1、CCITT RECMN*I=372 93 4862591 O580736 215 INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARD IZATI ON SECTOR OF ITU 1.372 (03/93) INTEGRATED SERVICES DIGITAL NETWORK (ISDN) OVERALL NETWORK ASPECTS AND FUNCTIONS FRAME RELAYING BEARER SERVICE REQUIREMENTS NETWORK-TO-NETWORK INTERFA
2、CE ITU-T Recommendation 1.372 (Previously “CCIIT Recommendation”) CCITT RECMNxI.372 93 M 48b259L 0580737 151 M FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, opera
3、ting and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their
4、turn, produce Recommendations on these topics. ITU-T Recommendation 1.372 was prepared by the IT-T Study Group XVIII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT c
5、eased to exist as of 28 February 1993. In its place, the ITU Telecommunication Smdardization Sector (IT-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommend
6、ation, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunica
7、tion administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1993 Ail rights reserved. No part of this Publication may be reproduced or utilized in any form or by any means, electronic or mechanical, i
8、ncluding photocopying and microfilm, without permission in writing from the ITU. 1 2 3 4 5 6 7 8 9 CCITT RECMN*I-372 93 IpI 48b2C9L 0580738 O98 = CONTENTS Page Introduction . Definitions . Network-to-network interface reference model . 3.1 Locations of network-to-network interface 3.2 PVC Network-to
9、 network multi-network reference model . Network-to-network interface performance parameters Frame relaying network functional architecture . 5.1 Data transfer (U-plane) . 5.2 Control plane (C-plane) requirements . 5.3 Network management . 5.4 Operation Administration and Maintenance (OM) . Congesti
10、on m.anagement PVC ManagementProvisioning requirements PVC network-to-network parameter coordination 7.2 PVC network-to-network management SVC call control requirements . 8.1 SVC network-to-network parameter negotiation Lower layer requirements . 9.1 Digitai hierarchies 9.2 Broadband ISDN . 7.1 1 1
11、2 2 2 3 4 4 5 5 5 6 6 6 7 9 9 9 9 10 Recommendation 1.372 (0-3) 1 CCITT RECflN*I-372 93 m 48b2591 0580739 T24 Network-to-network interface Frame relaying network Rec. G.702 1.372 or 8-ISDN Recommendation I372 Frame relaying network Rec. G.702 or B-ISDN FRAME RELAYING BEARER SERVICE NETWORK-TO-NETWOR
12、K INTERFACE REQUIREMENTS (Helsinki, 1993) 1 Introduction Recognizing the range of data applications and bit rates supported by frame relaying bearer services (FRBS) there is a need to develop the functionaiities of the ISDN FRBS network-to-network interface as well as the UNI. Recommendation 1.233.1
13、 defines the frame relaying bearer service (FRBS) requirements at the user-to-network interface. The bearer service provides, bi-directional transfer of protocol data units (PDU) (layer 2 frames) from one S- or T-reference point to another with the order preserved (see 3.1L.233.1) and uses Recommend
14、ation Q.922 WIE functions (see Annex MQ.922). The congestion management and control procedures are described in Recomen- dationI.370. The interworking requirements for the FRBS and other services are to be described in a future Recommendation. The scope of this Recommendation is to define network-to
15、-network interface requirements independently of the Lower Layer transport used (see Figure 1). This Recommendation primarily defines permanent virtual circuit (PVC) requirements. Switched virtual circuit (SVC) requirements are outlined in 8, however, additional details are for further study. Lower
16、Layer requirements: - digitai hierarchies up to level 3 rates (34 368 kbit/s or 44 736 kbit/s) (see 9.1); - broadband ISDN (B-ISDN) (see 9.2). I I FIGURE UI.372 Defmition of scope 2 Definitions Terms and definitions are given in Recommendations 1.113,1.233.1 and 1.370. I I T1817530-92/dOl Recommenda
17、tion 1.372 (03193) 1 3 Network-to-network interface reference model 3.1 Locations of network-tenetwork interface Figure 2 illustrates possible locations of the network-to-network interfaces in a generic frame relaying network. The interfaces connect public frame relaying networks. Ti81 5470-9Zd02 UN
