Switching node in label multiplexing type switching network

• US 5,287,535 A
• Filed: 05/07/1992
• Issued: 02/15/1994
• Est. Priority Date: 05/07/1991
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakamura, Teruhisa, Iida, Ichiro, Sakagawa, Kazuo
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US07/880,066
• Time in Patent Office: 649 Days
• Field of Search: 370/60, 370/94.1, 370/53, 370/94.2, 370/58.1, 370/58.2, 370/58.3, 370/60.1
• US Class Current: 370/389
• CPC Class Codes: H04L 2012/564 Connection-oriented
• CPC Class Codes: H04L 2012/5645 Connectionless
• CPC Class Codes: H04L 49/104 Asynchronous transfer mode [ATM] switching fabrics
• CPC Class Codes: H04L 49/20 Support for services
• CPC Class Codes: H04L 49/254 Centralised controller, i.e. arbitration or scheduling
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports
• CPC Class Codes: H04L 49/3009 Header conversion, routing tables or routing tags
• CPC Class Codes: H04L 49/501 Overload detection
• CPC Class Codes: H04L 49/506 Backpressure
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A switching node in a label multiplexing type switching network includes a switch for selectively coupling input logical communications paths and output logical communications paths with each other, m permanent logical communications paths being included in the input logical communications paths where m is an integer larger than or equal to 1, n permanent logical communications paths being included in the output logical communications paths where n is an integer larger than or equal to 1. The switch node includes a call control unit for receiving connection-oriented type information through any of the input logical communications paths and for controlling the switch so that the connection-oriented type information are selectively transferred to the output logical communications paths via the switch on the basis of routing address information related to the connection-oriented type information. The switch node comprises a routing unit for receiving connectionless type information through any of the m logical communications paths and for controlling the switch so that the connectionless type information are selectively transferred to the n permanent logical communications paths via the switch on the basis of routing address information related to the connectionless type information.

Claims

1. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication parts with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media, and

each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means; and

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means.

2. A switching node as claimed in claim 1, wherein:

the connectionless type information is a cell which is one of a group of cells obtained by segmenting a message to be transferred;

the connectionless type information contains segment type information showing a position of the connectionless type information in the group of cells, and message identifier information identifying said message, and

wherein said routing means comprises control means for controlling said switch means so that the connectionless type information is transferred to one of the transmission media on the basis of routing address information related thereto when the connectionless type information is a first cell which is located at a beginning of the message and for controlling said switch means so that the connectionless type information is transferred to one of the transmission media on the basis of the message identifier when the connectionless type information is one of the group of the cells other than said first cell, so that each of the group of the cells other than the first cell is transferred to one of the transmission media to which the first cell is also transferred.

3. A switching node as claimed in claim 2, wherein said routing means comprises:

first table means for storing a first relation between the routing address information and addresses of said ports; and

second table means for storing a second relation between the message identifier information and the addresses of the ports, and

wherein said control means comprises means for searching for the address of one of the ports relating to the routing address information contained in said first cell and for searching for the address of one of the ports relating to the message identifier information contained in each of the group of the cells other than the first cell.

4. The switching node as claimed in claim 1, wherein said transfer control means transfers said connectionless type information in said second buffer when there is no connection-oriented type information in said first buffer.

5. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information; and

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information, wherein;

the connectionless type information is a cell which is one of a group of cells obtained by segmenting a message to be transferred,

the connectionless type information contains segment type information showing a position of the connectionless type information in the group of cells, message identifier information identifying said message, and sequence number information sequentially assigned to the group of cells, and

said routing means comprises;

first means for detecting a lost cell by referring to said sequence number information; and

second means, coupled to said first means, for abandoning a subsequent cell which is the connectionless type information and has the same message identifier information as the lost cell.

6. A switching node as claimed in claim 5, wherein said first means comprises means for determining, for each message, whether or not the sequence number information is sequentially changed each time the connectionless type information is received.

7. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media,

said routing means comprises control means for monitoring traffic of each of the transmission media and for selecting one of the transmission media on the basis of the traffic of each of the transmission media, the connectionless type information being transferred to one of the n logical communication paths formed on said one of the transmission media selected by said control means, and

each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means; and

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means.

8. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication path being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media, and each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means; and

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means, wherein;

said transfer control means of each of the ports comprises monitor means for comparing the quantity of the connectionless type information stored in said second buffer means with first and second threshold values where the second threshold value is greater than the first threshold value, and

said routing means comprises means for executing a regulated routing control in which the connectionless type information is inhibited from being transferred to one of the ports in which the second buffer means stores the connectionless type information having a quantity grater than said second threshold value and for canceling said regulated routing control when the quantity of the connectionless type information has become smaller than said first threshold value.

9. A switching node as claimed in claim 8, wherein:

said routing means comprises register means for storing flag information showing comparison results obtained by said monitor means respectively provided in the ports; and

said switching node comprises a plurality of buses connecting said monitor means respectively provided in the ports and said register means to each other.

10. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media, and

each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means; and

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means, wherein;

said transfer control means of each of the ports comprises monitor means for comparing the quantity of the connection-less type information stored in said second buffer means with first and second threshold values where the second threshold value is greater than the first threshold value, and

said call control means comprises means for inhibiting said call control means for executing a call process when the quantity of the connectionless type information stored in the second buffer means is greater than said second threshold value and for canceling inhibition of said call process when the quantity of the connectionless type information has become smaller than said first threshold value.

11. A switching node as claimed in claim 10, wherein:

said call control means comprises register means for storing flag information showing comparison results obtained by said monitor means respectively provided in the ports; and

said switching node comprises a plurality of buses connecting said monitor means respectively provided in the ports and said register means to each other.

12. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media, and

each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means; and

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means, wherein;

said transfer control means of each of the ports comprises monitor means for comparing the quantity of the connectionless type information stored in said second buffer means with first and second threshold values where the second threshold value is greater than the first threshold value,

said routing means comprises means for executing a regulated routing control in which the connectionless type information is inhibited from being transferred to one of the ports in which the second buffer means stores the connectionless type information having a quantity greater than said second threshold value and for canceling said regulated routing control when the quantity of the connectionless type information has become smaller than said first threshold value, and

said call control means comprises means for inhibiting said call control means from executing a call process when the quantity of the connectionless type information stored in the second buffer means is greater than said second threshold value and for canceling inhibition of said call process when the quantity of the connectionless type information has become smaller than said first threshold value.

13. A switching node as claimed in claim 12, wherein:

said routing means comprises first register means for storing flag information showing comparison results obtained by said monitor means respectively provided in the ports;

said call control means comprises second register means for storing the flag information showing comparison results obtained by said monitor means respectively provided in the ports; and

said switching node comprises a plurality of buses connecting said monitor means respectively provided in the ports and said first register means connected to said second register means.

14. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media,

each of said ports comprises;

first buffer means, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means;

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either of the connection-oriented type information in said first buffer means for the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means;

input regulation buffer means, coupled to said switch means and said one of the transmission media, for storing information transferred via one of the transmission media; and

monitor means, coupled to said second buffer means, for detecting a predetermined storage status in which a transfer congestion is about to take plate in said one of the transmission media, and

said routing means comprise regulation control means, coupled to said input regulation buffer means and said monitor means, for controlling said input regulation buffer means so that cells relating to said traffic congestion are inhibited from being input to said switch means.

15. A switching node as claimed in claim 14, wherein each of said ports comprises feedback means for feeding back the cells related to said traffic congestion to said input regulation buffer means.

16. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network wherein;

each of the output logical communication paths is formed on one of the transmission media,

each of said ports comprises;

first buffer mean, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means;

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either of the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means;

input regulation buffer means, coupled to said switch means and said one of the transmission media, for storing information transferred via one of the transmission media; and

monitor means, coupled to said second buffer means, for detecting a predetermined storage status in which a traffic congestion is about to take place in said one for the transmission media, and

said routing means comprises regulation control means, coupled to said input regulation buffer means and said monitor means, for controlling said input regulation buffer means so that cells relating to said traffic congestion are inhibited from being input to said switch means, wherein;

said regulation control means comprises table means for storing regulating routing address information for each of the transmission media, and

said regulation control means comprises means for controlling, by referring to said table means, said input regulation buffer means so that cells relating to the regulated routing address information concerning said one of the transmission media in which said traffic congestion is about to take place are inhibited from being input to said switch means.

17. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network wherein;

each of the output logical communication paths is formed on one of the transmission media,

each of said ports comprises;

first buffer mean, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means;

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either of the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means;

input regulation buffer means, coupled to said switch means and said one of the transmission media, for storing information transferred via one of the transmission media; and

monitor means coupled to said second buffer means, for detecting a predetermined storage status in which a traffic congestion is about to take place in said one for the transmission media, and

said routing means comprises regulation control means, coupled to said input regulation buffer means and said monitor means, for controlling said input regulation buffer means so that cells relating to said traffic congestion are inhibited from being input to said switch means, wherein;

each of said ports comprises decision means, coupled to said input regulation buffer means, for allowing cells which are the connectionless type information and which do not relate to said cell congestion to be input to said switch means from said input regulation buffer means.

18. A switching node is a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information, and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media,

each of said ports comprises;

first buffer mean, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means;

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either of the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means;

input regulation buffer means, coupled to said switch means and said one of the transmission media, for storing information transferred via one of the transmission media; and

monitor means, coupled to said second buffer means, for detecting a predetermined storage status in which a traffic congestion is about to take place in said one for the transmission media, and

said routing means comprises regulation control means, coupled to said input regulation buffer means and said monitor means, for controlling said input regulation buffer means so that cells relating to said traffic congestion are inhibited from being input to said switch means, wherein

each of said ports further comprises feedback means for feeding back the cells relating to said traffic congestion to said input regulation buffer means, wherein

said feedback means of each of said ports comprises conversion means for converting the message identifier information contained in each of the cells to be fed back into new message identifier information in order to distinguish the cells fed back from cells applied to said switch means.

19. A switching node in a label multiplexing type switching network, comprising:

switch means for selectively coupling input logical communication paths and output logical communication paths with each other, m permanent logical communication paths being included in said input logical communication paths where m is an integer larger than or equal to 1, n permanent logical communication paths being included in said output logical communication paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communication paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communication paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of them permanent logical communication paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communication paths via the switch means on the basis of routing address information related to the connectionless type information; and

a plurality of ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network, wherein;

each of the output logical communication paths is formed on one of the transmission media,

each of said ports comprises;

first buffer mean, coupled to said switch means and said one of the transmission media, for storing the connection-oriented type information from said switch means;

second buffer means, coupled to said switch means and said one of the transmission media, for storing the connectionless type information from said switch means;

transfer control means, coupled to said first and second buffer means and said one of the transmission media, for transferring either of the connection-oriented type information in said first buffer means or the connectionless type information in said second buffer means on the basis of a quantity of information stored in at least one of said first and second buffer means;

input regulation buffer means, coupled to said switch means and said one of the transmission media, for storing information transferred via one of the transmission media; and

monitor means, coupled to said second buffer means, for detecting a predetermined storage status in which a traffic congestion is about to take place in said one for the transmission media, and

said routing means comprises regulation control means, coupled to said input regulation buffer means and said monitor means, for controlling said input regulation buffer means so that cells relating to said traffic congestion are inhibited from being input to said switch means, wherein

each of said ports comprises means, coupled to said second buffer means, for turning ON a congestion notification bit contained, as a reservice bit, in the connectionless type information read from said second buffer means when said input regulation buffer means is about to overflow.

20. A switching node as claimed in claim 19, wherein each of said ports comprises:

check means for detecting a state where the congestion notification bit contained in each cell received is ON; and

means, coupled to said check means and said second buffer means, for stopping outputting the connectionless type information in said second buffer means to one of the transmission media.

21. A switching node in a label multiplexing type switching network, said switching node comprising:

switch means for selectively coupling input logical communications paths and output logical communications paths with each other, m permanent logical communications paths being included in said input logical communications paths where m is an integer larger than or equal to 1, n permanent logical communications paths being included in said output logical communications paths where n is an integer larger than or equal to 1;

call control means, coupled to said switching means, for receiving connection-oriented type information through any of the input logical communications paths and for controlling said switch means so that the connection-oriented type information are selectively transferred to said output logical communications paths via the switch means on the basis of routing address information related to the connection-oriented type information;

routing means, coupled to said switch means, for receiving connectionless type information through any of the m permanent logical communications paths and for controlling said switch means so that the connectionless type information are selectively transferred to the n permanent logical communications paths via the switch means on the basis of routing address information related to the connectionless type information; and

ports which connect said switch means to a plurality of transmission media provided in the label multiplexing type switching network,

each of the output logical communications paths being formed on one of the transmission media, and

wherein said routing means comprises control means for monitoring traffic of each of the transmission media and for selecting one of the transmission media on the basis of the traffic of each of the transmission media,

the connectionless type information being transferred to one of the n logical communications paths formed on said one of the transmission media selected by said control means.