CA2042164C - A communication network - Google Patents
A communication networkInfo
- Publication number
- CA2042164C CA2042164C CA002042164A CA2042164A CA2042164C CA 2042164 C CA2042164 C CA 2042164C CA 002042164 A CA002042164 A CA 002042164A CA 2042164 A CA2042164 A CA 2042164A CA 2042164 C CA2042164 C CA 2042164C
- Authority
- CA
- Canada
- Prior art keywords
- niu
- nius
- subnetwork
- data
- tunable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/2801—Broadband local area networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/028—WDM bus architectures
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/0283—WDM ring architectures
Abstract
A communications network comprising a plurality of "subnetworks"
multiplexed onto a single communications medium. A separate group of network interface units (NIUs) communicate on each predetermined "subnetwork", and each NIU also includes a tunable transmitter for transmitting data to NIUs of other subnetworks. Data from a user equipment is transmitted via the tunable transmitter if it is destined for an NIU from another subnetwork, and via a fixed transmitter if it is destined for an NIU on the same subnetwork. In one embodiment, fiber optics is utilized in order to provide a high speed network with tunable lasers. (FIG. 2).
multiplexed onto a single communications medium. A separate group of network interface units (NIUs) communicate on each predetermined "subnetwork", and each NIU also includes a tunable transmitter for transmitting data to NIUs of other subnetworks. Data from a user equipment is transmitted via the tunable transmitter if it is destined for an NIU from another subnetwork, and via a fixed transmitter if it is destined for an NIU on the same subnetwork. In one embodiment, fiber optics is utilized in order to provide a high speed network with tunable lasers. (FIG. 2).
Description
204216~
A COMMUNICATIONS NETWORK
Technical Field This invention relates to communications networks and more particularly, to a Network Interface Unit (NIU) for constructing a tunable laser, multihop communications network.
5 Description of the Prior Art Recently, multihop lightwave networks have been proposed in an effort to fully utilize the large bandwidth of optical transmission media. One such proposal is described in the article "Terabit Lightwave Networks: The Multihop Approach" by Acampora et al. in AT&T Technical Journal~ Vol. 66, Issue 6, Nov. 1987. In the 10 Acampora system, each NIU employs one or more optical tr~n~mittçrs and receivers of fixed wavelength, where the transmit and receive frequencies for the NIUs may be the same or dirr~,lelll for dirr~lel.l NIUs. Data is transmitted among the NIUs by "hopping" data packets through one or more intermediate NIUs until the packets reach a NIU which is arranged to llansl~ on the receive frequency of the destination NIU
15 for the packets. The data packets are then transmitted to the ~estin~tion NIU. This system avoids the need to continually retune optical receivers or transmitters, a process which would waste considerable bandwidth.
One drawback of the Acampora system may be appleciated by considering the transmission of a large data file which comprises a large number of packets. All of the 20 NIUs through which the data packets are 'hopped' are unnecessarily burdened with excess traffic. Thus, the need has arisen to design a network which can utilize the large bandwidth of the optical medium, yet avoid some of the drawbacks of multihop systems.
In one prior known system, both multihop techniques and retunable optical 25 receivers are utilized. This prior known system, however, is slightly more complex and architecturally dependent than is desirable.
The problem le.l-~i"il~g in the prior art is to provide a flexible and simple network ar~hitect -re which may utilize the advantages of multihop networks, yetoperate somewhat more efficiently.
~`:
. -2- 204216~
Summary of the Invention These and other problems are overcome in accordance with the present invention which provides a communications network comprising: a common - communications medium; a plurality of network interface units (NIUs) coupled to said 5 common communications medium, said NIUs being arranged into a plurality of subnetworks with each subnetwork including a predet~rmined sequence of NIUs; each particular NIU including means for determining if data to be tran~mi1ted by the particular NIU is destined for a receiving NIU on the subnetwork including the particular NIU or for a receiving NIU on a subnetwork other than the subnetwork 10 including the particular NIU, means for transmitting data to a next NIU in the sequence of NIUs of the subnetwork including the particular NIU, tunable transmitter means for transmitting data to NIUs on subnetworks other than the subnetwork including the particular NIU, said tunable transmitter means being tuned to a particular subnetwork frequency in response to an address in the data to be transmitted, and 15 means for detecting if data is being transmitted by any other NIU on said common communications medium on the frequency to which said tunable transmitter means is tuned and for inhibiting said tunable tran~milter means from transmitting data during intervals that data is detected as being transmitted on said frequency to which said tunable transmitter means is tuned.
In one embodiment, optical fiber is employed as the communications medium, and passive optical taps are utilized at each NIU. This embodiment has the further advantage that the passive taps attenuate the optical signal and, thus, allow reuse of the same wavelength in various nonoverlapping portions of the communications medium.Brief D~ ;~,lion of the Drawin~
FIG. 1 shows a logical diagram of an exemplary network in accordance with the invention;
FIG. 2 is a high level block diagram of a Network Interface Unit (NIU) which may be used in the arrangement of FIG. 1; and FIG. 3 depicts the structure of an exemplary packet which may be used in the invention.
-- 2a - 204216~
Detailed Description FIG. 1 shows a logical block diagram of a Local Area Network (LAN) in accordance with the invention. The arrangement shown in FIG. 1 comprises communications medium 122 and NIUs 101-121. Each NIU may be used to interface - one or more user equipments to communications medium 122 in accordance with techniques which are well known in the art. It is to be understood that although the arrangement of FIG. 1 is shown as a ring architecture, the NIUs may be connected in other topologies also, such as a bus for example.
