Updating neo4j relationship properties without duplicating the existing relationship

Neo4j Graph Platform
1

I have the following

MATCH (a: node)
MATCH (b: node)
MERGE (a) -[c:connect]-> (b)
on match set c.packets_transmitted = 200,
             c.packets_recieved    =350

I want to update the properties without duplicating the relationship which is already exist. Now whenever I run the cypher, the relationship between the nodes connect duplicates. What should I do?

Note: below is the cypher I used to create the relationship connect

MATCH (a:node), (b:node) 
WHERE a.name = sw1 AND b.name = sw2
merge (a)-[:connect {packets_transmitted:0,packets_recieved:0}]->(b)
2

The cypher will be:

merge (a : node { name : "sw1" } ) -[c : connect]-> (b : node { name : "sw2"}
on match set c.packets_transmitted = 200,
c.packets_recieved = 350