Update MulticastNextHopRewrite.md

Signed-off-by: Manali Holankar <manali.holankar@gmail.com>

doc/IP-Multicast/MulticastNextHopRewrite.md

@@ -5,20 +5,22 @@
 ```
 Author:mholankar@
 ```
+
 ## Overview
 
-This document discusses requirements and the SAI spec proposal for disabling rewriting fields
-(SourceMAC,VLAN) as part of IPMC routing.
+This document discusses requirements and the SAI spec proposal for disabling rewriting fields (SourceMAC, VLAN) as part of IPMC routing.
 
 ## Background
 
-#### SAI pipeline for IPMC forwarding. After Multicast Replication, the egress
-#### pipeline is very similar to Unicast Forwarding. The reference pipeline is
-#### fromUnicastForwarding.
+### SAI pipeline for IPMC forwarding. After Multicast Replication, the egress
+
+### pipeline is very similar to Unicast Forwarding. The reference pipeline is
+
+### fromUnicastForwarding.
 
 - Nexthop sets the egress RIF and NextHopIP
-- Neighbor table lookup on NextHopIP to set packet’s destination MAC address
-- Egress RIF lookup to set packet’s source MAC address, VLAN and port.
+- Neighbor table lookup on NextHopIP to set packet's destination MAC address
+- Egress RIF lookup to set packet's source MAC address, VLAN and port.
 
 ## Requirements
 
@@ -29,58 +31,50 @@ We require knobs for disabling rewrites to following fields as part of Multicast
 ● Vlan rewrite disable
 ```
 
-We have scenarios where we need knobs for disabling header field rewrites, for Multicast 
-Replication.
+We have scenarios where we need knobs for disabling header field rewrites, for Multicast Replication.
 
-Case1:For certain flows, the switch does MulticastReplication for a VLAN tagged packet. However,
-we do not want the VLAN tag to be over-written during replication, we want the replication to retain
-the VLAN tag. For such a case we would like to disable L3 VLAN rewrite.
+Case1:For certain flows, the switch does MulticastReplication for a VLAN tagged packet. However, we do not want the VLAN tag to be over-written during replication, we want the replication to retain the VLAN tag. For such a case we would like to disable L3 VLAN rewrite. Please note: that when a disable L3 Vlan rewrite
+flag is enabled, it does allow for untagged packets to get replicated.
 
-Case2: For some scenarios, we may want to rewrite the SRC MAC. Having NextHop based knobs
-for such rewrites would be very helpful.
+Case2: For some scenarios, we may want to rewrite the SRC MAC. Having NextHop based knobs for such rewrites would be very helpful.
 
-In summary, with SDN based forwarding, Controller treats the L2 fields like any other header field
-which can be controlled and requires them to be configured flexibility as part of MulticastReplication.
+In summary, with SDN based forwarding, Controller treats the L2 fields like any other header field which can be controlled and requires them to be configured flexibility as part of MulticastReplication.
 
 ## Proposal
 
-Since we require capability to disable the rewrites for certain Multicast flows and not for all flows
-via/to neighbor, the best option is to have these as part of NextHop object:
+Since we require capability to disable the rewrites for certain Multicast flows and not for all flows via/to neighbor, the best option is to have these as part of NextHop object:
 
 - SAI_NEXT_HOP_ATTR_DISABLE_SRC_MAC_REWRITE
 - SAI_NEXT_HOP_ATTR_DISABLE_DST_MAC_REWRITE
 - SAI_NEXT_HOP_ATTR_DISABLE_VLAN_REWRITE
 
 ### Example SAI object creation for an IPMCGroup:
 
-- Create a **SAI_OBJECT_TYPE_IPMC_GROUP** for the multicast group with the following
-    attributes.
+- Create a **SAI_OBJECT_TYPE_IPMC_GROUP** for the multicast group with the following attributes.
 - Create a SAI_OBJECT_TYPE_ROUTER_INTERFACE with following attributes:
-    ● SAI_ROUTER_INTERFACE_ATTR_VIRTUAL_ROUTER_ID
-    ● SAI_ROUTER_INTERFACE_ATTR_SRC_MAC_ADDRESS
-    ● SAI_ROUTER_INTERFACE_ATTR_TYPE=SAI_ROUTER_INTERFACE_TYPE_
-       PORT
-    ● SAI_ROUTER_INTERFACE_ATTR_PORT_ID
+● SAI_ROUTER_INTERFACE_ATTR_VIRTUAL_ROUTER_ID
+● SAI_ROUTER_INTERFACE_ATTR_SRC_MAC_ADDRESS
+● SAI_ROUTER_INTERFACE_ATTR_TYPE=SAI_ROUTER_INTERFACE_TYPE_
+
+  ```
+  PORT
+  ```
+
+● SAI_ROUTER_INTERFACE_ATTR_PORT_ID
 - Create a SAI_OBJECT_TYPE_NEIGHBOR_ENTRY for each neighbor with:
-    ● “ip”=Link local address
-    ● “rif”
-    ● “switch id”
-    ● SAI_NEIGHBOR_ENTRY_ATTR_DST_MAC_ADDRESS(optional)
-    ● SAI_NEIGHBOR_ENTRY_ATTR_NO_HOST_ROUTE=true
+● "ip"=Link local address ● "rif" ● "switch id"
+● SAI_NEIGHBOR_ENTRY_ATTR_DST_MAC_ADDRESS(optional)
+● SAI_NEIGHBOR_ENTRY_ATTR_NO_HOST_ROUTE=true
 - Create SAI_OBJECT_TYPE_NEXT_HOP with:
-    ● SAI_NEXT_HOP_ATTR_TYPE=SAI_NEXT_HOP_TYPE_IPMC
-    ● SAI_NEXT_HOP_ATTR_ROUTER_INTERFACE_ID
-    ● SAI_NEXT_HOP_ATTR_IP=“ip”of neighbor
-
+● SAI_NEXT_HOP_ATTR_TYPE=SAI_NEXT_HOP_TYPE_IPMC
+● SAI_NEXT_HOP_ATTR_ROUTER_INTERFACE_ID
+● SAI_NEXT_HOP_ATTR_IP="ip"of neighbor
 
 ```
 ● SAI_NEXT_HOP_ATTR_DISABLE_SRC_MAC_REWRITE=true
 ● SAI_NEXT_HOP_ATTR_DISABLE_VLAN_REWRITE=true
 ```
-- Create a **SAI_OBJECT_TYPE_IPMC_GROUP_MEMBER** with following attributes:
-    ● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_GROUP_ID with ipmc_group_oid
-    ● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_OUTPUT_ID with rif_oid
-    ● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_NEXT_HOP with next_hop_oid
-
-
 
+- Create a **SAI_OBJECT_TYPE_IPMC_GROUP_MEMBER** with following attributes:
+● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_GROUP_ID with ipmc_group_oid
+● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_OUTPUT_ID with next_hop_oid