Note: Descriptions are shown in the official language in which they were submitted.
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DYNAMIC INFRA~'l'KU~'l'U~
BACKGRO ~ D OF THE INVENTION
This invention relates to telecommunication networks, in parti-
cular to allocation of resources in a stratified reference model.
A stratified reference model is a generalization of the OSI re-
ference model that enables a description of complicated network-
on-network structures. Each network level is referred to as a
stratum. A stratum is a logical model of a physical transmission
network. A stratum describes nodes and routes between the nodes.
The physical transmission network modelled by a stratum comprises
nodes and links. Links are grouped into trunks which extend be-
tween the nodes. The various stratum networks are defined by con-
figuration data. The different strata together make up a stra-
tified transport network. Each stratum is associated a respective
bearer service. With bearer service is meant a service providing
transport of data. Different strata have different bearer
services.
In order to avoid misconceptions the following definitions are
used: A connection is used to transfer information between two
end points. A connection is created in various ways. For example
a connection is created by cross connection, by manual switching
or by switching. Cross connected connections are created in for
example cross connecting devices, manually switched connections
are created for example in connector matrixes by soldering and
switched connections are created on demand, for example by dial-
ling a directory number on a telephone.
A channel is a'means for unidirectional transmission. A channelis used to carry information from one point to another. To tran-
smit information from A to B one channel is required, said one
channel having a direction from A to B. To transmit information~ 30 from B to A another channel is required, said another channel ha-
ving the opposite direction of said one channel.
Two oppositely directed channels extending between the same pair
of points are in the following referred to as a channel pair.
SUB STITUTE S ~ E E~ (RU LE 263
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Several channel pairs together make up a link. A link is a
physical system (that transports information). Accordingly, a
link carries channel pairs. The maximum number of channel pairs
a link can carry depends on the bearer service and on the proper-
ties of the physical system.
A route is a logical conception. A route comprises a number of
channel pairs and is used to interconnect two nodes. In theory
there is no m~X; mllm number of channel pairs a route can comprise.
The conception of route is used to define the way a connection
follows between nodes of a stratum. This is referred to as rou-
ting and is conventional.
At each end of a link there is an ~xrh~nge terminal ET. An ET
operates to "insert" or multiplex together a number of channel
pairs on one and the same link and to "extract" or demultiplex
channel pairs from said same link.
The above definitions are explained in connection with FIG. 1 and
FIG. 2. In FIG. l there is one route R1 extending between two
nodes N1 and N2. As an example route R1 carries 96 channels so
distributed that there are 48 channels in each one of two
opposite directions, i.e. route R1 carries 48 channel pairs.
FIG.1 is a logical description of the physical transmission
system shown in FIG. 2. In FIG. 2 there are two links Ll and L2
extending between nodes Nl and N2. At each end of links Ll and L2
there is a respective exchange terminal ET. Suppose the bearer
service is STM 64, the link L1 will carry 64 channels so
distributed that there are 32 channels in each one of the two
opposite directions. Accordingly link L1 carries 32 channel
pairs. In the same manner link L2 carries 32 channel pairs. All
32 channel pairs of link L1 but only 16 channel pairs of link L2
are grouped into route R1 which accordingly will hold 48 channel
pairs. In the physical transmission system shown in FIG. 2 the
remaining 16 link elements of link L2 not used in route R1 may
form part of another route, not shown in FIG. l. In FIG. 2 nodes
N1 and N2 correspond to nodes N1 and N2 in FIG.1.
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In FIG. 3 three strata 1, 2, 3 are shown, each such stratum
representing a logical view of a non shown physical transport
network. Stratum 1 comprises three nodes 10-12, stratum 2 three
nodes 20-22, and stratum 3 four nodes 30-33. Stratum 1 comprises
three routes 13-15, stratum 2 three routes 23-25 and stratum 3
three routes 34-36. As an example the bearer service at stratum
1 is 64 kbps STM (synchronous tr~nsm;~sion mode). As an example
the bearer service at stratum 2 is 2 Mbps STM (in the U.S.A. 1.5
Mbps STM). As an example the bearer service at stratum 3 is 155
Mbps STM. As an example routes 13, 14, 15, 25 and 34 are shown to
comprise the channel pairs of two links, while routes 23, 24, 35
and 36 are shown to comprise the channel pairs of just one link.
