Update v3.0.0-beta.md

Signed-off-by: Yacov Manevich <yacov.manevich@ibm.com>

release_notes/v3.0.0-beta.md

@@ -17,6 +17,11 @@ Fabric v3.0.0-beta provides a BFT ordering service based on the [SmartBFT](https
 Consider using the BFT orderer if true decentralization is required, where up to and not including a third of the parties running the orderers may not be trusted due to malicious intent or being compromised.
 For more details of the BFT ordering service and other recent features, see the [What's New documentation](https://hyperledger-fabric.readthedocs.io/en/latest/whatsnew.html).
 
+The v3.0.0-beta release differs from the v3.0.0-preview release by making the peer and orderer block replication resistant to block withholding. 
+Block withholding is when an orderer receives a request for blocks it possesses, but it delays sending the blocks and by doing so, slows down the requester's block reception.
+As described in [the RFC](https://hyperledger.github.io/fabric-rfcs/text/0010-bft-signatures.html), block withholding resistance incurs a bandwidth and CPU cost,
+and therefore an operator of an orderer may opt out and use the standard mechanism by specifying `ReplicationPolicy`: `simple` in the local configuration.
+
 **Query all approved chaincodes on a channel**
 
 The updated `peer lifecycle chaincode queryapproved` command allows you to pass only a channel name.
@@ -119,4 +124,4 @@ peer.gossip.orgLeader: true
 peer.gossip.useLeaderElection: false
 peer.gossip.state.enabled: false
 peer.deliveryclient.blockGossipEnabled: false
-```
+```