Abstract:
A signaling aggregator and method for signal aggregation alleviate port exhaustion at network nodes such as mobile switching centers (MSCs), home location registers (HLRs), and other signaling network nodes. The signaling aggregator is inserted between any signaling node requiring a plurality of signaling links, to relieve signaling port exhaustion. The signaling aggregator is connected to the signaling node by a high-speed linkset and transparently transfers signaling messages between the signaling node and other signaling nodes connected to the signaling aggregator. The signaling aggregator masquerades as the signaling node to the other signaling nodes, utilizing the point code of the signaling node in the originating point code (OPC) field of signaling messages sent to the other signaling nodes. The signal aggregator may also provide protocol conversion between two or more signaling protocols. Mated signaling aggregators are used to provide redundancy.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/191,888 filed Mar. 23, 2000. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates in general to telecommunications signaling network implementations and, in particular, to a signaling network element that serves as a signaling aggregator for use in an out-of-band signaling network. 
     BACKGROUND OF THE INVENTION 
     It is well known that the use of telecommunications services is growing at unprecedented rates. Not only is usage growing rapidly, but the size of the subscriber base is also growing. This is particularly true for wireless services such as cellular telephone and personal communications system (PCS) wireless services. 
     As is well known, modern telephone networks employ an out-of-band signaling network for call setup and control known as “common channel signaling” (CCS). The currently most widely used implementation of common channel signaling is Signaling System 7 (SS7). The SS7 protocol was designed without comprehension of the network size or usage requirements to which the modern Public Switched Telephone Network (PSTN) is being subjected. Consequently, parts of the PSTN are experiencing what is referred to as “signaling port exhaustion”. Signaling port exhaustion occurs when the capacity for connecting signaling links to a network node is consumed. Signaling port exhaustion is particularly common in wireless services networks because of rising demand for connectivity as a result of explosive subscriber growth. The problem is further exacerbated by the fact that certain elements in the wireless telephone network require “fully associated” signaling links. A fully associated signaling link is a direct link between two signaling elements in the network. To date, the only solution for supporting such signaling elements has been the expansion of signaling port capacity at an associated element such as a mobile switching center, which supports a plurality of base station controllers in a wireless communication network. The only alternative would be to upgrade the base station controllers to permit them to support quasi-associated signaling. This is, however, a very expensive alternative which appears to be untenable in today&#39;s competitive telecommunications environment. 
     There therefore exists a need for a signaling network element that is adapted to help reduce signaling port exhaustion in an out-of-band signaling network such as a common channel signaling network to permit the signaling network to be expanded to service the needs of a growing number of telecommunications services subscribers. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a network element adapted to relieve signaling port exhaustion in an out-of-band signaling network. 
     The invention therefore provides a new signaling network element for aggregating signaling network traffic in a telecommunications signaling network in order to reduce signaling port exhaustion. The new network element permits an economical expansion of the network to support a larger subscriber base. The signaling network element is referred to as a Signaling Aggregator (SA). The SA is associated with one or more network nodes and mimics those nodes to the rest of the signaling network, so that network nodes incapable of quasi-associated signaling require no modification. The SA may also be provisioned to perform protocol conversions to permit elements to be connected to the signaling network that are not adapted to receive messages in the signaling protocol of the network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
     FIG. 1 is a block diagram illustrating a prior art GSM telecommunications network; 
     FIG. 2 is a block diagram illustrating an exemplary GSM telecommunications network that includes a Signaling Aggregator in accordance with an embodiment of the present invention; 
     FIG. 3 is a block diagram illustrating an exemplary GSM telecommunications network provisioned with linkset and routeset tables in accordance with the embodiment of the invention shown in FIG. 1; 
     FIG. 4 is a block diagram illustrating signaling traffic flow in the exemplary GSM telecommunications network shown in FIG. 3; 
     FIG. 5 is a block diagram illustrating an alternative exemplary MTX telecommunications network that includes a Signaling Aggregator in accordance with the first embodiment of the invention used to aggregate signaling messages sent through mated STPs; 
     FIG. 6 is a block diagram illustrating an alternative exemplary MTX telecommunications network provisioned with mated signaling aggregators in accordance with the invention, respectively used to aggregate signaling messages sent through mated STPs; 
     FIG. 7 is a block diagram illustrating a further exemplary MTX telecommunications network in which a Signaling Aggregator in accordance with the invention aggregates signaling message traffic and provides protocol conversion for a single network node; 
     FIG. 8 is a block diagram illustrating a further exemplary MTX telecommunications network in which a Signaling Aggregator in accordance with the invention aggregates signaling message traffic and provides protocol conversion for two network nodes; 
     FIG. 9 is a block diagram illustrating a further exemplary MTX telecommunications network provisioned with a Signaling Aggregator in accordance with the invention for aggregating signaling message traffic for two network nodes and providing protocol conversion for one of the two network nodes; 
     FIG. 10 is a block diagram illustrating a further exemplary GSM telecommunications network provisioned with a Signaling Aggregator in accordance with the invention for aggregating signaling message traffic for a plurality of network nodes; and 
     FIG. 11 is a schematic diagram of a portion of a common channel signaling network in which a Signaling Aggregator is used to expand a capacity of a signal transfer point (STP) in the network. 
