Packet Buffer Reference

Packet Buffer Reference

Data quality note: Information here is by rumor, innuendo, and extrapolation. Manufacturers rarely publish packet buffer information in their data sheets. See the summary page for context on why buffers matter, or read about microbursts.

Shared memory means hardware permits buffers to be used by any port that needs them. In a shared memory design, it is not possible to let ALL memory go to queued packets (no room for new arrivals → head-of-line blocking). Some switches have multiple switch ICs, each managing their own memory pool — memory from one IC cannot be loaned to ports on another chip. Max TX buffer is the most a single queue/port can claim from the shared pool.

Trident+ — Broadcom BCM56840, Shared Memory, 9 MB on-chip
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
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 12Q — 9 MB — 5? MB
Arista 7050S-64 48 SFP+ and 4 QSFP 8Q — 9 MB/switch — 5 MB
Dell 8132F & 4032F 24 SFP+ and 2x QSFP 8Q — 9 MB — —
Dell 8164F & 4064F 48 SFP+ and 4x QSFP 8Q — 9 MB — —
Pica8 P-3920 48 SFP+ and 4x QSFP — — 9 MB — —
Penguin 4804x 48 SFP+ and 4x QSFP — — 9 MB — —
Cisco Nexus 3064X 48 SFP+ and 4 QSFP 12Q — 9 MB — 5 MB
IBM G8264 48 SFP+ and 4 QSFP 8Q — 9 MB/switch — not on data sheet See Tolly report for microburst testing
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 — — — — — No buffer data available
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 12Q — 9 MB — 5? MB
Arista 7050S-64 48 SFP+ and 4 QSFP 8Q — 9 MB/switch — 5 MB
Dell 8132F & 4032F 24 SFP+ and 2x QSFP 8Q — 9 MB — —
Dell 8164F & 4064F 48 SFP+ and 4x QSFP 8Q — 9 MB — —
Pica8 P-3920 48 SFP+ and 4x QSFP — — 9 MB — —
Penguin 4804x 48 SFP+ and 4x QSFP — — 9 MB — —
Cisco Nexus 3064X 48 SFP+ and 4 QSFP 12Q — 9 MB — 5 MB
IBM G8264 48 SFP+ and 4 QSFP 8Q — 9 MB/switch — not on data sheet See Tolly report for microburst testing
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 — — — — — No buffer data available
Trident II — Broadcom BCM56850/56854, Shared Memory, 12 MB on-chip
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
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 4-chip design
Brocade 7750-26Q 26 QSFP + expansion 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
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
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
HP 5930 32 QSFP 8Q — 12.2 MB — Dynamic up to 8 MB
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 4-chip design
Brocade 7750-26Q 26 QSFP + expansion 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
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
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
HP 5930 32 QSFP 8Q — 12.2 MB — Dynamic up to 8 MB
Mellanox — Mellanox Spectrum ASIC, Shared Memory
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Mellanox SX1024 48 SFP+ and 12 QSFP ?? — 4.6 MB — 64 KB to 1 port Spectrum ASIC
Mellanox SX1036 36 QSFP ?? — 4.6 MB — 128 KB to 1 port Spectrum ASIC
Mellanox SX1024 48 SFP+ and 12 QSFP ?? — 4.6 MB — 64 KB to 1 port Spectrum ASIC
Mellanox SX1036 36 QSFP ?? — 4.6 MB — 128 KB to 1 port Spectrum ASIC
Other Shared Memory — Various ASICs
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Brocade FCX624S 24 GigE with 4 SFP+ 8Q — 2 MB — 1.04 MB to 1 port
Juniper EX4500 40 SFP+ plus 8 SFP+ 8Q — — — 230 KB
Brocade ICX6610-24 24 GigE with 8 SFP+ 8Q — 4 MB — 1 MB to 1 port
HP 3800 24 GigE with 4 10Gb/s 8Q or 4Q or 2Q — — — 0.23 MB
HP 2920-24 24 twisted-pair GigE with 4 optional 10Gb/s 8Q — 11.25 MB 4.5 MB shared 6.75 MB shared
HP A5800-24G 24 GigE with 4 10Gb/s 8Q — 4 MB — 4 MB
