CN1134955C - Vertical package of adaption method for integrating internet with quasi-synchronous digital system - Google Patents

Abstract

The present invention relates to the frame encapsulation of an adaptation method for integrating the internet with a quasi-synchronous digital system. The present invention provides a PDH link access procedure and other techniques by improving the defects of no standards support, over-high cost of partial treatment of hardware retransmission, unclear definition of the value of a retransmitting timer, very low efficiency due to a filling function, etc. in the prior art. Version fields in an Ipv4 packaged end and an Ipv6 packaged end are used as parameters and are mapped to a second layer along with primitives to realize multi-protocol encapsulation; a similar method can be used for supporting more than 250 kinds of protocols comprising the fourth version and the sixth version of an internet protocol.

Description

A kind of data transmission method that is used for internet and PDH (Pseudo-synchronous Digital Hierarchy) fusion

Technical field

The data that the present invention relates to internet transmit the field, it is a kind of frame method for packing that is used for the adaptation method of internet and PDH (Pseudo-synchronous Digital Hierarchy) fusion, be mainly used in the core switch router, the edge switch router, based on the high low-end switch of packet switch, user side integrated access equipment and interconnecting and interworking equipment relevant etc. with internet.

Background technology

Now be used for the frame encapsulation of the adaptation method of internet and PDH (Pseudo-synchronous Digital Hierarchy) fusion, " point-to-point protocol " (english abbreviation PPP) arranged.At internet engineering duty group (english abbreviation IETF), (RFC is the request comment it to be defined as (code name) RFC1619, English RequestFor Comments), it can encapsulate 30 multiple network agreements, contain and be useful on internet " internet protocol the 4th edition (English IPV4); this protocol fitting method is successful by the MODEM online; also have fire compartment wall; but if be used for Synchronous Optical Network (english abbreviation SONET) or PDH (Pseudo-synchronous Digital Hierarchy) (english abbreviation SDH), just come with some shortcomings and defective.Mainly show:

(1) encapsulation of the frame of RFC1619 is finished by point-to-point protocol and two of senior synchronous data-link rules, and the encapsulation of upper-layer protocol is finished by " protocol fields (8/16 bit) " in the PPP frame;

(2) for the application of IP over PDH, there is not the support of frame encapsulation standard, cause IP over PDH can not be used for internet marginal layer and core layer;

(3) for per second 140 megabits and above speed thereof, hardware forwarding part expense is too big during development equipment, because the RFC1619 regulation: recommend to use " LCP (english abbreviation LCP) " sharp magic number (English is expressed as Magic Number).These two more complicated;

When (4) adopting RFC1619, because PPP need connect, the default value of retransmission timer is decided to be 3 seconds in PPP.For high-speed link, this method is too blunt.Use for concrete engineering, should require to support speed range all (differing from 4032 times approximately) from per second 2 megabits to per second 10000 megabits.So the value of retransmission timer should be determined according to the time delay that circuit comes and goes.These are not all made stipulations in RFC 1619, thereby uncertainty can occur when the apparatus interconnection of different manufacturers;

(5) fill function (English is expressed as Padding Function), the information field of PPP generally will be filled into maximum receive unit (english abbreviation MRU, general provision is 1500 bytes on internet).For general internet packet, as the application of browser (English is expressed as WWW) online (this kind application account for 75% that whole internet uses), the average data packet length is 330 bytes, has average about 350% to be to flog a dead horse like this, and efficient is very low.In addition, it is information field that this filling field also needs a function which is distinguished at receiving terminal, and which is to fill field.This has increased processing expenditure again;

Summary of the invention

The objective of the invention is, improved, and propose and design the frame encapsulation of the adaptation method that is used for internet and PDH (Pseudo-synchronous Digital Hierarchy) fusion that is applicable to various situations at deficiency and defective that existing frame encapsulation technology exists; The present invention only keeps bit-oriented PDH Link Access Procedure (english abbreviation LAPP) between internet protocol (english abbreviation IP) and PDH (Pseudo-synchronous Digital Hierarchy) (english abbreviation PDH), replace address field with many service access points, the encapsulation of realization multi-protocols, can support whole speed ranges of from the Lower Order Virtual Container to the higher order virtual container, (comprising cascade), also be particularly suitable for using packet switch interface based on light, uncertainty without any agreement, the present invention can not only solve new equipment development and problems of operation, and has found an extraordinary outlet for the existing telecommunication transmission resource of China.