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention provides a new signaling network element hereinafter referred to as a Signaling Aggregator (SA). The SA relieves signaling port exhaustion in a out-of-band signaling network, such as a common channel signaling network, by aggregating signals from a plurality of low-speed signaling links onto a high-speed and high-capacity signaling linkset. In order to obviate any requirement to upgrade or reconfigure other signaling nodes in the signaling network, the SA mimics signaling node(s) with which it is associated to the rest of the network. Network elements that require fully associated signaling links are therefore supported without modification. The SA in accordance with the invention is therefore economically installed in a signaling network without disruption and functions substantially transparently to all elements of the network. 
     FIG. 1 is a block diagram illustrating a wireless Global System for Mobile Communications (GSM) network  20  in accordance with the prior art. The GSM network  20  supports wireless telephone devices referred to as mobile stations (MS)  22 . Each MS  22  is connected by a wireless connection to a base transceiver station (BTS)  24 . A base station sub-system (BSS)  26  includes a base station controller (BSC)  28  and at least one BTS  24  which is controlled by the BSC  28 . A mobile services switching center (MSC)  30  generally controls a plurality of base station sub-systems  26 . Each of the BSCs  28  is connected to the MSC  30  by a digital signaling linkset  32  in a fully associated manner. The MSC  30  is also connected by signaling links  34  to other GSM network nodes such as other MSCs  36 , a home location register (HLR)  38 , a visitor location register (VLR)  40 , signal transfer points (STPs)  42 , and other network elements. The STPs  42  connect the MSC  30  to service control points (SCPs) (not shown) and to other telephone networks such as the Public Switched Telephone Network (PSTN). As is well understood in the art, a GSM network  20  is generally provisioned with International Telephone Union (ITU) Signaling System # 7  (SS 7 ) Signaling Protocol, which is well known in the art. 
     As is also well known in the art, certain of the signaling elements in the network shown in FIG. 1 have limited signaling functionality and do not implement a full SS7 protocol stack. The BSCs  28  are one example. They are connected to the MSC  30  by direct signaling links, and are only configured to work in a point-to-point signaling configuration because the BSCs  28  only support a single far-end point code. 
     FIG. 2 is a schematic diagram of a portion of the network shown in FIG. 1, showing a Signaling Aggregator (SA)  44  in accordance with the invention. The SA  44  terminates a plurality of signaling linksets  32  connected to BSCs  28  and aggregates signaling messages destined to the MSC  30  over a single high-capacity signaling linkset  46 . Signaling port exhaustion on the MSC  30  is thereby relieved, permitting more BSCs  28  to be controlled by the MSC  30  or, alternatively, for the MSC  30  to be connected to a greater number of other nodes in the network, or in other networks. At a physical layer, the linkset  46  consists of high-speed links (ATM or IP based) having a high capacity to provide at least a 2:1, for example, aggregation ratio of the relatively low speed signaling linksets  32  (typically 64 Kbps). Alternatively, the linkset  46  can be implemented as an aggregate of low-speed, parallel linksets. The SA  44  may be, for example, a conventional signal transfer point (STP) provisioned with high signaling capacity and configured by software, hardware or firmware to provide the functionality of the SA  44  described below. The SA  44  includes at least one device  48  for terminating the signaling linkset  46 . The device  48  is, for example, a card for supporting one or more signaling ports in a manner well known in the art. The SA  44  also includes devices  50  for terminating the signaling linksets  32 . The devices  50  are likewise, for example, cards supporting one or more signaling ports. An aggregator proxy  52  transparently and selectively transfers signals between the devices  48  and  50 , as will be explained below in more detail. 
