Abstract:
A routing processing system in a packet transmission is capable of restricting a delay in a routing process based on particular applications being utilized. The packet transmission routing processing system performs a routing process for an input packet and includes parsing and timer processing for identifying an application corresponding to an intended transmission of an input packet and monitoring a timer value provided for the application. Routing and transferring processes determine a transmission destination port on the basis of a destination address stored in a routing table, and dispose of the packet or transfer packet to a preliminary determined route depending on the identified application when routing process exceeds the timer

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a routing processing method in a packet transmission and a system therefore. More particularly, the invention relates to a routing processing method in a packet transmission and a system therefore, for performing delay control of a packet in an internet telephone communication in a Transmission Control Protocol/Internet Protocol (TCP/IP) network. 
     2. Description of the Related Art 
     Conventionally, a router disposed in the CP/IP network of this type (such as intranet, intemet, extranet, hereinafter only referred to intemet) retrieves a routing table from a destination address to read out a data transmission path to a transmission destination for transmitting a packet to the read out transmission path. In this case, packet transmission cannot be carried out until completion of routing retrieval. Therefore, a transmission period of the packet is significantly variable depending upon a retrieval period of the routing table. 
     In the recent internet performing packet transmission, a best effort type service is typical. The best effort type service is a service to do the best effort for accomplishing a processing considering the entire network but does not guarantee end-to-end service. Therefore, in the worst case, service cannot be provided. The recent internet is apt to exceed traffic in the existing wired and radio telephone services. As a result, even in the intemet which has provided the best effort type service conventionally, a service quality (Qos: quality of service) comparable with the conventional type communication network is require to be realized. 
     In such TCP/IP communication network, guarantee for delay of packet transmission is becoming important. Particularly, in the case of transmission telephonic speech (talk signal) in a form of a packet, clarity of telephonic conversation can be degraded to make delay unacceptable if end-to-end delay becomes in excess of about 100 msec. Accordingly, it becomes necessary to restrict the delay of packet transmission in the TCP/IP communication network to be a predetermined value or less. In such TCP/IP communication network, one of the important causer of packet transmission delay is the routing process in the router. Accordingly, when a processing amount in the routing process in the router is large (upon a high load condition) and when the routing process cannot be performed at high speed, it becomes impossible to restrict the delay to be less than or equal to the predetermined value. 
     Various proposals have been made for the routing process of this kind. For example, in Japanese Unexamined Patent Publication No. Heisei 4-183044, for “Routing Control System with Modification of Transmission Source Data”, correction of a user data of a transmitted PUD (Protocol Unit Data) can be corrected only by transmitting a user data modification PUD within a transmission holding period when correction becomes necessary after transmission of PUD containing the large amount user data by a transmission source end system or when the correction amount is small. 
     On the other hand, in Japanese Unexamined Patent Publication No. Heisei 6-244867, for “Back-up Route Connection Stand-by Routing System”, connection of a backup path is conditioned upon the occurrence of a failure in a junction line. In this method, real-time routing depending upon the condition of the back-up path is enabled, and in conjunction therewith, traffic and node load in the network can be reduced. Furthermore, by restricting increase of the number of junction stages, the possibility of abandonment or dropping of packets can be reduced. In addition, by preventing the back-up path from unnecessarily opening, the communication period can be reduced to reduce wasting of communication cost. 
     As set forth above, in the prior art, delay in packet transmission due to the routing process in the router is caused in the communication network. If the amount of routing process in the router is large for high load and thus the routing process cannot be executed at high speed, it becomes impossible to restrict the delay for internet telephone communication to be less than or equal to the allowable predetermined value. 
     SUMMARY OF THE INVENTION 
     The present invention has been worked out in view of the problem in the prior art as set forth above. It is therefore an object of the present invention to provide a routing process in a packet transmission and a system therefor, which does not effect abandonment of packet for an application not given importance for a delay value to restrict delay in the routing process adapting to the application for enabling reduction of process period required for routing process. 
     In order to accomplish the above-mentioned object, according to the first aspect of the present invention, a routing processing method in a packet transmission for an input packet as an object for routing, comprises the steps of: 
     performing a process for identifying an application adapting for transmission of an input packet; 
     performing a process for setting a timer value preliminary provided for the identified application: 
     performing a process for routing to determine a port of transmission destination on the basis of a destination address stored in a routing table; and 
     performing a process for abandoning a packet or transferring the packet to a predetermined route adapting the identified application when routing process cannot be completed exceeding the set timer value. 
