SBC Manager — Header Manipulation (HMR)

Why Header Manipulation Is Needed

Different carriers and PBX systems implement SIP differently — headers may be missing, formatted differently, or conflict with what the other side expects. HMR normalizes SIP at the border so both sides interoperate without changing the PBX or the carrier configuration.

A special case is P-Asserted-Identity (PAI): the trusted caller-identity header that overrides From for caller-ID delivery. Typical policy is to pass PAI through unchanged inbound, and normalize or strip it outbound depending on what the carrier supports (see the examples below).

Header manipulation rule sets (HMR) rewrite, remove, or add SIP headers on calls passing through the SBC — the primary tool for carrier and PBX interoperability. Go to HMR to manage rule sets.

Creating a Rule Set

1. Go to HMR → New Rule Set
2. Set the name and direction (Inbound or Outbound)
3. Add rules — each rule specifies:
   • Header (e.g., P-Asserted-Identity)
   • Action (rewrite, remove, or add)
   • Match pattern (regular expression)
   • Replacement value (supports regex capture groups, e.g., $1)
   • Priority (execution order within the set; lower runs first)

Assigning Rule Sets

A rule set is assigned to one or more trunks or routes from its detail page. The same set can be reused across multiple assignments — edit once, updated everywhere.

Examples

Normalize outbound P-Asserted-Identity — present a consistent domain to the carrier:

Strip a Privacy header the carrier doesn't support: Action Remove, match .*.

Add a carrier-required header: Header X-Carrier-Account, Action Add, Replacement ACCT-10294.

Teams Direct Routing normalization — a multi-rule set run in priority order:

Changes to HMR rule sets take effect after the next Apply.