ATM and Frame Relay to MPLS Control Plane Interworking: Client-Server. MFA Forum

Transcription

1 ATM and Frame Relay t MPLS Cntrl Plane Interwrking: Client-Server MFA Frum MFA Frum September 2006

2 Nte: The user s attentin is called t the pssibility that implementatin f the MPLS implementatin agreement cntained herein may require the use f inventins cvered by patent rights held by third parties. By publicatin f this MPLS implementatin agreement the MFA Frum makes n representatin that the implementatin f the specificatin will nt infringe n any third party rights. The MFA Frum take n psitin with respect t any claim that has been r may be asserted by any third party, the validity f any patent rights related t any such claims, r the extent t which a license t use any such rights may nt be available. Editr: Chris Metz chmetz@cisc.cm Fr mre infrmatin cntact: The MFA Frum Suite Califrnia Street Fremnt, CA USA Phne: +1 (510) FAX: +1 (510) inf@mplsfrum.rg WWW: Full Ntice Cpyright 2006 MFA Frum. All rights reserved. This dcument and translatins f it may be cpied and furnished t thers, and wrks that cmment n r therwise explain it r assist in its implementatin may be prepared, cpied, published and distributed, in whle r in part, withut restrictin f any kind, prvided that the abve cpyright ntice and this paragraph are included n all such cpies and derivative wrks. Hwever, this dcument itself may nt be mdified in any way, such as by remving the cpyright ntice r references t the MFA Frum, except as needed fr the purpse f develping MPLS implementatin agreements (in which case the prcedures cpyrights defined by the MFA Frum must be fllwed), r as required t translate it int languages ther than English This dcument and the infrmatin cntained herein is prvided n an "AS IS" basis and THE MPLS & FR ALLIANCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. September 2006

3 Revisin Histry Versin Change Date MFA Initial versin September 2006 September 2006

4 Table f Cntents 1 INTRODUCTION PURPOSE SCOPE AND REQUIREMENTS OVERVIEW DEFINITIONS AND TERMINOLOGY DEFINITIONS ACRONYMS REFERENCES Nrmative Infrmative REFERENCE MODEL COMPONENTS CLIENT/PSEUDO-WIRE CONTROL PLANE INTERACTIONS THE PSEUDO-WIRE CONTROL PLANE THE CLIENT CONTROL PLANE LOGICAL LINKS ESTABLISHMENT OF CONTROL PSEUDO WIRES Cntrl Pseud-Wire Signaling ATM AND FR TO LDP SIGNALING INTERWORKING ATM AND FR TO LDP SIGNALING INTERWORKING PROCEDURES THE SAI AND THE TAI IN LDP SIGNALING...17 September 2006 Page 1

5 1 Intrductin Many service prviders derive significant revenues by ffering and delivering VC-based services acrss dedicated Frame Relay (FR) and ATM netwrks. In a desire t reduce capital and peratinal expenditures, many f these same prviders have embarked upn a strategy f cnvergence, where many per-service netwrks (including FR and ATM) and their attendant technlgies and services are migrated t a single IP/MPLS packet-switched netwrk (PSN). It is envisaged that existing netwrk services such as FR and ATM and emerging new services, including IP VPN, will perate ver this multi-service cnverged PSN. Native FR and ATM netwrks emply dynamic signaling and ruting prtcls t expedite cnnectin setup and recvery. PNNI is an example f ne such prtcl used t dynamically set up switched ATM cnnectins acrss a native ATM netwrk [4]. Pseud-wire (PW) technlgy enables tunneling f ATM and FR cnnectins thrugh a PSN [2]. When transitining t a PSN, service prviders will expect ATM (and Frame Relay) signaling and ruting prtcls (e.g. PNNI) t interperate with pseud-wire signaling and IP ruting prtcls fr the purpse f establishing switched cnnectins acrss the PSN. This prtends a need t define methds by which the cntrl plane functins f a client (i.e. FR, ATM) netwrk can be interwrked with crrespnding server (i.e. IP/MPLS) netwrk cntrl plane functins. The net result is an ability t dynamically establish switched cnnectins between client netwrk end-pints that crss an IP/MPLS netwrk. 1.1 Purpse The purpse f this specificatin is t define the cntrl plane and prtcl interwrking prcedures fr ATM and Frame Relay cnnectins acrss an IP/MPLS PSN using pseud wires. 1.2 Scpe and Requirements The scpe and requirements fr the functins described in this dcument are as fllws: The architecture is general in nature. It supprts a wide range f ATM and Frame Relay cntrl plane prtcls, including intra-netwrk and inter-netwrk (NNI) prtcls such as PNNI, AINI, IISP, X.76, etc., and UNI prtcls such as ATM Frum UNI 3.1 and 4.0, Q.2931, and X.36. Where apprpriate and applicable, aspects f these native prtcls pertaining t ruting, signaling, OAM, etc, shuld nt be reduced t subsets f their functinality. This apprach needs t be scalable in a number f dimensins, t allw it t be used effectively in service prvider netwrks, t supprt signaling rates cmmnly fund in tday s ATM netwrks, and t allw netwrk grwth and expansin. These dimensins include: Perfrmance: This apprach must nt reduce the signaling capabilities required in current netwrks. Netwrk resurces: This apprach must make effective use f netwrk resurces. Future grwth: As netwrks grw, the netwrk resurce usage t supprt this architecture must be similar t that required fr the grwth f current PNNI netwrks. September 2006 Page 2

