The state machine at the transmitter can be in one of the following five states:. If this is not the case, then the other members with sequence numbers between the newly deleted member and the highest sequence number are renumbered. As long as no return bandwidth is available, the transmitter uses the last received valid status. The following is a typical sequence for adding a member to the group. The LCAS mechanism can also automatically decrease the capacity if a member in a VCG experiences a failure in the network, and increase the capacity when the fault is repaired.
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If this is not the case, then the other members with sequence numbers between the newly deleted member and the highest sequence number are renumbered. Wdh a frame boundary, the source includes the VC in the byte interleaving and sets the control command to F EOSindicating that this VC is in use and it is shd last in the sequence.
The transmitter and the receiver communicate using control packets to ensure smooth transition from one state to another. This member is provisioned to participate in the VCG and has a failed path to the receiver. Indicate that this member is normal part of the group and does not have the highest sequence number. Virtual concatenation uses 4 of the 16 bytes for its MFI and sequence numbers. In the descriptions below, we use the term member to denote a VC.
Status messages are continuously exchanged and consequent actions taken. Each word is associated with a specific member i. Although autonomous addition after a failure is repaired is hitless, removal of a member due to path layer failures is not hitless. The incoming signal for this member experiences no failure condition. Multiple members can be added simultaneously for fast resizing.
This capability is particularly useful in environments where dynamic adjustment of capacity is important. Or, the receiver has received and acknowledged a request for addition of this member.
The LCAS mechanism can also automatically decrease the capacity if a member in a VCG experiences a failure in the network, and increase the capacity when the fault is repaired. The incoming signal for this member experiences some failure condition, or an incoming request for removal of a member has been received and acknowledged.
This member is not provisioned to participate in the VCG. As long as no return bandwidth is available, the transmitter uses the last received valid status. This member is in the process of being added to the Ij. Although SONET and SDH were originally designed to transport voice traffic, advent of these new mechanisms has made it perfectly suitable for carrying more dynamic and bursty data traffic.
LCAS is resident in the H4 byte of the path overhead, the same byte as virtual concatenation. Indicate that this VC is currently not a member of the group.
The status of all the members is returned to the transmitter in the control packets of each member. These actions are independent of each other, and they are not required to be synchronized.
This acknowledgment is used to synchronize the transmitter and the receiver. This member is provisioned to participate in the VCG and has a good path to the receiver. The source node starts sending F ADD sdn commands in the selected member. The state machine at the transmitter can be in one of the following five states:. LCAS uses 7 others for its purposes, leaving 5 reserved for future development. The network management system orders the source to add a new member e.
The operation of LCAS is unidirectional. These messages capture the status of all the VCG members at the receiver. This member is in the process of being deleted from the VCG. In this example, the deleted member has the highest sequence number.
The source sees the R OKassigns the member a sequence number that is one higher than the number currently in use. See All Related Store Items. The destination notices the F IDLE command and immediately drops the channel from the reassembly process. The following is a typical sequence for adding a member to the group. The following control words are sent from source to the receiver in order to carry out dynamic provisioning functions. Related Resources Store Articles Blogs. This is a bit used to acknowledge the detection of renumbering of the sequence or a change in the number of Pcas members.
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