JPH03263952A - Terminal adaptor - Google Patents

Abstract

PURPOSE:To simplify the processing of a data link layer and to save the hardware for realization by allowing a terminal adaptor to apply its station busy notice independently when an information frame is received from a network so as to prevent link interrupt due to timeout. CONSTITUTION:When a frame processing section 6-1 detects an I frame, a frame processing section 6-1 sends information required for frame generation to a busy notice processing section 7 and starts frame generation. The busy notice processing section 7 uses an inserter 8 at the completion of a frame to send a busy notice frame to a network. Then a busy notice is returned by the operation similar to above for busy monitor at the network. The speed matching is taken for the received I frame at a speed conversion section 9 and the result is sent to a terminal equipment. When the confirmation of reply from the terminal equipment receiving the I frame is detected by a frame processing section 6-2, the busy state is relieved and the reply confirmation is sent to the network. Thus, the network recognizes busy release and the operation restores the normal processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data link layer protocol processing method in a terminal adapter used when connecting a CCIT TV series recommended version terminal to a digital line.

[Conventional technology]

Conventionally, methods for connecting V series terminals to digital networks have been studied by CCITT, and Recommendation V, 11
It is standardized as 0, V, 120. Here, it is considered that the data link layer protocol is once terminated at the terminal adapter and then connected.

[Problem to be solved by the invention]

In the above conventional technology, even if the data link layer protocol is the same on the network side and the terminal side, it is necessary to terminate to the data link layer once to absorb the speed difference in the physical layer, which complicates the processing of the terminal adapter. There was a problem.

The present invention aims at simplifying data link layer processing in a terminal adapter.

[Means to solve the problem]

To achieve the above purpose, data link processing in the terminal adapter is deleted. However, if you simply delete it, the data link may not be maintained due to the retransmission monitoring timer timing out, so when an information frame is received from the network, the terminal adapter independently sends a busy notification to its own station to prevent link disconnection due to timeout. It is.

[Effect]

When the terminal adapter receives an information frame from the network, it converts the speed and sends the frame to the terminal, while notifying the network that its own station is busy. This prevents the network from going into a link-disconnected state due to timeout. The network side continues to send busy notifications until a response is received from the terminal, and when the response is returned to the network, it is considered that the busy state has been released.

This allows the terminal adapter to connect the network and the terminal without terminating the data link layer.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. First, the configuration will be shown. In the figure, 1 is the terminal adapter for connecting the V series terminal to the digital line, 2 is the line from the network side and is the S/T reference point, 3 is the line to the terminal and is the R reference point, and 4 is the network side layer 1 processing unit; 5 is a terminal side layer 1 processing unit; 6-1 is a frame processing unit that identifies layer 2 frames from the network side and performs necessary processing; 6-2 identifies layer 2 frames from the terminal 7 is a busy notification creation unit that creates a busy notification to be sent to the network side when the frame processing unit 6-1 notifies that it has received an l frame; 8 is a busy notification creation unit that performs necessary processing; An inserter 9 inserts the frame created in the line data into the line data, and a speed converter 9 absorbs the speed difference between the line and the terminal.

Next, the operation of this embodiment will be explained. Figure 2 shows the operating sequence. In this example, LAPB is used as the data link protocol for both DCE and DTE, but it is assumed that the retransmission monitoring timer value T1 is different due to the difference in line speed. When a call arrives at a terminal, a SABM frame is transmitted from the DCE. The terminal adapter 1 receives the frame at the network side layer 1 processing unit 4, performs predetermined layer 1 processing, and then passes the frame to the frame processing unit 6-1. The frame processing section 6-1 analyzes the header and after confirming that it is not an 1 frame, sends it to the speed conversion section 9. Here, the frame is converted to the terminal speed and transmitted to the terminal side via the terminal side layer 1 processing section 5. A terminal that receives the SABM returns a UAL frame. This goes through the reverse route above and then is passed to the DCE.

During this time, a T1 timeout may occur on the network side depending on the speed difference, but in this example, it is assumed that the terminal's UA returns within the maximum number of retransmissions N2. Actually, since the S frame has no information field and is short, timeouts hardly occur. A data link is established through the above operation, and thereafter, 1 frame is transmitted and received. An l frame can be as many as 4 bytes, and if speed conversion is simply performed, T1 timeouts will occur N2 or more times, and the link may not be maintained. In this embodiment, the frame processing unit 6-1
When a frame is detected, the frame processing unit 6-1 transmits information necessary for frame creation to the busy notification creation unit 7 and activates frame creation.

When the frame is completed, the busy notification creation unit 7 uses the inserter 8 to transmit the busy notification frame to the network side.

Thereafter, a busy notification is returned to the network side busy monitor in the same manner as above. During this time, the received e-frames are speed-matched by the speed converter 9 and then sent to the terminal. l
When the frame processing unit 6-2 detects a response confirmation from the terminal that received the frame, it releases the busy state and transmits the response confirmation to the network.

As a result, the network also recognizes the release from busy and returns to normal processing. When receiving l frames, the above operation is performed for each l frame. The net side is l for the outstanding number (K)
Although frames may be transmitted continuously, a busy message is returned every time one frame is received, so the device essentially operates with an outstanding number of 1. The network maintains the link for terminals that return a busy notification within a certain period of time in response to the network's busy monitoring, and waits for the terminal to be released from the busy state.
Processing can continue normally even if a waiting time occurs due to speed matching.

At the end of a call, there is a sequence of sending a DISC frame and responding to a UA frame, which is similar to the SAB mentioned earlier.
The process is similar to M/UA.

According to this embodiment, in the terminal adapter, network/
It becomes possible to connect the network and the terminal without performing layer 2 termination for the terminal. This reduces the processing load and facilitates the configuration of the terminal adapter.

〔Effect of the invention〕

According to the present invention, processing of the data link layer in the terminal adapter can be simplified, which has the effect of reducing the amount of hardware required for implementation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a terminal adapter according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of an operation sequence. 1-m-terminal adapter, 2-m-line (network side),
3-m-line (terminal side), 4--network side layer 1 processing section, 5-m-one terminal side layer 1 processing section, 6-1---frame processing section, 6-2-m-frame processing part, 7--busy notification creation part, 8-m-inserter, 9--one speed conversion part

Claims (1)

[Claims] 1. In a terminal adapter that is located between a communication network and a communication terminal and enables communication between the two, when an I frame from the network is detected, it returns a busy notification frame to the network and also sends an I frame to the terminal. means for transmitting, and means for returning a busy notification frame to the network when a busy monitoring frame is detected from the network;
means for relaying frames received from the network to the terminal when a frame other than an I frame or a busy monitoring frame from the network is detected; and means for relaying all frames from the terminal to the network. A terminal adapter characterized by: