HP StorageWorks XPath OS 7.4.X Administrator Guide (AA-RVHDD-TE, February 2006)

XPath OS 7.4.x administrator guide 71
5 Using the FCIP Tunneling Service
The optional FCIP Tunneling Service enables Fibre Channel frames to tunnel through IP networks by
dividing frames, encapsulating the result in IP packets upon entering the tunnel, and then reconstructing
them as they leave the tunnel. The FCIP Tunneling Service is discussed in the following sections:
• Synchronizing time, page 71
• Configuring an FCIP interswitch link, page 72
• Disabling and enabling an FCIP interswitch link, page 76
XPath OS supports eight FCIP interswitch links between two MP Routers. All 16 links can be used as FCIP
links with the remaining links going to other routers.
Ports configured for FCIP are called virtual E_Ports (VE_Ports). After you configure the VE_Ports on the two
MP Routers, an FCIP connection is established between them.
Fibre Channel frame encapsulation on one VE_Port and the reconstruction of Fibre Channel frames on the
other VE_Port are transparent to the initiator and target, but the administration of VE_Ports is different than
the administration of other Fibre Channel port types.
Figure 13 shows a portion of a Fibre Channel network using FCIP. The FCIP interswitch link (VE_Ports
connected through the IP network) joins the two SANs (Fabric 1 and Fabric 2) into parts of a larger SAN.
Figure 13 Network using FCIP
Synchronizing time
Fibre Channel framing and signaling standards require that a Fibre Channel fabric define and enforce a
frame lifetime. The standard defined timeout values are R_A_TOV and E_D_TOV.
The FCIP and Fibre Channel frame encapsulation RFCs add wide-area-network (WAN) timeout value
(WAN_TOV). When a Fibre Channel frame is encapsulated, the encapsulation header includes a
timestamp. The current time, WAN_TOV, and the timestamp are checked when the frame is reconstructed
upon leaving the tunnel. If the lifetime of the frame exceeds the WAN_TOV, the frame is discarded.
If the time settings for the MP Routers at the two ends of an FCIP interswitch link are not synchronized,
frame lifetime calculations are not meaningful. If the receiving MP Router time lags the sending router time,
frames that should be discarded are not discarded; if the receiving router time leads the sending router
time, frames are discarded that should not be discarded.
You can avoid this problem by synchronizing both ends to the same NTP server. Use the tsClockServer
command to specify an NTP server for time service. See ”Synchronizing time with an NTP server” on
page 23 for a procedure. Use the configure command to set WAN_TOV to a value higher than 1000
ms. Enable WAN_TOV enforcement on an FCIP port with the portCfgFcip command.
Fibre Channel
initiator
Fibre Channel
target
Multiprotocol
Router
VE_Port
Fabric 1 Fabric 2
VE_Port
IP
network
Multiprotocol
Router