SAS Expander Logical Zone Routing
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Solution Overview
Problem
Current SAS protocols lack mechanisms for traffic isolation and access control, allowing unrestricted access between devices in a physical domain, which is undesirable in environments requiring controlled access or protection against unauthorized access.
Innovation Solution
Implementing virtual domains by assigning logical zones to SAS expanders, allowing access control through zone identifiers and access policy matrices to manage connection requests and route messages accordingly, thereby segmenting the physical SAS domain into logical zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SAS expanders allow unrestricted access between devices in a physical domain, then device connectivity and ease of operation are improved, but security and access control are worsened
Solution Approach 1:
The patent segments the physical SAS domain into multiple virtual domains using virtual domain identifiers (VDIDs). Each expander is configured with virtual domain information that restricts routing decisions to only those destinations within the same virtual domain. This segmentation allows unrestricted connectivity within each virtual domain while providing access control between different virtual domains, resolving the contradiction between ease of operation and security.
2Reliability
If SAS protocols implement virtual domains with access control, then security and access control are improved, but device complexity and routing overhead are worsened
Solution Approach 1:
The patent implements preliminary action by pre-configuring expanders with virtual domain information during system initialization. The virtual domain routing tables are populated in advance with destination VDIDs and corresponding physical routing information. When a connection request is made, the expander only needs to perform a simple VDID match rather than complex access control checks, significantly reducing routing overhead while maintaining security.
3Reliability
If physical SAS domain is segmented into logical zones, then traffic isolation and security are improved, but routing complexity and device complexity are worsened
Solution Approach 1:
The patent changes the routing parameter from physical device addresses to virtual domain identifiers (VDIDs). By using VDIDs as the primary routing parameter, the system achieves traffic isolation between logical zones without requiring complex routing logic. The expander simply compares the VDID in the connection request with its configured virtual domain information to make routing decisions, greatly simplifying the routing process while maintaining traffic isolation.
Data Source
AI summary
A method and apparatus are provided for routing in an SAS expander for logical zoning. Common SAS topology defined by the ANSI T10 specification only relates to physical topology with multiple end devices, as well as to expander devices and the broadcast handling mechanisms in such physical topologies. The present invention introduces the concept of virtual topologies that can be non-overlapping or overlapping subsets of the physical topology and the routing mechanism that handles the routing issues with the virtual topologies.