3Com 3C63400-3AC-C - PathBuilder S700 Switch, Справочное руководство

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192 C
HAPTER
5: C
ONFIGURING
P
ATH
B
UILDER
S700 M
ODULES
, P
ORTS
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AND
A
PPLICATIONS
Common Virtual Circuit Parameters
The following virtual circuit parameters are available for most PathBuilder S700
cards:
For descriptions of the virtual circuit parameters for the MCPU card, see
“Configuring In-band Management” in Chapter 3.
Virtual Interface —Side A (or B) Virtual Interface number.
Priority —The priority for this circuit: 0 , 1 , 2, or 3 . The STX supports four priority
queues per virtual interface, and each virtual circuit can be mapped to a priority
queue. Priority
0 is the highest.
Early Packet Discard —Enable or disable early packet discard (EPD) for use with
the Congestion On/Off setting. See “Configuring the STX Module” for details. For
every connection where early packet discard is enabled, a status is kept when
there is a partial packet for that connection in the queue. Once the queue cell level
exceeds the congestion ON thresholds, only connections with partial packets
already existing in the queue are allowed in. Cells from other connections are
dropped.Once the congestion has subsided to the congestion OFF level, then all
remaining connections are allowed.
Policing —Select [0] to disable , [1] to choose Config . 1 , or [2] to choose Config. 2 .
If you select Config. 1, the following occurs:
n
For priority = 0 VCs, CLP=0 cells are policed and non-conforming CLP=0 cells
are tagged. CLP=1 cells are not policed. The policing for CBR traffic is based on
PCR and CDVT.
n
For priority = 1-3 VCs, CLP=0 cells are policed, SCR is enforced, and
non-conforming CLP=0 cells are tagged. Additionally, CLP=0+1 (all cells) are
policed, and PCR is enforced such that any cells exceeding PCR are discarded.
The policing for non-CBR traffic is based on PCR, SCR, and MBS.
If you select Config. 2, the following occurs:
n
For priority = 0 VCs, CLP=0+1 cells are policed and non-conforming cells are
dropped. The policing for CBR traffic is based on PCR and CDVT.
n
For priority = 1-3 VCs, CLP=0 cells are policed and SCR is enforced such that
non-conforming CLP=0 cells are tagged. Additionally, CLP=1 cells are policed
and PCR is enforced such that non-conforming CLP=1 cells are discarded. The
policing for non-CBR traffic is based on PCR, SCR, and MBS.
PCR/CDVT/SCR/MBS— Set the policing parameters.
PCR —Peak Cell Rate; the maximum cell rate which the source may never
exceed. This is the interval from the first bit of one cell to the first bit of the
next cell.
CDVT —Cell Delay Variation Tolerance; the acceptable tolerance of CDV. CDV is
a Quality of Service parameter that measures the peak-to-peak cell delay
through the network. It represents the difference between the worst case delay
and the best case delay achievable on the VC.
SCR —Sustainable Cell Rate—the maximum average rate (in cells/sec) that a
bursty on-off traffic source that can be sent at the peak rate.
MBS —Maximum Burst Size; t he maximum number of cells that can be sent at
the peak rate.