Configure LLC2 directory

Configuring idle time value

Configuring the time value of waiting for acknowledgement

Configuring busy time value of remote end

Configuring time value of Response

Configuring the time of reject

Configuring the redial times

Configuring the size of window for resend

Configuring the size of accumulated data packet

Setting the acknowledgement time-delay

Setting the maximum numbers of acknowledgement

Showing LLC2 link information

Debugging LLC2 link information

Example of LLC2 Configuration

 

LLC2 (logic link control, class 2) protocol is a network protocol providing connection acknowledgement and it is widely applied to the local area network (LAN), especially to the network connection of token ring of IBM communication system. Currently LLC2 only supports the connection on the Ethernet.

The function provided by the command “LLC2” is to support the implementation of DLSW (Data Link Switch) protocol. The detail of DLSW can be referred to the related documents.

Configuring idle time value

The command is used for controlling the frequency of query at the idle time (no data exchanged) 

The command “no” can be used for restoring to the default value.

llc2 idle-time seconds

no llc2 idle-time

Seconds   The interval seconds of sending RR frame at the idle time. The maximum is 60 seconds, the minimum is 1 second, and the default is 10 seconds.

Configuration mode: Interface Configuration

Notes: At idle time, no I (information) frame is exchanged and RR (receive ready) frame is sent to the remote end periodically to tell the remote end that the local end is ready to receive data. The relative small value should be set for ensuring the prompt advice to the remote end. If the value is set too small, too many RR frames is likely to be sent on the network.

Example: Setting RR frame sent every 12 seconds 

int ethernet1/1

llc2 idle-time 12

 

Configuring the time value of waiting for acknowledgement

The command is used for controlling the waiting time of expecting remote acknowledgement. The command “no” can be used for restoring to the default value.

llc2 t1-time seconds

no llc2 t1-time

Seconds  The seconds of waiting for remote acknowledgement. The maximum is 60 seconds, the minimum is 1 second and the default is 1 second.

Configuration mode: Interface configuration

Notes: When the local end sends I frame, it will wait for remote acknowledgement. If no acknowledgement is received within a given time, the I-frame will be resent. The relative big value should be set on the network where the data is transmitted at a slow rate.

Example         Setting 12 seconds as the time value of waiting for acknowledgement.

int ethernet1/1

llc2 t1-time 12

 

Configuring busy time value of remote end

The command is used for controlling the waiting time when the remote end is busy. The command “no” can be used for restoring to the default value.

llc2 tbusy-time seconds

no llc2 tbusy-time

Seconds  The waiting seconds when the remote end is busy. The maximum is 60 seconds, the minimum is 1 second and the default is 10 seconds.

Configuration mode: Interface configuration

Notes: a LLC2 connective end is able to inform the opposite end that local end is busy and prevent the opposite end from sending data to local end by sending a RNR (receive not ready) The relative big value can be set for averting the timeout.

Example: Setting 12 seconds as the busy time value of remote end.

int ethernet1/1

llc2 tbusy-time 12

 

Configuring time value of Response

The command is used for controlling the time of waiting for the response of remote end. The command “no” can be used for restoring to the default value.

llc2 tpf-time seconds

no llc2 tpf-time

Seconds  The seconds of waiting for the response of remote end. The maximum is 60 seconds, the minimum is 1 second, and the default is 1 second.

Configuration Mode: Interface Configuration

Notes: A LLC2 connective end sometimes needs to know the status of opposite end. For this purpose, a command frame that requires a response from the opposite end needs to be sent. When the opposite end receives the command frame, it will reply a response frame. If the error occurs in the process, the send end will keep waiting. In order to avoid the situation, a clock needs to be enabled. When the arrival time is hit, the clock will think that the error occurs and it will send a separate command frame. The command is used for setting the time of waiting for the response of the opposite end to the command frame.

Example: Setting 12 seconds as the time of waiting for the response of the opposite end.

int ethernet1/1

llc2 tpf-time 12

 

Configuring the time of reject

The command is used for controlling the time of waiting for the response of remote end to the reject frame. The command “no” can be used for restoring to the default value.

llc2 trej-time seconds

no llc2 trej-time

Seconds  The seconds of waiting when the remote end is busy. The maximum is 60 seconds, the minimum is 1 second and the default is 3 seconds.

Configuration mode: Interface configuration

Notes: The data receive and send on the two ends of LLC2 link is carried out on the set sequence. When a LLC2 connective end receives I frame of opposite end whose sequence number is not the expected one, it will send a REJ (reject) frame and enable a clock. If no response is made at the arrival time, LLC2 link will be disconnected. The command is used for setting the time of waiting for the response of the opposite end to the REJ (reject) frame. 