6 This architecture shuld be standards-based, meaning that existing specificatins and implementatins shuld be used t the greatest extent pssible. In particular: Minimal changes t current ATM and Frame Relay netwrks shuld be required t supprt the architecture. Existing IETF mechanisms shuld be used whenever pssible. Any standards-based IP r MPLS PSN tunnel capable f carrying MPLS pseud wires is nt precluded Specific t MPLS, existing mechanisms and features cmmnly in use (especially fr netwrk resilience and efficiency), such as traffic engineering, fast rerute, standby LSPs, equal cst multipath, penultimate hp ppping, diff-serv supprt, the ability t multiplex multiple pseud wires and traffic types thrugh the same PSN tunnels, etc., cannt be precluded frm use. The use f MPLS netwrk resilience mechanisms is encuraged t allw ATM and FR VCs t survive switch r link utages within the MPLS netwrk, if at all pssible. ATM and FRlayer VC clearing shuld be avided if at all pssible. Supprt multiple ATM service categries efficiently Only pint-t-pint pseud wires are supprted. In the apprach identified in this specificatin (since the mapping between client cnnectins and pseud wires is ne-t-ne), this may restrict the ability t supprt pint-t-multipint client cnnectins. There are methds t wrk arund this limitatin, e.g. use f the "restricted branching" flag in PNNI ruting [4]. The fllwing items ARE NOT within the current scpe f this dcument: Service interwrking between ATM and Frame Relay cntrl planes [12]. Cntrl Plane interwrking between ATM (r Frame Relay) AND IP/MPLS cntrl planes fr setting up and managing switched cnnectins between ATM (r Frame Relay) and IP/MPLS end-pints and netwrks. User plane interwrking between ATM (r Frame Relay) and IP/MPLS [14]. L2TPv3 pseud wires [13] September 2006 Page 3

7 1.3 Overview Figure 1 depicts the high-level architecture f the slutin described in this dcument. Client netwrks perating a native client (ruting and signaling) cntrl plane attach t Label Edge Ruters (LER) that are part f an IP/MPLS PSN. The LERs perate an IP/MPLS cntrl plane (e.g. IGP/BGP, LDP, PWE3, RSVP-TE, etc.) t set up and manage label-switched paths (LSP) acrss the server netwrk. In additin the LERs perate ne (r mre) instances f a client cntrl plane. Client netwrk cntrl plane messages used t dynamically rute, set up, manage and tear dwn interclient netwrk pint-t-pints cnnectins (e.g. PNNI) are prcessed by client netwrk devices and the client cntrl plane instances running n the LERs. Receipt f client cntrl plane messages by an LER will dynamically trigger the crrespnding IP/MPLS server netwrk cntrl plane functins necessary t carry encapsulated client netwrk paylads cntained in pseud wires acrss the IP/MPLS PSN frm ne client netwrk device t anther. The high-level principles behind this design are: Use f separated client and pseud-wire cntrl planes with a distinct (and implementatinspecific) pseud-wire service interface between them. Use f pseud-wire cntrl mechanisms defined in [1] as the initial pseud-wire cntrl plane in all scenaris except thse with a null pseud-wire cntrl plane. Future specificatin f ther pseud-wire cntrl plane mechanisms is nt precluded. PSN and underlying pseud wire prtcl suite are prviding a cntrl plane interwrking functin t the attached client netwrks. Techniques enabling switched cnnectin setup acrss an MPLS netwrks have previusly been defined[6] [10]. In these appraches, the client netwrks are ATM and the client cntrl plane is ATM UNI, AINI, r PNNI. They define extensins fr ATM signaling t distribute pseud-wire labels between the MPLS edge ndes. The client and pseud-wire cntrl functins are cllapsed int a single ATM signaling prtcl. The slutin defined in this dcument pts fr a different apprach by decupling the client and pseudwire cntrl planes s as t lessen the dependencies f ne n the ther. This will allw fr future additins t the pseud-wire cntrl plane t be used in ATM and Frame Relay t MPLS cntrl plane interwrking scenaris. This als enables different client cntrl planes (e.g. Frame Relay) t emply the same pseud-wire cntrl plane. Cnversely different pseud-wire cntrl planes may be used t supprt inter-client netwrk cnnectin setups. Anther apprach uses virtual trunks thrugh which ATM switches can transparently establish and maintain Virtual Circuit Cnnectins (VCCs) and Virtual Path Cnnectins (VPCs)[11]. Each virtual trunk is transprted acrss an MPLS netwrk as a single pseud wire. September 2006 Page 4

8 This specificatin describes a cntrl plane interwrking apprach in which bth cntrl planes run n the same physical internetwrking element at the edge f the MPLS netwrk. This apprach: interwrks each client virtual cnnectin with a single pseud wire that emulates the cnnectin acrss the PSN, requires n change t deplyed client netwrk switches, and allws the LER t ptimize utilizatin f resurces in the MPLS netwrk since it is aware f the traffic and QS requirements f each client cnnectin. Figure 1 High-Level Architecture 2 Definitins and Terminlgy 2.1 Definitins Must, Shall r Mandatry the item is an abslute requirement f this implementatin agreement. Shuld the item is desirable. May r Optinal the item is nt cmpulsry, and may be fllwed r ignred accrding t the needs f the implementer. September 2006 Page 5

9 2.2 Acrnyms Acrnym AI ATM BFD CE FR IANA IE IETF IWF LDP LER MP-BGP MPLS PE PGL PNNI PSN PW PWE3 RSVP-TE RVPI SAI TAI VC VCC VCI VP VPC VPI VT Definitin Attachment Identifier Asynchrnus Transfer Mde Bidirectinal Frwarding Detectin Custmer Edge Frame Relay Internet Assigned Numbers Authrity Infrmatin Element Internet Engineering Task Frce Interwrking Functin Label Distributin Prtcl Label Edge Ruter Multi-Prtcl BGP Multi-prtcl Label Switching Prvider Edge Peer Grup Leader Private Netwrk-Netwrk Interface Packet-Switcheded Netwrk Pseud wire Pseud wire Emulatin Edge-t-Edge Resurce Reservatin Prtcl Traffic Engineering Relative VPI Surce Attachment Identifier Target Attachment Identifier Virtual Cnnectin Virtual Channel Cnnectin Virtual Cnnectin Identifier Virtual Path Virtual Path Cnnectin Virtual Path Identifier Virtual Trunk September 2006 Page 6

10 2.3 References Nrmative [1] RFC4447, Pseudwire Setup and Maintenance using LDP. Martini, L., et al., April, [2] RFC3985, Pseud Wire Emulatin Edge-t-Edge (PWE3) Architecture., IETF, S. Bryant, Ed., P. Pate, Ed. March (Status: INFORMATIONAL) [3] ATM Frum, af-cs , Signalling Cngestin Cntrl Versin 1.0, April 2002 [4] ATM Frum af-pnni , Private Netwrk-Netwrk Interface Specificatin Versin 1.1, April [5] RFC3036, LDP Specificati, IETF, January 2001 [6] ATM Frum, af-aic , ATM-MPLS Cntrl Plane Netwrk Interwrking), May 2005 [7] RFC2277, IETF Plicy n Character Sets and Languages, Internet Engineering Task Frce, January [8] IANA-assigned Pseud Wires Name Spaces, available at: parameters Infrmative [9] ATM Frum. af-cs pdf. ATM-MPLS Interwrking Signalling Specificatin Versin 1.0. August, 2003 [10] ITU-T, Q Bradband integrated services digital netwrk (B-ISDN) Digital Subscriber Signalling System N. 2 (DSS 2): Call/cnnectin cntrl fr the supprt f ATM-MPLS netwrk interwrking. September, [11] MFA Frum, The Use f Virtual Trunks fr ATM/MPLS Cntrl Plane Interwrking, MFA Frum 9.0.0, February 2006 [12] Frame Relay Frum, FRF.18, Netwrk-t-Netwrk FR/ATM SVC Service Interwrking Implementatin Agreement, Frame Relay Frum Technical Cmmittee April 2000 [13] RFC3931, Layer Tw Tunneling Prtcl - Versin 3 (L2TPv3), Internet Engineering Task Frce, March 2005 [14] Martini, L., et al., Encapsulatin Methds fr Transprt f ATM Cells/Frames Over IP and MPLS Netwrks. IETF, draft-ietf-pwe3-atm-encap-11.txt, May, September 2006 Page 7