A link is indicated by a solid line. The links of route 13 are
denoted 40 and 41. At each stratum there are access points to the
different networks. These access points are shown schematically
by filled points at each stratum. Each access point has a
~o~n~tion to a node in a respective stratum. In stratum 1 the
connections from the access points to node 10 are collectively
shown at 16, the connections from the access points to node 11
are collectively shown at 17 and those to node 12 are shown at
18. Similar connections 26 and 27 exist at stratum 2. Similar
connections 37, 38 at stratum 3 do also exist. Access units are
connected to access points. The access units are used for
communication. As an example of access units two telephone sets
A and B are shown at stratum 1. Access unit are also present at
stratum 2 and are symbolically shown at C and D respectively.
Examples of access units at stratum 2 are main frame computers.
At stratum 3 access units are shown symbolically at E and F
respectively. In the non shown physical transport network each
one of the connection 16, 17, 18, 26, 27, Z8,37, 38, is at its
respective node side connected to its respective node by way of
an exchange terminal ET. Still speaking in terms of the physical
transport network such exchange terminals could be ordinary line
interface circuits; LIC:s, in case the bearer service is STM 64
Mbps.
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An exchange terminal ET in a stratum is shown as a small unfilled
rectangle in the accompanying drawings.
The nodes 10-12 at stratum 1 generally comprise switch fabrics.
An exchange in the physical transport network would correspond to
one or more switch fabrics in different strata. Cross connectors
in the physical transport network would correspond to the nodes
20-22 in stratum 2. Wire conn~ctions in the physical transport
network would correspond to the nodes 30-33 in stratum 3.
Stratum 1 forms a switched network in the sense that it is
possible to route a connection from an originating access unit to
a terminating access unit by dialling, at the originating access
unit, the telephone number to the terminating access unit.
Stratum 2 is generally a non-switched network. A connection from
C to D is generally a fixed leased connection which is set up, on
a long time basis, by a network operator. Stratum 1 is a non-
switched network.
At stratum 1 each route 13, 14, 15 represents a number of re-
sources between two nodes, said resources existing in the form of
channel pairs.
The nodes 10, 20 and 30 may or may not correspond to each other
depending on the structure of the physical transport network.
Generally they do not correspond to each other since their
physical counterparts in the physical transport network are
located at geographically different sites. The nodes 10, 20 and
30 would correspond to each other if the exchange, the cross
connector and the wired connection are all located at the same
geographical site. The same considerations apply for nodes 11,
21, 31 and for nodes 12, 22, 32.
The items described above together make up a traffic system. The
traffic at each stratum varies depending on the time of the day,
the day of the week and may also depend on other criterions. As
an example a head office of a company that has sales offices in
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several cities wants the sale offices to report back to the head
office all items sold during a day. The corresponding information
should be sent to the head office nighttime. The time it takes to
complete such a data transmission may be unacceptable long if
' 5 transmission takes place using the bearer service at the stratum
1 level. This is so because of the restricted bandwidth offered
by the 64 kbps STM network. Instead the company has leased a
number of 2 Mbps connections connecting the sales offices with
the head office. The 2 Mbps connections are set up in stratum 2
by the network operator of stratum 2. Such set up is done
manually by the network operator with the aid of an operating and
support system, OSS, 29. The leased 2 Mbps connections at stratum
2 are set up nighttime between for example 8 pm and 5 am. At
daytime said leased connections at stratum 2 are used for other
traffic. In this manner the network operator reconfigures the
resources of stratum 2 at predetermined times in order to make
use of his resources as efficiently as possible. The OSS 29 con-
trols and monitors the operation of the nodes and routes at stra-
tum 2. There is also an OSS 39 for controlling and monitoring the
corresponding items at stratum 3.
Manual set up of connections at stratum 2 at predetermined times
is a rigid method of meeting the traffic demand from users. The
users must notify the network operator of their demands and the
network operator must set up the connections manually. Should a
user need to use a leased connection at other times than agreed
upon the network operator must be contacted. The network operator
then has to ~X~m; ne the current traffic situation in stratum 2,
assign a link to the requesting user and manually set up the
connection for a fixed time period. The time delay between custom
demand and set up of a demanded connection may take days.
