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

The buffer size question discussed in 2012 on the nanog list and is reproduced. Buffer requirements for long RTT networks is less well understood than you might hope. IETF tests for burst management are not as well developed as bandwidth tests. There is a draft that hints at progress. Packet pacing can improve buffer effectiveness by making TCP less bursty.

Incast is a buffer exhaustion phenomena that is one consequence of running out of packet memory.

Shared memory means that the hardware permits buffers to be used by any port that needs them. An intel white paper compares shared memory with other architectures. 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. The other major option for a switch fabric is a crossbar matrix.

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 for burst absorption -- 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

Trident+ Shared Memory

Accton 5652

48 SFP+ and 4 QSFP+

8Q

9 MB

5? MB

Edge-corE 5600-52X

48 SFP+ and 4 QSFP+

8Q

9 MB

5? MB

Juniper QFX3500

48 SFP+ and 4 QSFP+

8Q

9 MB

5 MB

Arista 7050S-64

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

Pica8 P-3920

48 SFP+ and 4 x QSFP+

9 MB

Penguin 4804x

48 SFP+ and 4 x QSFP+

9 MB

Cisco Nexus 3064X

48 SFP+ and 4 QSFP+

12Q

9 MB

5 MB

Supermicro SSE-X3348T

48 10GTw-Pr and 4 QSFP+

8Q

9 MB

Supermicro SSE-X3348S

48 SFP+ and 4 QSFP+

8Q

9 MB

IBM G8264

48 SFP+ and 4 QSFP+

8Q

9 MB/switch

not on data sheet

Force10 S4810

48 SFP+ and 4 QSFP+

4Q

9 MB

Allied Telesis DC2552

48 SFP+ and 4 QSFP+

8Q

9 MB

5 MB

NEC PF5820

48 SFP+ and 4 QSFP+

HP 5900AF-48XG-4QSFP+

48 SFP+ and 4 QSFP+

9 MB

Edge-core-AS5600-52X

48 SFP+ and 4 QSFP+

9 MB

Brocade TOR custom

Brocade VDX 6740

48 SFP+ and 4 QSFP+

24 MB

Dynamic up to 8 MB

Dynamic up to 8 MB

Brocade VDX 6940

96 SFP+ and 12 QSFP+

24 MB

Dynamic up to 8 MB

Dynamic up to 8 MB

Trident II and II+

Arista 7050X

32 QSFP+

8Q

12 MB

Dynamic up to 8 MB

Arista 7250X

64 QSFP+

8Q

12 MB/ASIC, 48 MB total

Dynamic up to 8 MB

Brocade 7750-26Q

26 QSFP+ and slot

8Q

12.2 MB

Dynamic up to 8 MB

Brocade 7750-48F

48 SFP+ and 6 QSFP+ and expansion

8Q

12.2 MB

Dynamic up to 8 MB

Brocade 7750-48C

48 10GbaseT and 6 QSFP+ and expansion

8Q

12.2 MB

Dynamic up to 8 MB

Quanta BMS T3048-LY8

48 SFP+ and 6 QSFP+

8Q

12 MB

8 MB

Pluribus E68

44 SFP+ and 6 QSFP+

8Q

Extreme Summit 770

32 QSFP+

8Q

No info

No info

Cisco Nexus 3100

32 QSFP+ or 31 QSFP+ and 4 SFP+

8Q

12.2 MB

Dynamic up to 8 MB

Cisco Nexus 3132Q-V

32 QSFP+ or 26 QSFP+ and 6 QSFP28

8Q

16 MB

Dynamic up to 12 MB

Cisco Nexus 31108PC-V

48 SFP+ and 6 QSFP28

8Q

16 MB

Dynamic up to 12 MB

