[j-nsp] Memory Allocation per FPC

[Hannes Gredler]

each stream (= a port on a PIC) will be assigned a buffer space
equal to 200ms (m-series) and 100ms (t-series) of bandwidth-delay
product so a STM-4 does consume 622/8*0.2 = 15.55MB buffers space;

now the difficult part:

the buffer is not statically allocated to a single FPC but rather
to the pooled memory of all FPCs on a PFE. also the packet itself
will be sprayed in quantums of 64-bytes called j-cells across
the contributing FPC SRAMs; so for example it would well be
that a 250 bytes packet enters the router on FPC0 and its
fragments are stored on FPC{1,2,3,4}; on the egress stage
the packets are reassembled and passed to the I/O manager ASIC
for queuing/rewrite etc.

the difficult^2 part:
is not a pure static allocation but also has a dynamic component;
however the application/purpose of static/dynamic allocation
i believe would go beyond what you have been asking, right ;-)

/hannes

On Mon, May 02, 2005 at 12:49:07PM +0000, The Drifter wrote:
| How is the memory of an FPC allocated per PIC. Is it allocated equally per 
| each PIC? Or is it allocated by the Buffer Manager (PFE) per data packet 
| received?
| Therefore a STM4 PIC will useup more memory of the FPC then a DS-3 PIC?