Of the present inventionly comprise following technical scheme: receive packet from the network layer device of internet, the type of recognition data bag produces the SAPI identifier according to the type of identification, and converts described packet to first kind frame; Described first kind frame is packaged into the frame format that comprises beginning flag, address field, control field, information field, Frame Check Sequence field and termination flag, to form the second class frame; With the above-mentioned second class frame X ⁴³+ 1 multinomial carries out scrambler; The second class frame after the above-mentioned scrambler is encapsulated into payload part, inserts suitable expense, form the 3rd class frame and output to PDH (Pseudo-synchronous Digital Hierarchy) equipment.Described address field comprises the SAPI identifier, and described information field comprises described first kind frame, and the beginning flag of the described second class frame and termination flag are " 0x7E ", and the value of the control field of the described second class frame is " 0x03 ".Utilize generator polynomial 1+x+x ²+ x ⁴+ x ⁵+ x ⁷+ x ⁸+ x ¹⁰+ x ¹¹+ x ¹²+ x ¹⁶+ x ²²+ x ²³+ x ²⁶+ x ³², all bits of the second class frame except that beginning flag, termination flag and Frame Check Sequence field are carried out verification, detect frame and in transmission course, whether go wrong.For the second class frame, the termination flag of former frame is the beginning flag of adjacent frame subsequently.For the second class frame, can between frame and frame, send one or more continuous filling signs.Above-described packet from network layer is IPv4 or IPv6 packet, described first kind frame is IPv4 or IPv6 frame or packet, the described second class frame is PDH Link Access Procedure (LAPP) frame, and described the 3rd class frame is the PDHE1/T1/E2/T2/E3/T3/E4 frame.

This invention is mapped to encapsulation that 2nd layer (LAPP) realize multi-protocols to version field in Ipv4 and Ipv6 packet header with primitive from the 3rd layer as parameter, replace " point-to-point protocol " (PPP) and " high-level data chain rules " (HDLC) two key element framings with key element of PDH Link Access Procedure (LAPP), fusion between solution internet protocol (IP) and the PDH (Pseudo-synchronous Digital Hierarchy) (PDH) and the encapsulation of adaptive frame, internet protocol the 4th edition (Ipv4) and internet protocol sixth version (Ipv6) are supported in this frame encapsulation simultaneously.

It is characterized in that, version field (Version) in Ipv4 and the Ipv6 packet header is mapped to encapsulation that 2nd layer (LAPP) realize multi-protocols with primitive from the 3rd layer as parameter, in internet protocol the 4th edition (Ipv4) and internet protocol sixth version (Ipv6) packet header, be 4 bits, be mapped to after the 2nd layer low four bits as service access point identifier (SAPI), keep its original order and value constant, high four bits of service access point identifier (SAPI) are filled out " 0000 ", this SAPI value are put into the position of the address field of LAPP frame again.Through this conversion, just finished LAPP the multi-protocols on it have been encapsulated.

