Kentrox AAC3


(ATM Access Concentrator v3)


8 Modular Slots (1 slot is taken, leaving 7 for the user). Each slot contains a protocol module that determines the traffic type (cell, CBR, packet, or Ethernet) and a physical layer module that determines the physical interface.

Speeds from T1/E1 to OC-3

Management access


120 VAC rating—100 to 132 volts AC, 57 to 63 Hz

240 VAC rating—190 to 264 volts AC, 47 to 53 Hz

42 to 60 volts DC

Power interruptions - Loss of all input line power for any length of time will not affect the configuration settings. Performance data will be maintained upon loss of power for 12 hours in typical cases.



NOTE:  each DS3 module needs a corresponding Enhanced Cell-Shaping module

DS3 Module – to Network     (Kentrox 10300)        

Input requirements

Signal level                   Recover DSX-3 signals from 0 to 450 ft. of WECO 728A

75 ohm coaxial cable or equivalent.

Jitter tolerance              Conforms to ITU-T Recommendation G.824 (03/93),

Output requirements :

Output level, Vo                       0.36 < Vo < 0.85 V peak1 at the cross-connect

Line build out:

DS3 high          For cable lengths:  225 to 450 feet

DSX-3             For cable lengths:  0 to 225 feet

Enhanced Cell-Shaping Module  (Kentrox 10204)

Connections – 255 VPC’s, 1023 VCC’s, or combinations up to 1023 total

Queue Depth – 128,000 Cells

Data Rate – up to 155 Mbps


HSSI Module – to Customer Router  (Kentrox 10300)

Line Speed Range – 1 to 52 Mbps

Interface -    EIA-613 Female Standard 50 Position.  Use cable with male :


Packet PM  (Packet Protocol Module) (Kentrox 10201) / Quad PM  (Quad Packet Protocol Module)  (Kentrox 10205)

NOTE:  an addendum on Kentrox’s website says that if you are using v2.20 or 2.21 software on your AAC3, and running Frame Relay UNI (our case) or ATM DXI - that the VPI/VCI’s must be in ascending order, or the connections will fail !!


NOTE:  for Frame Relay, these modules mate with Physical line modules HSSI or DS3 – and therefore, one of these is required when using either corresponding physical line module !!

 * can be used in conjunction with either DS3 ATM line module, or HSSI Module

* there are also Cell Protocol Modules for ATM available

Protocols Supported – Frame Relay, ATM DXI/FUNI, HDLC/PPP, SMDS DXI

Frame Relay Connections –

2047 VCC’s or DLCI’s (for AAL5) for Packet PM

            512 VCC’s or DLCI’s (for AAL5) per port for Quad Packet PM

Services Supported - 

FRF.5 and FRF.8

            FRF.5 describes how ATM can act as a high-speed backbone for FR

            FRF.8 describes how to map FR PVC’s to ATM PVC’s

1490 to 1483 Translation (although the Transparent method is preferred)

            RFC1490 describes IP encapsulation over Frame Relay

RFC1483 describes IP encapsulation over ATM

LMI (there are 3 versions of LMI, but the latest is Annex A, FRF.1.1) 

                                FRF.1 (superceded by FRF.1.1)

                        Annex D (T1.617)

                        Annex A (ITU Q.933 – referenced in FRF.1.1)

Speeds –

Packet PM – 1 port, 52 Mbps

Quad Packet PM – 4 ports, 2.048 Mbps per port


Pairing Modules (for ATM Modules)



Pairing Modules (for Frame Relay Modules)


IMA to DS3 Strategy for Growth

For customers with lower bandwidth needs but are expecting rapid growth.  Start out with NxT1, you can use an IMA (Inverse Multiplexing over ATM) card such as the Octal IMA physical layer module (1xT1 up to 8xT1), and then you can steadily add T1/E1

lines as your bandwidth needs increase. When eight T1 or E1 lines becomes insufficient, you can switch to a DS3/E3 physical layer module. You do not need to replace the protocol module, because it will match up with the new DS3/E3 physical layer module.



FRF Standards



Frame-toATM Conversion

2 Methods –

Transparent (Encapsulation or FR over ATM)

Translation – RFC1490-to-RFC1483, which translates FR headers to ATM  headers

*** Transparent is typically the preferred method

With either method, the frames must traverse an ATM PVC, and therefore mapping must be done.  Frame Relay DLCI’s are mapped to ATM VPI’s or VCI’s.  Also, for traffic control, the FR FECN bit is mapped to the ATM EFCI (Explicit Forward Congenstion Indicator).

The 3 Standards of Frame Relay to ATM


***  IWF = Inter-Working Function

***  ATM Service Interworking, which is the most common industry-wide.

FUNI (Frame relay UNI) –can accept FR frames of up to 2000 bytes and converts them to 53 byte ATM cells. FUNI is limited to VBR !!  It support T1 and Fract T1, with a max of 256 VC’s.

ATM DXI (ATM Data Exchange Interface) – like FUNI, also accepts FR frames of up to 2000 bytes and converts them to 53 byte ATM cells.  However, a DXI-enhanced DSU is required, as is DXI software in the customer equipment – to convert Frames into Cells prior to placing them on the access line.