Communications medium 122 includes three exemplary channels, each of which is implemented on a separate wavelength. Specifically, NIUs 101-103 each include a fixed tr~n~mit~r and receiver tuned to ~ 2, and ~3, respectively. Each of NIUs 104 through 121 includes a fixed tr~n.cmitter and receiver tuned to the same wavelength as the NIU located three before it on communications medium 122. Thus, NIUs 101, 104, 107, 110, 113, 116 and 119 each contain a fixed receiver and transmitter tuned to ~1, while NIUs 102, 105, 108, 111, 114, 117, and 120 each contain a fixed transmitter and receiver tuned to ~2. These connections are indicated via dashed lines in FIG. 1. Further, the rem~ining NIUs are connected via fixed transmitters and receivers tuned to ~3. Thus, the network of FIG. 1 can be thought of as three subnetworks, each implemented on a different wavelength, and each connecting a di~rent set of every third NIU.
Although each of the subnetw~ s of FIG. 1 is implen~l.ted on one wavelength, in practical systems, each of the sul,n~,lwo,Ls may be impleu-f .ne~ on several wavelength~. For example, NIU 116 of FIG. 1 includes a fixed receiver arranged to receive on ~1 and a fixed tr~ncmittçr tuned to ~1. The fixed ~:~n~ er, S however, could be tuned to some other wavelength, such as ~4. This would require, however, that the fixed receiver at NIU 119 be tuned to ~4. In general, as long as overlapping portions of the diL~,~nt subn~ lw-o,~s do not use the same wavelength, each subnetwork can operate subst~nti~lly independently. For pull oses of explanation herein, however, it is ~csllme~ that each subnetwork is imple..~e.-~ed on 10 one single wavelength.
Another ~op~ l ly of the arr~ngement of FIG. 1 is that the number of NIUs disposed between any two NIU's on the same subnelwc,lL is such that a signal traveling along co.~ ic~tions ms~ m 122 will be ~ n~ çd beyond recognidon after being received by the next NrU on the subnelwul~. This plo~ll~ has been 15 previously udlized advantageously to allow wavelength reuse. By way of example, NIU 104 of FIG. 1 transmits on wavelength ~1 to NIU 107. Each of the NIUs 105, 106, and 107, connectçd to cGl...~ -icationc ...~ 122 via passive couplers for example, would ~lenu~e the signal tr~ncmitted from NIU 104 to 107 so that after the signal tT~ncmitte~ from NIU 104 is received by NIU 107, no other of the N~Us20 can receive it; i.e. as the signal continues to propagate and thus reaches NIU 108, it is a~ ted beyond recognidon.
One other p[O~l l~ of the nelw~ of FIG. 1 is that each N~U includes a tunable acdvity detector for .~.ol~ . ;ng activity on subl~lwoll~s other than its own ~CSoci~t~i subn~ tw.,l~, and a tunable l,P ~ for l.,..~ ;.-g on these other 25 subnelwc,l~s when they are detected to be idle. For example, when NIU 101 tr~ncmitc on ~1 to NrU 104, NrU 102 can .~onitor such tr~ncmissions to detect idle dme slots on the subn.,lwci., connecdng N~Us 101 and 104. Further, NIU 102 can retune its tunable tr~ncmitter to transmit on ~1. This plOpe,~ly a,lows tr~ncmicsion bel...... cel, any two NIU's as described below.
Turning now to the operation of the nelwOssk, co.~.. -i~ztions among the NIUs on the same subnetwork is accomplished by t~ncmittin~ p~ etc~ in sequence and clockwise, from one NIU to the next NIU on the same subnetwork during predetermined dme slots. For example, a packet to be trzncmitt~A from NIU107 to N~U 119, is t~ncmitted first to NIU 110, whe,-e it is received and reamplified.
35 This reamplificadon is necessz.y ~allce~ as previously explained, the l,~ itled packet would be ~ttenn~ted beyond recognidon after it passes NIU 110. F~om NIU
-~4- 2042164 110, the packet is tran~mi~te~ to NIU 113, and then finally, to NIU 116 for final processing by an associated equi~ el t. Tr~n~mission~ among NIUs 107, 110, 113, 116 and 119 is accomplished on wavelength ~1, as shown in FIG. 1.
Co.. ~,nic~tiQns among NIUs not connected to the same subnetwork is S accomplished by the tr~n~mitting NIU ll,onito~ g the subnetwork with the ~Csoci~te~ receiving NIU and "ch~nging over" to that subl~ctwc.lL when it is idle.
For example, consider the case where NIU 106 is to transmit data to NIU 113. Note from FIG. 1 that NIU 113, the receiving NIU for the data, is arranged to receive data on ~1. NIU 106 therefore, would tune its tunable activity detector to ~1, and would 10 monitor tr~n~mi.~siQns from NIU 104 to NIU 107. Note that actual processing of these co.. ~.. ic~tions is unnecessa.~; the activity detector need only identify the absence or presence of a signal. A more det~ilecl description of the NIU hardwd~ is described hereinafter.
When NIU 106 detects an idle time slot on the subnelwc,l~ connP~ling NIUs 104 and 107, the packet from NIU 106 will be output onto co.. ~ Qns ~.~rA;I.... 122 using wavelength ~1. Because of the wavelength being used, the packet will be received by the fixed L~ue..cy receiver associated with NIU 107. It will then be conveyed from NIU 107 to NlU 113 via NIU 110, as previously described. In this manner, a NIU can cG.. ~l~ic~te to other NIUs on its own 20 subnetwolL via its acsoci~te~ fi~ced wavelength, and to NIUs on other subnelwolLs via a tunable l.ans.lfitt._l.
Having described the basic operation of the network, we turn now to FIG. 2, a Uock diagram of an exemplary NIU which may be used in the inventive nelw~,lL. User e~ ,...en~ 211 may be any of a variety of well known devices, as the 25 particulars of such user equi~ ent are uni-lll)ol tant to the invention.
Operation of the NIU is first desç~ibed with reference to its own ~soci~te~ subnetwork. Assume, for ~u~l,oses of expl~n~t~ n only, that the NIU
shown in FIG. 2 l~lGsents NIU 105 of FIG. 1. As can be seen from FIG. 1, NIU
105 is arranged to use the ~2 subnclwvlk. Accordingly, fixed ~ ",;t~r 207 is 30 arranged to transmit on ~2.
