Information here is by rumor, innuendo and extrapolation. Manufacturers rarely put info on packet buffers in their data sheets.

The buffer size question discussed in 2012 on the nanog list and is reproduced.

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.

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.

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.

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.

Model

Port Type

RX Queue

TX Queue

Total Buffer

RX Buffer

TX Buffer

Shared Memory

Juniper QFX3500 trident+

48 SFP+ and 4 QSFP

12Q

9 MB

5? MB

Brocade FCX624S

24Gig-E w 4 SFP+

8Q

2 MB

1.04 MB max to 1 port

Brocade ICX6610-24

24Gig-E w 8 SFP+

8Q

4 MB

1 MB max to 1 port

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

Arista 7124SX

24 x SFP+

8Q

2 MB/sw-chip

shared

1.238 +0.02 MB

Arista 7148SX

48 SFP+

8Q

2 MB/sw-chip, 8 MB total

1.238 + 0.02 MB

Arista 7050S-64 Trident+

48 SFP+ and 4 QSFP

8Q

9 MB/switch

5 MB

IBM BNT G8052

48 GE + 4 SFP+

8Q

4 MB/switch

4 MB

IBM G8264 Trident+

48 SFP+ and 4 QSFP

8Q

9 MB/switch

Not spec'd

Dell 8024

24 SFP+

2Q

2 MB

Dell 6248

48 Gig-E, 4 x SFP+

8Q

unknown

unknown

Dell 7024

24 Gig-E, 4 x SFP+

8Q

32 MB

4 MB

Dell 8132F (trident+)

24 SFP+, 4 x QSFP

4Q

9 MB

Force10 S4810 (trident)

48 SFP+, 4 x QSFP

4Q

9 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

Cisco Nexus 3064X trident+

48 SFP+ and 4 QSFP

12Q

9 MB

5 MB

Cisco Nexus 3548

48 SFP+

4

18 MB

5.8 MB

Virtual Output Port queuing

Force10 S60

48Gig-E w 4 10Gb/s

8Q

1250 MB

25 MB/port

GOBBS

Arista 7048

48Gig-E w 4 10Gb/s

8Q

768 MB

16 MB/port?

GOBBS

Arista 7504E/7508E

48 port sfp+ line card

8Q

3 GB per packet processor

50 MB/port-queue

VoQ

Cisco Nexus 5010

26 SFP+

8

1 (I think)

480 KB per port

480 KB

VoQ

Cisco Nexus 5548P

32 fixed SFP+ and 16-port expansion module

8 Uni 8 Multi

1 (I think)