Since the connections at stratum 2 are leased for fixed time
periods and since the traffic demand may change during said fixed
time periods the network resources of the physical network are
not used efficiently.
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RELATED ART
U.S. Patent 5,058,105, U.S. Patent 5,182,744, U.S. Patent
5,031,211 relate to methods and devices for enhancing the
reliability of a communication network so that traffic which is
disrupted by, for example, a faulty link, may quickly be
restored to service. Various methods are described for determin-
ing alternate routes to which the disrupted traffic is trans-
ferred.
U.S. Patent 4,669,113 relates to a nonhierarchial switching sys-
tem employing an algorithm for developing link sizes for paths
that connect switches in the switching system. This is achieved
by having each switch in the switching system to send idle trunk
information to a central integrated network controller on a per-
iodic, for example 5-second, basis when trunk status changes
occur, i.e. idle trunks are created or removed. Based on the
received traffic information the integrated network controller
determines the required number of trunks for each link using a
process that adjusts for the traffic handling capacity between
nodes based on the availability of alternate routes.
EP-A2-464 283 relates to allocating a limited common resource,
such as trunks for video conferencing, among a plurality of
demands for the resource. An allocation methodology is shown
which makes it possible to allocate the bandwidth of a communica-
tion path in the network among a plurality of customer demands
for that bandwidth. Examples of customer demands for a conference
are start time, stop time, maximum bandwidth and minimum band-
width. To each conference reservation there is associated "bin-
ding" comprising a four-tuple of the form (X1, X2, X3, X4) where
Xl and X2 refer to specific positions within the bandwidth of the
communication path and X3 and X4 refer to the start time and stop
time respectively of the conference. A customer site represents
one or more endpoints. An allocation arrangement receives demands
from a customer site for allocating the network for a communica-
tion among a plurality of customer sites. The allocation arrange-
ment stratifies the received demands in response to a grouping of
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endpoints to be conferenced and can then allocate the network
resources in response to the stratified demand. Accordingly the
allocation process takes place at predetermined points of time in
accordance with a customer's demands and is not driven by the
current traffic load.
In Ericsson Review, Vol. 67, Nr. 4, Dec. 1990, Stockholm, Walter
Widl, "Telekommunikationsnatets arkitektur", p 148-162 there is
described how a teleco~lln;cation network is given a layered
structure in respect to transmission. A number of static
connections are shown. In particular there is shown how informa-
tion, relating to a connection, is flowing in the various layers.
The article does not describe how and when the connections are
set up.
SUMMARY OF THE I~v~NllON
An object with the present invention is to provide a method and
a system for providing a connection along a route of a higher
stratum using dynamic allocation of an infrastructure of a lower
stratum in a stratified network structure avoiding the drawbacks
with prior art technique.
In particular the allocation of an infrastructure of a lower
stratum to a higher stratum takes place on demand in response to
the current traffic situation along a route of said higher stra-
tum.
In accordance with still another aspect of the invention the
allocation of an infrastructure of a lower stratum to a higher
stratum is controlled from within the traffic system. No system
external OSS is involved in the allocation process and according-
ly no operator needs to be contacted when the allocation should
be done. The allocation can therefore take place dynamically and
on demand.~
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In accordance with another aspect of the invention the allocation
process allows for repetitive allocations of infrastructures from
a number of underlying strata to an overlaying stratum.
The above objects are achieved by providing a route with a first
reference associated with one end of said route and a second
reference associated with the opposite end of said route. The
first reference refers to a first access point resident in a
lower stratum. The second reference refers to a second access
point resident in said lower stratum. From the node at said one
end of said route there is provided a wired connection to said
first access point in said lower stratum. Likewise, from the node
at said opposite end of said route there is provided a similar
wired connection to said second access point resident in said
lower stratum.
When control logic requests the set up of a connection in a first
stratum said connection typically extends along a number of
routes. Suppose that the traffic load along one of said routes is
so heavy that all the resources of said one route are busy.
Traditionally the connection request is rejected during such
circumstances. In accordance with the invention the control logic
at first ~x~;nes said one route to see if it has associated
therewith the above mentioned references. If it hasn't the
connection request is rejected, but if it has, the control logic
will take the references and send them, in a second connection
request, to the stratum associated with the access points. The
second connection request requests set up of a connection between
the two access points with which the references are associated.