Packets to be relayed by NIU 105, i.e., packets which must be tr~n~mitted on subnetwork ~2 from NIU 102 to NIU 108, arrive at fixed filter 204.
Fixed filter 204 removes energy at ~1 and ~3 and supplies the desired signal, i.e., the data from ~2 to receiver 205. Receiver 205 completes recepdon of the packet by 35 p~,.rO.~ g dem~ tion, and reading the address. Packets destined for NIU 105 are removed from the co.. ~ ations .n~ .. n and supplied to user e~luiplll.nt 211 ~ 2042169 as inrlir~ted in FIG. 2. However, packets to be relayed to NIU 108 are placed inqueue 206 for later tr~n~mi~sion on a first-in-first-out basis, for example.
Queue 206 may also receive packets from user equipment 211. For example, with reference to FIG. 1, if it is desired to transmit packets from NIU 105 S to NIU 108, such packets are conveyed to queue 206 from NIU 105 as shown.
Queue 206 must thelcfore include some means for avoiding contelllion ~ween packets arriving from user equipment 211 and packets arriving from receiver 205.This can be accomplished by alternatively polling the two sources, for example, although many other techniques are well known in the art.
Packets from queue 206 are conveyed se tuel1lially, during predetermined time slots, to fixed tr~n~mitter 207. In the case of an optical c~. n. . .~ ;c~l ;Qns system, fixed tr~n~ 207 would be a laser, and would be optically coupled to the co--~.. nications l~le~lillll~.
Packets which need to be ~ n~ A from NIU 105 to NIUs from other 15 subnelwo~s are tran~ cd via tunable tr~n~mitter 208. By way of exarnple, assume a packet is to be ~ n.;~rl from NIU 105 to NIU 110. As is shown in FIG.
1, such a packet must first be ~ nsn~ c~ to NIU 107 on wavelength ~1 for conveyance to NrU 110. Such packets are burr~d in queue 210 as they arrive from the user equipln~nt associ~te~ with NIU 105. Note that of the plurality of packets in 20 queue 210 at any dme, many of them may be ~estine~ for various subn~ tw~lks and thus must be tr~n~mitt~.d at dirrel~llt wavelen th~ from other p~rl~et~.
In operadon, as a packet arrives to the front of queue 210, its address is read by tuning circuit 212. Tuning circuit 212, based upon a s~ldd~ table lookup, will det~ -;ne what wavelength the packet must be l~n~ on by det~ ining 25 which sul n~ lwoll the destin~tion NIU for the packet is ~soci~ted with. Tuning circuit 212 will then cause tunable tr~n~mitter 208 to tune to the proper wavelength, while ~imlllt~neously causing tunable filter 201 to tune to the same wavelength.The next idle tdme slot which exists on the pardcular subnelwolk associated with the ælected wavelength will then be detected by acdvity detector30 203. Specifically, acdvity detector 203 will detect the absence of energy at the wavelength to which tunable filter 201 is tuned. When this occurs, actdvity detector 203 will enable tunable tr~ns...;~ . 208 and the packet will be tr~n~mitted ontoco... nic~tions medium 122. Combiner 209 serves to combine the signals from tunable transmitt~r 208 with those from fixed tran~mitt~r 207 and to couple the 35 combination to co~ n~ications llledium 122.
`~ -6- 2042164 Contention among NIUs co~ ,c~ g for the same idle time slot on a given subnetwork must be resolved. With reference to FIG. 1, note, for example, that NIUs 102 and 103 are both disposed ~cell NIU 101 and 104. Consider the case where both NIUs 102 and 103 sim~llt~neously require tr~ncmission of a packet S onto the subnetwork ~csoci~ted with ~1. There needs to exist some way of det~ll.lining which of these two NIUs will utilize the next idle dme slot which is to be tTan.cmitte~l from NIU 101. If this is done il~ ,lly, collisionc may result, as described below.
FM. 3 shows an e~remrl~ry packet format, with two bits reserved for 10 activity detection. ~csllming that the ~etection of activity requires one bit time, a re~so.~ble assumption in today's high speed n~,~wolks, at least two bits must bereserved in the packet to implement the system. Using the example from above with NIUs 102 and 103, it can be seen from FIG. 1 that NIU 102 will detect the empty time slot first, as co....~ ir~tiQns flows clockwise. Next, NIU 102 will retune and 15 utilize this time slot as previously ~les~ihe~ However, by the time that happens, NIU 103 would receive the first bit of the idle time slot, detect the idle time slot, and thus transmit its data packet in the same time slot.
In order to avoid the above described problem, two bit times, as shown in FIG. 3, are reserved for activity dete~tiol NIU 102 will assume a time slot is empty if the first bit, labeled "a", of FIG. 3 is set to a logical "0". NIU 102 may then use that time slot to "change over" to the new subne~w~,lk and l- ~sll~it data from tunable tr~ncmi~er 208 onto the new subne~wolk. Further, NIU 102 would set the bit labeled "b" to a logical 1. As the packet propagPtes past NIU 103, NIU 103 would check the bit labeled "b" and, if set to a logical "0", NIU 103 would assume 25 that the time slot is empty. By allowing two bits for activity detection, collisions are comrletely avoided.
The concept described extends in a straightforward manner to the case where more than two NIUs are disposed be~een any two NIUs on the same subnetwork. In general, if there exists NIUs 1 through N which are disposed in 30 sequence bcL~ n a pair of NIUs on the same subnetwork, then N bit times should be reserved in the packet header for activity detection. Each NIU uses a specified bit to detect that the time slot is idle, and each NIU, if it uses such an idle time slot, sets all of the l~ ining activity detection bits to a logical "1". In practice, if an optical fiber is used as the co.~ nic~tions ,,,.~.1;.. and passive couplers are used at each 35 NIU, a~lv,~i-llately 10 or 12 NIUs may be disposed ~l~,.,n any two NIUs on the same subnc~wolL before the signal becoll}es a~ ed beyond recognition.
