Information Technology Reference
In-Depth Information
3.2 Label Table
The label table includes labels, instructions and services. The matching field is
labels of packets, and the instruction field indicates packets forwarding actions,
and the service field indicates the index of the method to process packets.
Labels are allocated by the LabelCast controller. The first packet of flows are
sent to LabelCast controller due to missing against the Label table. Labelcast
controller analyzes the packet and dispatches it to the target network applica-
tion, which registers to process the protocol type of the packet. The network
application allocates the label from the subspace of labels and assigns the label
to the flow, and make the process policy for the flow. Based on the label and
the policy the Labelcast controller generates rules of Label table, and notify
the rules to the upstream and downstream nodes, as illustrated in Fig.2. At the
same time, the Labelcast controller notify the label to the source node of the
flow. After the configuration, the host sends the following packets of the flow
with the label, which are marked by the Labelcast adapter of hosts.
Fig. 2.
Label Allocation and Distribution
In the forwarding layer lookup of the fixed-length labels of packets against
the label table gets the method of packet processing, such as action instructions
of light semantics or pointing to service atoms. The forwarding plane packet
processing is usually implemented by multi-stage processing, including simple
packet option modifications, such as TTL minus 1, look-up and output, as well
as label replacement. Multi-stage processing are decomposed into the flow pro-
cessing in the coarse-grained, firstly light semantics-related modifying options
and matching against rules, then the semantics-related packet processing, and
finally the light semantic output control. In Labelcast, modifying basic options
and output control of packet forwarding are denoted by instructions and imple-
mented by forwarding hardware, intermediate stage of packet processing as a