11 3 Reference Mdel This sectin describes the reference mdel and cmpnents. IWF Client Cntrl PWs IWF Client Cntrl Client Cntrl Client Cntrl Client Cntrl Client-PW SI Client-PW SI Client Netwrk PW Cntrl PW Cntrl PSN PW Cntrl Client Netwrk Ingress LER1 Cnnectivity Egress LER2 Client Layer VC PSN Tunnel PW Segment Figure 2 Reference diagram fr client/pseudwire cntrl plane interwrking. 3.1 Cmpnents Figure 2 illustrates the reference mdel and its cmpnents. A Packet-Switched Netwrk (PSN) prvides IP r MPLS infrastructure t supprt pseud wires. A Label Edge Ruter (LER) prvides an interwrking functin (IWF) that cnnects the PSN and a segment f the client netwrk. In the user plane, the LER interwrks each client virtual cnnectin with a single pseud wire that emulates the cnnectin acrss the PSN. The IWF als supprts interwrking between a client cntrl plane and a set f functins which supprt setup, teardwn, and maintenance f pseud wires, which is called the pseud-wire cntrl plane. This is dne by means f a pseud- wire service interface within the IWF. Pseud wires may als be used t carry client cntrl plane traffic between LERs. With respect t a given client setup request, an LER is cnsidered an ingress LER if it is the first LER alng the signaling path t prcess a client cntrl plane SETUP message. An LER is cnsidered an egress LER if it is the last LER alng the signaling path t prcess a client cntrl plane SETUP message. Between the ingress and egress LERs, PSN tunnels are established, and pseud wires are carried encapsulated in these PSN tunnels. PSN tunnels can be any technlgy, as described in [2]. The mapping between client cnnectins and pseud wires is as fllws: One client cntrl plane pseud wire is established fr each client cntrl plane cnnectin. Each client virtual cnnectin is mapped t a single pseud wire which meets the service requirements f the client virtual cnnectin, and which is established n-demand. These pseud wires are carried in PSN tunnels which satisfy cnnectin service requirements. September 2006 Page 8

12 3.2 Client/Pseud-Wire Cntrl Plane Interactins Separatin f client and pseud-wire cntrl planes, with a distinct service interface between them, is a basic principle. The pseud-wire cntrl plane manages pseud wire set up and tear dwn, multiplexing, and service differentiatin. Other functinality is left t the client cntrl plane thus allwing supprt fr client cntrl planes that have significant differences frm pseud-wire cntrl planes in state machine, timers, and semantics. The pseud-wire service interface supprts the fllwing: Request establishment f a pseud wire Request tear dwn f a pseud wire Pseud wire status ntificatin t client cntrl plane (e.g. teardwn ntificatin, establishment cmpleted ntificatin) Managing a pseud wire and its related resurces. Fr example, traffic and QS parameters f each client cnnectin may be passed acrss the pseud-wire service interface. This infrmatin wuld allw the LER t dynamically track the resurces required by the PSN Tunnels that transprt the pseud wires acrss the MPLS netwrk, and can als be used when selecting resurces fr lcal supprt f pseud wires and attachment circuits. These requests will have parameters. Fr example, the client user plane encapsulatin and cnnectin identifiers used t bind the pseud wire t be established t the attachment circuits created by the client cntrl plane. The pseud wire service interface is an internal interface, it is nt frmally specified in this specificatin. 4 The Pseud-Wire Cntrl Plane This specificatin uses the pseud-wire cntrl mechanisms defined in [1] as the initial pseud-wire cntrl plane in all scenaris except thse with a null pseud-wire cntrl plane. Future specificatin f ther pseud-wire cntrl plane mechanisms is nt precluded. In prviding services t the client cntrl plane, the ffered pseud-wire cntrl plane capabilities can be: Null, with all pseud-wire management dne by cnfiguratin. When the client cntrl plane makes a request, it can nly be satisfied by precnfigured pseud wires. Cnnectin management. The pseud-wire cntrl plane may knw where the cnnectin pints are that the client cntrl plane might want, but pseud wires are nt set up until they are needed. When th epseud-wire cntrl plane is used, at a minimum it is respnsible fr setup and teardwn f pseud wires between LERs. This requires exchange f pseud wire-related infrmatin between the LERs (such as the pseud-wire labels, the encapsulatin used t transprt client data in the pseud wire, and sme identificatin f the attachment circuits t which the pseud wire is bund at the LERs). September 2006 Page 9