Dell S6000

32 QSFP+

8Q

12 MB

Dynamic up to 8 MB

Juniper QFX5100-24Q

24 QSFP+ + expansion slots

8Q

12 MB

Dynamic up to 8 MB

Juniper EX4600

24 SFP+ + 4 QSFP + expansion slots

8Q

12 MB

Dynamic up to 8 MB

HP 5930

32 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

HP 5930 w 2 modules

48 SFP+ and 4 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

HP Altoline 5712

48 SFP+ and 6 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

HP Altoline 6712

32 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

Accton Edge-corE AS5712-54X

48 SFP+ and 6 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

Accton Edge-corE AS6712-32X

32 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

Accton Edge-corE AS5812-54X

48 SFP+ and 6 QSFP+

8Q

16 MB

Dynamic up to 12 MB

Inventec D6232Q

48 SFP+ and 6 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

Wedge - Facebook OCP

16 QSFP+

8Q

12.2 MB

Dynamic up to 8 MB

Broadcom Tomahawk

Dell Z9100

32 port QSFP28 100 Gb/s

8Q

16 MByte

Est 3 MByte per core

Cisco Nexus 3232C

32 port QSFP28 100 Gb/s

8Q

16 MByte

Est 3 MByte per core

Arista 7060CX-32

32 port QSFP28 100 Gb/s and 2 SFP+

8Q

16 MByte

Est 3 MByte per core

Arista 7260CX-64

64 port QSFP28 100 Gb/s and 2 SFP+

8Q

64 MByte

Est 3 MByte per core

Arista 7320X

256 port QSFP28 100 Gb/s

8Q

64 MByte

Est 3 MByte per core

Juniper QFX5200-32C

32 port QSFP28 100 Gb/s

8Q

16 MByte

Est 3 MByte per core

Juniper QFX5200-64Q

32 port QSFP28 OR 64 QSFP

8Q

16 MByte

Est 3 MByte per core

Aurora 720 with ONIE

32 QSFP28 100 Gb/s

8Q

16 MByte

Est 3 MByte per core

Inventec D7032Q28B

32 QSFP28 100 Gb/s

8Q

16 MByte

Est 3 MByte per core

Edge-core-7710 and 7712

32 QSFP28 100 Gb/s

8Q

16 MB

Est 3 Mbyte per core

HP 6960

32 QSFP28 100 Gb/s

8Q

16 MB

Est 3 Mbyte per core

Broadcom DUNE a.k.a. StrataDNX

Arista 7280E-64

48 port SFP+ and 4 x QSFP

8Q

9 GB

VoQ 125 MB per 10 gig port

Arista 7280E-68

48 port SFP+ and 2 x QSFP28 100 Gb/s

8Q

9 GB

VoQ 125 MB per 10 gig port

Arista 7280E-72

48 port SFP+ and 2 x MXP

8Q

9 GB

VoQ 125 MB per 10 gig port

Cisco NCS 5500

288 QSFP28 100 Gb/s ports

EZChip NP-5

PARPRO N5R-100

24 SFP+ and 4 QSFP+

??

12 GByte

VoQ very large

Cavium

Edge-corE AS7500-32X

32 QSFP28 100 Gb/s

??

A mystery (for now)

Telco Systems T-Metro-8100

2 x QSFP28 100G and 48 x SFP+ 10G

Huawei S6720-54C-EI-48S

48 SFP+ and 2 QSFP and 4 QSFP expansion

??

8 MB to 1 port

Huawei S6720-30C-EI-24S

24 SFP+ and 2 QSFP and 4 QSFP expansion

??

8 MB to 1 port

Mellanox

Mellanox SX1024

48 SFP+ and 12 QSFP+

??

4.6 MB

64 KB to 1 port

Mellanox SX1036

36 QSFP+

??

4.6 MB

128 KB to 1 port

Mellanox Spectrum

32 QSFP28 100Gb/s

??