     In accordance with the invention, the SA  44  mimics the MSC  30  to the BSCs  28  because the BSCs  28  are not capable of quasi-associated signaling. The SA  44  is therefore transparent to the BSCs  28 . The MSC  30  is, however, capable of quasi-associated signaling and the SA  44  is therefore visible to the MSC  30  with which it is associated. As viewed by the BSCs  28 , however, the MSC  30  and associated SA  44  are perceived as a virtual MSC  31 . Thus, BSCs  28  that support less than full SS7 protocol level 3 (L3) functionality may be connected to the virtual MSC  31  without alteration. The SA  44  mimics the MSC  30  to the BSCs  28  by accepting messages addressed to the point code of the MSC  30 . As will be understood by those skilled in the art, the SA  44  must also provide message transfer part (MTP) functionality in order to operate under the SS7 protocol. The SA  44  must therefore modify normal L3 routing in traffic management message signaling units (MSUs) to appear substantially transparent to the BSCs  28  while keeping the MSC  30  informed of the status of the associated BSCs  28 . 
     FIG. 3 is a schematic diagram of the network configuration shown in FIG. 2, illustrating exemplary linkset and routeset tables for SS7 signaling traffic flows between the MSC  30  and the BSCs  28  provisioned with an SA  44  in accordance with the invention. For simplicity of illustration, capital letters are used for identifying the respective network elements for the sake of defining linksets and routesets. The STPs are therefore identified by the letter T; the MSC  30  is identified by the letter X; the SA  44  is identified by the letter Z; and, the BSCs  28  are identified by the letters Y(i) where i=1 . . . n. Furthermore, for the sake of illustration, the point codes of the respective network elements are represented by capital letters. The MSC  30  has a point code “M”. The SA  44  has two point codes. The point code “M” is used externally because the SA  44  mimics the MSC  30  to the rest of the network, as described above. The internal point code of the SA  44  is, however, represented by the letter “S”. The internal point code of the SA  44  is only known to the MSC  30 , and the MSC  30  and the SA  44  form the virtual MSC  31 , as described above. As is apparent, the MSC  30  recognizes only two linksets, a linkset ls_XZ (linkset  46 ) and a linkset ls_XT which connects the MSC  30  to the STPs  42 . The SA  44  has a linkset ls_ZX that connects the SA  44  to the MSC  30  via linkset  46 , and a linkset ls_ZY (i)  that connects the SA  44  to the BSCs  28  via linksets  32 . Each BSC  28  has only one linkset, ls_Y (i) X, since the BSCs, as explained above, typically support only point-to-point, fully associated signaling connections. 
     As is also shown in FIG. 3, the routesets for the MSC show that the signaling routes to the BSCs (Y) use routesets rs_XY (i)  (rte_XY (i) ). As is also shown in FIG. 3, the routesets from the BSCs  28  are perceived as direct links between the BSCs (Y) and the MSC (X) and M is used as the destination point code (DPC). Each signaling message sent from a BSC  28  is therefore assigned a destination point code (DPC) of M, the point code of the MSC  30 . As explained above, SA  44  accepts all messages received by devices  50  (FIG. 2) having a point code M, and the aggregator proxy  52  aggregates the messages onto the linkset  46  without changing the DPC or an originating point code (OPC) of the message. 
     FIG. 4 illustrates signaling message traffic flow from the MSC  30  to the BSCs  28 , and vice versa. Signaling link management messages such as signal link test (SLT) messages are generated by MSC  30  and each of the BSCs  28 , as well as by the SA  44 . The SA  44  uses its internal point code “S” when generating SLT messages that are sent to the MSC  30 . The SA  44 , however, uses the point code “M” when generating SLT messages for the BSCs  28  in order to mimic the MSC  30 . In order to indicate the status of the respective BSCs  28 , the SA  44  generates route management messages expressed as TFx. The route management messages include messages such as transfer-prohibited (TFP), transfer-allowed (TFA), transfer-restricted (TFR), etc. Because the BSCs  28  do not receive TFx messages which are handled by the MSC X. Consequently, the SA  44  does not send TFx messages to the BSCs. However, SA  44  does need to keep the BSCs  28  informed of the status of MSC  30  and, in turn, the status of linkset  46  as well. If MSC X or linkset  46  fails, SA  44  will take all links to BSCs Y out of service. This is in accordance with the behavior of the system without SA  44 . 
