JPH10257070A - Method and device for relaying packet made into cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for relaying an original packet without assembling it by encapsulating an intermediate protocol without assembling a packet by adding a new cell before the leading cell of an original cell string and putting the header of the intermediate protocol in the payload of the new cell. SOLUTION: When the original cell string 11 is received, the leading cell is detected by a leading cell detection part 15 and the payload information of the cell is reported to a high-order layer header analysis part 16. Relating to the high-order layer header analysis part 16, the processing of an IP layer is performed by using IP header information included in the payload and then, the identifier VCI of set ATM connection is decided. Relating to a new leading cell generation part 17 which receives VCI information and the connectionless server, the header information of the intermediate protocol is generated and the new leading cell is constituted. The cell is inserted before the leading cell and the VCI value of an input cell is rewritten by a VCI conversion part 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ATM (Asynchronous Transfer Mode), and more particularly to an SMDS (Switched Mode).
Multimegabit Data Service
e) CLNAP (Connection L
ess Network Access Protocol
ol) using an intermediate protocol such as IP (Int
ATM over a wide area (public) network that relays connectionless packets in an internetwork layer, such as the Internet Protocol (Ethernet Protocol).
-When interconnecting ATM networks that do not require an intermediate protocol such as a LAN (Local Area Network), the present invention relates to a method of relaying cellularized packets in an interconnecting device (IP router) for connecting ATM networks. Things.

[0002]

2. Description of the Related Art There are the following two conventional cell packet relay systems.

[0003] From the ATM-LAN side, IALs formed into cells by AAL (ATM adaptation layer) type 5
When a P packet is received, an original IP packet is once assembled, IP relay processing is performed based on the header information of the packet, and an AAL type 5 is again transmitted using an ATM connection determined as a result and sent to the next router. To transmit the IP packet decomposed into cells. [Method 1]

[0004] Alternatively, upon receiving the first cell of an IP packet cellized by AAL type 5, the header information of the IP packet in the payload of the cell is extracted and IP relay processing is performed. The ATM cell is transmitted using the ATM connection to be sent to the router, and the ATM connection is simultaneously stored for the subsequent cell. Subsequent cells transmit the stored connection without performing the IP relay process. [Method 2]

[0005]

As described above, according to the conventional cell packet relaying method [method 1], an original packet is once assembled, IP relay processing is performed, and the packet is further decomposed into an original cell string. Therefore, a delay occurs in the packet assembling / disassembling process.

[0006] On the other hand, according to the above-described cellized packet relay method [method 2], IP relay processing is performed only with the information in the payload of the first cell without assembling the packet, and the cell is originally cellized. Since the packet is relayed as it is in the form of a cell string, the above-mentioned problem of delay for assembling / disassembling processing is solved.

[0007] However, the above-described cell packetized packet relaying method [method 2] uses an intermediate protocol to access an original IP packet when one of the ATM networks requires an intermediate protocol to access the network. However, there is a problem that the method cannot be applied because a process of encapsulating in a payload is required.

The present invention provides a method for relaying a cellularized packet,
It is an object of the present invention to provide a method and an apparatus for relaying an ATM packet without assembling it into an original packet even when an ATM network requires an intermediate protocol for accessing the network.

[0009]

In order to solve the above-mentioned problem, in the method of relaying a cellularized packet according to the present invention, a new cell is added before the head cell of the original AAL type 5 cell string. By inserting the header of the intermediate protocol into the payload of the new cell, encapsulation to the intermediate protocol can be performed without assembling the packet.

In the second network, if there is an apparatus for processing an intermediate protocol, the trailer information existing in the last cell of the original cell row is rewritten,
A new AAL type 5 behind the last cell in the cell row
The new AAL type 5 payload is encapsulated in a new AAL type 5 payload by adding a new last cell having the trailer information of (1), and removing the last cell indication bit in the cell header of the original last cell.

[0011] In the method for relaying a cellularized packet according to the present invention,
By adding a new cell before the first cell when relaying the original AAL type 5 cell string, it is possible to include the header information of the intermediate protocol used in the destination network in the payload of the new cell. become.

Further, the trailer information contained in the last cell of the original cell row is rewritten, or information indicating the last cell is removed from the header of the last cell, and a new last cell is added instead, and the payload is added. Including the new AAL type 5 trailer information in the network allows the destination network to handle the new AAL type 5 cell string by a standard procedure.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a network model diagram for explaining the present embodiment, FIG. 2 is a diagram for explaining a cell sequence before a relay process, and FIG. 3 is a diagram for explaining a cell sequence after a relay process. FIG. 4 is a functional block diagram of the interconnection device according to the present embodiment.

