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AR Router
C613-03031-01 REV E
Dual Mode
Throughput of an encrypted link can be dramatically increased by using data
compression. To support this, ECMACs support both encryption and
compression to provide a dual mode which allows combined compression and
encryption operations. So that the compression phase will have the best
opportunity at finding non-random data, compression occurs before
encryption, in the order:
compression
→
encryption
→
//
→
decryption
→
decompression
Adding compression to an encrypted link increases line throughput. Once
compression has been carried out there is less data requiring encryption,
passing back to the base system, and transferring across the network, so less
base system bus and network link bandwidth is required for a given amount of
data. This results in the dual operation being very effective where encryption is
required.
PCI Accelerator Cards (PACs)
PCI Accelerator Cards (PACs) provide additional processing features or
performance, but do not add extra physical interfaces to the router. A PAC can
be installed in the dedicated PAC slot on AT-AR725, AT-AR740, and AT-AR745
routers.
Where a MAC and PAC are installed in the same router, only the PAC will
function.
PACs should only be installed by authorised service personnel. Unauthorised
opening of the router’s lid may cause danger of injury from electric shock,
damage to the router, and invalidation of the product warranty.
Two PACs are available:
■
AT-AR060 EPAC, Encryption PAC.
■
AT-AR061 ECPAC, Encryption/Compression PAC.
See “
” on page 93 for more information on the PAC
installation procedure.
How PACs work
PACs provide AR725, AR740, and AR745 routers with high performance
hardware-based encryption and/or compression services. PACs have a DMA
slave processor, which operates independently of the base system. This
processor is responsible for the transfer of data between the base system and
the PAC, and the control of local high speed encryption and compression data
processing devices.
This architecture allows data encoding to be performed off-line without
involving the base router processor, thereby maximising PAC performance
while at the same time minimising impact on the router.
The PAC is a single card. Figure 28 on page 61 shows the layout of the board for
an AT-AR061 ECPAC.