16 MB

12 MB to 1 port?

Other Shared Memory

Cisco NCS5001

40 1/10-Gbps SFP+ and 4 QSFP28 100G

8Q

16 MB

Cisco NCS5002

80 1/10-Gbps SFP+ and 4 QSFP28 100G

8Q

16 MB

Cisco NCS5011

32 QSFP28 100G

8Q

16 MB

Extreme 620X-16

16 10-Gbps SFP+

8Q

2 MB

2 MB

Extreme 620X-10

10 10-Gbps SFP+

8Q

2 MB

2 MB

Cisco Nexus 9372TX

48 10-Gbps BASE-T and 4 QSFP+

12 MB NFE + 25 MB ALE

21 MB max burst

Cisco Nexus 9396PX

48 SFP+ and {12 QSFP+ or 4 CPAK 100G}

12 MB NFE + 40 MB ALE

21 MB max burst

Brocade FCX624S

24Gig-E w 4 SFP+

8Q

2 MB

1.04 MB to 1 port

Juniper Ex4500 / Ex4550

40 SFP+ plus 8 SFP+

8Q

4 MB per ASIC

230 KBytes

Brocade ICX6610-24

24Gig-E w 8 SFP+

8Q

4 MB

1 MB to 1 port

HP 3800

24Gig-E w 4 10Gb/s

8Q or 4Q or 2 Q

0.23 MB

HP 2920-24

24 tw-pr Gig-E w 4 optional 10Gb/s

8Q

11.25 MB

4.5 MB shared

6.75 MB shared

HP 2824

20 tw-pr Gig-E w 4 SFP

4Q

0.512 MB shared

0.512 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

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 DCS-7150S-24

24 SFP+

8Q

9.5 MB

Arista DSC-7150S-52

52 SFP+

8Q

9.5 MB

Arista DCS-7150S-64

48 SFP+ and 4 QSFP+

8Q

9.5 MB

Dell 8024

24 SFP+

2Q

2 MB

Dell 6248

48 Gig-E, 4 x SFP+

8Q

6.1 MByte

98 KB per port

Dell 7024

24 Gig-E, 4 x SFP+

8Q

4 MB

4 MB

IBM BNT G8052

48 GE + 4 SFP+

8Q

4 MB/switch

4 MB

Arista 7010T

48 GE + 4 SFP+

8Q

4 MB/switch

4 MB

Nortel 5520-48T ver 1-3

48 GE + 4 SFP shared

8Q fixed

786 KB per 12-port

131 KB w 8 Queues

Nortel 5520-48T ver 4-5

48 GE + 4 SFP shared

1 to 8Q

786 KB per 12-port

786 KB w 1 Queue

Catalyst 3750G-48TS, 2960G

12 ASICs w/ 4 GE ports ea

8Q

1P3Q3T

576KB per ASIC

192KB per ASIC

384 KB per ASIC

Catalyst 3750E, 3560E, 3750X & 3560X

ASIC support 24 GE ports or 2 x 10G

2Q

1P3Q3T

2750KB per ASIC

750KB per ASIC

2 MB per ASIC

Catalyst 2960-X

ASIC support 48 GE ports AND uplink and stack

4Q

4 MB per ASIC

Catalyst 3850, 3650

ASIC support 24 GE ports AND 2 x 10GE

8Q

2P6Q3T

6 MB per ASIC

4 MB per ASIC

Catalyst C3850-12XS

12 SFP+ (6 ports per ASIC)

8Q

2P6Q3T

6 MB per ASIC

4 MB per ASIC

Catalyst 4948E

48 GigE + 4 SFP+

4

17.5 MB

Max 16 MB to 1 port

Cisco Ctalyst 4510R+E

Chassis w 8 interface slots -- 12 port SFP+ line card

8

1P7Q1T

32 MB on Supervisor

Max 14 MB to 1 port

Cisco Catalyst WS-C4500X-32SFP+

1 RU w 32 SFP+ ports and module for 8 more

8

1P7Q1T

32 MB

see note above

Cisco Nexus 3548

48 SFP+

4

18 MB

5.8 MB

Large queue 1RU switches

Force10 S60

48 Gig-E + 4 SFP+

4Q

1250 MB

enough

Arista 7048

48 Gig-E + 4 SFP+

8Q

768 MB

16 MB/port?

GOBBS

Corsa DP2100

32 1/10 G SFP+

8Q

6 GB

see note

Corsa DP2200

32 1/10 G SFP+ and 2 QSFP28 100G

8Q

6 GB

see note

Corsa DP2400

32 1/10 G SFP+ and 2 QSFP28 100G + stack

8Q

6 GB

see note

Corsa DP6430

24 SFP+ and 2 CFP/2 100G

8Q