In FIG. 1, the network is an ATM wide area network (1A), and two ATM-LANs (1B, 1C),
Interconnection device for connecting networks (2A, 2B)
It is composed of

In the ATM wide area network (1A), ATM-LA
An internetwork layer connectionless packet (typically an IP packet) received from the N side
It is assumed that the data is transferred to the exit of the ATM wide area network using another connectionless network protocol (intermediate protocol) to transfer the data in the TM wide area network (1A). This intermediate protocol is positioned as a so-called subnet access protocol. In particular, when the physical network is an ATM, a protocol such as CLNAP is known. The relay devices (3A, 3B) in the ATM wide area network (1A) perform relay processing according to such a subnet access protocol, and are called connectionless servers.

On the other hand, in an ATM-LAN (1B, 1C), an IP packet generated at a terminal is directly converted into a cell by AAL type 5 and transferred without having the above-described subnet access protocol. Here, RFC1
It is assumed that an IP packet encapsulation method according to H.483 is used.

In the following, the transmitting terminal (4A) in FIG.
The operation of the interconnection apparatus that implements the method for relaying a cellularized packet according to the present invention will be described, taking as an example a case where an IP packet is transferred from a terminal to a receiving terminal (4B).

(First Embodiment) FIG. 2 shows a cell string received by the interconnection device (2A) before the relay processing.

In the transmitting terminal (4A), the receiving terminal (4B)
When the data (5) to the destination is generated, an IP header (6) including the IP address of the receiving terminal is added to the head of the data, and
Construct a P packet. Next, an IP router (interconnecting device (2A) in this embodiment) to be transmitted next to transfer to the receiving terminal (4B) is determined according to the IP routing process.

Next, AAL type 5 CPCS trailer information (7) is added after the IP packet, and the CPCS
-Construct the PDU. This trailer includes information such as a payload length and an error correction code of the payload portion.

Next, the CPCS-PDU is divided for every 48 bytes, which is the payload length of the ATM cell, and a cell header (8) is added to each of them to form an ATM cell (9). Here, ATM-LAN (1B) is included in each cell header.
Of the ATM connection (VCI) set with the interconnection device (2A) which is the destination of the ATM connection.
Further, with respect to a cell string generated from one CPCS-PDU, information indicating that the cell is the last cell is added to the header of the last cell (9D) (10).

A cell sequence generated from one CPCS-PDU is transmitted in order from the first cell (9A). Note that the IP header of the original IP packet is included in the payload of the first cell.

Next, the operation of the interconnection device (2A) for receiving the cell sequence from the transmitting terminal will be described.

FIG. 4 is a processing functional block diagram of the interconnection apparatus for realizing the cell assembling / disassembling method according to the present invention.

When the original cell sequence (11) in FIG. 3 is received, the head cell detector (15) detects the head cell (9A).
And notifies the payload information of the cell to the upper layer header analysis unit (16). In the upper layer header analysis unit, the IP of the original IP packet contained in the payload is
The IP layer is processed using the header information, and an ATM connection identifier (VCI) set between the connectionless server (3A) to be transmitted next and the connectionless server is determined. This connectionless server and the new head cell generation unit (1
In 7), header information (12) of an intermediate protocol used in the ATM wide area network (1A) is generated, and a new head cell (13) is formed together with the cell header including the VCI value.
This new head cell is inserted in the cell insertion part (18) before the head cell in the original cell row and passed to the VCI conversion part (19). The VCI conversion unit rewrites the VCI value of the input cell using the VCI value separately specified by the new head cell generation unit. The intermediate cells (9B, 9C) in the original cell row are not subjected to any processing in the head cell detecting section, but are rewritten and transmitted in the VCI converting section in the VCI converting section.

When the last cell (9D) in the original cell row is input, it is detected by the first cell detector and instructs the VCI converter to reset the VCI value after the processing of the cell is completed.

By the above operation, the original cell row (11) input to the processing block is output as a new cell row (14) with a new head cell added thereto, as shown in FIG. The VCI value of each cell in this new cell row is V
All are rewritten to the same VCI value by the CI conversion unit. Also, ATM is added to the payload of the new top cell.
Note that header information of an intermediate protocol used in the wide area network (1A) is included.

Thereafter, the new cell sequence output from the interconnection device (2A) is transmitted by the connectionless server (3) by the connectionless server (3) in the ATM wide area network based on the routing information in the header of the intermediate protocol contained in the new head cell. Is transferred to the interconnection device (2B) on the receiving side.

When receiving the above-mentioned new cell string, the interconnection device on the receiving side removes the new head cell from the new cell string, and removes the IP header included in the head cell (9A) in the original cell string. The ATM-LAN (1
In C), an ATM connection to the receiving terminal (4B) is determined, and the original cell string is transmitted.

(Second Embodiment) In the first embodiment, the last cell in the new cell row (14) is the same as the last cell (9D) in the original cell row. Therefore, the information in the CPCS trailer information (7) included in the last cell is for the original cell row.

