Intermediary Device L2 Context Preservation via MAC-Based Forwarding
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Solution Overview
Problem
In clustered environments, data link layer information such as VLAN, Interface, and MAC are often lost when traffic is routed between intermediary devices, leading to challenges in maintaining the L2 context of network flows, especially when MAC-based forwarding is enabled.
Innovation Solution
The solution involves piggybacking L2 information like VLAN, Interface, and MAC onto transport layer packets and caching this information at intermediary devices to ensure it is preserved and correctly routed, allowing the flow processor to retrieve and tunnel it back to the flow receiver, maintaining the L2 context throughout the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traffic is routed between intermediary devices in a cluster, then network flow can be distributed across multiple devices, but data link layer information (VLAN, Interface, MAC) is lost
Solution Approach 1:
The patent embeds data link layer information (VLAN, Interface, MAC) within the transport layer packet structure. The L2 information is piggybacked as additional fields inside the L3/L4 packet, allowing it to be carried through the cluster without being lost during routing between intermediary devices
Solution Approach 2:
The patent introduces a special MAC address as an intermediary identifier to mark packets that contain piggybacked L2 information. This special MAC acts as a mediator that helps flow receiver nodes identify and process packets with embedded L2 context, enabling proper forwarding decisions
2Loss of information
If L2 information is piggybacked onto transport layer packets, then L2 context is preserved across cluster nodes, but packet structure complexity increases
Solution Approach 1:
The patent uses existing transport layer packet structures to carry multiple functions simultaneously. The same packet structure that carries application data also carries L2 information through piggybacking, and the special MAC address serves both as a standard network identifier and as a marker for packets with embedded L2 context
3Productivity
If MAC based forwarding is enabled on intermediary devices, then forwarding efficiency is improved, but L2 information is lost when flow receiver steers traffic to flow processor
Solution Approach 1:
The patent performs preliminary action by piggybacking L2 information onto packets at the point of entry into the cluster, before the traffic is steered between flow receivers and flow processors. This ensures the L2 context is already embedded and will be preserved throughout subsequent forwarding operations
Solution Approach 2:
The L2 information is nested within the transport layer packet structure, allowing it to be carried through MAC-based forwarding operations without being lost. The nested structure ensures that even when packets are forwarded based on MAC addresses, the embedded L2 information remains intact and accessible
Data Source
AI summary
The present application is directed towards sharing data link layer information of network traffic distributed across a cluster of intermediary devices. A method for sharing data link layer information across a cluster includes receiving a request packet at a first intermediary device. The first intermediary device identifies a first set of data link layer information from a data link layer of the request packet. The first intermediary device modifies the request packet for transmission on a common data backplane of the cluster to include the first set of data link layer information in the request packet. The modified request packet includes a second set of data link layer information that differs from the first set of data link layer information at the data link layer. The first intermediary device transmits the modified request packet on the common data backplane of the cluster to other devices of the cluster.