640 KB per port

640 KB

VoQ

Cisco Nexus 7000

48-port Tw-Pr GE

2q4t

1p3q4t

Not meaningful

7.56 MB

6.15 MB

Cisco Nexus 7000

2-port 100GE

8q2t

1p7q4t

Not meaningful

62.46 MB

31.23 MB

Cisco Nexus 7000

8 x 10GE

8q2t

1p7q4t

Not meaningful

96 MB

80 MB

Cisco Nexus 7000

32-port 10GE shared 4-port groups

8q4t

1p7q4t

Not meaningful

65 MB per group

80 MB per group

Catalyst 6500 bits and pieces

WS-SUP720-3B

2 x GE

1P1Q4T

1P2Q2T

512KB

80KB

432KB

VS-S720-10G-3C

2 x 10GE

2Q4T

1P3Q4T

191.8MB

105MB

88MB

VS-S720-10G-3C

3 x 1GE

2Q4T

1P3Q4T

17.7MB

9.6MB

8.1MB

CEF720 Modules

WS-X6716-10GE-3C

16 x 10GE

8Q4T

1P7Q4T

199MB

109MB

90MB

WS-X6716-10GE-3CXL

16 x 10GE

8Q4T

1P7Q4T

199MB

109MB

90MB

WS-X6708-10GE-3CXL

8 x 10GE

8Q4T

1P7Q4T

199MB

109MB

90MB

WS-X6708-10GE-3C

8 x 10GE

8Q4T

1P7Q4T

199MB

109MB

90MB

WS-X6704-10GE

4 x 10GE

1Q8T

1P7Q8T

16MB

2MB

14MB

WS-X6724-SFP

24 x GE SFP

1Q8T

1P3Q8T

1.3Mb

166KB

1.2MB

WS-X6748-GE-TX

48 x GE TX

1Q8T

1P3Q8T

1.3Mb

166KB

1.2MB

WS-X6748-SFP

48 x GE SFP

1Q8T

1P3Q8T

1.3Mb

166KB

1.2MB

WS-X6516-GBIC

16 x GE GBIC

1P1Q4T

1P2Q2T

512KB

73KB

439KB

WS-X6516A-GBIC

16 x GE GBIC

1P1Q4T

1P2Q2T

1MB

135KB

946KB

WS-X6516-GE-TX

16 x 10/100/1000

1P1Q4T

1P2Q2T

512KB

73KB

439KB

WS-X6524-100FX-MM

24 x 100FX Multimode

1P1Q0T

1P3Q1T

1.1MB

28KB

1088KB

WS-X6548-RJ-21

48 x 10/100

1P1Q0T

1P3Q1T

1.1MB

28KB

1088KB

WS-X6548-RJ-45

48 x 10/100

1P1Q0T

1P3Q1T

1.1MB

28KB

1088KB

WS-X6548-GE-TX

48 x 10/100/1000

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

WS-X6548V-GE-TX

48 x 10/100/1000 with Cisco inline power

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

WS-X6548-GE-45AF

48 x 10/100/1000 with 802.3af inline power

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

dCEF256 Modules

WS-X6816-GBIC

16 x GE GBIC

1P1Q4T

1P2Q2T

512KB

73KB

439KB

Classic Modules

WS-X6024-10FL-MT

24 x 10Base FL

1Q4T

2Q2T

64KB

8KB

56KB

WS-X6148-RJ-21

48 x 10/100

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-RJ-21V

48 x 10/100 with Cisco inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-21AF

48 x 10/100 with 802.3AF inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-RJ-45

48 x 10/100

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-RJ-45V

48 x 10/100 with Cisco inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-45AF

48 x 10/100 with 802.3AF inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6148-GE-TX

48 x 10/100/1000 no jumbo

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

WS-X6148A-GE-TX

48 x 10/100/1000 jumbo 9216

1Q2T shared between 8 ports

1p3q8t shared between 8 ports

5.5 MB per port

120KB

5.4MB

WS-X6148V-GE-TX

48 x 10/100/1000 with Cisco inline power

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

WS-X6148-GE-45AF

48 x 10/100/1000 with 802.3AF inline power

1Q2T shared between 8 ports

1P2Q2T shared between 8 ports

1.4MB shared between 8 ports

185KB shared between 8 ports

1.2MB shared between 8 ports

WS-X6224-100FX-MT

24 x 100FX

1Q4T

2Q2T

64KB

8KB

56KB

WS-X6248-RJ-45

48 x 10/100

1Q4T

2Q2T

64KB

8KB

56KB

WS-X6248-TEL

48 x 10/100 (RJ21)

1Q4T

2Q2T

64KB

8KB

56KB

WS-X6248A-TEL

48 x 10/100 (Telco)

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6316-GE-TX

16 x 10/100/1000

1P1Q4T

1P2Q2T

512KB

73KB

439KB

WS-X6324-100FX-MM

24 x 100FX

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6324-100FX-SM

24 x 100FX

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6348-RJ-45

48 x 10/100

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6348-RJ-45V

48 x 10/100 with Cisco inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6348-RJ-21V

48 x 10/100 with Cisco inline power

1Q4T

2Q2T

128KB

16KB

112KB

WS-X6408-GBIC

8 x GE GBIC

1P1Q4T

1P2Q2T

512KB

80KB

432KB

WS-X6408A-GBIC

8 x GE GBIC

1Q4T

2Q2T

512KB

73KB

439KB

WS-X6416-GE-MT

16 x 10/100/1000

1P1Q4T

1P2Q2T

512KB

73KB

439KB

WS-X6416-GBIC

16 x GE GBIC

1P1Q4T

1P2Q2T

512KB

73KB

439KB