X.25：
它是一个标准的ITU-T标准协议。它由PSE分组交换交换节点组成。X.25模型基于传统的电话概念。
帧中继：
它是一种用于有效数据传输的分组交换电信，可加快传输速度。用于将 LAN 与公共广域网连接。
帧中继和X.25的区别：
| Frame Relay | X.25 |
|---|---|
| It has informal data rate | It has fixed data rate |
| It performs Multiplexing and switching at data link layer | It performs Multiplexing and switching at network layer |
| Frame Relay does not support Hop-to-Hop error and flow control. | It performs Hop-to-Hop error and flow control at data link layer. |
| It does not support End-to-End flow and error control. | It performs End-to-End flow and error control at network layer |
| Congestion control is required in frame relay. | Congestion control is not required in X.25. |
| Call control signaling requires seperate logical connection from user data. | X.25 uses same data for call control signaling. |