     According to the second aspect of the present invention, a packet transmission routing processing system performing a routing process for an input packet as a routing object, comprises: 
     parsing and timer processing means for identifying an application corresponding to transmission of an input packet and monitoring a timer value preliminary provided for the application; and 
     routing and transferring means for determining a port of a transmission destination on the basis of a destination address stored in a routing table and disposing the packet or transferring the packet to a preliminary determined route adapting to the identified application when routing process is continued beyond the timer value monitored by the parsing and timer processing means. 
     In the preferred construction, the parsing and timer processing means and the routing and transferring processing means may comprise: 
     a packet accumulating portion accumulating the input packet; 
     a packet parsing portion performing parsing for identifying the application corresponding to the packet from the packet accumulating portion and reading out of a destination address; 
     a packet waiting portion waiting the packet from the packet parsing portion and transmitting the packet in response to a packet output command; 
     packet transferring portion for transferring the packet output from the packet waiting portion to a packet output port on the basis of a transmission destination designation and next process designation; 
     a timer value determining portion outputting a timer value and a next process code corresponding to the application identified by the packet parsing portion; 
     a monitoring timer portion outputting a time out signal upon termination of measurement of the timer value from the timer value determining portion; and 
     a routing retrieving portion outputting a packet output designation signal to the packet waiting portion and outputting a transfer path number and a process code to the packet transferring portion when the routing process based on the destination address from the timer value parsing portion or a time out signal is input from the monitoring timer portion. 
     The timer value may be a timer for executing a predetermined process when routing retrieval is not completed within a period designated by the timer value, and 
     the next processing code may be a code designating the process of packet to be object for the routing process when retrieving process in the routing retrieving portion is not completed within the period designated by the timer value. 
     The predetermined process in the timer value may be to terminate the routing process irrespective of normal or abnormal of the result of process within the period designated by the routing retrieval period of the timer value, and the process of the packet in the next process code may be abandonment of the packet or transferring to a predetermined path when the transmission destination cannot be determined. 
     In the monitoring timer portion, a counter may be employed, the counter outputs a time out signal generated by measuring the timer value from the timer value determining portion to the routing retrieving portion. 
     The timer value determining portion may comprise: 
     an application judgment portion for generating an address at a value the same as an application identification number from the packet parsing portion or a value derived by multiplying or dividing the application identification number by an integer; and 
     a random access memory reading out the preliminary stored timer value and the next process code for outputting to the monitoring timer and the routing retrieving portion corresponding to the address from the application judgment portion. 
     The timer value determining portion comprises: 
     a content-addressable memory storing the application identification number, the timer value and the next process code in combination, the content-addressable memory outputs the timer value and the next process code stored therein on the basis of the input application identification number. The random access memory or the content accessable memory may be a detachable and rewritable storage element. The packet transmission may further include input operation and storage processing means for rewriting the timer value in the random access memory or the content addressable memory. In the alternative, the packet transmission routing processing system may further include an external storage data modifying device connected to the random access memory or the content-addressable memory for rewriting the timer value. In the further alternative, the packet transmission routing processing system may further include an external storage data modifying and communicating device receiving a designation data from a communication network for modifying the timer value of the random access memory or content-addressable memory. 
     The routing retrieving portion may comprise a processing unit including a microprocessor or a digital signal processor executing a sequence for outputting a packet output command signal to the packet waiting signal, and outputting a transfer path number and the process code to the packet transferring portion when the routing process based on the destination address from the packet paring portion is completed or after input of the time out signal from the monitoring timer. 
     The application identified by the parsing and timer processing means may be at least an internet telephone protocol in a TCP/IP communication network. The timer value may be a period for obtaining clarity of telephone conversation in a TCP/IP communication network. The period to obtain clarity in the telephone conversation may be in a range of 10 msec. to 50 msec. 
     As set forth above, the routing processing method in the packet transmission and the system therefor sets the preliminary provided timer value for the application identified by the input packet to determine the port of the transmission destination on the basis of the destination address stored in the routing table. In this case, when the routing process cannot be completed even after elapsing of the set timer value, the packet is abandoned or transferred to the predetermined route depending upon the identified application. 