While the above describes the basic operation of the invention, it is to be undcl~lood that other variations are possible wilLoul viol~ting the scope or the spirit of the invention. For example, the architecture may be a bus rather than a ring type, or a tunable filter can be imp!e...~ l~ using a tunable laser and a heterodyne receiver S arrangemP-nt, and any if a number of co. . .n~ tions media may be used instead of optical fiber.
Another variation involves eliminating the need to provide two sources of data from the user equipment. Specifically, referring to FIG. 2, it is shown that the exemplary user equipment must supply two separate data streams; one for the 10 tunable tr~n~mitter, and one for the fixed tr~n~mitter. An ~ltem~tive emborlim~ont could allow the user e~luiplllent to supply only one data stream, and the NIU could separate the data for the tunable tr~nsmitter from the data for the fixed tr~n~mittPr based upon the address in the packet of data.
Another variation in~ludes a technique for providing protection against 15 NIUs being "locked out" of a subl~lwu,L. Specifically, and with l~fe.~.lce to FIG. 1, it can be appreciated that if NIU 101 is l~n~ ;ng a long and continllolls stream of data to NIU 104, then NIU 102 would be "locked out" of the ~1 subn~,lw-JlL, since there will exist no idle dme on that subllelw~lL for the duration of the tr~n~mi~.~ion from NIU 101. Accordingly, it may be desirable to reserve, for example, an out of 20 band back up channel, over which infol~llation would flow counLel~;lockwise and allow NIU 102 to signal NIU 101 and thus cause NIU 101 to leave one or more timeslots empty.
The network can also be duplicated on two or more co.~ -ic~tions media to provide subst~nti~lly instant recovery from failures, as is well known in the 25 art.
A COMMUNICATIONS NETWORK
Technical Field This invention relates to communications networks and more particularly, to a Network Interface Unit (NIU) for constructing a tunable laser, multihop communications network.
5 Description of the Prior Art Recently, multihop lightwave networks have been proposed in an effort to fully utilize the large bandwidth of optical transmission media. One such proposal is described in the article "Terabit Lightwave Networks: The Multihop Approach" by Acampora et al. in AT&T Technical Journal~ Vol. 66, Issue 6, Nov. 1987. In the 10 Acampora system, each NIU employs one or more optical tr~n~mittçrs and receivers of fixed wavelength, where the transmit and receive frequencies for the NIUs may be the same or dirr~,lelll for dirr~lel.l NIUs. Data is transmitted among the NIUs by "hopping" data packets through one or more intermediate NIUs until the packets reach a NIU which is arranged to llansl~ on the receive frequency of the destination NIU
15 for the packets. The data packets are then transmitted to the ~estin~tion NIU. This system avoids the need to continually retune optical receivers or transmitters, a process which would waste considerable bandwidth.
One drawback of the Acampora system may be appleciated by considering the transmission of a large data file which comprises a large number of packets. All of the 20 NIUs through which the data packets are 'hopped' are unnecessarily burdened with excess traffic. Thus, the need has arisen to design a network which can utilize the large bandwidth of the optical medium, yet avoid some of the drawbacks of multihop systems.
In one prior known system, both multihop techniques and retunable optical 25 receivers are utilized. This prior known system, however, is slightly more complex and architecturally dependent than is desirable.
The problem le.l-~i"il~g in the prior art is to provide a flexible and simple network ar~hitect -re which may utilize the advantages of multihop networks, yetoperate somewhat more efficiently.
~`:
. -2- 204216~
Summary of the Invention These and other problems are overcome in accordance with the present invention which provides a communications network comprising: a common - communications medium; a plurality of network interface units (NIUs) coupled to said 5 common communications medium, said NIUs being arranged into a plurality of subnetworks with each subnetwork including a predet~rmined sequence of NIUs; each particular NIU including means for determining if data to be tran~mi1ted by the particular NIU is destined for a receiving NIU on the subnetwork including the particular NIU or for a receiving NIU on a subnetwork other than the subnetwork 10 including the particular NIU, means for transmitting data to a next NIU in the sequence of NIUs of the subnetwork including the particular NIU, tunable transmitter means for transmitting data to NIUs on subnetworks other than the subnetwork including the particular NIU, said tunable transmitter means being tuned to a particular subnetwork frequency in response to an address in the data to be transmitted, and 15 means for detecting if data is being transmitted by any other NIU on said common communications medium on the frequency to which said tunable transmitter means is tuned and for inhibiting said tunable tran~milter means from transmitting data during intervals that data is detected as being transmitted on said frequency to which said tunable transmitter means is tuned.
In one embodiment, optical fiber is employed as the communications medium, and passive optical taps are utilized at each NIU. This embodiment has the further advantage that the passive taps attenuate the optical signal and, thus, allow reuse of the same wavelength in various nonoverlapping portions of the communications medium.Brief D~ ;~,lion of the Drawin~
FIG. 1 shows a logical diagram of an exemplary network in accordance with the invention;
FIG. 2 is a high level block diagram of a Network Interface Unit (NIU) which may be used in the arrangement of FIG. 1; and FIG. 3 depicts the structure of an exemplary packet which may be used in the invention.
-- 2a - 204216~
Detailed Description FIG. 1 shows a logical block diagram of a Local Area Network (LAN) in accordance with the invention. The arrangement shown in FIG. 1 comprises communications medium 122 and NIUs 101-121. Each NIU may be used to interface - one or more user equipments to communications medium 122 in accordance with techniques which are well known in the art. It is to be understood that although the arrangement of FIG. 1 is shown as a ring architecture, the NIUs may be connected in other topologies also, such as a bus for example.
