Serial Interface 219HDLC/SDLC ModeTransparent HDLC mode is used for point-to-point HDLC connections across theATM network. No service-based encapsulation other than AAL5 is needed. Allpackets are terminated and SAR’d to a single VP/VC in the ATM network.Transparent mode functionality is best implemented with a PRBS type of patternincluded in a sequence of frames. The TTC Firebird V.35 frame relay interfaceprovides that simple capability.When using transparent HDLC mode, you set the following parameters:n Minimum number of flags between HDLC framesn CRC typeThe PathBuilder S330/S310 will SAR AAL5 and map HDLC/SDLC frames onto anATM VCC. You could use the HDLC service for router to router and X.25 to X.25links. You could use the SDLC service for IBM FID2 3270 SNA Peripheral or IBMFID4 372X SNA Backbone.Figure 160 shows HDLC/SDLC applications.You should disable NRZI on the FEP (i.e., IBM 3745). NRZI is commonly used whenthe FEP is connected to DSUs over a non-digital line. The PathBuilder S330 doesnot require NRZI to be enabled.Figure 160 HDLC/SDLC ApplicationsFrame Relay ModeFrame relay mode is used to terminate a frame relay router, across the ATMnetwork, for example. This protocol mode converts the frame relay DLCI to aVP/VC ATM connection.A PathBuilder S330/S310 provides two interworking features to interconnect aFrame relay network with an ATM network:n Service Interworkingn Network InterworkingHDLCX.25FID 4FID 2 32703725X.25X.25Host3725X.25PADHDLCFID 4FID 2SDLCSDLCSNAPathBuilderS330/S310 PathBuilderS330/S310