Typically the access points are resident in a stratum , referred
to as the second stratum, next below the one in which said one
busy route is resident. The second connection request will there-
fore be transmitted to the second stratum. Control logic asso-
ciated wi~h the second stratum will examine the second stratum
network to see if a connection between the access points can be
set up. Suppose there are free resources along a route between
the access points in the second stratum. The control logic asso-
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ciated with the second stratum will now set up a connection be-
tween the access points. This ~-o~n~ction constitutes an infra-
structure for the first stratum. In this way the infrastructure
be~o~~~ available to the first stratum at said opposite end
nodes. In the following the infrastructure is said to be assigned
to the stratum. The resources of the infrastructure comprises a
number of channel pairs as will be explained below. In the
assigned infrastructure one channel pair is seized and is used
for setting up the originally requested connection, while the
rest of its channel pairs are ready for use by future connec-
tions.
Accordingly the allocation of an infrastructure takes place on
demand when, at said higher stratum, there are no more channel
pairs available for traffic along a route at said higher stratum,
but there is still a demand for setting up new connections along
said route. When the allocated resources no longer are used by
said higher stratum the infrastructure is returned to the lower
stratum and can now be accessed by said lower stratum. In this
way the combined structures of the two strata involved in the
allocation process are used efficiently. The resources of the
infrastructure will thus be used more efficiently than before.
In accordance with an embodiment of the invention the first
reference refers to a group of first access points resident in
said lower stratum and the second reference refers to a group of
second access points also resident in said lower stratum. Between
the node at said one end of said route and each of the first
access points there is provided a respective wired connection.
Likewise there are provided wired connections from the node at
said opposite end of said route to each one of the second access
points resident in said lower stratum. When reference is made to
said first and second references one access point in the group
of said first access points are selected and a one in the group
of said second access points is selected and a connection, in
said lower stratum, is set up between the said two selected
access points.
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BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are
set forth in the appended claims. The invention itself, however,
as well as other features and advantages thereof, will be best
understood by reference to the detailed description of the
specific embodiment which follows, when read in conjunction with
the ~ omranying drawings, wherein;
FIG. 1 is a block diagram of a route ext~n~;ng between two
nodes,
FIG. 2 is a detailed view of the route shown in FIG.l,
FIG. 3 is a simplified schematic view showing a stratified
network structure in accordance with known technique,
FIG. 4 is a simplified schematic view of the stratified network
structure in FIG. 3 modified in accordance with the
invention,
FIG. 5 is a schematic block diagram of nodes 10 and 20 in
strata l and 2 respectively in FIG. 4,
FIG. 6 is a list of idle resources associated with a route to
which an infrastructure can be allocated,
FIG. 7 is the list of idle resources in FIG.6 to which an
infrastructure has been dynamically allocated,
FIG:s
8-10 are flow diagrams, illustrating traffic system control
logic involved in the process of dynamic allocation of
an infrastructure, and
FIG. 11 is a routing table,
FIG. 12A
and 12B are lists of idle resources similar to those shown in
FIG. 6,
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FIG. 13 is a simplified stratified network showing a variant of
the dynamic allocation process in accordance with the
invention,
FIG. 14 is a simplified stratified network showing an example of
an iterative dynamic allocation process, and
FIG. 15 is a schematic diagram showing a second embodiment of
the invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
FIG. 4 is similar to FIG. 3 with the exception that there are two
physical connections 4 and 5 between stratum 1 and stratum 2. In
particular physical connection 4 extends from ET1 of node 10 to
ET4 of node 20. The physical access point at ET4 of node 20 is
labelled A1. Physical connection 5 extends in a similar fashion
from ET2 of node ll to ET3 of node 21. The physical access point
at ET3 of node 21 is labelled A2. In this manner there is created
two physical connections between stratum 1 and 2. At stratum 2 it
is possible to set up a connection between A1 and A2 using 2-
Mbps connections of stratum 2. As an example a connection can be
set up between Al and A2 using route 23. As another example an
connection between A1 and A2 can be set up using routes 25 and
24. For the moment, and in order to explain the mechanism of the
present invention, it is supposed that a non shown control system
in stratum 2 receives a request from another non shown control
system in stratum 1 to set up a connection between Al and A2. The
OSS 29 checks its traffic to find out a free route between Al and
A2. Say for example that route 23 is free. Said non shown control
system in stratum 2 seizes route 23 and connects the ET:s at each
end of the seized route to the respective ET:s at which A1 and A2
are. Such connections are schematically indicated by the broken
lines C1 and C2 and are done internally in the nodes 20 and Z1 of
the respective connections points Al and A2. Now there is a 2
Mbps connection 4-Al-Cl-23-C2-A2-5 which terminates at ETl and
ET2. ETl and ET2 in stratum 1 will now determine the bit rate at
which said connection 4-A1-C1-23-C2-A2-5 is operated. Since ETl
and ET2 multiplex at a bit rate of 64 kBit/s said connection 4-
Al-Cl-23-C2-A2-5 will also be driven at this speed. Said
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co~ction will accordingly add resources in the form of 32
~h~nn~l pairs to route 13, each such channel pair being propagat-
ed at a speed of 64 kB/s and being carried by the 2 MBit/s
connection at stratum 2. Typically one or two of the added 32
5 ~h~n~l pairs are used for signalling purposes.
