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Information here is by rumor, innuendo and extrapolation. Manufacturers rarely put info on packet buffers in their data sheets. There are some summary thoughts |
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The buffer size question discussed in 2012 on the nanog list and is reproduced. |
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Shared memory means that the hardware permits buffers to be used by any port that needs them. In a shared memory design it is not possible to let ALL the memory go to queued packets. There would be no room for new arrivals which would lead to head of line blocking. |
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Some switches have multiple switch ICs that each manage their own memory pool. Examples are the Brocade FCX648S and the Cisco 3750-48. Memory from one IC can be shared among the ports in that IC's group but cannot be loaned out to ports controlled by other switch chips. Here we are interested in queue resources that can be claimed by a single flow -- not the total RAM in the system. |
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Tolly (tolly.com) occasionally reports on the ability of switches to sustain microbursts in his reports on data center switches. These measurements relate directly to output port buffering. See esp the IBM G8264 below. |
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Max buffer queue depth requires that all packet memory can be put into a single queue. QoS schemes divide buffer resources among defined queues. As such, I am not interested in the QoS descriptions and these are even less reliable than the rest of this doc. |
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|
Model |
Port Type |
RX Queue |
TX Queue |
Total Buffer |
RX Buffer |
TX Buffer |
|
Trident+ Shared Memory |
||||||
|
48 SFP+ and 4 QSFP |
8Q |
9 MB |
5? MB |
|||
|
48 SFP+ and 4 QSFP |
8Q |
9 MB |
5? MB |
|||
|
Juniper QFX3500 |
48 SFP+ and 4 QSFP |
12Q |
9 MB |
5? MB |
||
|
48 SFP+ and 4 QSFP |
8Q |
9 MB/switch |
5 MB |
|||
|
Dell 8132F & 4032F |
24 SFP+ and 2 x QSFP |
8Q |
9 MB |
|||
|
Dell 8164F & 4064F |
48 SFP+ and 4 x QSFP |
8Q |
9 MB |
|||
|
48 SFP+ and 4 x QSFP |
9 MB |
|||||
|
48 SFP+ and 4 x QSFP |
9 MB |
|||||
|
48 SFP+ and 4 QSFP |
12Q |
9 MB |
5 MB |
|||
|
48 SFP+ and 4 QSFP |
8Q |
9 MB/switch |
||||
|
48 SFP+ and 4 QSFP |
4Q |
9 MB |
||||
|
Allied Telesis DC2552 |
48 SFP+ and 4 QSFP |
8Q |
9 MB |
|||
|
48 SFP+ and 4 QSFP |
||||||
|
32 QSFP |
8Q |
12 MB |
Dynamic up to 8 MB |
|||
|
64 QSFP |
8Q |
12 MB/ASIC, 48 MB total |
Dynamic up to 8 MB |
|||
|
26 QSFP + slot |
8Q |
12.2 MB |
Dynamic up to 8 MB |
|||
|
48 SFP+ and 6 QSFP and expansion |
8Q |
12.2 MB |
Dynamic up to 8 MB |
|||
|
32 QSFP |
8Q |
No info |
No info |
|||
|
32 QSFP or 31 QSFP and 4 SFP+ |
8Q |
12.2 MB |