Communications medium 122 includes three exemplary channels, each of which is implemented on a separate wavelength. Specifically, NIUs 101-103 each include a fixed tr~n~mit~r and receiver tuned to ~ 2, and ~3, respectively. Each of NIUs 104 through 121 includes a fixed tr~n.cmitter and receiver tuned to the same wavelength as the NIU located three before it on communications medium 122. Thus, NIUs 101, 104, 107, 110, 113, 116 and 119 each contain a fixed receiver and transmitter tuned to ~1, while NIUs 102, 105, 108, 111, 114, 117, and 120 each contain a fixed transmitter and receiver tuned to ~2. These connections are indicated via dashed lines in FIG. 1. Further, the rem~ining NIUs are connected via fixed transmitters and receivers tuned to ~3. Thus, the network of FIG. 1 can be thought of as three subnetworks, each implemented on a different wavelength, and each connecting a di~rent set of every third NIU.
Although each of the subnetw~ s of FIG. 1 is implen~l.ted on one wavelength, in practical systems, each of the sul,n~,lwo,Ls may be impleu-f .ne~ on several wavelength~. For example, NIU 116 of FIG. 1 includes a fixed receiver arranged to receive on ~1 and a fixed tr~ncmittçr tuned to ~1. The fixed ~:~n~ er, S however, could be tuned to some other wavelength, such as ~4. This would require, however, that the fixed receiver at NIU 119 be tuned to ~4. In general, as long as overlapping portions of the diL~,~nt subn~ lw-o,~s do not use the same wavelength, each subnetwork can operate subst~nti~lly independently. For pull oses of explanation herein, however, it is ~csllme~ that each subnetwork is imple..~e.-~ed on 10 one single wavelength.
Another ~op~ l ly of the arr~ngement of FIG. 1 is that the number of NIUs disposed between any two NIU's on the same subnelwc,lL is such that a signal traveling along co.~ ic~tions ms~ m 122 will be ~ n~ çd beyond recognidon after being received by the next NrU on the subnelwul~. This plo~ll~ has been 15 previously udlized advantageously to allow wavelength reuse. By way of example, NIU 104 of FIG. 1 transmits on wavelength ~1 to NIU 107. Each of the NIUs 105, 106, and 107, connectçd to cGl...~ -icationc ...~ 122 via passive couplers for example, would ~lenu~e the signal tr~ncmitted from NIU 104 to 107 so that after the signal tT~ncmitte~ from NIU 104 is received by NIU 107, no other of the N~Us20 can receive it; i.e. as the signal continues to propagate and thus reaches NIU 108, it is a~ ted beyond recognidon.
One other p[O~l l~ of the nelw~ of FIG. 1 is that each N~U includes a tunable acdvity detector for .~.ol~ . ;ng activity on subl~lwoll~s other than its own ~CSoci~t~i subn~ tw.,l~, and a tunable l,P ~ for l.,..~ ;.-g on these other 25 subnelwc,l~s when they are detected to be idle. For example, when NIU 101 tr~ncmitc on ~1 to NrU 104, NrU 102 can .~onitor such tr~ncmissions to detect idle dme slots on the subn.,lwci., connecdng N~Us 101 and 104. Further, NIU 102 can retune its tunable tr~ncmitter to transmit on ~1. This plOpe,~ly a,lows tr~ncmicsion bel...... cel, any two NIU's as described below.
Turning now to the operation of the nelwOssk, co.~.. -i~ztions among the NIUs on the same subnetwork is accomplished by t~ncmittin~ p~ etc~ in sequence and clockwise, from one NIU to the next NIU on the same subnetwork during predetermined dme slots. For example, a packet to be trzncmitt~A from NIU107 to N~U 119, is t~ncmitted first to NIU 110, whe,-e it is received and reamplified.
35 This reamplificadon is necessz.y ~allce~ as previously explained, the l,~ itled packet would be ~ttenn~ted beyond recognidon after it passes NIU 110. F~om NIU
-~4- 2042164 110, the packet is tran~mi~te~ to NIU 113, and then finally, to NIU 116 for final processing by an associated equi~ el t. Tr~n~mission~ among NIUs 107, 110, 113, 116 and 119 is accomplished on wavelength ~1, as shown in FIG. 1.
Co.. ~,nic~tiQns among NIUs not connected to the same subnetwork is S accomplished by the tr~n~mitting NIU ll,onito~ g the subnetwork with the ~Csoci~te~ receiving NIU and "ch~nging over" to that subl~ctwc.lL when it is idle.
For example, consider the case where NIU 106 is to transmit data to NIU 113. Note from FIG. 1 that NIU 113, the receiving NIU for the data, is arranged to receive data on ~1. NIU 106 therefore, would tune its tunable activity detector to ~1, and would 10 monitor tr~n~mi.~siQns from NIU 104 to NIU 107. Note that actual processing of these co.. ~.. ic~tions is unnecessa.~; the activity detector need only identify the absence or presence of a signal. A more det~ilecl description of the NIU hardwd~ is described hereinafter.
When NIU 106 detects an idle time slot on the subnelwc,l~ connP~ling NIUs 104 and 107, the packet from NIU 106 will be output onto co.. ~ Qns ~.~rA;I.... 122 using wavelength ~1. Because of the wavelength being used, the packet will be received by the fixed L~ue..cy receiver associated with NIU 107. It will then be conveyed from NIU 107 to NlU 113 via NIU 110, as previously described. In this manner, a NIU can cG.. ~l~ic~te to other NIUs on its own 20 subnetwolL via its acsoci~te~ fi~ced wavelength, and to NIUs on other subnelwolLs via a tunable l.ans.lfitt._l.
Having described the basic operation of the network, we turn now to FIG. 2, a Uock diagram of an exemplary NIU which may be used in the inventive nelw~,lL. User e~ ,...en~ 211 may be any of a variety of well known devices, as the 25 particulars of such user equi~ ent are uni-lll)ol tant to the invention.