     As a result, it becomes possible to restrict the period required for routing process in the packet transfer to be the predetermined value or less. In this case, for the application which does not give importance for the delay value, the packet is not abandoned. As such, delay in the routing process is restricted per application. 
     Accordingly, for the application, for which small delay is required and abandonment ratio of packet to less important, the timer value is set at small value to restrict the relay value at smaller value. As a result, the process period required for routing process can be reduced. 
     For example, in the internet telephone, for voice transmission in real-time, preferred end-to-end delay period is less than or equal to 100 msec. If delay becomes longer than the preferred delay period, satisfactory clarity of telephonic conversation cannot be obtained and such delay is unacceptable. It has been established that, in case of telephone voice, the end-to-end delay less than or equal to 100 msec. is established rough standard. In case of the Internet telephone, it is possible that call connection is established through several hops of the routers. A delay per hop is 50 msec. or less in case of two hops, and 20 msec. or less in case of five hops. Accordingly, it becomes meaningless to transfer the packet for which a delay in excess of 100 msec. is caused. Therefore, such packet is abandoned. Namely, by setting the timer value of routing process of the packet of the internet telephone to be about 10 msec. to 50 msec. in which satisfactory clarity of telephone conversation can be obtained, for example, packet requiring process period in excess of the set period can be abandoned. 
     On the other hand, the packet transmission routing processing system according to the present invention rewrites the timer value corresponding to the delay value employing the detachable and rewritable storage element, input operation and storage processing means external storage data modifying device or the external storage data modifying and communicating device. 
     As a result, it becomes possible to set the timer value adapting to each application. Particularly, adapting to modification of the transmission standard of the TCP/IP communication network or establishing condition, modification of the period to obtain satisfactory clarity in telephonic conversation is facilitated. On the other hand, freedom of the device construction (design) can be improved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description given hereinafter with reference to the accompanying drawings of the preferred embodiment of the present invention, which, however, should not be taken to be limitative to the present invention, but are for explanation and understanding only. 
     In the drawings: 
     FIG. 1 is a block diagram showing a construction of an embodiment of a routing processing method in a packet transmission and a system therefor, according to the present invention; 
     FIG. 2 is an illustration showing a content of format of an IP packet in the shown embodiment; 
     FIG. 3 to a block diagram showing an example of an internal construction of a timer value determining portion shown in FIG. 1; 
     FIG. 4 Is a block diagram showing another example of an internal construction of a timer value determining portion shown in FIG. 1; 
     FIG. 5 is a flowchart showing a process procedure in a routing processing operation of a packet in the shown embodiment; 
     FIGS. 6A to  6 D are block diagrams showing construction of the major part of another embodiment; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will be discussed hereinafter in detail in terms of the preferred embodiment of the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instance, well-known structure are not shown in detail in order to avoid unnecessary obscurity of the present invention. 
     FIG. 1 is a block diagram showing a construction in an embodiment of a routing processing method in a packet transmission and a system therefor according to the present invention. 
     In FIG. 1, a routing processing system is arranged in an FDDI local area network (LAN) included In a TCP/IP communication network for routing process with other Ethernet LAN or communication network, for example. 
     The routing processing system includes a packet accumulating portion  10  for accumulating one or more input packets, a packet parsing portion  20  transmitting a signal identifying an application (application identification signal S 2 ) corresponding to a packet read out from the packet accumulating portion  10  on the basis of a read signal S 1  to a timer value determining portion  50  and performing parsing of the application for reading out a destination address S 3 . 
     On the other hand, the routing processing system has a packet waiting portion  30  for waiting a packet from the packet parsing portion  10  and outputting one packet to a packet transmitting portion  40  after inputting of a packet output designating signal S 4  from a routing retrieving portion  70 , the packet transmitting portion  40  outputting the packet output from the packet waiting portion  30  on the basis of a transmission destination designating signal and a next process designating signal (packet output designating signal S 4 ) from the routing retrieving portion  70 , to a packet output terminal corresponding to a predetermined path, and a timer value determining portion  50  outputting a preliminary provided (written) timer value S 5  to a monitoring timer portion  60  and outputting a next process code S 8  which will be discussed later, to the routing retrieving portion  70 , corresponding to the application identified by the packet parting portion  20  (the application identification signal S 2  output therefrom). 
