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More on FC-IP

You wrote, "FC-IP is more of an encapsulation protocol that allows FC messages to be packaged inside of IP frames. Name server information is not passed between sites so the SAN islands remain separate."

Are you sure about this? I remember hearing David Black, co-chair of the IETF IPS Working Group, describe the connection between two FCIP gateways as conceptually being the connection of the E_Ports of two switches that would propagate name server information.

Editor's note: This question refers to Mr. Poelker's 2002 predictions.

iFCP is a bit more intrusive into the data flow between SAN islands. iFCP end nodes are the actual FC_N_ports within the respective fabrics. Sessions can be device specific thereby providing more granularity of control between the FC sites. iFCP is a bit more like iSCSI in implementation where the iFCP devices providing the FC to IP "gateway" (not a tunnel like FC-IP) use iSNS naming services so device-to-device communication can take place. ("In iFCP, naming is handled through a DNS/SNS entity allowing devices to be named by referencing the IP gateway and the MAC address (D_ID) behind it".) FC-IP session end nodes are the FC-IP tunnel devices themselves.

You are correct in that FC-IP does provide an "e-port" like connection between the SAN islands and that the SAN islands now become a single fabric. The difference is how FC-IP devices provide that connection. iFCP is a "GATEWAY" approach, where FC-IP is a "TUNNEL" approach. A gateway can be more intelligent than a tunnel and thus provide for implementation specific ways to provide naming services, addressing, and flow control. A tunnel just passes everything from one side to the other, and must always be up for data to flow through it. A gateway can provide for less reliable transport between devices.

Nishan systems has some great whitepapers on this topic. For the actual drafts discussing this topic go to: http://www.ietf.org/html.charters/ips-charter.html


Editor's note: Do you agree with this expert's response? If you have more to share, post it in our Storage Networking discussion forum.

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