HP E6600-24G-4XG 24 GigE with 2 10Gb/s 8Q — 18 MB for GE — 18 MB
Arista 7124SX 24x SFP+ 8Q — 2 MB/switch-chip shared 1.238 + 0.02 MB
Arista 7148SX 48 SFP+ 8Q — 2 MB/switch-chip, 8 MB total — 1.238 + 0.02 MB
Arista DCS-7150S-24 24 SFP+ 8Q — 9.5 MB — —
Arista DCS-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 GigE, 4x SFP+ 8Q — 6.1 MB — 98 KB per port
Dell 7024 24 GigE, 4x SFP+ 8Q — 32 MB — 4 MB
IBM BNT G8052 48 GE + 4 SFP+ 8Q — 4 MB/switch — 4 MB
Cisco Catalyst 3750G-48TS 6 ASICs, 8 GE ports each 8Q 1P3Q3T 576 KB per ASIC 192 KB per ASIC 384 KB per ASIC Multiple switch ICs – memory not shared across chips
Cisco Catalyst 3750E / 3560E / 3750X / 3560X ASIC supports 24 GE ports or 2x 10G 2Q 1P3Q3T 2750 KB per ASIC 750 KB per ASIC 2 MB per ASIC
Cisco Catalyst 4948E 48 GigE + 4 SFP+ 4Q — 17.5 MB — Max 16 MB to 1 port
Cisco Nexus 3548 48 SFP+ 4Q — 18 MB — 5.8 MB Algorithmic buffer; see detail page
Brocade FCX624S 24 GigE with 4 SFP+ 8Q — 2 MB — 1.04 MB to 1 port
Juniper EX4500 40 SFP+ plus 8 SFP+ 8Q — — — 230 KB
Brocade ICX6610-24 24 GigE with 8 SFP+ 8Q — 4 MB — 1 MB to 1 port
HP 3800 24 GigE with 4 10Gb/s 8Q or 4Q or 2Q — — — 0.23 MB
HP 2920-24 24 twisted-pair GigE with 4 optional 10Gb/s 8Q — 11.25 MB 4.5 MB shared 6.75 MB shared
HP A5800-24G 24 GigE with 4 10Gb/s 8Q — 4 MB — 4 MB
HP E6600-24G-4XG 24 GigE with 2 10Gb/s 8Q — 18 MB for GE — 18 MB
Arista 7124SX 24x SFP+ 8Q — 2 MB/switch-chip shared 1.238 + 0.02 MB
Arista 7148SX 48 SFP+ 8Q — 2 MB/switch-chip, 8 MB total — 1.238 + 0.02 MB
Arista DCS-7150S-24 24 SFP+ 8Q — 9.5 MB — —
Arista DCS-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 GigE, 4x SFP+ 8Q — 6.1 MB — 98 KB per port
Dell 7024 24 GigE, 4x SFP+ 8Q — 32 MB — 4 MB
IBM BNT G8052 48 GE + 4 SFP+ 8Q — 4 MB/switch — 4 MB
Cisco Catalyst 3750G-48TS 6 ASICs, 8 GE ports each 8Q 1P3Q3T 576 KB per ASIC 192 KB per ASIC 384 KB per ASIC Multiple switch ICs – memory not shared across chips
Cisco Catalyst 3750E / 3560E / 3750X / 3560X ASIC supports 24 GE ports or 2x 10G 2Q 1P3Q3T 2750 KB per ASIC 750 KB per ASIC 2 MB per ASIC
Cisco Catalyst 4948E 48 GigE + 4 SFP+ 4Q — 17.5 MB — Max 16 MB to 1 port
Cisco Nexus 3548 48 SFP+ 4Q — 18 MB — 5.8 MB Algorithmic buffer; see detail page
Large Queue 1RU Switches — External DRAM, Very Large Buffers
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Force10 S60 48 GigE + 4 SFP+ 4Q — 1250 MB — enough External DRAM; designed for speed-step scenarios
Arista 7048 48 GigE + 4 SFP+ 8Q — 768 MB 16 MB/port? GOBBS External DRAM; claims 50ms buffers per port simultaneously
Force10 S60 48 GigE + 4 SFP+ 4Q — 1250 MB — enough External DRAM; designed for speed-step scenarios
Arista 7048 48 GigE + 4 SFP+ 8Q — 768 MB 16 MB/port? GOBBS External DRAM; claims 50ms buffers per port simultaneously
Virtual Output Port (VoQ) — Per-egress queues at ingress, eliminates head-of-line blocking
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Arista 7504E / 7508E 48-port SFP+ line card 8Q — 3 GB per packet processor 50 MB/port-queue 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
Cisco Nexus 5010 26 SFP+ 8Q 1 (uncertain) 480 KB per port 480 KB VoQ
Cisco Nexus 5548P 32 fixed SFP+ and 16-port expansion module 8 Unicast + 8 Multicast 1 (uncertain) 640 KB per port 640 KB VoQ
Cisco Nexus 6001 48 fixed SFP+ and 4 QSFP 8 Unicast + 8 Multicast 1 (uncertain) 25 MB per 12-port 10G ASIC 14 MB shared per ASIC VoQ
Cisco Nexus 7000 M1 48-port twisted-pair GE 2q4t 1p3q4t — 7.56 MB per port 6.15 MB per port
Cisco Nexus 7000 F3 6-port 100GE 4q 4q 144 MB shared — VoQ
Cisco Nexus 7000 F2 48 SFP+ 4q1t 1p3q1t 72 MB shared — VoQ
Cisco Nexus 7000 M1 32-port 10GE shared 4-port groups 8q4t 1p7q4t — 65 MB per group 80 MB per group