13 5 The Client Cntrl Plane A pseud-wire service interface can prvide services fr a diversity f client cntrl planes, varying bth in prtcl family and in functinality. Just as the pseud-wire cntrl plane can vary, the client cntrl plane functins at the service interface can be any f: Null, with all client prtcl management dne by cnfiguratin. Cnnectin management nly. Cnnectins are set up dynamically but the client cntrl plane expects a particular tplgy frm the PSN. Cnnectin and cnnectivity management. The client cntrl plane explres its cnnectivity, determines paths t use, and sets up cnnectins dynamically. An example is ATM PNNI. When a client cntrl plane is used at the LERs, it is respnsible fr establishment, maintenance, and release f attachment circuits n the LERs interfaces facing the client netwrks, as well as prpagatin f end-t-end client cntrl plane infrmatin acrss the PSN. The infrmatin exchanged by the client cntrl plane includes bth end-t-end infrmatin such as the called party address, traffic descriptrs, and endpint applicatin infrmatin, and (at the interfaces cnnecting the client netwrks t the LERs) lcal infrmatin such as the ATM VPI/VCI r the Frame Relay DLCI. The lcal infrmatin is nt needed fr the user plane cnnectin segment acrss the PSN (pseud wire-related infrmatin is handled by the pseud-wire cntrl plane), but this infrmatin may still be exchanged between the LERs t be used by the cntrl and management planes. There are several ptins fr ruting client cntrl plane cnnectin establishment messages acrss the PSN: Static rutes may be cnfigured at the client netwrk and at the LERs, based n prefixes f client cntrl plane addresses. Dynamic ruting may be included in the client cntrl plane, bth between the client netwrk and the LERs, and between LERs acrss the PSN. Fr example, if the client layer is ATM, PNNI may be used, with each LER represented as ne lwest level nde in the PNNI tplgy. Peer Grup Leader (PGL) and brder nde functinality may be used at LERs. The PSN places n restrictins n the use f PNNI hierarchy. Prefixes f client cntrl plane addresses can be exchanged acrss the PSN netwrk using a PSN ruting prtcl such as MP-BGP. When this infrmatin is exchanged between LERs, each LER uses this infrmatin t decide dynamically hw a setup request shuld be directed, based upn tplgy and resurce availability at the time, and t respnd well t failures. The use f MP-BGP fr exchanging ATM reachability acrss the PSN is fr further study. Cmbinatins f the abve may be used. September 2006 Page 10

14 5.1 Lgical Links Frm the client cntrl plane's pint f view, the cnnectivity between a pair f LERs appears as a lgical link ver which client cnnectins can be established. The lgical link may have a set f resurces assciated with it, fr example, fr advertisement in a client ruting prtcl such as PNNI. Nte that these resurces need nt be exclusive t this client cntrl plane instance. They can be shared by all r a subset f applicatins at the LER. A set f client cntrl channels (e.g. ATM signaling, PNNI ruting, and ILMI) is assciated with each lgical link. Typically there will be nly ne instance f a lgical link between a pair f LERs fr each client cntrl plane (thugh presence f multiple lgical links is nt precluded). If a client ruting prtcl is used, nly ne instance f that client ruting prtcl needs t run between the LERs. The fact that the cnnectivity between the LERs appears t the client cntrl plane as a lgical link des nt imply that there is any restrictin n the usage f PSN tunnels. Any PSN tunnel between the LERs is a candidate fr transprt f the pseud wires that carry client user cnnectins and client cntrl channels between the LERs, subject t plicy, QS, r ther cnstraints as fr any ther pseud wire between the LERs. 5.2 Establishment f Cntrl Pseud Wires The supprt f dynamic client (ATM r Frame Relay) cnnectins acrss an intermediate IP r MPLS netwrk requires the transprt f client signaling messages and depending upn the cnfiguratin client ruting and link management messages between the LERs. Sme client layer prtcls (i.e.atm) emply reserved native client encapsulatin headers (i.e. ATM uses VPI/VCI values) t identify cnnectins assciated with varius prtcls r functins. These values may have a per-interface cntext, which means that a native client nde can receive the same client encapsulatin header frm ther native client ndes with the understanding that <client encapsulatin header, interface> prvides a cmbinatin that uniquely identifies the sender. MPLS pseud wires, n the ther hand, use a per-platfrm label range. Befre client cntrl messages can be carried acrss a PSN tunnel, the LER at each end f the PSN tunnel must be made aware f the labels that will carry the cntrl channel traffic fr that instance f the client cntrl plane between the LERs. These client cntrl channels must be identified s that the data n the crrespnding cntrl pseud wire is delivered t the crrect instance f the client cntrl plane and nt frwarded ut an egress interface. There are three distinct cntrl pseud wires that can be established between peering LERs: Signaling cntrl PW. This is mandatry if the client cntrl plane is nn-null. Ruting cntrl PW. This is ptinal. Link Management PW. This is ptinal. September 2006 Page 11

