Which tunneling protocol can be described by these characteristics: 1) Handles multiple connections at the same time, 2) Provides secure authtentication and encryption, 3) Supports only IP networks, 4) Used to be focused mostly on LAN-to-LAN communication rather than dial-up protocol, 5) Works at the network layer and provides security on top of IP.以下選項中，那個隧道協(xié)議可以被描述為以下特點1.同一時間處理多個連接 2.提供安全認(rèn)證和加密3.僅支持IP網(wǎng)絡(luò)4.主要用于局域網(wǎng)到局域網(wǎng)的通信5.工作在網(wǎng)絡(luò)層以及提供IP安全（）