The public ATM network supports the IP service the technology and the plan

----Has used the ATM technology operation business, facing the IP service rapid development, all is seeking ATM to support IP the preferred plan.

----The present universal mutual recognition is selects MPLS to take the public backbone net the solution. MPLS 000-741 first in the public ATM backbone on-line introduction, it will use the integrated pattern, the IP technology and the ATM technology good will unify in together, concurrently has had the ATM high speed performance, the QoS 000-741 performance, the flow control performance and the IP flexibility, may the 000-741 expansion, will be one kind of more ideal backbone IP net technology.

----The international telecommunication standard organized ITU-T to put the IP standard research on the 000-741 first place, this September, the SG13 IP expert group conference transmits to the public ATM net IP the MPLS technology plan to propose suggestion draft I.ipatm. This draft comprehensively proposed the network overall request, the network system structure, the agreement system structure, the service mapping request and so on, and used MPLS to the public ATM net the solution to give explicit showing. 000-741 This article makes a summary introduction to this suggestion draft main content.

Network system structure

----ATM transmits the IP technology to have some overall requests, must be independent including the 000-741 network technical plan to the IP agreement edition which supports; Must have the support large-scale network to be enough may the extension; Must contain in the ATM network supports highly effective moreover has may the expansion IP group broadcast the ability; Must have the enough robustness to support the large-scale 000-741 network. These requests regarding all determinations IP service all is suitable.

----Supports the IP level service on ATM the frame system structure to define for supports the network system structure and the agreement system structure union which the IP service needs.

----The IPOA reference 000-741 network architecture like chart 1 shows, this disposition had demonstrated supports the IP service each kind of possibility situation. The dashed 000-741 line frame demonstrates is the public net. In the dashed line frame square demonstration is in the public net general disposition, they including ATM core, IPOA network and edge router. Outside the dashed line frame is some different networks, they had demonstrated the public net provides each kind of specific IP service to each 000-741 kind of specific network the situation. Looked from the public net angle that, these networks all may think is the user network. Here need explanation is, involves the public net in this article to be only restricted in has the ATM core the public network.


----In chart 1, some two kind of reference points. The 1st kind of reference point is the public net and the user network boundary. But the 2nd kind of reference point is the public net and the IPOA network connection. The reference point 1 disposition may rely on to the user network facility as well as provides the IP service the definition. The edge router 000-741 possibly needs the interworking function iwf with/or suitably matches the function. This article key point is a technology which 2nd kinds of reference point as well as in the public net uses.

----Chart 2 has demonstrated the public ATM network and special-purpose ATM the on-line IP service reference 000-741 disposition. In special-purpose and public IPOA network, the IP service is (IPSF) realizes using the ATM exchange function and the IP service function. In this kind of situation, between the ATM exchange function and the IP service function connection should define in P or is in the M reference point. The IP service function refers is realizes the function which IPOA needs, a IPSF typical example is the address analysis service. As one kind of terminal system, IPSF is in fact has the ATM connection the router.


----The IPSF function and the ATM exchange function may realize on the identical equipment, we was not on unnecessary definition reference point P in this kind of situation the connection. 000-741The IPSF function and the ATM exchange function also may separately realize on the different equipment, in this kind of situation, to relies on with M or P on connection definition to IPSF is inside the core ATM network or outside.

----Outside ATM network ISP and the terminal system (ES) may turn on special-purpose or is the public ATM network. Each terminal system all has a set of complete IPOA agreement stack, if is connected with special-purpose IPOA, then uses special-purpose UNI; If is connected with public IPOA, then uses public UNI.

----This network main 000-741 characteristic is the network and the service exchanges. Exchanges in the environment in the network, with the aid of between two networks interworking function iwfs (IWF), the IP agreement control information (PCI) may transparently transmit with the load data through the ATM network other IP network. The typical situation is, IWF merely uses one kind for the IP grouping suitably to match the function to carry on the seal and its transparently passes to far-end IWF.

----Regarding existing IP and ATM network exchanging, the typical situation is the network exchanges, that is provides the backbone with ATM or is the core network transmits the IP agreement. In this kind of situation, the ATM network may regard as is third (or higher level) the agreement lower level transmission.

Agreement system structure

----Chart 3 described the public net to transmit IP on ATM the agreement reference model. Must pay attention is: The lower level about the level management, the plane (or system) managed and the 000-741 control plane concept all obtained the expansion, in order to contained third as well as the upper formation function block.