     Furthermore, the routing processing system further includes the monitoring timer portion  60  having a timer value table and outputting a time out signal S 6  to a routing retrieving portion  70  upon completion of time measurement of the preliminary stored timer value S 5 , and the routing retrieving portion  70 . The routing retrieving portion  70  outputs the packet output designating signal S 4 , and outputs a transmission path number S 10  and the process code S 11  to the packet transmission portion  40  when the routing process is completed on the basis of the destination address S 3  output by the packet parsing portion  20  or after inputting of the time out signal S 6  output by the monitoring timer portion  60 . 
     Next, operation of the shown embodiment will be discussed. 
     At first, discussion will be given for operations in respective portions. 
     FIG. 2 is an illustration showing an example of content of a format of an IP packet. 
     In FIG. 1, the packet accumulating portion  10  sequentially accumulates input packets from a packet transmission path. The packet accumulating portion  10  accumulates one or more packets therein, and feeds one packet to the packet parsing portion  20  when the packet waiting portion  30  outputs the read out signal Si. 
     In FIGS. 1 and 2, the packet parsing portion  20  reads out a content of a header of the IP packet. From the format, judgment is made what application will use the packet. For example, a number in a destination port A in FIG. 2 stored in a TCP header, is one data for making judgment what is the protocol higher than or equal to a layer  4  in the packet transmission, normally. With this data, the application is identified. 
     As the application to be the object for Identification, an Internet telephone protocol (such as NetMeeting, InternetPhone, CU-SeeMe, Net2Phone, CoolTalk, FPPhone, HTTP, RealAudio), Telnet (service/program for remote login to a computer of the TCP/IP communication network), FTP (File Transfer Protocol: file transfer protocol In the TCP/IP communication network) have been known. 
     It should be noted that TOS (Type of Service) in FIG. 2 is a parameter (minimum delay, maximum throughput, maximum reliability, minimum cost) for a route determining matrix of the routing process (routing protocol/OSPF: Open Shortest-Path First Interior Gateway Protocol). 
     In the shown embodiment, the destination port number is used as the application identification number as is. The application identification number obtained set forth above (application identification signal S 2 ) Is output to the timer value determining portion  50 . Furthermore, the packet parsing portion  20  reads out the destination address from the header of the packet to output the destination address S 3  to the routing retrieving portion  70 . Furthermore, the packet is transferred to the packet waiting portion  30 . 
     In FIG. 1, the packet waiting portion  30  is responsive to inputting of the packet output by the packet parsing portion  20 , to stop transmission of the read out signal S 1  output to the packet accumulating portion  10 , and to output a retrieval start signal S 7  to the routing retrieving portion  70 . Then, when the packet output command signal S 4  from the routing retrieving portion  70  is input, the packet waiting portion  30  outputs the accumulated packet to the packet transmission portion  40 . 
     In FIGS. 1 and 2, a timer value determining portion  50  determines the timer value S 5  and the next process code S 8  on the basis of the application identification number when the application identification signal S 2  indicative of the identification number of the application format content of the IP packet shown in FIG. 2 which is output by the packet parsing portion  20 . The timer value S 5  is fed to the monitoring timer portion  60  and the next process code S 8  is fed to the routing retrieving portion  70 . For example, in the intemet telephone communication, an end-to-end delay period has to be less than or equal to 100 msec. If a delay longer than this is caused, telephonic conversation becomes unacceptable for lack of clarity. Accordingly, if delay in excess of 100 msec is caused, it becomes meaningless to transmit the packet. Thus, packet is abandoned. 
     It should be noted that the end-to-end delay period is preferably within a range of 10 msec to 50 msec in view of various materials and actually measured values. 
     FIG. 3 is a block diagram showing an example of an internal construction of the timer value determining portion  50 . 
     The timer value determining portion  50  shown in FIG. 3 has an application judgment portion  50   a  and a random access memory  50   b.    
     In the timer value determining portion  50 , the application identification signal S 2  indicative of the identification number of the application from the packet parting portion  20  is input to the application judgment portion  50   a . In the application judgment portion  50   a , an address which is the same as the application identification number or a value derived by multiplying or dividing the application identification number by an integer is generated. The address is input to the random access memory  50   b . Data stored in the address is read out as the timer value S 5  and the next process code S 8  to output to the monitoring timer portion  60  and the routing retrieving portion  70 . It should be noted that a predetermined value is written in the random access memory  50   b.    