15 5.2.1 Cntrl Pseud-Wire Signaling The native client cntrl channel t pseud-wire label bindings are distributed as defined in [1]. The LERs establish an LDP sessin using the Extended Discvery mechanism described in [5]. An LDP Label Mapping message is used t establish the relatinship between the client cntrl channels and labels. An LDP Label Mapping message cntains a FEC TLV, a Label TLV, and zer r mre ptinal parameter TLVs. T remain cnsistent with the signaling prcedures fr the establishment f data-bearing pseud wires utlined in sectin 6, it is mandatry that LDP signaling f cntrl pseud wires emply the Generalized ID FEC element (type 129). MPLS packets n a given cntrl PW (r any PW) are frwarded within an LER by a frwarder; the frwarder is the cmpnent inside an LER that selects the cntrl pseud wire thrugh which packets will be sent. The cncept f an attachment identifier (AI) is used t identify the frwarder t which a pseud wire is attached. The AI is unique within the cntext f the LER in which the frwarder resides, s the cmbinatin f <LER, AI> is glbally unique in the netwrk. Frwarders within an LER can be assciated with a grup, where pseud wires may nly be set up amng members f the grup. Frwarders assciated with the grup are identified by an Attachment Grup Identifier (AGI) and an Attachment Individual Identifier (AII). This pair represents the AI. The AGI, surce AII (SAII), and target AII (TAII) are encded as TLVs and described in [1]; this specificatin des nt define any restrictins n the cntents f the AGI. The frmat fr an AII is illustrated in Figure 3. This frmat is used fr bth the SAII and the TAII AII Type Length Cntrl Channel Type Cntrl Plane Instance Identifier Cntrl Plane Instance Identifier (cnt d) Figure 3: SAI and TAI Frmat fr Cntrl PW Setup AII (type) field This ne-byte field cntains the AII type cdepint used fr establishing cntrl PWs as defined in Table 1. The length f the crrespnding value assciated with this AII type is als prvided as defined in [8]. AII Type Cdepint Length Meaning September 2006 Page 12

16 0x03 Variable (1-33 bytes) ATM/FR Cntrl Channel Table 1 AII Type Cdepint fr Cntrl PW Setup Cntrl Channel Type This ne-byte field indicates the cntrl channel type as specified in Table 2 belw. The ATM-specific values are cmmn with thse defined in [6]. Cntrl Channel Type Meaning 0 PNNI_Ruting Cntrl Channel 1 ATM Signalling 2 ILMI 3 Frame Relay Signaling Table 2: Cntrl Channel Type Field Values Cntrl Plane Instance Identifier The Cntrl plane instance identifier is used t distinguish amng multiple client cntrl plane instances running between the same tw LERs, in the same grup (in which case pseud wires established in respnse t thse client cntrl plane instances wuld use the same AGI value in the pseud-wire cntrl plane). This culd be due t the pssibility f multiple different cntrl planes being used between the tw LERs, e.g. ATM and Frame Relay, r due t multiple instances f the same client cntrl plane being used between the tw LERs [6]. Cnnectins fr the same lgical link shall use the same value f the CPII in the AII. Cnnectins fr different lgical links between the same tw LERs that use the same value fr the AGI shall use different values in the AII. The Cntrl plane instance identifier takes the frm f a variable length human-readable character string cnfrming t [7] and nt t exceed 32 ctets in length. The default value fr the CPII is the null string specified by setting the length field t 1. September 2006 Page 13

17 6 ATM and FR t LDP Signaling Interwrking This sectin cntains the prcedures fr interwrking ATM and FR signaling with PWE3 (LDP) signaling, and will emply the fllwing terminlgy: PW Surce LER first LER t initate a PW cntrl plane message directed twards the PW Target LER PW Target LER Receiver f initial PW cntrl plane message sent frm the PW surce LER. The ingress and egress LERs respectively are defined in sectin ATM and FR t LDP Signaling Interwrking Prcedures When the client cntrl plane s SETUP message arrives at the ingress LER, the setup request is passed t the client cntrl plane s call cntrl in the usual fashin. Pseud-wire signalling shall nt be initiated. If pseud-wire cnnectin admissin cntrl is supprted, the LER shall determine whether the PSN has adequate resurces t supprt the cnnectin acrss the PSN t the egress LER. If the PSN des nt have adequate resurces, the call shall be cleared (pssibly using crankback) using nrmal client cntrl plane prcedures. When the client cntrl plane s SETUP message arrives at the egress LER, the setup request is passed t the client cntrl plane s call cntrl in the usual fashin. If pseud-wire cnnectin admissin cntrl is supprted, the LER shall determine whether the PSN has adequate resurces t supprt the cnnectin acrss the PSN t the ingress LER. If the PSN des nt have adequate resurces, the call shall be cleared (pssibly using crankback) using nrmal client cntrl plane prcedures. If the PSN has adequate resurces r if pseud-wire cnnectin admissin cntrl is nt supprted, the client cntrl plane s call cntrl shall trigger the pseud-wire cntrl plane t initiate pseud wire establishment using the Generalized PW ID FEC Element (FEC Type 129), as defined in [1]. Details f cnstructin f the TAI are discussed in Sectin 6.2. If the egress LER s pseud-wire cntrl plane is unable t send the Label Mapping message fr any reasn such as n label resurces available, the call shall be cleared (pssibly using crankback) using nrmal client cntrl plane prcedures. If the client cntrl plane is ATM PNNI r AINI (including supprt fr Signalling Cngestin Cntrl), and the reasn why the pseud-wire cntrl plane is unable t send the Label Mapping message is cngestin in the pseud-wire cntrl plane (i.e. lack f internal resurces such as queuing resurces, memry and CPU realtime), then, the call shall be cleared using crankback with cause and crankback cause (#42 "Switching Equipment Cngestin") fields set. In the absence f errrs, the egress LER shall start the PseudWireFailureTimer with initial value the same as T310 (as defined fr ATM and Frame Relay Signalling) fr this client cntrl plane instance. The egress LER has tw ptins fr the prpagatin f the SETUP message in the client cntrl plane: 1. Hld the SETUP message until the pseud-wire cntrl plane indicates that pseud-wire establishment has been cmpleted, r 2. Immediately frward the SETUP message twards the called party. Optin 1 must be emplyed if the client cntrl plane requires that the data plane be established as the SETUP message is prgressed. This is the case when the setup request indicates susceptible t clipping September 2006 Page 14

18 in the Bradband bearer capability infrmatin element. Figure 4 illustrates ptin 2, and als clarifies that the egress LER is perfrming the rle f PW surce LER. When the Label Mapping message is received at an LER, the nrmal prcedures fr the Generalized PW ID FEC Element defined in [1] shall be fllwed. If the TAI des nt indicate a knwn pseud wire fr which an LSP has already been set up in the ppsite directin, then it is assumed that this is the ingress LER (i.e. PW target LER). The TAI is used t assciate the cntrl infrmatin fr the client cnnectin and pseud wire. If the TAI cntains a call reference value that is nt knwn t the indicated client cntrl plane instance, then the prcedures fr a TAI that cannt be mapped t a frwarder shall be fllwed (defined in [1]), causing the Label Mapping message t be rejected. If the TAI cntains a call reference value that is knwn t the indicated client cntrl plane instance, then that call reference shall be used t determine the apprpriate frwarder as the pseud-wire end-pint. If a frwarder has been determined but the crrespnding client cntrl cnnectin is nt in a cmpatible pending state n the lgical link (fr example, if this ruter is nt an ingress LER fr this client cnnectin), then the Label Mapping message shall be rejected and the client cnnectin shall be cleared in bth directins using nrmal client cntrl plane prcedures. If a frwarder has been determined and there are any errrs in the Label Mapping message that cause it t be rejected, then the client cnnectin shall be cleared in bth directins using nrmal client cntrl plane prcedures. If the ingress LER s pseud-wire cntrl plane is unable t send the Label Mapping message fr the secnd LSP f the pseud wire fr any reasn such as n label resurces available, then the first LSP f the pseud wire shall be released and the client cnnectin shall be cleared using nrmal client cntrl plane prcedures. If the client cntrl plane is ATM PNNI r AINI (including supprt fr Signalling Cngestin Cntrl), and if the reasn why the ingress LER s pseud-wire cntrl plane is unable t send the Label Mapping message fr the secnd LSP is cngestin in the pseud-wire cntrl plane (i.e. lack f internal resurces such as queuing resurces, memry and CPU realtime), then, the call shall be cleared using crankback with cause and crankback cause (#42 "Switching Equipment Cngestin" [3]) fields set. When the Label Mapping message is received at an LER and the TAI indicates a knwn pseud wire fr which an LSP has already been set up in the ppsite directin, then it is assumed that this is the egress LER (i.e. PW surce LER). If there are any errrs in the Label Mapping message that cause it t be rejected, then in additin t replying with a Label Release message as per nrmal pseud-wire cntrl plane prcedures, the label fr the ther directin f the pseud wire shall be withdrawn using nrmal pseud-wire cntrl plane prcedures and the client cnnectin shall be cleared in bth directins using nrmal client cntrl plane prcedures. Otherwise, in additin t the nrmal prcedures defined in [1], an indicatin shall be passed t the client cntrl plane that the PW cntrl plane has cmpleted pseud-wire establishment and the PseudWireFailureTimer shall be stpped. If ptin 1 was emplyed abve, the egress LER shall prpagate the client cntrl plane s SETUP message twards the called party. When the client cntrl plane s CONNECT message arrives at the egress LER frm the directin f the called party, the cnnect request is passed t the client cntrl plane s call cntrl in the usual fashin. If n indicatin has been received indicating that the pseud wire cntrl plane has cmpleted pseud-wire establishment (this is never the case if ptin 1 was emplyed abve), then the client cntrl plane s call cntrl shall hld the cnnect request. Once the indicatin is received frm the pseud-wire cntrl plane, the client cntrl plane shall resume prcessing f the cnnect request, causing the egress LER t prgress the CONNECT message t the ingress LER accrding t nrmal client cntrl plane prcedures. The egress LER shall enable traffic flw ver the user plane fr the client cnnectin and the crrespnding pseud wire befre prgressing the CONNECT message. If n indicatin that the pseudwire cntrl plane has cmpleted pseud-wire establishment is received befre the September 2006 Page 15