----Between the function module connection may be between the internal, the sub- level or the plane non- standardization correspondence connection, also may be exterior, the standardized agreement connection.

----In the general model each level all has corresponding the level management function module. The level management function module is only responsible for this management and the agreement control information (PCI) processing; The level correspondence only can carry on through the plane management function, in this function use plane management cooperation function (CoF) the module carries out.

----In the IPOA each kind of network application does not need all to contain all functions module. Thus, the above function module may regard as is realizes each kind of specific network (or NE) application basic "the component". The network must maintain between the different module the basic relations and the order, in order to guaranteed consistent may be operational.


----Under carries on the description to the IPOA agreement reference model function.

----IP-SSCS/AAL5 function

----The IP-SSCS/AAL5 function module integrated has mapped each kind of transmission function the IP load which on AAL5 needed, this module provided in RFC1483 the IETF acceptance, has duplicate attached the seal based on the IEEE802.2 link level control/sub- net which the dot (LLC/SNAP) in the agreement defined with the multi- agreements duplicate to use the function.

----IP level function

----The IP level function has provided retransmits (IP data newspaper transmission) the system realization source which exchanges through to destination IP the ability. IP retransmits refers is receives to a grouping, uses one kind of expenses very low decision procedure to decide how processes this grouping the process.

----The IPOA agreement structure must be independent to the IP edition. At present, IP has two editions, IPv4 (the IP edition 4) and IPv6 (the IP edition 6). The IP level function should (separately corresponds with IETF in RFC791 and RFC2460 to IPv4 and IPv6) the center definition is same.

----The IP level function certainly cannot provide one kind of reliable correspondence facility. In data transmission process between, regardless of is end-to-end or each as soon as jumps all does not have the confirmation the process.

----IP level management function

----The IP level management function has two kind of basic functions: Addressing and partition. The IP level function uses the address which in the IP first prize carries the IP data packet to transmit the destination. Is the letter makes and the route function module regarding the transmission route choice use. If has the necessity, the IP level function also will use in the IP first prize the special localization to come to the IP data packet to carry on the partition and 重装.

----IPv4 mainly uses 4 kind of mechanisms to provide its service: Service type, lifetime, option and first prize verification sum. IPv6 is the Internet agreement new edition, its change mainly has following four aspects: The expansion addressing ability, the first prize form simplification, with may choose the function support regarding the expansion the enhancement, flows the mark ability and the authentication (security ability).

----The IP level management function certainly logarithm according to does not provide the mistake control, besides has a verification in the first prize and, in the agreement does not have the re-transmit and the class controls the mechanism.

----Transmission level function

----Transmission level including face connection TCP function and connectionless UDP function.

----The TCP function provides the reliable connection for the advancement between. The TCP function and IETF in the RFC793 definition are consistent, TCP function including following facility: The basic data transmission, the reliability, the class control, turns round with, connects, the priority and the security.

----The UDP function provides is the data newspaper transmission. The UDP function and IETF in the RFC768 definition are consistent, UDP faces business, the transmission and the repetition protection has not safeguarded. Uses the transmission level function on ATM not to be supposed to change the transmission level itself function.

----Network management function module

----The network management function relies on the specific IPOA network application. Usually, they including with under management related some TMN function, like fault management, performance management, disposition management, safety control and so on.

----The letter makes and the route control function

----This function has included IP and in the ATM control letter makes and the route function module. The IP control and the letter command included contained chooses the road each kind of IP control, the ATM control to include the ATM letter to make and to choose the road.

IP service mapping

----The IP service is (the Internet agreement) the package (data packet) the form transmits the data through between the user and the tenderer connection by IP one kind of data transmission service. In this kind of situation, the request tenderer does not need to know IP package of in the data attribute. Between the user and the tenderer actual either the concealment contract is the tenderer does not only change (control territory to the Dutch content to be allowed to change or to be invariable) transmits the IP package to the destination (a IP address or another operation/user connection). This contract may conceal a group by the user in to the tenderer to propose when conversation request assigns the transmission quality parameter (for example BER, end-to-end detention, sequence are correct or not and so on). When concrete realization may use assigns the data attribute shorthand way which the IP package carries to assign these parameters. For example, if the user assigns these packages to carry the voice, then may directly map a group of specific transmissions quality parameter. But must pay attention, this kind of situation is different to the user requested a time of voice call, it is in fact expected the tenderer takes the user data the voice data processing. Also for example, carries on the transformation code or in the TDM facility the load bearing data, this kind of situation is the voice feature but is not the IP service.

