Egress Flow Table for Flexible Packet Output Control
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Solution Overview
Problem
In Software Defined Networking (SDN) technologies, particularly with OpenFlow switches, once a packet is forwarded to output ports, further actions cannot be linked based on the output port action or group table execution, limiting flexibility in packet processing.
Innovation Solution
Introducing an egress table as an output-dedicated flow table that processes packets after passing through (N-1) flow tables, allowing for actions such as VLAN tagging, packet counting, and fragmentation based on predetermined thresholds, enabling flexible control over packet output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a packet is forwarded to output ports using traditional flow tables, then packet output is achieved, but further actions cannot be performed on the packet
Solution Approach 1:
The patent segments the packet processing function by introducing a dedicated egress flow table (N-th flow table) that is separated from the traditional (N-1) flow tables. This segmentation allows the egress table to specifically handle post-forwarding actions such as VLAN tagging, packet counting, and fragmentation, while the earlier flow tables handle packet forwarding decisions. This resolves the contradiction by enabling further packet processing actions after forwarding without compromising forwarding efficiency.
2Adaptability or versatility
If actions are accumulated in an action set for later execution, then flexible processing is enabled, but the action cannot be executed immediately after packet input
Solution Approach 1:
The patent applies preliminary action by pre-configuring the egress flow table with specific actions (VLAN tagging, packet counting, fragmentation) that will be executed immediately after packet forwarding. The egress table is prepared in advance with the necessary processing logic, allowing actions to be executed immediately when a packet matches the egress table rules, rather than accumulating actions in a delayed execution queue. This reduces processing delay while maintaining flexibility.
3Adaptability or versatility
If a group table is used for multicast operation, then packets can be transmitted through multiple output ports, but further actions cannot be linked based on group table execution results
Solution Approach 1:
The egress flow table serves as an intermediary between the group table multicast operation and subsequent packet processing actions. When a packet is forwarded through multiple output ports via group table, the egress table intercepts these packets and applies additional actions (such as VLAN tagging or fragmentation) based on the output port. This intermediary structure enables action linking for multicast operations without increasing overall device complexity, as the egress table handles all post-forwarding actions in a unified manner.
Data Source
AI summary
Disclosed are a packet output controlling method and a network device using the same. A packet output controlling method according to the present invention, as a method for processing flow in a plurality (N, where N is a natural number of 2 or greater) of flow tables connected by a pipeline, may comprise the steps of: passing a packet input into a flow from a first table to an N−1st table from among a plurality of tables; processing an output-dedicated Nth table (egress table) guided by the N−1st table with respect to the packet after the packet passes the N−1st table; and outputting the packet after processing the Nth table. Accordingly, the flexible control of a final output is made possible through various operations using output port information.