19 PseudWireFailureTimer expires, then the pseud wire shall be cleared using nrmal pseud-wire cntrl plane prcedures, and the client cnnectin shall be cleared in bth directins using nrmal client cntrl plane prcedures. When the client cntrl plane s CONNECT message arrives at the ingress LER, nrmal client cntrl plane prcedures are fllwed. The ingress LER shall enable traffic flw ver the user plane fr the client cnnectin and the crrespnding pseud wire befre prgressing the CONNECT message twards the called party. If there is n active pseud wire fr this client cnnectin, then the call shall be cleared in bth directins using nrmal client cntrl plane prcedures and the remaining state in the pseud-wire cntrl plane, if any, shall als be cleared. If a Label Withdraw r Label Release message is received fr any pending r active cnnectin, then the pseud wire shall be cleared using nrmal pseud-wire cntrl plane prcedures, and the client cnnectin shall be cleared in bth directins using nrmal client cntrl plane prcedures. If a client cntrl plane call clearing message is received fr any pending r active cnnectin, r upn initiating call clearing due t client cntrl plane errr handling prcedures, then in additin t nrmal client cntrl plane prcedures, the pseud wire shall be cleared using nrmal pseud-wire cntrl plane prcedures. September 2006 Page 16

20 Figure 4 PW Establishment Triggered by Client Cnnectin SETUP at Egress LSR 6.2 The SAI and the TAI in LDP Signaling The TAI is used as the key that allws the PW Target LER t crrelate an incming Label Mapping message with an ATM r Frame Relay cnnectin created in respnse t client cntrl plane messages. Fr switched cnnectins established using the client and pseud-wire cntrl planes, the TAII and SAII are encded as illustrated in Figure 5: LDP Call Reference Flag (1 bit) and Call Length AII Type Reference Value Call Reference Value (cnt d) Cntrl Plane Instance Identifier Figure 5 SAI and TAI Encding fr Client Cnnectin PW Setup AII (type) field This ne-byte field cntains the AII type cdepint fr data-plane PWs as specified in Table 3. The length f the crrespnding value assciated with this AII type cdepint is als prvided as defined in [8]. AII Type Cdepint Length Meaning 0x04 Variable (3-35 bytes) ATM/FR Signaling Call Reference Table 3 AII Type Cdepint fr Data Plane PW Setup LDP call reference flag Bit 8 0 The LER that riginated the call reference has a smaller IP address than the ppsite LER, based n the IP addresses used t establish this LDP sessin between the LERs. 1 The LER that riginated the call reference has a larger IP address than the ppsite LER, based n the IP addresses used t establish this LDP sessin September 2006 Page 17

21 between the LERs. Call reference value The call reference value used in the client (i.e., ATM r Frame Relay) cntrl plane between the LERs. Cntrl plane instance identifier See sectin END OF DOCUMENT September 2006 Page 18