     FIG. 4 is a block diagram showing another example of the internal construction of the timer value determining portion  50  in FIG.  1 . 
     The timer value determining portion  50 A shown in FIG. 4 has a content-addressable memory  50 A a  storing the application identification number S 2 , the timer value S 5  and the next process code S 8  in combination and outputs the timer value S 5  and the next process code S 8  on the basis of the input application identification number. It should be noted that a predetermined value is written in the content-addressable memory  50 A a.    
     The timer value S 5  and the next process code S 8  are determined by the timer value determining portion  50  ( 50 A). 
     The timer value S 5  is a value defined for performing a particular abnormal process when the routing retrieval cannot be completed within the period designated by the value. Namely, a process is always terminated within the period designated by the routing retrieval period (timer value S 5 ) irrespective whether the result of the process is normal or abnormal. 
     When the retrieval process in the routing retrieving portion  70  cannot be completed within the period designated by the timer value S 5 , it designates how the packet to be the object for the routing process is to be processed. In the shown embodiment, the process is defined as follow. When the value of the next process code S 8  is “0”, the packet is abandoned. When the value of the next process code S 8  Is “1”, the packet is fed to the default path. The default path is a predetermined path to transfer the packet when it cannot be determined where the packet is to be transferred. 
     When the timer value S 5  output by the timer value determining portion  50  is input, the monitoring timer portion  60  outputs the time out signal S 6  to the routing retrieving portion  70  when the period determined by the timer value S 5  is measured. On the other hand, when a timer stop signal from the routing retrieving portion  70  is not input, the monitoring timer portion  60  does not output the time out signal S 6  until the timer value S 5  is input from the timer value determining portion  50 . 
     The monitoring timer portion  60  can be realized using the counter. In this construction, the timer value S 5  is stored in the counter to decrement the count value by one per expiration of the given period. When the count value becomes 0, the time out signal S 6  is output. 
     Next, if the destination address S 3  is input from the packet parsing portion  20 , or when both of the destination address S 3  and the next process code S 8  from the timer value determining portion  50  are input, the routing retrieving portion  70  initiates an output path determining process. In connection with information for routing retrieval, a routing table is normally established by a routing protocol or so forth, each an entry corresponding to the best matching with the destination address S 3  is selected among the routing table to determine the output path. As a structure and retrieving method of the routing table concerning the determining process of the output path, a known structure and method may be used. 
     In the routing retrieving portion  70 , when the time out signal S 6  is input from the monitoring timer portion  60  during the determining process of the output path, a number preliminary determined as a vacant number or a number designating the default path is output as the transfer path number S 6 . The next process code S 8  received from the timer value determining portion  50  as the process code Sil in advance, is output to the packet transferring portion  40 . 
     Furthermore, in the routing retrieving portion  70 , when the output path determination process is completed before inputting of the time out signal S 6  from the monitoring timer portion  60 , the timer stop signal S 9  is output to the monitoring timer portion  60 . 
     Next, on the basis of the transfer path number S 10  and the process code Sell from the routing retrieving portion  70 , the packet transfer portion  40  abandons packet received from the packet waiting portion  30  or feeds to the packet output line. The transfer path number S 10  represents any one of a plurality of packet outputs in the packet transferring portion  40 . Here, when the process code S 11  is “0”, the packet is abandoned. On the other hand, when the process code S 11  is “1”, the packet is fed to the packet output line indicated by the transfer path number S 10 . 
     Next, discussion will be given for the major part in the routing processing operation. 
     FIG. 5 is a flowchart showing a processing procedure in the routing processing operation of the packet. 
     In FIGS. 1 and 5, the packet input to the packet accumulating portion  10  through the packet input line is accumulated in the packet accumulating portion  10  until the read out signal S 1  is input from the packet waiting portion  30  (sep S 1 ). When the read out signal S 1  is output to the packet accumulating portion  10  from the packet waiting portion  30  (step S 2 : Yes), the packet accumulated in the packet accumulating portion  10  is output to the packet parsing portion  20 . 
     The header content of the packet input to the packet parsing portion  20  is read out, the application identification signal S 2  identifying the internet telephone protocol, Telnet, FTP or so forth is transmitted to the timer value determining portion  50 , or the destination address S 3  is transmitted to the routing retrieving portion  70 . Furthermore, the packet is fed to the packet waiting portion  30  (step S 3 ). 
