Question: In X.25 defines the protocols from ____layer to _______layer

Answer:

In the X.25 protocol suite, the protocols are defined from the Data Link Layer to the Network Layer.

Specifically, the X.25 protocol suite defines protocols that operate at the following layers of the OSI (Open Systems Interconnection) model:

1. Data Link Layer (Layer 2): X.25 includes the LAPB (Link Access Procedure, Balanced) protocol, which is responsible for establishing reliable data link connections over the physical layer.

2. Network Layer (Layer 3): X.25 defines the Packet Layer Protocol (PLP), which is responsible for packetizing data and providing error control, flow control, and sequencing at the network layer. It also includes the X.25 addressing scheme.

It's important to note that the X.25 protocol suite predates the OSI model, and while it aligns closely with the Data Link Layer and Network Layer of the OSI model, it doesn't strictly adhere to the exact layering.