It is characterized in that, replace " point-to-point protocol " (PPP) and " high-level data chain rules " (HDLC) two key element framings with key element of PDH Link Access Procedure (LAPP), concrete scheme is as follows, all LAPP frames all stop with binary code " 01111110 " initial sum, being located immediately at address field sign before is beginning flag, immediately following Frame Check Sequence (FCS) afterwards be masked as termination flag, in some applications, termination flag also can be used as the beginning flag of next frame, all receiving ends should be able to receive one or more continuous signs, fill with sign between frame and frame; Address field is made up of one eight hyte, the order of bit arrangement is that lowest order is rightmost (being bit 1), highest order is Far Left (being bit 8), address field is used as service access point identifier (SAPI), finish the encapsulation of LAPP to all upper-layer protocols, at receiving terminal, determine it is any agreement according to the value of this field, when having the IP bag to send for the 3rd layer, at first call " DL-UNACK-DATA asks (user data; version field; DS code-point or IPv4 business type field) " primitive, user data, version field and DS code-point correspond respectively to three kinds of parameters, i.e. whole protocol Data Unit (PDU) in the layer 3 IP bag, " version field " (Version) and " segmentation professional (Differentiated Services) code-point or IPv4 business type field (TOS) ", shine upon " version field " of getting off service access point identifier (SAPI) with primitive as LAPP, for Ipv4 and Ipv6, low four of address field are respectively (binary system): " 0100 " and " 0110 ", corresponding with the version number in Ipv4 and the Ipv6 data packet head, their Gao Siwei fills out binary system " 0000 ", in the regulation of address field, decimal number " 4 " expression is to the encapsulation based on the business of Ipv4, " 6 " expression is to the encapsulation based on the business of Ipv6, as broadcast address, other also has 252 values to give over to use in the future " 255 "; Control field is made up of one eight hyte, and its value is 0x03, and all frames all use as command frame, seeks/stops bit and be made as 0, and other value keeps when function expands in the future to be used; Information field is immediately following after control field, eight hytes by integral multiple are formed, when having the IP bag to send for the 3rd layer, at first call " DL-UNACK-DATA asks (user data; version field; DS code-point or IPv4 business type field) " primitive, user data, version field and DS code-point correspond respectively to three kinds of parameters, i.e. whole protocol Data Unit (PDU) in the layer 3 IP bag, " version field " (Version) and " segmentation professional (DifferentiatedServices) code-point or IPv4 business type field (TOS) ", shine upon " the whole protocol Data Unit " that get off " information field " with this primitive as LAPP, at receiving terminal, the 3rd layer of utilization " DL-UNACK-DATA indicates (user data) " primitive scoops out the 2nd layer of " information field " that transfers as the 3rd layer PDU; The afterbody of each frame comprises the Frame Check Sequence of one 32 bit, be used for checking issuable mistake when frame passes through link transmission, FCS is produced by transmit leg, its basic thought is to calculate the redundant code (being FCS) that produces 32 bits by the bit stream to be sent to completely random, invest the afterbody of frame, make to have correlation between frame and the FCS, whether destroyed at receiving terminal by this correlation of identification, detect frame and mistake whether occurred in transmission course, the FCS generator polynomial is:

G (x)=x ³²+ x ²⁶+ x ²³+ x ²²+ x ¹⁶+ x ¹²+ x ¹¹+ x ¹⁰+ x ⁸+ x ⁷+ x ⁵+ x ⁴+ x ²+ x+1 computer capacity first after the opening flag of a frame is than rising abruptly, last bit before FCS ends, total bit number is m, as data polynomial Q (x), wherein also the reason transparency is transmitted the conversion (should not comprise that the needs because of the transparency insert eight hytes) that causes, FCS is the sequence of one 32 bit, its value be following two remainders mould 2 and radix-minus-one complement

----x ^m* (x ³¹+ x ³⁰+ ...+x ²+ x+1)/remainder of G (x)