     When the packet is input to the packet waiting portion  30 , the retrieval start signal S 7  is output to the routing retrieving portion  70 . The packet in the packet waiting portion is held (waited) by the packet waiting portion  30  until the packet output command signal S 4  is output from the routing retrieving portion  70 . Once the packet output command signal S 4  is input from the routing retrieving portion  70 , the packet waiting portion  30  transfer the packet to the packet transfer portion  40  (steps S 4  and S 5 ). 
     The packet transfer portion  40  operates to abandons the packet or to select any one of a plurality of packet output lines on the basis of the transfer path number SIO and the process code Sib from the routing retrieving portion  70  (steps S 6 ,S 1 S 8 ). The process code is to determine whether the packet is to be abandoned or transferred, the transfer path number Sb is to determine which packet output lines is to be selected upon transferring the packet. 
     FIGS. 6A to  6 D are block diagrams showing constructions of major parts of other embodiments. 
     FIG. 6A is an embodiment, in which EEPROM  80  which is detachable and rewritable of the timer value S 5 , as the random access memory  50   b  of the timer value determining portion  50  shown in FIG.  3  and the content-addressable memory  50 A a  shown in FIG.  4 . 
     On the other hand, FIG. 6B shows an embodiment, in which a flash memory is employed as the random access memory  50   b  of the timer value determining portion  50  shown in FIG. 3 or the content-addressable memory  50 A a  shown in FIG. 4, and an input/output (I/O) circuit  91  is provided together with an operating device (keyboard)  90  as an input operation and storage processing means. 
     FIG. 6C shows an embodiment, in which a flash memory is employed as the random access memory  50   b  of the timer value determining portion  50  shown in FIG. 3 or the content-addressable memory  50 A a  shown in FIG. 4, and an interface (I/F) circuit  100  is provided for connection with a compact general purpose computer (maintenance terminal) PC as an external storage data modifying device. Though this compact general purpose computer, the timer value S 5  is re-written. 
     On the other hand, FIG. 6D shows an embodiment, in which a flash memory is employed as the random access memory  50   b  of the timer value determining portion  50  shown in FIG. 3 or the content-addressable memory  50 A a  shown in FIG. 4, and an ATM transmission device  111  as an external storage data modifying and communicating device for rewriting the timer value S 5  from an ATM communication (such as a wide band (B) ISDN)  110 . The ATM transmission device receives the rewriting designating packet from a host unit or an ATM communication terminal  112  to perform rewriting of the timer value S 5 . It should be noted that other communication network may be employed in place of the ATM communication network. 
     With the construction illustrated in FIGS. 6A to  6 C, setting of the timer value adapting to respective application becomes possible to facilitate modification the allowable period for achieving satisfactory clarity of telephonic conversation upon modification transmission standard of the TCP/IP communication network, or use condition (network establishing condition) in a service provider. Also, sufficient freedom in designing associated with variation of the standard of the TCP/IP communication network can be obtained. 
     As can be clear from the foregoing discussion, with the routing processing method in the packet transmission and the system therefor in accordance with the present invention, when the routing process is not terminated even after exceeding of the preliminary set timer value for the application identified by the input packet, the packet is abandoned adapting to the identified application or the packet is transferred to the preliminary determined route. 
     Accordingly, for the application requiring small delay and abandonment rate of the packet is less important, the time value is set at a small value to restrict the delay amount to a small value. As a result, process period required for routing process can be reduced. 
     As a result, the timer value can be set adapting to each application. In particular, concerning a modification of the transmission standard of the TCP/IP communication network or establishing condition, the period to obtain clarity of telephonic conversation can be modified easily. Furthermore, a freedom in designing the system construction can be enhanced. 
     With the packet transmission routing process system according to the present invention, the timer value corresponding to the delay value is re-written by means of detachable or rewritable storage element, the input operation and storage processing means, the external storage data modifying device or the external storage data modifying and communicating device. 
     As a result, the timer value can be set adapting to each application. In particular, concerning a modification of the transmission standard of the TCP/IP communication network or establishing condition, the period to obtain clarity of telephonic conversation can be modified easily. Furthermore, a freedom in designing the system construction can be enhanced. 
     Although the present invention has been illustrated and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various changes, emission and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalent thereof with respect to the feature set out in the appended claims.