----IPIntserv technology

----Intserv is flows the QoS rank according to each IP the precise description, by has RSVP the function in the router RSVP agreement and flows admits the control to support IP the QoS classification.

----Flows in Intserv, has defined two kind of services - guarantees service (GuaranteedService, GS) and is controlled the load service (ControlledLoadService, CLS). Regarding the GS service, flows most greatly lines up when extends receives the control, on route any o'clock extends can affect most greatly lines up when extends. When CLS not fixed extends the guarantee, but the service class must with in the network 轻载 situation class quality quite, in fact the CLS request have the long-term band width guarantee. In brief, these two kind of services all request with the characteristic which is defined the sign funnel agreement flows, the superhigh service flows is treated as "does everything possible" business volume processing.

----IPDiffserv technology

----The IETF diffserv model is based on each 跳行 for (PerHopBahaviors, PHB) the concept, diffservPHB 前转 the behavior which has by route on each local router defines. At present, IETF has defined two kind of main PHB:

Acceleration 前转 PHB (ExpeditedForwardingPHB, EF-PHB)
----The EF-PHB characteristic is the band width has may the disposition and on the identical link not other business volumes influences. EF-PHB may use for when the Diffserv territory to establish the request has the low loss rate, low extends with is low when extends the vibration the end-to-end service.
May determine 前转 the PHB group (AssuredForwardingPHBGroup, the AF-PHB group)
----The AF-PHB group's characteristic has 4 AF rank, each rank assignment has a quota to retransmit the resources (for instance in a Diffserv pitch point buffer and band width and so on). In each AF rank, each IP grouping is marked on three kind of possibilities to discard the priority. When has the jam, the grouping will discard the priority to decide in some AF rank each grouping relative importance. Between 4 AF rank relative performance does not have the standard the relations, the AF-PHB group to be allowed to realize by a higher possibility guaranteed the service requests information speed.
----Supports QoS to be sensitive (aware) the IP service network model

----In the frame which IETF produces, end-to-end QoS is provides together by the network edge Intserv region and the network core Diffserv region, this way is often called "the core edge" the way. Certainly here proposed network model, but also can consider other some possibilities, moreover the link level media in here always hypothesis is ATM.

----Supports QoS sensitive IP service possible network model like chart 4, chart 5 and chart 6 shows.

----Situation 1: In ATM network Intserv

----In this model, two Intserv terminal (stub) between the network correspondence supports by the IPOA core network. In the core network IPOA equipment may simultaneously provide Intserv and the Diffserv ability. Must support the end-to-end integration service, the network only needs to activate IPOA on the equipment the Intserv function. Two services levels agreement (SLA1 and SLA2) all request to be able to satisfy the intserv service the request.


----Situation 2: In ATM network Diffserv

----In this model, two Diffserv terminal (stub) between the network correspondence supports by the IPOA core network. In the core network IPOA equipment may simultaneously provide Intserv and the Diffserv ability. Must support the end-to-end difference service, the network only needs to activate IPOA on the equipment the Diffserv function. Two services levels agreement (SLA1 and SLA2) all request to be able to satisfy the diffserv service the request.


----Situation 3: Region supports the Intserv service through ATM in the network Diffserv.

----In this model, two Intserv terminal (stub) between the network correspondence supports by the IPOA core network. In the core network, has some regions only to support Diffserv, but other regions may simultaneously provide Intserv and the Diffserv ability. In this kind of situation, Intserv transparently will transmit through the Diffserv region, moreover the network will have two kind of services levels agreement.


----Service mapping function detailed list

----The service mapping function does not rely on the periphery network architecture, it only relies on to needs to carry on the mapping the contact surface two sides to support IP and the ATMQoS way.

----Chart 7 had demonstrated we consider the IP service which must in the network architecture to the ATM service mapping each kind of possibility combination.


----ATM will support IP only to solve maps 6 and maps 12 services, in this kind of situation, in the ATM partial networks exportation, certainly will not need to have 5 with the 10th kind of mapping function, this will be because in the goal IP network, regarding the QoS support will be completely based on the IP information (for instance, the RSVP news or will be IP in grouping DS territory), but these information will be transparently transmit by the ATM network. When the local ATM business volume must by way of a pure IP network transmission or the destination be a pure IP network, possibly will need to have 5 and the 10th kind of mapping function.

