IP Network Evolution(1) First Stage ( Before IPv4) Second Stage(Current IPv4) Interconnection between Global network through IPv4 heterogeneous networks Integration of heterogeneous through gateway networks No global connectivity Internet revolution ALG ALG ALG IPy4 ALG Pv4」 ALG 1 IPv4 ALG: Application Layer GatewayALG : Application Layer Gateway ALG ALG ALG ALG IPv4 IPv4 IPv4 IPv4 IP Network Evolution ( 1 ) IP Network Evolution ( 1 ) First Stage (Before IPv4) - Interconnection between heterogeneous networks through gateway - No global connectivity Second Stage(Current IPv4) - Global network through IPv4 - Integration of heterogeneous networks - Internet Revolution ALG IPv4