----x ³²* the remainder of Q (x)/G (x) FCS that said process is produced adds Q (x) and sends afterwards, at receiving terminal, claims M (x) the whole bit sequences between two signs, is calculated as follows [x ^(m+32)* (x ³¹+ x ³⁰+ ...+x ²+ x+1)+x ³²* M (x)]/G (x), wherein m+32 is the length of M (x) sequence, if M (x)=Q (x)+FCS then transmits zero defect, otherwise, just think that transmission has mistake; In frame structure, the bit arrangement of each eight hyte shows for level in proper order, the order of bit arrangement is that lowest order is rightmost (being bit 1), highest order is Far Left (being bit 8), a plurality of eight hytes are vertically arranged, uppermost eight hytes are numbered " 1 ", increase progressively successively and be " 2 " ... " N ", in this structure, a certain bit can be so that (o represents the serial number of eight hytes for o, b) sign, b is illustrated in the serial number of one eight hyte Nepit, send at first at one eight hyte Nepit 8, and in a frame structure, the sending order of eight hytes is 1, (2...N increasing progressively from small to large), but, 4 bytes of FCS are exceptions, are exactly specifically, 1 the bit of being numbered of the 1st eight hytes of FCS is highest orders of FCS long word, and 8 the bit of being numbered of the 4th eight hytes of FCS is lowest orders of FCS long word; The invalid frame of LAPP has following several:

1) by two frames that indicate the ill-considered demarcation that produces,

2) frame length of two signs is less than the frame of 6 eight hytes,

3) include the frame of fcs error,

4) service access point identifier (SAPI) does not match or the unsupported frame of receiving end,

5) include the frame of uncertain control field,

6) frame to finish more than 6 " 1 ", invalid frame will be dropped, and not notify transmit leg, also not produce any action; After FCS calculates and finishes, transmit leg will be checked two entire frame between the sign, if find that five continuous " 1 " are arranged, promptly automatically insert one " 0 " subsequently, at receiving terminal, and before calculating FCS, this " 0 " that deletion is automatically automatically inserted.At transmitting terminal, the LAPP frame needs with (x before being mapped to PDH ⁴³+ 1) multinomial carries out scrambler, equally in receiving end, will use (x after SPE takes out payload ⁴³+ 1) multinomial carries out descrambling and could be for further processing as the LAPP frame, with (x ⁴³+ 1) multinomial carries out scrambler and descrambling is necessary, higher order virtual container signal mark hexadecimal number " 18H " indication " uses (x ⁴³+ 1) multinomial carries out the LAPP of scrambler ", Lower Order Virtual Container signal mark binary number " 101 " indication " uses (x ⁴³+ 1) multinomial carries out the LAPP of scrambler ".

Advantage of the present invention with respect to existing RFC1619, has following innovation:

(1) at present more external manufacturers (are RFC1619 according to the PPP over PDH that internet engineering duty group (english abbreviation IETF) proposes, SONET is meant the Synchronous Optical Network of North America) exploitation, with regard to RFC 1619 itself, link layer has PPP (point-to-point protocol) and two kinds of agreements of HDLC (high-level data link rules), more complicated, hardware spending was too big when it was used for the above speed of per second 140 megabits, the present invention only adopts a LAPP key element by contrast, its complexity and HDLC are suitable, saved " LCP (english abbreviation LCP) " and magic number (English the is expressed as Magic Number) mechanism of the complexity among the PPP, the expense of used protocol adaptation reduces greatly;

(2) RFC 1619 does not still support IP over PDH at present, does not have the standard support when application of PPP over PDH is to Internet marginal layer and core layer like this, and the present invention was both simple by contrast, and was complete again;

When (3) adopting RFC1619, because PPP need connect, the default value of retransmission timer is decided to be 3 seconds for high-speed link in PPP, too blunt, use for concrete engineering, should require all to support to the speed range of per second 140 megabits from per second 2 megabits, so the value of retransmission timer should be determined according to the time delay that circuit comes and goes, these are not all made stipulations in RFC 1619, thereby when the apparatus interconnection of different manufacturers uncertainty may appear, the present invention adopts and does not confirm formula information transfer service mode by contrast, do not need to connect, also do not need to use retransmission timer, the uncertainty of communicating by letter between any peer-entities can not occur, the application of the speed range from per second 2 megabits to per second 140 megabits is all supported;

