There is a note of interest here for users of network protocol analyzers. Because there is no requirement that PDUs begin on a TCP Data Segment boundary, it is possible that simply grabbing an Ethernet frame with a protocol analyzer may result in an incorrect interpretation. To determine the start of a PDU, the end of the previous PDU must be known. While analyzers do use various heuristics to determine the start of a PDU within the first few TCP Data Segments seen, the heuristics are not foolproof, and there may be “false positives” possibly interpreting real data as the start of a PDU for a specific protocol. The potential existence of “false positives” should always be considered when debugging network problems.
5.Network Entities and iSCSI nodes
A network entity is an abstraction for any
Figure 5. iSCSI Network Entity
Network Entity
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Network | Network | Network |
Portal 1 | Portal 2 | Portal m |
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Within the network entity, iSCSI defines one or more iSCSI nodes. An iSCSI initiator or target is typically defined by a single iSCSI node within a network entity. Multiple iSCSI nodes may be defined within a network entity. A network entity may contain both initiator and target iSCSI nodes, as well as unrelated network protocols such as NFS.
Each iSCSI node is identified by a worldwide unique iSCSI name (an ASCII string). iSCSI uses target node names to uniquely identify available SCSI storage on a TCP/IP based network. Because of the vastness of the internet, and the possibility that a small isolated LAN may someday be attached to larger LANs, the uniqueness of all iSCSI node names must be maintained. iSCSI vendors typically
Accessibility of an iSCSI node from all network portals of a network entity is not mandatory. The number of network portals actually providing access to an iSCSI node is a function of the network
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