Operation of the NIU is first desç~ibed with reference to its own ~soci~te~ subnetwork. Assume, for ~u~l,oses of expl~n~t~ n only, that the NIU
shown in FIG. 2 l~lGsents NIU 105 of FIG. 1. As can be seen from FIG. 1, NIU
105 is arranged to use the ~2 subnclwvlk. Accordingly, fixed ~ ",;t~r 207 is 30 arranged to transmit on ~2.
Packets to be relayed by NIU 105, i.e., packets which must be tr~n~mitted on subnetwork ~2 from NIU 102 to NIU 108, arrive at fixed filter 204.
Fixed filter 204 removes energy at ~1 and ~3 and supplies the desired signal, i.e., the data from ~2 to receiver 205. Receiver 205 completes recepdon of the packet by 35 p~,.rO.~ g dem~ tion, and reading the address. Packets destined for NIU 105 are removed from the co.. ~ ations .n~ .. n and supplied to user e~luiplll.nt 211 ~ 2042169 as inrlir~ted in FIG. 2. However, packets to be relayed to NIU 108 are placed inqueue 206 for later tr~n~mi~sion on a first-in-first-out basis, for example.
Queue 206 may also receive packets from user equipment 211. For example, with reference to FIG. 1, if it is desired to transmit packets from NIU 105 S to NIU 108, such packets are conveyed to queue 206 from NIU 105 as shown.
Queue 206 must thelcfore include some means for avoiding contelllion ~ween packets arriving from user equipment 211 and packets arriving from receiver 205.This can be accomplished by alternatively polling the two sources, for example, although many other techniques are well known in the art.
Packets from queue 206 are conveyed se tuel1lially, during predetermined time slots, to fixed tr~n~mitter 207. In the case of an optical c~. n. . .~ ;c~l ;Qns system, fixed tr~n~ 207 would be a laser, and would be optically coupled to the co--~.. nications l~le~lillll~.
Packets which need to be ~ n~ A from NIU 105 to NIUs from other 15 subnelwo~s are tran~ cd via tunable tr~n~mitter 208. By way of exarnple, assume a packet is to be ~ n.;~rl from NIU 105 to NIU 110. As is shown in FIG.
1, such a packet must first be ~ nsn~ c~ to NIU 107 on wavelength ~1 for conveyance to NrU 110. Such packets are burr~d in queue 210 as they arrive from the user equipln~nt associ~te~ with NIU 105. Note that of the plurality of packets in 20 queue 210 at any dme, many of them may be ~estine~ for various subn~ tw~lks and thus must be tr~n~mitt~.d at dirrel~llt wavelen th~ from other p~rl~et~.
In operadon, as a packet arrives to the front of queue 210, its address is read by tuning circuit 212. Tuning circuit 212, based upon a s~ldd~ table lookup, will det~ -;ne what wavelength the packet must be l~n~ on by det~ ining 25 which sul n~ lwoll the destin~tion NIU for the packet is ~soci~ted with. Tuning circuit 212 will then cause tunable tr~n~mitter 208 to tune to the proper wavelength, while ~imlllt~neously causing tunable filter 201 to tune to the same wavelength.The next idle tdme slot which exists on the pardcular subnelwolk associated with the ælected wavelength will then be detected by acdvity detector30 203. Specifically, acdvity detector 203 will detect the absence of energy at the wavelength to which tunable filter 201 is tuned. When this occurs, actdvity detector 203 will enable tunable tr~ns...;~ . 208 and the packet will be tr~n~mitted ontoco... nic~tions medium 122. Combiner 209 serves to combine the signals from tunable transmitt~r 208 with those from fixed tran~mitt~r 207 and to couple the 35 combination to co~ n~ications llledium 122.
`~ -6- 2042164 Contention among NIUs co~ ,c~ g for the same idle time slot on a given subnetwork must be resolved. With reference to FIG. 1, note, for example, that NIUs 102 and 103 are both disposed ~cell NIU 101 and 104. Consider the case where both NIUs 102 and 103 sim~llt~neously require tr~ncmission of a packet S onto the subnetwork ~csoci~ted with ~1. There needs to exist some way of det~ll.lining which of these two NIUs will utilize the next idle dme slot which is to be tTan.cmitte~l from NIU 101. If this is done il~ ,lly, collisionc may result, as described below.
FM. 3 shows an e~remrl~ry packet format, with two bits reserved for 10 activity detection. ~csllming that the ~etection of activity requires one bit time, a re~so.~ble assumption in today's high speed n~,~wolks, at least two bits must bereserved in the packet to implement the system. Using the example from above with NIUs 102 and 103, it can be seen from FIG. 1 that NIU 102 will detect the empty time slot first, as co....~ ir~tiQns flows clockwise. Next, NIU 102 will retune and 15 utilize this time slot as previously ~les~ihe~ However, by the time that happens, NIU 103 would receive the first bit of the idle time slot, detect the idle time slot, and thus transmit its data packet in the same time slot.
In order to avoid the above described problem, two bit times, as shown in FIG. 3, are reserved for activity dete~tiol NIU 102 will assume a time slot is empty if the first bit, labeled "a", of FIG. 3 is set to a logical "0". NIU 102 may then use that time slot to "change over" to the new subne~w~,lk and l- ~sll~it data from tunable tr~ncmi~er 208 onto the new subne~wolk. Further, NIU 102 would set the bit labeled "b" to a logical 1. As the packet propagPtes past NIU 103, NIU 103 would check the bit labeled "b" and, if set to a logical "0", NIU 103 would assume 25 that the time slot is empty. By allowing two bits for activity detection, collisions are comrletely avoided.
