3Com S330 manual CTX Switch

PATHBUILDER S330/S310 MODULE B AND APPLICATION OVERVIEW

This chapter describes the operation and data flow for each of the SuperStack® II PathBuilder® S330 and S310 WAN access switch (PathBuilder S330/S310) modules and supported applications. It contains the following sections:

	■	Management CPU
	■	CTX Switch
	■	T1/E1 UNI Interface
	■	OC3/STM-1 Port
	■	DS3/E3 UNI Modules
	■	DS3/E3 UNI Modules
	■	Ethernet Interface
	■	CBR Module
	■	Voice Compression Module
Management CPU	The management CPU provides an intelligent user interface in addition to the
	other built-in interfaces available on the PathBuilder S330/S310. It also monitors
	and controls the activity on the shelf. These functions include:
	■ Providing a user interface through a VT100 terminal or Ethernet (Telnet).
	■	Programming configurations.
	■ Generating and filtering alarms and transmitting them to the NMS.
	■ Gathering performance-monitoring data.
	■ Checking and assigning an appropriate clock source.
	■ Communicating with other nodes via the management VC channel.
CTX Switch	The CTX switch interfaces to all ATM busses in the system. It handles address
	translation and switching among seven ATM ports. Up to four ports come from
	the T1/E1 UNIs. The other three ports come from the onboard OC3/STM-1, the
	SAR, and expansion slots 7, 8, and/or 9 (the optional CBR module, Voice
	Compression module, and DS3/E3 UNI module).

Address translation is done via two lookups. The first lookup is a VP lookup (all 8 bits included). If a VP circuit is set up, then a VP translation is done; otherwise, a second lookup consisting of 2 VPI bits and 8 VCI bits, is done. For VC connections, any four VPs in the range 0-255 are allowed. Once the VC is found, the CTX performs the address translation.

If a cell carries data, then the switch tries to place it in the proper output FIFO (First-In, First Out) order. If the queue is congested and early packet discard is