One might find it difficult to understand how physical connec-
tions can be made between logical layers as shown in Fig. 4. It
should be noted that Fig. 4 is just a picture of logical
networks. Behind the picture there is a non-shown physical
transport network and it is in this physical network the wired
connections are made. In particular they are made between links
belonging to the physical transport network.
How the physical network looks like is no part of the invention.
The manner in which applicant illustrates the invention is
independent of the exact layout of physical network. In the
example shown in Fig. 4 there are three nodes 10, 11, 12 at
stratum 1 and three nodes 20, 21, 22 in stratum 2 Node 20, for
example, is resident in the same physical node as that one in
which node 10 is resident. Node 21, for example, is resident in
a cabinet standing beside another cabinet in which node 11 is
resident. In the first case a physical connection is made within
one and the same node and in the second case the physical
connection is made between the nodes in the two cabinets. If the
physical layer looks different than the one just exemplified,
then the physical connections would be wired differently.
In FIG. 5 the node 10 is shown in detail and comprises further to
a switch 10, a processor 45 and control programs 46. Moreover
there is a data base 47 comprising i.a. a network description of
the resources of stratum 1. Such descriptions comprise i.a.
conventional routing tables used for routing of a call through a
network as well as link tables of the kind shown in FIG.s 6, 7
and 12B, such link tables being used to record the current state
of the individual channel pairs of a particular route, i.e.
whether an individual channel pair is occupied or not.
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The control program module 46 comprises several individual
programs, among these a call set-up program 48 and a resource
handler 49. In a similar way node 20 of stratum 2 comprises a
processor 55, a program module 56 and a data base 57. The program
module 56 comprises several control programs, i.a. a call set-up
program 58, and link tables of the kind shown in FIG. 12A.
In practice processors 45 and 55 may physically be one and the
same processor and this is also possible for the data bases 47
and 57.
A route at stratum 1 comprises one or more links. To each route
there is associated a respective route table. In FIG. 6 a route
table 52 is shown. As an example the route associated with route
table 52 is route 13. Route 13 comprises two links link 40, 41
each of which comprises 32 channel pairs, some of which may be
used for signalling purposes. The remaining 30 channel pairs are
available for traffic. This gives a total of 60 channel pairs for
route 13. The available channel pairs are numbered 1, 2... 60.
Each such channel pair has a status, busy and non-busy. In
accordance with the invention the route table 52 has two
references, symbolically shown at 50 and 51. Each reference
represents a relation. In particular there is: (i) a first
relation between a first end of route 13 and a first access point
situated at a lower stratum, said first end of the route being
connected to said first access point, and (ii) a second relation
between the other end, referred to as the second end, of the same
route 13 and a second access point, also situated at a lower
stratum, said second end being connected to said second access
point. The two access points, Al and A2 in the illustrated
example, must not coincide but must be located at the respective
ends of route 13 in stratum 1. In stratum 2 there can be several
nodes between the access points Al and A2. In particular the
presence of reference 50 at link table 52 indicates that the left
end of route 13 is connected to access point A1 in stratum 2 and
the presence of reference 51 at indicates that the right end of
route 13 is connected to access point A2 in stratum 2 In
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14
accordance with the present invention the two access points Al
and A2, which represent the two ends of route 13, should be
connected with each other in stratum 2. As indicated above such
a connection is referred to as an infrastructure.
