diff --git a/openbsc/doc/sgsn-remote-protocol.txt b/openbsc/doc/sgsn-remote-protocol.txt
index 3369d19..27b9abf 100644
--- a/openbsc/doc/sgsn-remote-protocol.txt
+++ b/openbsc/doc/sgsn-remote-protocol.txt
@@ -119,6 +119,7 @@
   IEI	Info Element		Type			Pres.	Format	Length
 	Message type		4.2.1			M	V	1
   01	IMSI			4.2.9			M	TLV	2-10
+  08	MSISDN			4.2.10			O	TLV	0-9
   04	PDP info complete	4.2.8			O	TLV	2
   05	PDP info		4.2.3			1-10	TLV
 
@@ -354,6 +355,7 @@
   | 0x05   PDP info       4.2.3                             |
   | 0x06   Cancel type    4.2.6                             |
   | 0x07   Freeze P-TMSI  4.2.8                             |
+  | 0x08   MSISDN         ISDN-AddressString/octet, 4.2.10  |
   | 0x10   PDP context id big endian int                    |
   | 0x11   PDP type       4.2.4                             |
   | 0x12   APN            04.08, 10.5.6.1                   |
@@ -397,3 +399,24 @@
 Note 1) Either '1 1 1 1 | Number digit N' (N odd) or
         'Number digit N | Number digit N-1' (N even),
         where N is the number of digits.
+
+4.2.10. ISDN-AddressString / MSISDN / Called Party BCD Number
+
+The MSISDN is encoded as an ISDN-AddressString in GSM 09.02 and Called Party
+BCD Number in GSM 04.08. It will be stored by the SGSN and then passed as is
+to the GGSN during the activation of the primary PDP Context.
+
+     8      7      6      5      4      3      2      1
+  +-----------------------------------------------------+
+  |     |  IEI                                          | octet 1
+  +-----------------------------------------------------+
+  |   Length of IE contents                             | octet 2
+  +-----------------------------------------------------+
+  | ext |  Type of num        |   Numbering plan        | octet 2
+  +-----------------------------------------------------+
+  |  Number digit 2           |   Number digit 1        | octet 3
+  +-----------------------------------------------------+
+  |  Number digit 4           |   Number digit 3        | octet 4
+  +-----------------------------------------------------+
+  :                                                     :   :
+  +-----------------------------------------------------+