(4) about filling the use of function, the information field of PPP generally will be filled into maximum receive unit (english abbreviation MRU, general provision is 1500 bytes on internet), for general internet packet, as the application of browser (English is expressed as WWW) online (this kind application account for 75% that whole internet uses), packet length is average out to 330 bytes, and average like this having an appointment 350% is to flog a dead horse, and efficient is very low; In addition, it is information field that this filling field also needs a function which is distinguished at receiving terminal, and which is to fill field, and this has increased processing expenditure again, and the present invention is irrelevant with the filling function by contrast, for any internet application, does not have this idle work;

(5) the present invention has considered Ipv4 that is using at present and the Ipv6 that is about to use, supports to have good real world applications characteristics and extensibility in the future with unified LAPP mechanism;

Generally, the present invention is so that very letter is refined, the mode with cheapness solves the protocol adaptation of internet to the PDH telecommunication transmission efficiently, " point-to-point protocol (english abbreviation PPP) and two key elements of high-level data chain rules (english abbreviation HDLC) are supported internet protocol the 4th edition (english abbreviation Ipv4) and the application of internet protocol sixth version (english abbreviation Ipv6) on PDH with key element replacement of connectionless PDH Link Access Procedure.

Description of drawings

Fig. 1, conception schematic diagram proposed by the invention

Fig. 2, the LAPP frame format by byte align proposed by the invention

Fig. 3, usefulness (x proposed by the invention ⁴³+ 1) schematic diagram of multinomial scrambler and descrambling

Fig. 4, the present invention uses conception figure in national IP over SDH (containing PDH in the SDH passage) core layer networking

Fig. 5, the present invention is in IP over SDH (containing PDH in the SDH passage) core layer networking application conception inside the province

Embodiment

Below, embodiments of the invention are described with reference to the accompanying drawings.Imagination proposed by the invention is mainly used in the core switch router, the edge switch router, and based on the high low-end switch of packet switch, user side integrated access equipment and interconnecting and interworking equipment relevant etc. with internet.Application framework of the present invention is seen Fig. 1, it is conception schematic diagram proposed by the invention, wherein adopt internet protocol (IP) (comprising Ipv4 and IPv6) in network layer, link layer adopts PDH Link Access Procedure (english abbreviation LAPP), physical layer adopts PDH (Pseudo-synchronous Digital Hierarchy) (E1/T1/E2/T2/E3/T3/E4 among the PDH), mainly comprises each time group of PDH.In this framework, the 3rd layer of service access point that provides of the 2nd course has two, respectively for using based on the packet of IPV4 with based on the packet of IPV6.Their service access point identifier (SAPI) is respectively a decimal number " 4 " and " 6 " (also can be other value).Whole protocol Data Unit in the layer 3 IP bag (english abbreviation PDU), " version field " (English Version), professional (the English Differentiated Services) code-point of segmentation or IPv4 business type field (english abbreviation TOS), when sending as 2 layers of the parameter maps to the of primitive.At the 2nd layer, the information field of the PDU that shines upon as LAPP; The version field of shining upon as service access point identifier (english abbreviation SAPI), and is transferred to the address field of LAPP; The professional code-point of the segmentation of shining upon or IPv4 business type field as a kind of foundation, control formation algorithm.Do not confirm formula information transfer service (UITS) the 2nd layer of employing, it and the 1st layer are also mutual with primitive and parameter by corresponding service access point.Fig. 2 is the frame structure of the LAPP by byte align proposed by the invention, the opening flag that uppermost that eight hyte is the LAPP frame, its value is defined as binary number " 01111110 ", and then be address field, one eight hyte is long, its value is " version field " of the frame format of Ipv4 or Ipv6, comes from the network layer mapping with " DL-UNACK-DATA request " primitive as parameter during operation.Fig. 3 is usefulness (x proposed by the invention ⁴³+ 1) schematic diagram of multinomial scrambler and descrambling, the part that impales in the empty frame is one 43 bit shift register, circle partly is expressed as an XOR and patrols and seize circuit, by the relation of seizing of patrolling among the figure, can finish the scrambler function to " the data flow output behind the scrambler " from " the data flow input before the scrambler "; Can finish the descrambling function from " input of scrambler data flow " to " the data flow output behind the descrambling ".Also can adopt the shift register of displacement from D1 to D43, also should adjust but patrol the relation of seizing accordingly.Adopting the benefit of scrambler is " often " low or " often " high level can not occur at receiving terminal.Fig. 4 is that the present invention uses conception figure in national IP over SDH core layer networking, this example is that existing resource is given an example the existing transmission network management of the computer representation at white interface with present Chinese 8 * 8 SDH or wavelength division multiplexing (english abbreviation WDM) trunk transit network; After each node city employing has the core switch router of IP over SDH interface, can form a packet switch core net that extends in all direction, in these links, can adopt IP over PDH equally, the computer representation at black interface is about to the webmaster of the core switch router net of layout.Fig. 5 is that the present invention is in IP over SDH core layer networking application conception inside the province, wherein black circle is represented the core route exchange device based on IP over SDH equipment, the Xiao Bai circle is represented the branch line route exchange device based on IP over SDH equipment, REG is a regenerative repeater, ADM is an add-drop multiplexer, and LAN is a local area network (LAN); The each province is mostly with the SDH ring-shaped network at present, and this example is that existing resource is given an example with present Chinese each province SDH looped network or wavelength-division multiplex system (english abbreviation WDM) trunk transit network; Each districts and cities node city inside the province adopt have the core switch router of IP over SDH interface after, can form one in the packet switch core net that extends in all direction inside the province, in these links, can adopt IP over PDH equally.