18、I User network interface * Network-t the C-plane information flows across the Network-to-Network Interface; - Operation, administration and maintenance (OM). Note - It is anticipated that the Network-to-network interface as given in this Recommendation may also be applied to public to private frame
19、relaying network interfaces and private to private frame relaying network interfaces. 3.2 PVC Network-to network multi-network reference model A multi-network PVC is a concatenation of two or more single PVC segments. A multi-network PVC should appear to each user as if only one network and one PVC
20、were involved; the multi-network aspects should not appear (see Figure 3). 2 Recommendation 1.372 (03/93) CCITT RECMN*I=372 73 m 4862571 0580743 682 m * * UNI II PVC segment PVC segment User A User B I I I I Multi-network PVC 1181 7540-9Zd3 FIGURE 3h.372 Multi-network PVC reference model 4 Network-t
21、o-network interface performance parameters Frame relaying quality of service refers to service performance from the end-user standpoint. network-to-network performance parameters apply at different interfaces in the network. For a multi-network frame relaying service, the values of performance param
22、eters at the network-to-network interface contribute to the service perormance from the end-user standpoint. The frame relaying quality of service parameters defined in Recommendation 1.233.1 also apply at the network-to- network interface. These parameters are: - throghput; - access rate (AR); - co
23、mmitted information rate (CIR); - committed burst size (Bc); - excess burst size (Be); - transit delay; - residual error rate; - delivered errored kames; - delivered duplicated frames; - delivered out-of-sequence frames; - lost frames; - misdelivered frames. The following descriptions identify other
24、 network-to-network interface performance parameters which should be taken in account: - Availability which refers to the percentage of time that the Frame Relaying service is available within a long term scheduled service interval. The service is viewed as unavailable if it does not meet minimum ac
25、ceptable service performance thresholds. Mean time between service outages: The mean time between service outages (MTBSO) is the average duration of any continuous interval during which the service is available. Mean time to restore: The mean time to restore (MTR) is the average elapsed time from th
26、e time that loss of service is detected by the service provider to the time the service is fully restored. The time of loss of service is measured from the moment the first network-to-network interface detects its occurrence. - - Recommendation 1.372 (03/93) 3 CCITT RECMN*I.372 93 48b2591 0580742 51
27、9 m 5 Frame relaying network functional architecture The frame relaying network node functional architecture is composed of four functional groups, as shown in Figure 4. Network “A o entity I U-piane t Network-to-network interface Network “8” 0 entity 4 U-piane 1 T1817550-9Id04 FIGURE 4D.372 Frame r
28、elaying network functional architecture The four functional groups are called the signalling plane (C-plane functional group), the user plane (U-plane functional group), the network management entity (NM-entity), and the operation, administration, and maintenance entity (OM-entity). A C-plane functi
29、onal group is required to perform all the necessary processing and transmission of signalling information through the signalling link between those network nodes sharing the network-to-network interface. A U-plane functional group is required to perform all the necessary processing and transmission
30、of data through the data transfer link between any two nodes providing the network-to-network interface. Within each network node providing a network-to-network interface, separate functional entities are required to govern the nodai operation. These entities can be grouped into the NM-entity and th
31、e OAM-entity. The NM-entity is the entity which performs the necessary network management functions, while the OM-Entity is the entity which performs the necessary OAM functions, OM and NM-entities interact with C and U-Planes for exchanging and updating status information about the C- and U-planes.
