From Sven Meier (on -dev in 6/2007):

This is a dissector for the Parallel Redundancy Protocol (PRP) defined in chapter
6 of the IEC 62439.

PRP uses two independent networks in parallel and allows redundancy without
switchovers.

The protocol is sending Mac multicast messages with Ethertype 0x88fb. In
addition to that it adds to every Ethernet frame a 4 byte trailer before
the FCS. The trailer is detected by checking a size field and an identifier
which are part of the trailer. Therefore, if the last 4 bytes of a frame
match a correct trailer they get interpreted as a trailer, although it was
probably not a real one.

Note:

This is a post-dissector which means it gets called for every frame.  So as
to not cause a performance hit for every Wireshark user (who may not even be
looking at Ethernet frames) it currently disables itself every time Wireshark
starts up.  (There should be a better way to do this--maybe different Profiles
(as discussed on -dev recently) is the way to go.)

From me:

Put ETHERTYPE_PRP (not IANA registered) in etypes.h and packet-ethertype.c

svn path=/trunk/; revision=24493

1 files changed, 23 insertions, 19 deletions

diff --git a/epan/etypes.h b/epan/etypes.h
index 956dd15f57..1978daa80e 100644
--- a/epan/etypes.h
+++ b/epan/etypes.h
@@ -312,28 +312,28 @@
 
 #ifndef ETHERTYPE_IEC61850_GOOSE
 #define ETHERTYPE_IEC61850_GOOSE	0x88b8  /* IEC 61850 is a global standard for the use in utility communication,*/
-#endif										/* in particular for the information exchange between IED's in a power */
-											/* transmission or distribution substation. */
-											/*  There are three types of application services
-												that use a specific EtherType. GOOSE uses
-												EtherType field 88b8, GSE management services
-												uses EtherType field 88b9. These two protocols
-												are defined in IEC 61850-8-1. SV (Sampled
-												Value Transmission) uses EtherType field
-												88ba; the protocol is defined in IEC 61850-9-1
-												and IEC 61850-9-2. */
+#endif						/* in particular for the information exchange between IED's in a power */
+						/* transmission or distribution substation. */
+						/*  There are three types of application services
+						    that use a specific EtherType. GOOSE uses
+						    EtherType field 88b8, GSE management services
+						    uses EtherType field 88b9. These two protocols
+						    are defined in IEC 61850-8-1. SV (Sampled
+						    Value Transmission) uses EtherType field
+						    88ba; the protocol is defined in IEC 61850-9-1
+						    and IEC 61850-9-2. */
 
 #ifndef ETHERTYPE_IEC61850_GSE
 #define ETHERTYPE_IEC61850_GSE		0x88b9  /* IEC 61850 is a global standard for the use in utility communication,*/
-#endif										/* in particular for the information exchange between IED's in a power */
+#endif						/* in particular for the information exchange between IED's in a power */
 
 #ifndef ETHERTYPE_IEC61850_SV
 #define ETHERTYPE_IEC61850_SV		0x88ba	/* IEC 61850 is a global standard for the use in utility communication,*/
-#endif										/* in particular for the information exchange between IED's in a power */
+#endif						/* in particular for the information exchange between IED's in a power */
 
 #ifndef ETHERTYPE_TIPC
 #define ETHERTYPE_TIPC	0x88ca  /* TIPC  (Transparent Inter Process Communication, */
-#endif							/* http://tipc.sourceforge.net/) Ericsson Research Canada Inc */
+#endif				/* http://tipc.sourceforge.net/) Ericsson Research Canada Inc */
 
 #ifndef ETHERTYPE_RSN_PREAUTH
 #define ETHERTYPE_RSN_PREAUTH	0x88c7  /* 802.11i Pre-Authentication */
@@ -349,11 +349,11 @@
 
 #ifndef ETHERTYPE_3GPP2
 #define ETHERTYPE_3GPP2	        0x88d2  /* This will be used in a revision of the Interoperabi */
-#endif									/* Specification (IOS) for cdma2000 Access Network Interfaces (document numbers A.S0011-B */
-										/* through A.S0017-B v1.0). This document already uses the Ether type 8881 */
+#endif					/* Specification (IOS) for cdma2000 Access Network Interfaces (document numbers A.S0011-B */
+					/* through A.S0017-B v1.0). This document already uses the Ether type 8881 */
 
 #ifndef ETHERTYPE_LLTD
-#define ETHERTYPE_LLTD			0x88d9  /* Link Layer Topology Discovery (LLTD) */
+#define ETHERTYPE_LLTD		0x88d9  /* Link Layer Topology Discovery (LLTD) */
 #endif
 
 #ifndef ETHERTYPE_MRP
@@ -366,9 +366,13 @@
 
 #ifndef ETHERTYPE_PTP
 #define ETHERTYPE_PTP		0x88F7	/* IEEE1588v2 (PTPv2) over Ethernet */
-#endif								/* in particular for the information exchange between IED's in a power */
-									/* transmission or distribution substation. */
-									/*  There are three types of application services */
+#endif					/* in particular for the information exchange between IED's in a power */
+					/* transmission or distribution substation. */
+					/*  There are three types of application services */
+
+#ifndef ETHERTYPE_PRP
+#define ETHERTYPE_PRP		0x88FB	/* Parallel Redundancy Protocol (IEC62439 Chapter 6) */
+#endif
 
 #ifndef ETHERTYPE_CFM
 #define ETHERTYPE_CFM		0x8902	/* IEEE 802.1ag Connectivity Fault Management */