Cisco Catalyst 6500 Various line cards — — — — — Complex architecture — see dedicated detail page
Arista 7504E / 7508E 48-port SFP+ line card 8Q — 3 GB per packet processor 50 MB/port-queue 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
Cisco Nexus 5010 26 SFP+ 8Q 1 (uncertain) 480 KB per port 480 KB VoQ
Cisco Nexus 5548P 32 fixed SFP+ and 16-port expansion module 8 Unicast + 8 Multicast 1 (uncertain) 640 KB per port 640 KB VoQ
Cisco Nexus 6001 48 fixed SFP+ and 4 QSFP 8 Unicast + 8 Multicast 1 (uncertain) 25 MB per 12-port 10G ASIC 14 MB shared per ASIC VoQ
Cisco Nexus 7000 M1 48-port twisted-pair GE 2q4t 1p3q4t — 7.56 MB per port 6.15 MB per port
Cisco Nexus 7000 F3 6-port 100GE 4q 4q 144 MB shared — VoQ
Cisco Nexus 7000 F2 48 SFP+ 4q1t 1p3q1t 72 MB shared — VoQ
Cisco Nexus 7000 M1 32-port 10GE shared 4-port groups 8q4t 1p7q4t — 65 MB per group 80 MB per group
Cisco Catalyst 6500 Various line cards — — — — — Complex architecture — see dedicated detail page
Nokia SR (FP-based)
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Nokia 7750 SR (FP4) Various line cards (up to 400G) 128k ingress queues 128k egress queues ~64 GB per line card shared shared Fully shared memory pool; pre-buffer multi-million packets; ~3 Tbps class NPU; 8k queue realloc increments
Nokia 7750 SR (FP5) Various line cards (400G/800G) 128k ingress queues 128k egress queues 32–64 GB per line card shared shared Fully shared memory pool; pre-buffer 10.8M–21.6M packets; ~6 Tbps class NPU; 16k queue realloc increments
Nokia 7750 SR (FP4) Various line cards (up to 400G) 128k ingress queues 128k egress queues ~64 GB per line card shared shared Fully shared memory pool; pre-buffer multi-million packets; ~3 Tbps class NPU; 8k queue realloc increments
Nokia 7750 SR (FP5) Various line cards (400G/800G) 128k ingress queues 128k egress queues 32–64 GB per line card shared shared Fully shared memory pool; pre-buffer 10.8M–21.6M packets; ~6 Tbps class NPU; 16k queue realloc increments
Nokia Access / Aggregation
Model Port Type RX Queue TX Queue Total Buffer RX Buffer TX Buffer Notes
Nokia 7210 SAS Various (access/demarcation/cell-site) — — 64–512 MB shared ingress/egress shared ingress/egress Merchant Ethernet silicon; ingress-dominant; hierarchical QoS; access edge role
Nokia 7250 IXR 100G/400G (aggregation/DC edge) — — moderate (shared) shared + VOQ VoQ Broadcom Jericho/Qumran family; VOQ reduces head-of-line blocking; low-latency DC/aggregation
Nokia 7705 SAR Various adapter cards — — ~200–300 MB per adapter card — — SAR ASIC; fixed 512B (chained) or 2304B buffer segments; MBS per queue; mobile backhaul / TDM transport
Nokia 7730 SXR Various (core/DCI) 256k queues — multi-GB (FP5-class) shared shared FP5 silicon; same family as 7750 SR FP5; fully shared buffer; deterministic QoS; core/DCI role
Nokia 7210 SAS Various (access/demarcation/cell-site) — — 64–512 MB shared ingress/egress shared ingress/egress Merchant Ethernet silicon; ingress-dominant; hierarchical QoS; access edge role
Nokia 7250 IXR 100G/400G (aggregation/DC edge) — — moderate (shared) shared + VOQ VoQ Broadcom Jericho/Qumran family; VOQ reduces head-of-line blocking; low-latency DC/aggregation
Nokia 7705 SAR Various adapter cards — — ~200–300 MB per adapter card — — SAR ASIC; fixed 512B (chained) or 2304B buffer segments; MBS per queue; mobile backhaul / TDM transport
Nokia 7730 SXR Various (core/DCI) 256k queues — multi-GB (FP5-class) shared shared FP5 silicon; same family as 7750 SR FP5; fully shared buffer; deterministic QoS; core/DCI role

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