The concept described extends in a straightforward manner to the case where more than two NIUs are disposed be~een any two NIUs on the same subnetwork. In general, if there exists NIUs 1 through N which are disposed in 30 sequence bcL~ n a pair of NIUs on the same subnetwork, then N bit times should be reserved in the packet header for activity detection. Each NIU uses a specified bit to detect that the time slot is idle, and each NIU, if it uses such an idle time slot, sets all of the l~ ining activity detection bits to a logical "1". In practice, if an optical fiber is used as the co.~ nic~tions ,,,.~.1;.. and passive couplers are used at each 35 NIU, a~lv,~i-llately 10 or 12 NIUs may be disposed ~l~,.,n any two NIUs on the same subnc~wolL before the signal becoll}es a~ ed beyond recognition.
While the above describes the basic operation of the invention, it is to be undcl~lood that other variations are possible wilLoul viol~ting the scope or the spirit of the invention. For example, the architecture may be a bus rather than a ring type, or a tunable filter can be imp!e...~ l~ using a tunable laser and a heterodyne receiver S arrangemP-nt, and any if a number of co. . .n~ tions media may be used instead of optical fiber.
Another variation involves eliminating the need to provide two sources of data from the user equipment. Specifically, referring to FIG. 2, it is shown that the exemplary user equipment must supply two separate data streams; one for the 10 tunable tr~n~mitter, and one for the fixed tr~n~mitter. An ~ltem~tive emborlim~ont could allow the user e~luiplllent to supply only one data stream, and the NIU could separate the data for the tunable tr~nsmitter from the data for the fixed tr~n~mittPr based upon the address in the packet of data.
Another variation in~ludes a technique for providing protection against 15 NIUs being "locked out" of a subl~lwu,L. Specifically, and with l~fe.~.lce to FIG. 1, it can be appreciated that if NIU 101 is l~n~ ;ng a long and continllolls stream of data to NIU 104, then NIU 102 would be "locked out" of the ~1 subn~,lw-JlL, since there will exist no idle dme on that subllelw~lL for the duration of the tr~n~mi~.~ion from NIU 101. Accordingly, it may be desirable to reserve, for example, an out of 20 band back up channel, over which infol~llation would flow counLel~;lockwise and allow NIU 102 to signal NIU 101 and thus cause NIU 101 to leave one or more timeslots empty.
The network can also be duplicated on two or more co.~ -ic~tions media to provide subst~nti~lly instant recovery from failures, as is well known in the 25 art.
Claims (5)
1. A communications network comprising:
a common communications medium;
a plurality of network interface units (NIUs) coupled to said common communications medium, said NIUs being arranged into a plurality of subnetworks with each subnetwork including a predetermined sequence of NIUs;
each particular NIU including means for determining if data to be transmitted by the particular NIU is destined for a receiving NIU on the subnetwork including the particular NIU or for a receiving NIU on a subnetwork other than the subnetwork including the particular NIU, means for transmitting data to a next NIU in the sequence of NIUs of the subnetwork including the particular NIU, tunable transmitter means for transmitting data to NIUs on subnetwork other thanthe subnetwork including the particular NIU, said tunable transmitter means being tuned to a particular subnetwork frequency in response to an address in the data to betransmitted, and means for detecting if data is being transmitted by any other NIU on said commoncommunications medium on the frequency to which said tunable transmitter means is tuned and for inhibiting said tunable transmitter means from transmitting data during intervals that data is detected as being transmitted on said frequency to which said tunable transmitter means is tuned.
a common communications medium;
a plurality of network interface units (NIUs) coupled to said common communications medium, said NIUs being arranged into a plurality of subnetworks with each subnetwork including a predetermined sequence of NIUs;
each particular NIU including means for determining if data to be transmitted by the particular NIU is destined for a receiving NIU on the subnetwork including the particular NIU or for a receiving NIU on a subnetwork other than the subnetwork including the particular NIU, means for transmitting data to a next NIU in the sequence of NIUs of the subnetwork including the particular NIU, tunable transmitter means for transmitting data to NIUs on subnetwork other thanthe subnetwork including the particular NIU, said tunable transmitter means being tuned to a particular subnetwork frequency in response to an address in the data to betransmitted, and means for detecting if data is being transmitted by any other NIU on said commoncommunications medium on the frequency to which said tunable transmitter means is tuned and for inhibiting said tunable transmitter means from transmitting data during intervals that data is detected as being transmitted on said frequency to which said tunable transmitter means is tuned.
2. A communications network as defined in claim 1 wherein said means for detecting includes tunable monitoring means for detecting time slots during which data is being transmitted on said communications medium on said frequency to which said tunable transmitter means is tuned and wherein said intervals are time slots.
3. A communications network as defined in claim 2 wherein each particular NIU
further includes means for receiving data on a frequency assigned to the subnetwork including the particular NIU.
further includes means for receiving data on a frequency assigned to the subnetwork including the particular NIU.
4. A communications network as defined in claim 3 Claims wherein said means for transmitting data to a next NIU transmits at a frequency assigned to the subnetwork including the particular NIU.
