342-86400-498PS
Issue 1.2
April 2012
Page 160
Copyright
GE Multilin Inc. 2010-2012
How the ETHER-1000 units maps IP frames to priority queues?
The unit assigns priorities as follows:
Note that TOS[5:0] denotes the 6 msb of the byte where they reside.
D
T
R
0
0
0
1
2
3
4
5
6
7
TOS[5]
TOS[4]
TOS[3]
TOS[2]
TOS[1]
TOS[0]
Bits 0-2: Precedence
111 - Network Control
110 - Internetwork Control
101 - CRITIC/ECP
100 - Flash Override
011 - Flash
010 - Immediate
001 - Priority
000 - Routine
Bit 3:
0 = Normal Delay,
1 = Low Delay
Bit 4:
0 = Normal Throughput, 1 = High Throughput
Bit 5:
0 = Normal Reliability,
1 = High Reliability
Bits 6-7: Reserved for Future Use
D
T
R
0
0
0
1
2
3
4
5
6
7
TOS[5]
TOS[4]
TOS[3]
TOS[2]
TOS[1]
TOS[0]
Bits 0-2: Precedence
111 - Network Control
110 - Internetwork Control
101 - CRITIC/ECP
100 - Flash Override
011 - Flash
010 - Immediate
001 - Priority
000 - Routine
Bit 3:
0 = Normal Delay,
1 = Low Delay
Bit 4:
0 = Normal Throughput, 1 = High Throughput
Bit 5:
0 = Normal Reliability,
1 = High Reliability
Bits 6-7: Reserved for Future Use
Figure 55:
TOS Byte
If
TOS[2:0] = 000, set Priority[2:0] = TOS[5:3] (the “Precedence” field)
Else If TOS[0] = 1, set Priority[2:0] = 6 (if the “Reliability” bit is set)
Else If TOS[1] = 1, set Priority[2:0] = 5 (if the “Throughput” bit is set)
(So TOS[2] = 1),
set Priority[2:0] = 4 (the “Low Delay” bit is set)
The above ETHER-
1000 unit‟s mapping is a very arbitrary one, based on nothing
more intelligent than an interpretation of the original “Precedence” & TOS
concept.
The mapping is implemented by a 64x3-bit lookup table, so if a more useful
mapping surfaces, this table could easily be changed.
The same table is used for all traffic ingressing the unit. Although a separate
table could be provided for each port for the “WAN” switch queues, this could not
be provided for the Marvell‟s “LAN” switch.