Dynamic up to 8 MB |
|||
|
32 QSFP |
8Q |
12 MB |
Dynamic up to 8 MB |
|||
|
24 QSFP + expansion slots |
8Q |
12 MB |
Dynamic up to 8 MB |
|||
|
32 QSFP |
8Q |
12.2 MB |
Dynamic up to 8 MB |
|||
|
48 SFP+ and 12 QSFP |
?? |
4.6 MB |
64 KB to 1 port |
|||
|
36 QSFP |
?? |
4.6 MB |
128 KB to 1 port |
|||
|
Other Shared Memory |
||||||
|
Brocade FCX624S |
24Gig-E w 4 SFP+ |
8Q |
2 MB |
1.04 MB to 1 port |
||
|
40 SFP+ plus 8 SFP+ |
8Q |
230 KBytes |
||||
|
24Gig-E w 8 SFP+ |
8Q |
4 MB |
1 MB to 1 port |
|||
|
24Gig-E w 4 10Gb/s |
8Q or 4Q or 2 Q |
0.23 MB |
||||
|
24 tw-pr Gig-E w 4 optional 10Gb/s |
8Q |
11.25 MB |
4.5 MB shared |
6.75 MB shared |
||
|
HP A5800-24G |
24Gig-E w 4 10Gb/s |
8Q |
4 MB |
4 MB |
||
|
HP E6600-24G-4XG |
24Gig-E w 2 10Gb/s |
8Q |
18 MB for GE |
18 MB |
||
|
24 x SFP+ |
8Q |
2 MB/sw-chip |
shared |
1.238 + 0.02 MB |
||
|
48 SFP+ |
8Q |
2 MB/sw-chip, 8 MB total |
1.238 + 0.02 MB |
|||
|
24 SFP+ |
8Q |
9.5 MB |
||||
|
52 SFP+ |
8Q |
9.5 MB |
||||
|
48 SFP+ and 4 QSFP |
8Q |
9.5 MB |
||||
|
Dell 8024 |
24 SFP+ |
2Q |
2 MB |
|||
|
48 Gig-E, 4 x SFP+ |
8Q |
6.1 MByte |
98 KB per port |
|||
|
Dell 7024 |
24 Gig-E, 4 x SFP+ |
8Q |
32 MB |
4 MB |
||
|
48 GE + 4 SFP+ |
8Q |
4 MB/switch |
4 MB |
|||
|
Catalyst 3750G-48TS |
6 ASICs w/ 8 GE ports ea |
8Q |
1P3Q3T |
576KB per ASIC |
192KB per ASIC |
384KB per ASIC |
|
Catalyst 3750E, 3560E, 3750X & 3560X |
ASIC support 24 GE ports or 2 x 10G |
2Q |
1P3Q3T |
2750KB per ASIC |
750KB per ASIC |
2MB per ASIC |
|
Catalyst 4948E |
48 GigE + 4 SFP+ |
4 |
17.5 MB |
Max 16 MB to 1 port |
||
|
48 SFP+ |
4 |
18 MB |
5.8 MB |
|||
|
48 Gig-E + 4 SFP+ |
4Q |
1250 MB |
enough |
|||
|
48 Gig-E + 4 SFP+ |
8Q |
768 MB |
16 MB/port? |
GOBBS |
||
|
Virtual Output Port queuing |
||||||
|
48 port sfp+ line card |
8Q |
3 GB per packet processor |
50 MB/port-queue |
VoQ |
||
8Q |
3 GB | 256 MB/port-queue |
VoQ |
|||
|
8-port 10 Gb/s line card |
8Q |
3 GB | 256 MB/port-queue |
VoQ |
||
|
24-port 1 Gb/s line card |
8Q |
1 GB | 64 MB/port-queue |
VoQ |
||
|
26 SFP+ |
8 |
1 (I think) |
480 KB per port |
480 KB |
VoQ |
|
|
32 fixed SFP+ and 16-port expansion module |
8 Unicast 8 Multi |
1 (I think) |
640 KB per port |
640 KB |
VoQ |
|
|
48 fixed SFP+ and 4 QSFP |
8 Unicast 8 Multi |
1 (I think) |
25 MB per 12-port 10G ASIC |
14 MB shared per ASIC |
VoQ |
|
|
Cisco Nexus 7000 (M1 series) |
48-port Tw-Pr GE |
2q4t |
1p3q4t |
7.56 MB per port |
6.15 MB per port | |
|
Cisco Nexus 7000 (F3 Series) |
6-port 100GE |
4q |
4q |
144 MB shared |
VoQ | |
|
Cisco Nexus 7000 (F2 series) |
48 SFP+ |
4q1t |
1p3q1t |
72 MB shared |
VoQ | |
|
Cisco Nexus 7000 (M1 series) |
32-port 10GE shared 4-port groups |
8q4t |
1p7q4t |
65 MB per group |
80 MB per group | |
|
Cisco Catalyst 6500 gets its own table |
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Comments, suggestions, corrections to warner@ucsc.edu