packet is coming from going to in order to quickly detect whether a packet is going upstream from the access nodes towards the edge nodes or downstream from the edge nodes towards the access nodes a separate range of source mac addresses is specified uniquely for the access nodes and uniquely for the edge nodes when this split is made every intermediate switch will be able to detect by looking at both the source and the destination address what type of packet it is e g every packet coming from a customer receives a mac address from a first range of addresses and every edge node is configured with a mac address from a second range if an intermediate switch looks at both the source and destination address sa and da respectively it can conclude the following sa range 1 da range 2 upstream packet sa range 2 da range 1 downstream packet sa range 1 da range 1 user to user talk operators might want to discard this sa range 2 da range 2 edge to edge talk operators might want to discard this therefore the range of the newly defined addresses should be split up in 2 main parts the first main part is to be used by the access nodes in order to translate the mac addresses coming from a user in case of upstream this part can consist of some sub parts the second main part is.