MDU MIB MTB NE NGDLC OLT ONU OC-x OS OSS OSI PDU PON PPS RDT RFC ROSE SDH SONET STS-1 TCP TDM UDLC VDSL WLL ATM over Passve Optcal Networks Asynchronous Transfer Mode Common Management Informaton Servce Element Common Management Informaton Protocol Central Offce Central Offce Termnal Dgtal Loop Carrer Dgtal Sgnal 0 (64Kbps) Dgtal Sgnal 1 (1.54Mbps) Dgtal Subscrber Lne Dgtal Subscrber Lne Access Multplexer Embedded Operatons Channel Ethernet Over PON Fber To The Buldng Fber To The Curb Fber To The Home Hgh Level Data Lnk Control Integrated Access Devce Integrated Dgtal Loop Carrer Integrated Dgtal Termnal Interface Group Internetwork Protocol Integrated Servces Dgtal Network Local Area Network Lnk Access Procedure B-Channel Lnk-Access Procedure D-Channel Man Dstrbuton Frame Mult-Dwellng Unt Management Informaton Base Mult-Tenant Buldng Network Element Next Generaton Dgtal Loop Carrer Optcal Lne Termnaton Optcal Network Termnaton Optcal Network Unt Optcal Carrer-x Operatons System Operatons Support System Open System Interface Packet Data Unt Passve Optcal Network Path Protecton Swtchng Remote Dgtal Termnal Request For Comment Remote Operatons Servce Element Synchronous Dgtal Herarchy Synchronous Optcal Network Set Top Box Synchronous Transport Sgnal-1 Transmsson Control Protocol Tme Dvson Multplexng Unversal Dgtal Loop Carrer Very hgh bt-rate DSL Wreless Local Loop Page 17 of 18

GR-303 Soluton for Access Gateways WAN Wde Area Network Page 18 of 18