----3rd only belongs to the IP region with the 4th kind of mapping function, to their research is a IETF work part. At the same time, the outset to expands the ATM parameter and QoS rank all mappings to/the termination all belongs to the ATM forum the work (to support in the ATM special net).

----Maps the IP integration service the ATM service

----When two have Intserv the ability the router ATM connection to have to support has which GS [ RFC2212 ] or CLS [ RFC2211 ] requests IP flows, can produce the IP integration service maps the ATM service the question. This mapping mainly has two ways: A pair of mapping and are many to a mapping.

----The safeguard service (GS) will map ATM not to need to ATM to make any expansion. However, the choice mapping plan must satisfy the following request: Choice ATC must be able to support when extends the request; Choice ATC must be able for to flow the retention certain band width.

----(CLS) the service maps the load control ATM similarly not to need to ATM to do any expansion, but chooses the mapping plan must be able for to flow the retention certain band width.

----Maps the IP difference service the ATM service

----In the Diffserv territory, PHB may take defines the IP service the important essential factor. However, PHB itself is suitable for end-to-end IP the service which has nothing to do with with QoS. Thus, between Diffserv and the ATM mapping foundation must be the IP service and the ATM service. Specially, the IP service may define for conforms to a business volume adjustment standard group of PHB realization, the ATM service may define is a group has the QoS rank [ I.356 ] the ATM through-put capacity [ I.371 ].

----In order to provides the service to the user, the Diffserv service provider must unifies the PHB realization and the business volume adjustment and the provision of service strategy. But ATM has not solved the PHB problem, PHB and between the ATM through-put capacity mapping certainly is not suitable. Therefore, the service mapping may regard as is one kind of specific difference service to one kind of ATM service mapping. Based on the IP service definition which considered, Diffserv to the ATM mapping may through two services providers' between consultation be able to be clear about the realization.

MPLS plan superiority
----We suggested uses MPLS to take in the public net supports IP on ATM the best technology, this not only because the MPLS support at present determined all IP service, moreover also has the following reason.

----Adapts in the comparatively large-scale network

----Well known, MPOA extremely is suitable for the small scale network, applies must be restricted to the comparatively large-scale network. But MPLS is precisely for satisfies the large-scale network each kind of request (for example flexibility, may and manageability request and so on expansion) designs.

----Adapts in the many kinds of load bearings network

----The large-scale network may use including ATM the many kinds of load bearings technology. Says from a wider scope, should select one kind regarding IPOA is most superior, moreover regarding other link level technologies also is the most superior technology. MPLS is precisely can cover this scope the only technology.

---- The route controls flexibility

----From chooses the road the angle to say, the MPLS technology may cause us to obtain simultaneously chooses the use fixed route or is the dynamic route way possibility. Which way specifically uses to be decided by the network operator's choice.

----Can simultaneously support MPLS and the ATM controlling agreement

----A more ideal situation has one kind of independence to the link level agreement control technology. At the same time, on the identical switchboard also may use the ATM control, this kind of situation is called "shipsinthenight the" way.

----IP service business volume project

----At present, ATM has the most complete business volume project ability. MPLS has borrowed some ATM technology ability, like QoS, chooses the road, the resource management and so on, moreover has introduced the explicit route concept, it is helpful to maps the business volume request above the network analysis situs.

----Use existing investment

----Considered existing ATM with other technical investments, transmits the IP request in each kind of link level technology to have one kind of identical exchange technology. In the current load bearing network, the ATM hardware can use one fixed way to the IP business volume transmission, moreover MPLS was considered is the CIPOA evolution direction.

----Supports the VPN service

----The MPLS main merit is can or be the explicit route way provides by the connectionless way face the connection service. This kind of characteristic causes MPLS especially to be suitable for the dynamic tunnel technology, but the dynamic tunnel technology is at present supports the VPN service the effective transmission method.

----QoS guarantee

----IPDiffserv and MPLS have the obvious tacit understanding, because their design all meets the service provider's need. Because marks the expansion semantics may carry the Diffserv information, with the aid of to the mark, the end-to-end mark exchange way and the certain resources will reserve the mechanism, the network may guarantee the QoS mechanism in the specific MPLS territory uniformity.