Example: Setting 12 seconds as the waiting time.

int ethernet1/1

llc2 trej-time 12

 

Configuring the redial times

The command is used for controlling the times of re-sending the frame. The command “no” can be used for restoring to the default value.        

llc2 n2 retry-count

no llc2 n2

retry-count  The times of resending frame. The maximum is 255, the minimum is 1 and the default is 8.

Configuration mode: Interface configuration

Notes: When one end of LLC2 sends the data to the opposite end, it will wait for the acknowledgement of the opposite end. If the opposite end does not send the acknowledgement within a given time, the local end will resend the data. But the time of resend shall be limited. When the value of resend times exceeds retry-count, LLC2 will be disconnected. The command is used for setting the times of retry-count.

Example: Setting the times of re-send as 12 

int ethernet1/1

llc2 n2 12

 

Configuring the size of window for resend

The command is used for controlling the maximum size of I frame send (namely the size of window for resend) when I frame is not confirmed. The command “no” can be used for restoring to the default value.

llc2 local-window packet-count

no llc2 local-window

packet-count  The maximum size of I frame send. The maximum is 127, the minimum is 1 and the default is 7.

Configuration mode: Interface configuration

Notes: When one end of LLC2 link sends data to the opposite end, it can only send a certain amount of data before waiting for the acknowledgement of the opposite end. The command is used for setting the maximum value. When the set value is too big, it may lead to the loss of data because the opposite end is not able to receive all the data.

Example: Setting the size of send window as 12.

int ethernet1/1

llc2 local-window 12

 

Configuring the size of accumulated data packet

The command is used for controlling the maximum local accumulated size of data packet when I frame (the remote end is busy) cannot be sent. The command “no” can be used for restoring to the default value.

llc2 holdqueue packet-count

no llc2 holdqueue

packet-count  The maximum size of data packets reserved by I frame when I frame is not confirmed.

Configuration mode: Interface configuration

Notes: When the opposite end is busy, one end of LLC2 link is not able to send data (I frame). All the data shall be reserved before the busyness of the opposite end is cleared. But the reserved amount is limited. The command is used for setting the data amount to be reserved.

Example: Setting maximum data amount to be reserved as 120.

int ethernet1/1

llc2 holdqueue 120

 

Setting the acknowledgement time-delay

When an I-frame (information frame) is received, an acknowledgement frame shall be sent immediately. In order to reduce the unnecessary acknowledgement, the acknowledgement can be delayed. If information frame is sent, an information frame will be sent as an acknowledgement instead of acknowledge frame. When the information frame sent by the opposite end exceeds the acknowledged maximum size, an acknowledge frame will be sent immediately rather than at the timeout. The command below can be used for setting the value.

       llc2 ack-delay-time seconds

 

Setting the maximum numbers of acknowledgement

When the information frame sent by the opposite end exceeds the maximum number of acknowledgement in the process of acknowledging the time delay, the acknowledgement frame shall be sent immediately for clearing the network timeout perceived by the opposite end. The command below can be used for setting the value.

       llc2 ack-max number

 

Showing LLC2 link information

The command is used for showing the related information of LLC2 link connection

show llc interface [type number]

type          Interface type

         number         Interface number

Configuration Mode: Interface, configuration and global

Notes: Showing the related information of LLC2 link connection. Under interface mode, the command “show llc” is used for displaying LLC2 link information of the interface.

Example: Under interface mode, the command “show llc” is used for showing llc2 information on ethernet1/1.

int ethernet1/1

sho llc ethernet1/1

Debugging LLC2 link information

The command is used for opening LLC2 debug switch

debug llc2 [packet][error][state]

Configuration mode: Management Mode

Notes: packetOpening the debug switch of LLC2 link status information

Example, opening the debug switch of LLC2 link.

debug llc2 packet

debug llc2 state

debug llc2 error

 

Example of LLC2 Configuration

The number of LLC2 frame received before the response can be configured. For example, it is supposed that two information frames are received at the time 0 rather than at the maximum number 3, the responses of these frames are not sent. If the third frame that makes the router response is not received within 800 ms, the response will be transmitted as the time-delay timer is activated.

interface interface e1/1
  llc2 ack-max 3
  llc2 ack-delay-time 800

In this connection, as it is told that all the frames are received, the counter that calculates the maximum number of information frame is reset as 0.