Allocation of an infrastructure to a higher stratum is initiated
on ~em~n~ when predefined conditions are fulfilled. As one
example the allocation of an infrastructure is initiated when all
channel pairs of links 40 and 41 have been seized and the traffic
continues to increase along said route 13. As another example
allocation of an infrastructure is initiated when there are some
few, say for example 5, channels available in link table 52 and
the traffic load along said route 13 is at or above a predefined
level. Other parameters and combination of parameters may govern
the point of time at which allocation of an infrastructure is
initiated.
Two different means by which the allocation process of an
infrastructure is initiated are suggested in accordance with the
present invention. In accordance with one embodiment control
logic, resident in stratum 1 or stratum 2 or in both strata, is
the means by which the infrastructure allocation process is
initiated. This embodiment was described shortly above and will
be described in detail further down. In accordance with another
embodiment of the invention the means by which the allocation
process is initiated is a signalling procedure.
One signalling procedure is a signalling which is associated with
the access point Al and which uses an identification of access
point A2 (a roaming number). As an example such signalling is an
out of band signalling procedure.
Another signalling procedure is to request the connection between
Al and A2 by sending the request to the operation and support
system OSS 29 via a non shown traffic management system TMN using
the Q3 interface.
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In the particular example of FIG. 4 the connection that consti-
tutes an infrastructure is set up between access points A1 and
A2. This connection may follow either the direct way route 23
between Al and A2 or the multi way route formed by routes 25 and
24 via node 22.
When a connection is established between a user connected to node
10 and another user connected to node 11 a channel pair, for
example in link 41, is seized and is marked busy in the corre-
sponding route table 52. Suppose that the traffic increases and
that finally all channel pairs 1-60 are busy. The next connection
request re~uesting a resource from route 13 will trigger an
infrastructure allocation process. After completion of the
infrastructure allocation process described above stratum 1 has
now at its disposal a link in the route which extends between A1
and A2. The two exchange terminals ET1 and ET2 will now provide
30 additional channel pairs to route 13. Said additional 30
channel pairs can now be used for traffic that originates and
terminates at the stratum 1 level When said link in said route
has been assigned to stratum 1 the route table 52 will look like
the one shown in FIG. 7 wherein the new, additional, 30 channel
pairs are labeled 61-90. Among said additional channel pairs one
is seized for the connection that triggered the allocation
process. As traffic continues to increase further channel pairs
are seized among said additional ones. To a user the assignment
of said link in said route in stratum 2 to route 13 in stratum 1
is invisible, i.e. the user cannot distinguish a connection using
link 40 from a connection using a dynamically established
infrastructure through stratum 2.
As the traffic decreases and no channel pairs of the assigned
link are used, the control logic resident in the resource handler
49 gives back the unoccupied link to stratum 2 and releases the
connection Al-Cl-ET-23-C2-A2 set up in the stratum 2.
The above resource allocation process will next be described in
connection with FIG. 8-10. It is supposed a call should be set up
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between A and B in FIG. 4. In FIG. 8 the logic of the call set-up
program 48 is shown to the left. To the right the logic of a
routing analysis performed with the aid of the routing table of
FIG. 11 is shown. A connection request, represented by box 60 is
generated when user A dials the telephone number to user B. After
conventional digit analysis the destination of the call is
established. In order to find out the way to the destination
routing analysis starts, box 61. For routing analysis in node 10
a routing table 62 of the kind shown in FIG. 11 is used. As input
data for the routing analysis the destination of the call, in
this case the identity, represented by N11 to node 11 is given.
At the Nll entry the identities of the routes which are possible
to use to node 11 are indicated, in this case the identity of
route 13 represented as R13-ID. The search for the route to be
used is indicated by box 63 in FIG. 8 and the process of
returning the selected ROUTE-ID:s is represented by box 64. The
call set-up program 48 receives the possible routes, box 65, and
next the call set-up program orders that a resource, in the
particular example which relates to a telephone call, a channel
formed by a time slot that has fixed time position from frame to
frame, in the first identified route should be seized, box 66.
This seizure order is sent, ring 67, to the resource handler 49.
The resource handler ~X~m; nes the list 52 of idle resources which
corresponds to the selected resource to see if there is a
resource free. The result is returned to the call set-up program
as is represented by box 68. The result is either that a channel
is seized or not. Which is the case is decided in selection box
69. If resources are free, alternative YES, the call set-up
program 48 sets up a connection, box 70. If no resources are
free, alternative N0, it is tested, decision box 71, if other
routes were given in process step 64. If other routes were given,
alternative YES, the next route is tried, box 70A, to see if a
resource therein can be seized. This procedure is repeated until
there is found a route, among said other routes, that has
resources free. This repetitive procedure is illustrated by the
loop arrows 70B. If none of said other routes contains any free
resource, the connection request is rejected, box 70C.
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I FIG. 9 the logic of the resource handler 49 is illustrated. At
receipt of the seizure order, ring 67, the resource handler
~.X~m; nes the corresponding list 52 of idle resources to see if a
resource is free, selection box 72. If a resource is free,
alternative "YES", the resource handler 49 seizes the resource
and sends the identity of the seized resource to the call set-up
program 48 which will receive the resource identity at circle 68.
If no resource is free, alterative "N0" at decision box 72 the
resource handler checks to see if the selected resource has
relation to an infrastructure, selection box 74. If the resource
has no relation, alternative "N0", the resource handler communi-
cates this to the call set-up program which receives correspond-
ing message at circle 68. If there is a relation, alternative
"YES", the resource handler 49 communicates the access points of
the infrastructure, box 76, to the call set-up program 58 in
stratum 2, circle 77. The call set-up program in stratum 2 is
shown in FIG. 10 and is in principle similar to that shown in
FIG. 8 and will therefore not be described in detail. From the
call set-up program 58 the resource handler receives a communica-
tion, symbolized by circle 78, comprising information, box 79, onthe result of the call set up in stratum 2. Either the requested
connection was set up or not, alternative YES and N0 respectively
at decision box 80. If the connection was set up the additional
resources, in form of channel pairs, is added to the list of idle
resources, box 81, and a channel pair is seized, box 73, for the
connection requested at the stratum 1 level. The seized channel
pair is marked as "occupied for the requested connection " in the
list of idle resources. A corresponding message is sent to the
control logic 48, ring 68. If no connection could be set up at
the stratum 2 level a corresponding message, box 82, is sent to
the control logic 48 and the connection request made at the
stratum l level is rejected.
In FIG. lQ the control program 58 in stratum 2 is shown. Upon
receipt of the identity of the access points a connection
request, box 83, is made to control logic of stratum 2. This
connection request is processed in a manner similar to a
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18
connection request at the stratum 1 level as shown in FIG.8. and
will therefore not be described in detail. The various processes
involved in setting up a connection at the stratum 2 level are
shown collectively by box 84. The result is either that a
conn~ction is set up, box 85, or not, box 86. In both cases a
corresponding message is sent to the link handler, ring 78.
In the example described above the number of channel pairs of a
route at stratum 1 is expanded by providing said route with a
relation to two access points at stratum 2, said access points
establishing the two end points of a possible connection at the
stratum 2 layer. In accordance with the present invention a
route, for example route 13, at stratum 1 can also be expanded by
providing the route with a relation to two access points at the
stratum 3 layer. Such relations pointing to the end points of a
route at stratum 3 are shown at 87 and 88 respectively in FIG.
12A. To set up a connection at the stratum 3 level and use the
infrastructure thus created in order to expand the number of
available channel pairs at stratum 1 has been described above
and will therefore not be repeated. It will be sufficient to say
that in this embodiment there would be a first physical connec-
tion, similar to connection 4, between nodes 10 and 30 and a
second physical connection between nodes 11 and 31. In FIG. 13
the corresponding infrastructure at stratum 3 has been shown. For
the sake of clarity stratum 2 is not shown in FIG.13. In this
embodiment there is a first physical connection 93, similar to
connection 4, between nodes 20 and 30 and a second physical
connection 94 between nodes 21 and 31. The number of channel
pairs assigned to stratum 1 is in this case in the order of 2100
since stratum 3 provides an infrastructure carrying 155 Mbps. The
access points pointed out by the relations 87, 88 are labelled A5
and A6 respectively.
Also, in ~accordance with the invention, the number of channel
pairs of a route at stratum 2 can be expanded by providing said
route at stratum 2 with a relation to two access points at
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19
stratum 3. In FIG. 12B route 25 is provided with two such
references 89, 90.