     For signaling payload messages, the MSC  30  uses its own point code M as the originating point code (OPC) in the messages, and routes the messages to the respective BSCs  28  through the SA  44  using a destination point code (DPC) of Y(i). Payload signaling messages sent from the respective BSCs  28  to the MSC  30  contain the respective point codes Y(i) in the OPC and M in the DPC. As explained above, those messages are transparently forwarded by the SA  44 . 
     The MSC  30  typically handles SS7 level 3 signaling network management (SNM) messages for linkset or node failure management. Consequently, SA  44  may notify the MSC  30  if transmission problems occur between SA  44  and the BSCs  28 . Such notifications may be accomplished by sending a TFP[Y(i)] message to the MSC  30 . If a failure occurs on linkset  46 , the SA  44  may disable the links in linksets  32  for the respective BSCs  28 . The SA  44  may perform the same action in the event that the MSC  30  becomes inoperative. In either case, the SA  44  returns the linksets  32  to service after linkset  46  is back in service. If the SA  44  fails, the MSC  30  and the BSCs  28  react as they would if directly connected and failure occurred on all linksets. 
     FIG. 5 is a schematic diagram of another network configuration in which the SA  44  is adapted to enable equal cost linksets in a multiple-plane network configuration. In the example shown in FIG. 5, the SA  44  supports 4×L (where 4 represents the number of linksets, and L is integer that is less than or equal to 16 and represents the number of links in each of the 4 linksets) equal-cost linksets in a multiple-plane network configuration. The 4×L equal priority linkset to mated STPs  42  in the respective planes A and B of the network configuration shown in FIG. 5 provide increased capacity and high network reliability. As explained above, the MSC  30  and the SA  44  form a virtual node  31  which appears to the remainder of the network as a single node. As also explained above, the SA  44  uses a point code S when communicating with the MSC  30  and the point code M (the point code of the MSC  30 ) when sending or receiving messages from the rest of the network. As is further apparent, the presence of the SA  44  contributes significantly to reduction of signaling port exhaustion on the MSC  30 . A service control point (SCP) or home location register (HLR)  62  and a service switching point (SSP) or another MSC  64  illustrate the signaling ports required on those nodes for supporting signaling links to the multiple-plane network configuration in the absence of the SA  44 . 
     FIG. 6 illustrates a further network configuration in which reliability of the signaling network is enhanced by using mated SAs  44   a ,  44   b  to interface the MSC  30  with the STPs  42  of the multiple-plane network configuration. SA  44   a  has a point code S known to the MSC  30 , while SA  44   b  has a point code R known to the MSC  30 . Both SAs  44   a  and  44   b  use point code M and mimic the MSC  30  when sending or receiving signaling messages to the balance of the multiple-plane network. The combination of the three nodes, MSC  30 , SA  44   a  SA  44   b , form a virtual node  31  which mimics the MSC  30  to the remainder of the multiple-plane network  50 . The structure of the remainder of the multiple-plane network  50  is the same as described above with reference to FIG.  5 . 
     In the event of a linkset failure on signaling linksets  46   a ,  46   b , which connect to SAs  44   a ,  44   b  to the MSC  30 , or failure of the MSC, the SAs  44   a ,  44   b  will take down the respective links to the STPs, for example by generating LPO messages on the concerned links. The SAs  44   a ,  44   b  may tandem route to the MSC  30  all incoming messages except signaling link test (SLT) messages; change over order (COO) messages and change over answer (COA) messages, emergency change over (ECO) message, and emergency change over answer (ECA) messages; change back directive (CBD) and change back answer (CBA); link inhibit (LIN) and link inhibit answer (LIA); link uninhibit (LUN) and link uninhibit answer (LUA); link inhibit denied (LID); link forced inhibit (LFI) ; local link inhibit test (ILT) and inhibit remote test (IRT). 