Claims (9)

1. a data transmission method that is used for internet and PDH (Pseudo-synchronous Digital Hierarchy) fusion comprises the following steps;

Receive packet from the network layer device of internet, the type of recognition data bag produces the service access point identifier according to the type of discerning, and converts described packet to first kind frame; Described first kind frame is packaged into the frame format that comprises beginning flag, address field, control field, information field, Frame Check Sequence field and termination flag, to form the second class frame; With the above-mentioned second class frame X ⁴³+ 1 multinomial carries out scrambler; The second class frame after the above-mentioned scrambler is encapsulated into payload part, inserts suitable expense, form the 3rd class frame and output to PDH (Pseudo-synchronous Digital Hierarchy) equipment.

2. data transmission method as claimed in claim 1, the address field of the described second class frame are the service access point identifier.

3. data transmission method as claimed in claim 1, the information field of the described second class frame comprise described first kind frame.

4. data transmission method as claimed in claim 1, the beginning flag of the described second class frame and termination flag are " 0x7E ".

5. data transmission method as claimed in claim 1, the value of the control field of the described second class frame are " 0x03 ".

6. data transmission method as claimed in claim 1 also comprises calculation procedure, utilizes generator polynomial 1+x+x ²+ x ⁴+ x+x ⁵+ x ⁷+ x ⁸+ x ¹⁰+ x ¹¹+ x ¹²+ x ¹⁶+ x ²²+ x ²³+ x ²⁶+ x ³², all bits of the second class frame except that beginning flag, termination flag and Frame Check Sequence field are carried out verification, detect frame and in transmission course, whether go wrong.

7. data transmission method as claimed in claim 1, for the second class frame, the termination flag of former frame is the beginning flag of adjacent frame subsequently.

8. data transmission method as claimed in claim 1 for the second class frame, sends one or more continuous filling signs between frame and frame.

9. data transmission method as claimed in claim 1, described packet from network layer is IPv4 or IPv6 packet, described first kind frame is IPv4 or IPv6 frame or packet, the described second class frame is a PDH (Pseudo-synchronous Digital Hierarchy) Link Access Procedure frame, and described the 3rd class frame is a PDH E1/T1/E2/T2/E3/T3/E4 frame.

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