-
It is also possible to apply the inventive idea repetitively from
~ stratum to stratum. This is illustrated in FIG. 14. As an
example, suppose a connection is requested from A to B at stratum
1 and that route 13 has no resources available. Route 13 has the
above relations 50 and 51 to access points Al and A2 at stratum
2. Suppose there are no resources available along route 23 that
extends between access points Al and A2. Along the alternative
route between Al and A2, that is along the combined route 25 and
24, route 25 is supposed to have no resources free, but route 25
has two references 89, 90, similar to those shown in FIG. 12B,
that are associated with two access points A3 and A4 at stratum
3 via two physical connections 93 and 94. At stratum 3 there are
resources free and an infrastructure, represented by the intra
node connections C3 and C4 in nodes 30 and 33 and route 36, is
assigned to stratum 2. Thus the connection requested at stratum
1 is set up using a connection set up at the stratum 3 level.
In FIG. 15 a further embodiment of the invention is shown. In
FIG. 15 the architecture of stratum 1 is generally the same as
that shown in FIG. 3. From each of the nodes 10, 11 and 12 there
are, however, a number of physical connections to exchange
terminals ET residing in the second stratum 2, said second
stratum being symbolically indicated by the area within the
closed line 22. Node 1 has four such physical connections which
collectively are indicated by reference numeral 444, node 11 has
two such physical connections labeled 555 and node 12 has four
physical connections 666. Each physical connection extends
between two exchange terminals ET:s. The ends of the physical
connections 444, 555, 666 to stratum 2 are symbolized by filled
circles and are referred to as access points. The access points
of connections 444 are collectively marked at 93, the access
points of connections 555 are marked at 94 and the connections
points of connections 666 are collectively referred to as 95.
Outside the stratum 2 network and between the nodes 10, 11, 12
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the routes 13, 14 and 15 are present. Each route has a relation
in the form of pointers pointing out the end points of the
respective route. Accordingly route 13 has two pointers 99, 100
of which 99 points to the group of access points 95 while 100
points to the group of access points 93. In a similar way route
14 has two pointers 101, 102 pointing out its respective end
points in stratum 2. Pointer 101 points to the group of access
points 94 and pointer 102 points to the group of access points
95. Route 15 has two pointers 103, 104 pointing out its respec-
tive end points in stratum 2. In particular pointer 103 points tothe group of access points 93 while pointer 104 points to the
group of access points 95. If a route, for example route 15,
which extends between nodes 10 and 12 needs resources from
stratum 2 the link handler 49 selects the group of access points
93 and the group of access points 95 since these two groups of
points represent the end points of a link in the route which
extends between nodes 10 and 12. In stratum 2 a connection is set
up between two selected access points in groups 93 and 95. The
individual connection to be set up in stratum 2 may be selected
using a conventional resource allocation algorithm which examines
the traffic along the routes of stratum 2 and based upon this
~X~m; n~tion selects which route to follow in stratum 2.
Although three strata 1, 2 and 3 have been described above the
telecommunication network may comprise four strata or more, or
even just two strata, and the inventive method and the inventive
construction would be applicable.
A route may extend over several links, some of them being fixed
and some of them being allocated dynamically as described above.
The effect of this is that a route will comprise a fixed number
of resources which are always present. On top of these there are
a number of resources that can be dynamically allocated to the
route.
The control logic for requesting a connection at stratum 1 has
above been described to be resident in stratum 1 and has been
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described to be executed by a processor which belongs to stratum
1 while the control logic for setting up a connection in stratum
- 2 has been described to be resident in stratum 2 and has been
described to be executed on a processor which belongs to stratum
2. It is, however, not necessary to split up the control logic
and its execution on processors which belong to different strata.
The invention is e~ually well achieved if one and the same
processor executes the control logic of the two strata and it is
of no difference if this processor belongs to one stratum or the
other. The processor may even be distributed among several nodes
of one and the same stratum. The control logic which above has
been described as split up between different strata may, in
accordance with the present invention, be integrated and may be
executed on a single processor or on a distributed processor. The
control logic, be it structured in several strata or not, and the
processor, be it a single processor or a distributed processor,
on which it executes forms a control system of the telecommunica-
tion network.
