SBC interface assignment with capacity guidance

Last Updated : Dec 19, 2025 |

Interface

Function

Typical Usage

Capacity Guidance (Throughout per interface)

M1

Primary Management

EMS ↔ SBC management, CLI/GUI access

Low bandwidth (<100 Mbps). Management traffic only

A1

Primary Access Data

Access-side SIP/media traffic

SBC: ~500 Mbps

Medium SBC: ~1 Gbps

Large SBC: >1 Gbps (up to NIC line rate; may require 10/25 GbE NICs)

B1

Primary Core Data

Core-side SIP/media traffic

SBC: ~500 Mbps

Medium SBC: ~1 Gbps

Large SBC: >1 Gbps (up to NIC line rate; may require 10/25 GbE NICs)

M2

Secondary Management / HA Heartbeat

SBC HA sync, state replication

Low bandwidth (<100 Mbps). Critical for HA sync. Must be dedicated.

A2

Secondary Access Data

Redundant/high-capacity access-side traffic

SBC: up to 1 Gbps

Large SBC: >1 Gbps (requires 10/25 GbE NICs for scaling)

B2

Secondary Core Data

Redundant/high-capacity core-side traffic

SBC: up to 1 Gbps

Large SBC: >1 Gbps (requires 10/25 GbE NICs for scaling)
Note:

  • Exact capacity depends on the SBC license, number of sessions, codec usage, and percentage of encrypted calls.

  • Capacity Note: The maximum capacity per SBC VM or EMS+SBC VM using 1 Gbps bandwidth is 5,000 non-encrypted sessions. Refer to the Overview and Specification document for additional capacity details.

Note:

  • Small SBC Deployment: Uses 4 interfaces (M1, M2, A1, B1). Supports up to ~1 Gbps of aggregate media throughput.

  • Medium SBC Deployment: Can extend to 6 interfaces (M1, M2, A1, B1, A2, B2). Supports up to ~2 Gbps of aggregate media throughput.

  • Large SBC Deployment: Requires 10/25 GbE NICs (A2, B2) for scaling beyond 2 Gbps of aggregate media throughput.

  • Management (M1, M2): Always low bandwidth, but isolation is critical for security and High Availability (HA) stability.

Table 1: SBC capacity and interface sizing guidance

Deployment Tier

Session Capacity

Encryption Profile

Recommended Interfaces

Bandwidth Guidance

Notes

Tier 1 - Small

SBC/EMS Combo

~1,000

Encrypted

4 interfaces (M1, M2, A1, B1)

~1 Gbps aggregate (500 Mbps A1 + 500 Mbps B1)

Fits within dual 1 GbE data ports. No 10/25 GbE required.

Tier 2 - Medium

~5,000

Unencrypted

4 interfaces (M1, M2, A1, B1) or 6 (add A2/B2)

~1 Gbps aggregate (500 Mbps A1 + 500 Mbps B1)

NICs and CPU must be correctly sized.

Tier 2 - Medium

~3,000

Mixed (encrypted and unencrypted)

4 interfaces (M1, M2, A1, B1) or 6 (add A2/B2)

~1 Gbps per side (encryption overhead reduces efficiency

Encryption consumes additional CPU. NICs and CPU must be correctly sized. Capacity can be increased by adding more than 4 vCPUs.

Tier 2 - Medium (Secure)

~3,000

Encrypted

4 interfaces (M1, M2, A1, B1) or 6 (add A2/B2)

~1 Gbps per side (encryption overhead reduces efficiency)

Encryption consumes additional CPU. NICs and CPU must be correctly sized. Capacity can be increased by adding more than 4 vCPUs.

Tier 3 - Large

~14,000

Mixed (encrypted and unencrypted)

6 interfaces (M1, M2, A1, A2, B1, B2)

~2–4 Gbps aggregate

Requires bridged VLANs on 10/25 GbE ports for A2/B2. Traffic shaping is recommended if 1G and 10G are mixed. TBD (Not qualified)

Tier 4 - Extra Large

~25,000

Mixed (encrypted and unencrypted)

6 interfaces (M1, M2, A1, A2, B1, B2)

~5–8 Gbps aggregate

Mandatory use of 10/25 GbE NICs with VLAN bridging. Each side (Access/Core) requires a minimum of 2 Gbps guaranteed. TBD (Not qualified)
Note:

  • Encrypted sessions require more CPU per call, which may limit throughput before the NIC line rate is reached.

  • Bridged VLANs on 10/25 GbE NICs should be used for Tier 3 and Tier 4 deployments.

  • Traffic shaping is required when sharing ports across 1G and 10/25G to ensure that latency-sensitive flows (A1, B1, A2, B2) receive guaranteed throughput.