32、 5.1 Data transfer (U-plane) The network-to-network interface shall use core functions as specified in 3.1.1h.233.1 and as given in Annex NQ.922, for the user-network interface. Figure 5 shows the U-piane reference architecture for the transport of FRBS. 4 Recommendation 1.372 (03/93) CCITT RECMN*I=
33、372 93 48b259L 0580743 455 Userspecified Q.922 CORE Physical .I- I -lll-_lllllll_-llllll i ll_llll_lll_l_-II-.- I I_ a Userspecified- 4.922 -+- CORE I- 9.922 Q.922 4.922 Q.922 -+- CORE CORE I CORE CORE I I, I I Physical Physical Physical Physical FIGURE 5h.372 U-plane protocol reference architecture
34、 The network-to-network interface must support a two octet DLCI address field. In situations requiring more than two octets in the address field, the network-to-network interface should support a 4 octet address field length with a 17 bit DLCI field and the fourth octet used as a DL control field. T
35、he procedures for the DL-CORE control are for further study. Note - The use of other Recommendation 4.922 defined address field formats is for further study. The Frame Relaying Bearer service provides the U-plane core functions at the network-to-network interface as described in Annex Ch.233.1. The
36、overview of core services, features of the core services, and data transfer are described in C.4.2D.233.1, C.4.3D.233.1, and C.4.4.5D.233.1 respectively. 5.2 Control plane (C-plane) requirements The C-plane within each frame relaying node (network) is responsible for all messaging between peer level
37、 network entities (e.g. the network management entity) connected via the network-to-network interface. In particular, the C-plane shall transport all network management entity and network-to-network related OAM information between two frame relaying nodes at the network-to-network interface referenc
38、e point. 5.3 Network management Network management functions include: - network-to-network interface trunk management; - route management; - PVC identification management. Additional details and specific requirements are for further study. 5.4 The OAM functions include: Operation Administration and
39、Maintenance (OAM) - - alarms reporting; - human (network operator) interface support; control and network procedures for problem diagnosis. Additional details and specific requirements are for further study. Recommendation 1.372 (03/93) 5 6 Congestion management Congestion management and control are
40、 described in Recommendation 1.370. Additional congestion management principles applicable to the network-to-network interface are as follows: Each network is responsible for protecting itself against congestion scenarios at the network-to-network interface (e-g. a given network should not rely sole
41、ly on the prior networks setting of the DE bit). Data relayed between the UNI and the network-to-network interface may modiy traffic characteristics at the network- to-network interface. If rate enforcement is performed at the network-to-network interface, using the same parameter values (CIR, Bc, B
42、e) as used at the UNI, frames accepted as Bc data at the UNI may be discarded or marked DE (and subsequentiy treated as Be data) at the network-to-network interface. Committed burst size (Bc) data should not be discarded at the network-to-network interface under normal operating conditions. One meth
43、od to assure this, is to limit the sum of the subscribed CIRs (egress from the network) of all PVCs on a given network-to-network interface to be less than the network-to-network interface transmission rate. 7 PVC Managemenhrovisioning requirements Coordination of service parameters is to be achieve
44、d through bilateral agreement of the network operators. Permanent virtual circuit (PVC) status management procedures should be implemented using symmetric operations between networks. Data link connection identifier (DLCI) assignment between networks is to be achieved through bilateral agreement. Ba
45、ndwidth ailocation between networks is to be achieved through bilateral agreement. Routing between networks is to be achieved through bilateral agreement. A PVC that spans multiple frame relaying networks will be engineered to an agreed quality of service through bilateral agreement. This may be in
46、accordance with Recommendation 1.370 or other agreed upon means. Each Frame Relaying service provider is responsible for the OAM of the PVC segment within its network boundaries only. Two service categories, which may impact parameter coordination, should be supported by frame relaying networks. One
47、 service category has characteristics expressed by a committed information rate (CIR) of O. The other service category has characteristics expressed by a CIR of O. These values are used to determine the measurement interval parameter T in Table 1. Table 1 shows the possible relationships of CIR, Com
48、mitted Burst Size (Bc), and Excess Burst Size (Be). It should be noted that the two cases of CIR O have been combined for simplicity of expressing service category characteristics. 7.1 PVC network-tenetwork parameter coordination The core service provided by the frame relaying bearer services, is de
49、scribed in C.4.3h.233.1. The network-to-network interface should provide the same quality of service as that supported between peer core service users. The FRBS service quality is characterized by quality of service (QOS) parameters as defined in 3.1h.233.1. For PVCs, these parameters are administratively coordinated at subscription time. 6 Recommendation 1.372 (03/93) CCITT RECMN*1.372 93 m 4862591 0580745 228 CJR o o =o TABLE 1A.372 Committed burst size Excess burst size Measurement interval (Bc) (Be) (TI o o T = Bc/CIR o =o T = Bc/CIR =o o Wok) Possible re
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