20 GB

see note

Corsa DP6440

48 SFP+ and 4 CFP/2 100G

8Q

20 GB

see note

Virtual Output Port queuing

Arista 7504E/7508E

48 port sfp+ line card

8Q

3 GB per each of 3 processors

50 MB/port-queue

VoQ

Arista 7504E Linecard 12CQ

12 QSFP28 100G

8Q

3 GB per each of 6 processors

500 MB/port-queue

VoQ

Arista 7500R Linecard 36CQ

36 x QSFP28 100G

8Q

24 GB

VoQ

Arista 7500R Linecard 36Q

30 x 40G QSFP and 6 x 100G

8Q

8 GB

VoQ

Arista 7500R Linecard 48S2CQ

48 port sfp+ and 2 x 100G

8Q

4 GB

VoQ

Arista 7280SR-48C6

48 x 10 G SFP+ and 6 x QSFP28

8Q

4 GB

4 GB VoQ

Arista 7280TR-48C6

48 x 10GBASE-T and 6 x QSFP28

8Q

4 GB

4 GB VoQ

Arista 7280QR-C36

24 QSFP+ and 12 QSFP28

8Q

8 GB

8 GB in 2 groups VoQ

Brocade MLX

2-port 100 Gb/s line card

8Q

3 GB

256 MB/port-queue

VoQ

Brocade MLX

8-port 10 Gb/s line card

8Q

3 GB

256 MB/port-queue

VoQ

Brocade MLX

24-port 1 Gb/s line card

8Q

1 GB

64 MB/port-queue

VoQ

Extreme BlackDiamond X8

96-port SFP+ line card

48-port QSFP+ line card

4-port CFP2 100 Gb/s line card

8Q

9 MB per 24 10-Gb/s ports

9 MB per 6 40-Gb/s ports

36 MB per fabric module

Who knows??

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 Unicast 8 Multi

1 (I think)

640 KB per port

640 KB

VoQ

Cisco Nexus 5672UP

48 fixed SFP+ and 6 QSFP+

8 Unicast 8 Multi

1 (I think)

25 MB per 12-port 10G ASIC

14 MB shared per ASIC

3 MB Unicast + 6 MB Multicast

Cisco Nexus 6001

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

3 MB Unicast + 6 MB Multicast

Cisco ASR-9000

Chassis solution. 1-6 ports per ASIC

ASICs have 0.5 to 3.3 GB/port

VoQ

Juniper QFX10002-36

QSFP: 12 x 100 Gb/s OR 36 x 40 Gb/s

8Q

4 GByte per ASIC

VoQ 100 mS per port

Nexus 7000/7700

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 CPAK

4q

4q

72 MB shared

VoQ

Cisco Nexus 7000 (F2 series)

48 SFP+ across 12 ASICs

4q1t

1p3q1t

72 MB shared

VoQ

Cisco Nexus 7000 (F3 series)

12 QSFP+ across 6 ASICs

4q1t

1p3q1t

72 MB shared

VoQ

Cisco Nexus 7000 (M1 series)

32-port 10GE shared 4-port groups SFP+

8q2t

1p7q4t

65 MB per group

80 MB per group

Cisco Nexus 7000 (M1 series)

8-port 10GE X2

8q2t

1p7q4t

92 MB

80 MB

Cisco Nexus 7000 (M2 series)

2-port 100GE CFP2

8q2t

1p7q4t

62.46 MB

31.23 MB

Cisco Nexus 7000 (M2 series)

24-port 10GE SFP+

8q2t

1p7q4t

5.21 MB

5.21 MB

Cisco Nexus 7700 (F3 Series)

12-port 100GE CPAK across 12 ASICs

4q

4q

144 MB shared

VoQ

Cisco Nexus 7700 (F3 Series)

24-port 40GE QSFP+ across 12 ASICs

4q

4q

144 MB shared

VoQ

Cisco Nexus 7700 (F3 Series)

48-port 10GE SFP+ across 6 ASICs

4q

4q

144 MB shared

VoQ

Cisco Catalyst 6500 gets its own table

Comments, suggestions, corrections to warner@ucsc.edu

Opinions herein are solely those of jim warner. The University has no opinions, and if they did, these would not be them.