When each connectionless server (3) in the ATM wide area network uses the CPCS trailer information, it is necessary to set correct trailer information for a new cell row.

In the second embodiment of the present invention, in order to solve the above-mentioned problem, when the last cell is detected by the head cell detector in the processing block diagram of FIG. 4, the VCI information is simply reset. And rewrite the CPCS trailer information in the last cell.

(Third Embodiment) In the second embodiment described above, the CPCS trailer information rewritten in the interconnecting device (2A) on the transmitting side to the one for the new cell sequence is transmitted to the interconnecting device on the receiving side. When returning to the original cell column in (2B), it is necessary to rewrite again.

In the third embodiment of the present invention, in order to solve this problem, a new final cell is added after the original cell row without rewriting the CPCS trailer information in the final cell, and the new final cell is added. The payload of the cell includes CPCS trailer information corresponding to the new cell sequence. In this case, information indicating that the cell is the last cell is removed from the cell header (10) indicating the last cell of the last cell (9D) of the original cell row, and the cell header of the newly added new last cell is added to the cell header. Information indicating that the cell is the last cell is added.

The operation in the interconnection device (2B) on the terminating side with the new cell train configured as described above is as follows.
It is as follows.

The first cell and the last cell are removed from the received new cell string, and information indicating that the cell is the last cell is added to the cell header of the cell immediately before the last cell. This makes it possible to reconstruct the original cell column.

[0037]

As described above, according to the present invention, the IP processing is performed only with the information in the payload of the head cell,
It is possible to prevent an increase in delay in relay processing, and to easily add information necessary for transfer in one network like an intermediate protocol.

[Brief description of the drawings]

FIG. 1 is a network model diagram for explaining the present embodiment.

FIG. 2 is a diagram illustrating a cell row before a relay process.

FIG. 3 is a diagram illustrating a cell row after a relay process.

FIG. 4 is a processing function block diagram of the interconnection device in the present embodiment.

[Explanation of symbols]

 1A ATM wide area network 1B, 1C ATM-LAN 2 Interconnection device 3 Connectionless server 4 Terminal 5 Data 6 IP header 7 CPCS trailer 8 Cell header 9 ATM cell 10 Cell header indicating last cell 11 Original cell string 12 Intermediate protocol header 13 New Head cell 14 New cell row 15 Head cell detection unit 16 Upper layer header analysis unit 17 New head cell generation unit 18 Cell insertion unit 19 VCI conversion unit

Claims (4)

[Claims] A connection between physical networks using an ATM, and a connectionless connection of an internetwork layer.
In order to relay a packet, a connectionless packet of the internetwork layer formed into cells by AAL type 5 is received from the first network, and the packet is relayed at the internetwork layer. In a method of relaying cellularized packets to be re-cellularized according to AAL type 5 and transmitted to a second network, the second network needs to be encapsulated in an intermediate protocol in order to transfer connectionless packets of the internetwork layer. Transmitting a new cell including the header information of the intermediate protocol in the second network generated based on the header information of the packet included in the head cell of the received cell sequence, before the head cell, The subsequent cell is the same as the new cell A cell which performs protocol processing of an internetwork layer without assembling the packet and performs encapsulation to an intermediate protocol used in a second network. How to relay encrypted packets. 2. A signal included in the last cell of the received cell sequence
By rewriting the AL type 5 trailer information,
AAL type 5 by adding the new top cell
2. The method according to claim 1, wherein the validity of the payload information is maintained. 3. A new last cell having new AAL type 5 trailer information is added after the last cell of the received cell string, and a last cell indication bit in a cell header of the original last cell is removed. The original AAL
2. The method according to claim 1, wherein the entire type 5 protocol data unit is encapsulated in a new AAL type 5 protocol data unit payload and transmitted. 4. A connection between physical networks using an ATM and a connectionless connection of an internetwork layer.
In order to relay a packet, a connectionless packet of the internetwork layer formed into cells by AAL type 5 is received from the first network, and the packet is relayed at the internetwork layer. In a repeater for cellularized packets to be re-cellularized according to AAL type 5 and transmitted to the second network, the second network must be encapsulated in an intermediate protocol in order to transfer the internetwork layer connectionless packets. The relay device comprises: a head cell detection unit (15) for detecting a head cell from a received cell sequence and notifying payload information of the cell to an upper layer header analysis unit (16); The analysis unit (16) transmits the next connection to be transmitted. A new head cell generator (17) for determining an ATM connection identifier (VCI) and intermediate protocol information set for the address server, and generating a new head cell based on the identifier and the intermediate protocol information. A VCI conversion unit (19) for converting a VCI value of another cell into a VCI value of the first cell; A cell packet relay device, characterized in that a new head cell is added and relayed without assembling / disassembling a cell string.