3Com S330 manual HDLC/SDLC Mode, Frame Relay Mode

Serial Interface 219

HDLC/SDLC Mode

Transparent HDLC mode is used for point-to-point HDLC connections across the ATM network. No service-based encapsulation other than AAL5 is needed. All packets 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 pattern included in a sequence of frames. The TTC Firebird V.35 frame relay interface provides that simple capability.

When using transparent HDLC mode, you set the following parameters:

■Minimum number of flags between HDLC frames

■CRC type

The PathBuilder S330/S310 will SAR AAL5 and map HDLC/SDLC frames onto an ATM VCC. You could use the HDLC service for router to router and X.25 to X.25 links. You could use the SDLC service for IBM FID2 3270 SNA Peripheral or IBM FID4 372X SNA Backbone.

Figure 160 shows HDLC/SDLC applications.

You should disable NRZI on the FEP (i.e., IBM 3745). NRZI is commonly used when the FEP is connected to DSUs over a non-digital line. The PathBuilder S330 does not require NRZI to be enabled.

Figure 160 HDLC/SDLC Applications

		PathBuilder	PathBuilder
		S330/S310	S330/S310
	HDLC		HDLC
X.25				X.25
X.25				X.25
PAD
				3
	3	FID 4	FID 4	7
S				2
	7	SDLC		5
N	2	FID 2	FID 2	3270
A
	5	SDLC
Host

Frame Relay Mode

Frame relay mode is used to terminate a frame relay router, across the ATM network, for example. This protocol mode converts the frame relay DLCI to a VP/VC ATM connection.

A PathBuilder S330/S310 provides two interworking features to interconnect a Frame relay network with an ATM network:

■Service Interworking

■Network Interworking