     FIG. 6 also shows an example of a routeset from SAs  44   a ,  44   b  to an STP  42  having a point code of T as well as routesets for the respective SAs  41   a ,  41   b  to the MSC  30 . As shown in FIG. 6, each linkset (LS) indicates a source and destination, followed by a relative cost of using the linkset. Thus, the linksets for SAs  44   a ,  44   b  to the STP  42  with point code “T” include a direct route MT with a cost of 5 and an indirect route (SR) through the paired SAs with a cost of 20. With respect to the linksets to MSC  30 , the direct link (SM) has a cost of 5 while the indirect linkset (SR) through the paired SA  44   b  has a cost of 20. Likewise, for SA  44   b , the direct route (RM) has a cost of 5 while the indirect route (RS) through the paired SA  44   a  has a cost of 20. The respective cost factors force the SAs  44   a ,  44   b  to choose the lower cost in-service route for transferring messages to the MSC  30 . Otherwise, the alternate higher cost in-service route may be selected. 
     FIG. 7 is a schematic diagram illustrating another embodiment of a Signaling Aggregator in accordance with the invention. In this embodiment, an SA  70  masquerades as a Home Location Register (HLR)  72  to the remainder of the multiple-plane network  50 . The HLR  72  is an Internet Protocol (IP) node having an IP linkset  73  to the SA  70 , and SA  70  performs a protocol conversion from SS7 to IP signaling protocol, and vice versa, to permit the HLR  72  to be transparently connected to the multiple-plane network  50 . As shown in FIG. 7, the HLR  72  has an IP address “I” and a point code “C”. The SA  70  also has an IP address “J”, of which only HLR  72  is aware. The SA  70  has a point code “V” used to mimic the HLR  72  to the remainder of the multiple-plane network  50 . The sending and receiving of signaling messages is similar to that described above. The combination of HLR  72  and SA  70  from the virtual node  74  which, to the multiple-plane network  50 , appears as an HLR having a point code of “C”. When sending payload or link maintenance messages, the SA  70  mimics the HLR. In the event of a linkset failure or HLR node failure, the messaging proceeds as described above with reference to FIG. 6, with required compensation for the IP signaling, which is well understood in the art. 
     FIG. 8 is a schematic diagram illustrating a multiple-plane network  50  in which an SA  70  serves each of two HLRs  72   a ,  72   b , which are both IP devices. The HLR  72   a  has a point code of “V” and an IP address of “K”. The HLR  72   b  has a point code of “CP” and an IP address of “I”. The SA  70  has an IP address of “J” known only to the respective HLRs  72   a ,  72   b  and a point code of “C” or “V” towards the rest of the multiple-plane network  50 , to mimic the respective HLRs  72   a ,  72   b . The SA  70  in combination with the HLR  72   a  forms a virtual node  74   a  which appears to the multiple-plane network  50  as an HLR  72   a  having a point code of “V”. The SA  70  in combination with the HLR  72   b  forms a virtual node  74   b  which appears to the multiple-plane network  50  as an HLR having a point code of “U”. As also explained above with respect to FIG. 7, the SA  70  further provides message translation services to the respective HLRs  72   a ,  72   b  to convert SS7 messages to Internet Protocol format, and vice versa. Otherwise, the multiple-plane network  50  functions as described above, and the SSPs/MSCs  64   a ,  64   b  address their respective HLRs  72   a ,  72   b  as they would any other node in the multiple-plane network  50 . 
     FIG. 9 is a schematic diagram of a multiple-plane network  50  in which an SA  80  in accordance with the invention serves as a Signal Aggregator for an MSC  30  and an HLR  72 . The SA  80  therefore provides protocol conversion services to the HLR  72 , which is an IP device, and simultaneously serves as a Signal Aggregator for the MSC  30 , without protocol conversion. A signaling linkset  82  connecting the SA  80  to the MSC  30  is a high-capacity SS7 linkset. The signaling linkset  84  connecting the SA  80  to the HLR  72  is a high-capacity IP linkset. The MSC has a point code of “Q” while the HLR has a point code of “U”. The SA  80  has an IP address of “J” known only to the HLR  72 , which has an IP address of “I”. The SA  80  has a point code of “L” known by the MSC  30 . The SA  80  in combination with the MSC  30  forms a virtual node  86   a  which appears to the multiple-plane network  50  as an MSC  30  with the point code of “Q”. The SA  80  in combination with the HLR  72  forms a virtual node  86   b  which appears to the multiple-plane network  50  as an SS7-conversant HLR  72  with a point code of “U”. The SA  80  therefore uses point code “Q” when sending or receiving SS7 messages for the MSC  30  and a point code “U” when sending or receiving messages for the HLR  72 . The SA  80  is therefore adapted to mimic both the HLR  72  and the MSC  30  to the multiple-plane network  50 . The transfer of SS7 payload messages and signaling link maintenance messages is performed as described above with reference to FIGS. 6-8. 