5. A communication network as defined in claim 4 wherein said medium comprises an optical communications medium and each NIU further includes in optical coupler for interfacing to said medium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/561,852 US5101290A (en) | 1990-08-02 | 1990-08-02 | High-performance packet-switched wdm ring networks with tunable lasers |
| US561,852 | 1990-08-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2042164A1 CA2042164A1 (en) | 1992-02-03 |
| CA2042164C true CA2042164C (en) | 1996-09-03 |
Family
ID=24243749
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002042164A Expired - Fee Related CA2042164C (en) | 1990-08-02 | 1991-05-09 | A communication network |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5101290A (en) |
| EP (1) | EP0472296A1 (en) |
| JP (1) | JPH04234244A (en) |
| CA (1) | CA2042164C (en) |
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| IT1272486B (en) * | 1993-07-23 | 1997-06-23 | Alcatel Italia | HIGH CAPACITY DATA TRANSMISSION NETWORK AND NETWORK KNOT SUITABLE FOR THE SAME |
| US5517498A (en) * | 1993-09-20 | 1996-05-14 | International Business Machines Corporation | Spatial reuse of bandwidth on a ring network |
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| US6334219B1 (en) | 1994-09-26 | 2001-12-25 | Adc Telecommunications Inc. | Channel selection for a hybrid fiber coax network |
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| JPH09153907A (en) * | 1995-11-28 | 1997-06-10 | Matsushita Electric Ind Co Ltd | Bus type communication network |
| JPH09181774A (en) * | 1995-12-23 | 1997-07-11 | Nec Corp | Optical switch device and optical switch control system |
| US6262822B1 (en) * | 1998-05-13 | 2001-07-17 | Jds Fitel Inc. | Circuit for monitoring optical signals |
| US6525850B1 (en) | 1998-07-17 | 2003-02-25 | The Regents Of The University Of California | High-throughput, low-latency next generation internet networks using optical label switching and high-speed optical header generation, detection and reinsertion |
| US6111673A (en) | 1998-07-17 | 2000-08-29 | Telcordia Technologies, Inc. | High-throughput, low-latency next generation internet networks using optical tag switching |
| US6580537B1 (en) | 1998-07-17 | 2003-06-17 | Regents Of The University Of California, The | High-throughput, low-latency next generation internet networks using optical label switching and high-speed optical header generation, detection and reinsertion |
| EP0989702A1 (en) * | 1998-09-25 | 2000-03-29 | Eolring International | Local telecommunication network |
| US6271946B1 (en) * | 1999-01-25 | 2001-08-07 | Telcordia Technologies, Inc. | Optical layer survivability and security system using optical label switching and high-speed optical header generation and detection |
| ATE328419T1 (en) * | 2000-02-23 | 2006-06-15 | Thinprint Gmbh | METHOD FOR TRANSMITTING DATA IN NETWORKS VIA DATA LINES |
| US6519062B1 (en) * | 2000-02-29 | 2003-02-11 | The Regents Of The University Of California | Ultra-low latency multi-protocol optical routers for the next generation internet |
| US6813276B2 (en) | 2001-01-30 | 2004-11-02 | The Regents Of The University Of California | Optical layer multicasting using a single sub-carrier header with active header detection, deletion, and re-insertion via a circulating optical path |
| US6754450B2 (en) | 2001-01-30 | 2004-06-22 | The Regents Of The University Of California | Optical layer multicasting using a single sub-carrier header with active header detection, deletion, and new header insertion via opto-electrical processing |
| US6757497B2 (en) | 2001-01-30 | 2004-06-29 | The Regents Of The University Of California | Optical layer multicasting using a single sub-carrier header and a multicast switch with active header insertion via reflective single sideband optical processing |
| US6850707B1 (en) | 2001-01-30 | 2005-02-01 | The Regents Of The University Of California | Secure optical layer multicasting to effect survivability |
| US6873797B2 (en) | 2001-01-30 | 2005-03-29 | The Regents Of The University Of California | Optical layer multicasting |
| US6819666B2 (en) | 2001-01-30 | 2004-11-16 | The Regents Of The University Of California | Optical layer multicasting using multiple sub-carrier headers with header detection, deletion, and insertion via reflective single sideband optical processing |
| US6850515B2 (en) | 2001-01-30 | 2005-02-01 | The Regents Of The University Of California | Optical layer multicasting using a single sub-carrier header and a multicast switch with active header insertion via light circulation |
| US6768871B2 (en) | 2001-01-30 | 2004-07-27 | The Regents Of The University Of California | Optical layer multicasting using a multicast switch to effect survivability and security |
| US6757496B2 (en) | 2001-01-30 | 2004-06-29 | The Regents Of The University Of California | Optical layer multicasting using a single sub-carrier header and an optical multicasting switch |
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| KR20030010969A (en) * | 2001-07-28 | 2003-02-06 | 한국전자통신연구원 | Wavelength Sharing ONIC of DWDM Token Ring Network and Method therefor |
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| TWI381684B (en) * | 2008-08-05 | 2013-01-01 | Ind Tech Res Inst | Apparatus and method for medium access control in an optical packet-switched network, and the network thereof |
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| JPS5647138A (en) * | 1979-09-26 | 1981-04-28 | Nippon Telegr & Teleph Corp <Ntt> | Light loop network by light-wavelength-division multiplex transmission |
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| US4675866A (en) * | 1984-04-24 | 1987-06-23 | Nec Corporation | Broadband network systems |
| JPS62502234A (en) * | 1985-03-11 | 1987-08-27 | ブリティシュ・テレコミュニケ−ションズ・パブリック・リミテッド・カンパニ | optical communication network |
| US4759011A (en) * | 1986-03-03 | 1988-07-19 | Polaroid Corporation | Intranetwork and internetwork optical communications system and method |
| GB2189961B (en) * | 1986-04-30 | 1990-02-14 | Stc Plc | Optical transmission system |
| US4789980A (en) * | 1986-08-18 | 1988-12-06 | American Telephone & Telegraph Company, At&T Bell Laboratories | Switching techniques for FDM communication systems |
| JPH0695677B2 (en) * | 1988-11-16 | 1994-11-24 | 株式会社日立製作所 | Network transmission system with multiple channels |
| US4955021A (en) * | 1989-07-03 | 1990-09-04 | At&T Bell Laboratories | Efficient connection arrangements for multihop networks |
-
1990
- 1990-08-02 US US07/561,852 patent/US5101290A/en not_active Expired - Lifetime
-
1991
- 1991-05-09 CA CA002042164A patent/CA2042164C/en not_active Expired - Fee Related
- 1991-07-25 EP EP91306812A patent/EP0472296A1/en not_active Withdrawn
- 1991-07-30 JP JP3211326A patent/JPH04234244A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CA2042164A1 (en) | 1992-02-03 |
| US5101290A (en) | 1992-03-31 |
| EP0472296A1 (en) | 1992-02-26 |
| JPH04234244A (en) | 1992-08-21 |
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