Multilevel precedence and preemption: Difference between revisions

Revision as of 14:28, 17 March 2015

Multilevel precedence and preemption, or MLPP, is used to assign priorities to some calls, for example emergency calls.<br\> The MLPP is an SS7 ISUP Information element. The IE is identified by 4 parameters:

Look ahead for busy (LFB): Allowed, Path reserved or not allowed
Network identity: Information to identify the Network. A value from 0 to 999.
Service domain: Defines the specific MLPP domain. A value from 0 to 16777215 (24 bits).
Precedence Level: Flash override (Highest, 0), Flash (1), Immediate (2), Priority (3), Routine (lowest, 4)

In SIP, it is a header parameter called Resource-Priority. The parameter will be q735.x, "x" being the priority (same value as precedence level for SS7 ISUP).<br\>The priorities are defined as emergency (0), urgent (1), normal (2), non-urgent (3) and other-priority (4)

TelcoBridges and MLPP

It is possible to configure the MLPP options in the profiles. Profiles can be assigned to any network. There are 3 outgoing modes possible:

No MLPP insertion
Relay MLPP information
Always insert MLPP information
Forced MLPP information

MLPP can be inserted or removed from the call flows. Depending on the networks involved, these are the results of the calls:

Incoming	Outgoing
No MLPP Insertion
SS7 with or without MLPP	SS7: no MLPP
SS7 with or without MLPP	SIP: no Resource-Priority header
SIP with or without Resource-Priority	SS7: no MLPP
SIP with or without Resource-Priority	SIP: no Resource-Priority header

Incoming	Outgoing
Relay MLPP information
SS7 with MLPP	SS7: incoming MLPP
SS7 without MLPP	SS7: no MLPP
SS7 with MLPP	SIP: Resource-Priority=q735.[incoming precedence level]
SS7 without MLPP	SIP: no Resource-Priority header
SIP with Resource-Priority=q735.x	SS7: Precedence Level = x and profile MLPP info (LFB + Network ID + Service Domain)
SIP without resource priority	SS7: no MLPP
SIP with Resource-Priority=q735.x	SIP: Resource-Priority=q735.x
SIP without Resource-Priority	SIP: no Resource-Priority header

Incoming	Outgoing
Always insert MLPP information
SS7 with or without MLPP	SS7: MLPP info from profile
SS7 with or without MLPP	SIP: Resource-Priority=q735.[precedence level from profile]
SIP with or without resource priority	SS7: MLPP info from profile
SIP with or without resource priority	SIP: Resource-Priority=q735.[precedence level from profile]

Incoming	Outgoing
Forced MLPP information
SS7 with or without MLPP	SS7: MLPP info from profile
SS7 with or without MLPP	SIP: Resource-Priority=q735.[precedence level from profile]
SIP with or without resource priority	SS7: MLPP info from profile
SIP with or without resource priority	SIP: Resource-Priority=q735.[precedence level from profile]

In addition to this profile configuration, MLPP values can be set in the routing scripts.<br\> See MLPP Precedence values

@@ Line 15: / Line 15: @@
 * Relay MLPP information
 * Always insert MLPP information
+* Forced MLPP information
 MLPP can be inserted or removed from the call flows. Depending on the networks involved, these are the results of the calls:
@@ Line 58: / Line 59: @@
 |-
 | '''Always insert MLPP information'''
+|-
+! Incoming !! Outgoing
+|-
+| SS7 with or without MLPP || SS7: MLPP info from profile
+|-
+| SS7 with or without MLPP || SIP: Resource-Priority=q735.[precedence level from profile]
+|-
+| SIP with or without resource priority || SS7: MLPP info from profile
+|-
+| SIP with or without resource priority || SIP: Resource-Priority=q735.[precedence level from profile]
+|}
+{| class="wikitable"
+|-
+| '''Forced MLPP information'''
 |-
 ! Incoming !! Outgoing