     FIG. 10 shows an embodiment of the invention in which a Signaling Aggregator  90  serves to aggregate control messages exchanged between a plurality of BSCs  28   a-c  and a plurality of MSCs  30   a-c . The respective BSCs/HLRs  28   a  are connected to a high-capacity SA  90  by a plurality of linksets  32   a . The BSCs/HLRs  28   a  have point codes of W(k). The BSCs/HLRs  28   a  are IP devices having IP addresses of B(k), k=1 . . . g. The BSCs  28   b  have a point code of Y(i) and are connected to the SA  90  by linksets  32   b . The BSCs  28   b  are SS7 enabled devices with point codes of Y(i), i=1 . . . n. The BSCs  28   c  are connected to the SA  90  by linksets  32   c . The BSCs  28   c  are SS7 enabled devices that have a point code of P(j), j=1 . . . h. The SA  90  is connected to the respective MSCs  30   a - 30   c  by high-capacity linksets  46   a - 46   c . The SA  90  mimics each of the respective MSCs  30   a - 30   c . Consequently, the SA  90  forms three virtual nodes  92   a-c  with the respective MSCs  30   a-c . The SA  90  uses a point code of “M” towards the BSCs  28   b  because the MSC  30   b  controls BSCs  28   b . The SA  90  has a point code of “Q” towards the BSCs  28   c  because the MSC  30   a  controls BSCs  28   c . The SA  90  uses a point of “U” towards BSCs/HLRs  28   a  because the MSC  30   c  controls BSCs/HLRs  28   a . The SA  90  uses a point code of “L” towards each of the MSCs  30   a - 30   c . The SA  90  also provides protocol conversion for all messages exchanged between the MSC  30   c  and the BSCs/HLRs  28   a , as explained above with reference to FIG.  7 . 
     FIG. 11 illustrates another embodiment of the invention that enables the creation of a large Signal Transfer Point (STP)  42  or a distributed STP by connecting one or more Signal Aggregators  100   a ,  100   b  to each STP  42   a ,  42   b . The respective SAs  100   a ,  100   b  are connected to the STPs  42   a ,  42   b  by respective high-capacity signaling linksets  104   a ,  104   b . The SA  100   a  in combination with the STP  42   a  forms a virtual STP  102   a  which is completely transparent to the network. Likewise, SA  100   b  in combination with STP  42   b  forms a virtual node  102   b  which is completely transparent to the rest of the signaling network. Since STPs are generally transparent to the network in any event, the SAs  100   a ,  100   b  need only masquerade to the rest of the network when sending or receiving signaling link management messages and simply forward payload signaling messages received from other nodes over linksets  106   a ,  106   b  to the respective STPs  42   a ,  42   b  via linksets  104   a ,  104   b . Likewise, messages received from the respective STPs  42   a ,  42   b  are forwarded over the appropriate linksets  106   a ,  106   b  based on the destination point code (DPC) of the message using message routing tables well known in the art. For the purposes of MTP signaling, the SA  100   a  has a point code known only to STP  42   a , and mimics the STP  42   a  to other nodes connected to the signaling linksets  106   a . SA  100   b  likewise mimics STP  42   b  to other network nodes connected to the signaling linksets  106   b  for the purposes of signaling link maintenance using MTP messages. 
     The Signaling Aggregator in accordance with the invention therefore provides a versatile new element for use in a telecommunications signaling network. Although the invention has been described with particular reference to SS7 common channel signaling networks, it will be understood by those skilled in the art that the same principles may be applied to utilize the Signaling Aggregator in accordance with the invention in any out-of-band signaling network. It should also be understood that the uses of the Signaling Aggregator described above is not an exhaustive list. The Signaling Aggregator may be used in any configuration in a out-of-band signaling network in which transparent signal message aggregation and/or protocol conversion are beneficial. 
     The embodiments of the invention described above are therefore intended to be exemplary only and the scope of the invention is to be limited solely by the scope of the appended claims.