diff --git a/src/lib.rs b/src/lib.rs
index f0108f0..bf37dc2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,3 +3,4 @@
 mod common;
 
 pub mod tpm2;
+pub mod tpm2net;
diff --git a/src/tpm2net.rs b/src/tpm2net.rs
new file mode 100644
index 0000000..3786b97
--- /dev/null
+++ b/src/tpm2net.rs
@@ -0,0 +1,119 @@
+pub const PACKET_START_BYTE: u8 = 0x9C;
+
+pub const PAYLOAD_SIZE_MAX: usize = 1490;
+
+pub use crate::common::{PacketType, PACKET_END_BYTE};
+
+#[derive(PartialEq)]
+#[non_exhaustive]
+pub enum Tpm2NetError {
+    IndexOutOfBounds,
+    PayloadTooLarge,
+}
+
+pub struct Packet<'a> {
+    packet_type: PacketType,
+    index: u8,
+    total: u8,
+    payload: &'a [u8],
+}
+
+impl<'a> Packet<'a> {
+    pub fn new(packet_type: PacketType) -> Self {
+        Packet {
+            packet_type,
+            index: 1,
+            total: 1,
+            payload: &[] as &[u8],
+        }
+    }
+
+    pub fn with_payload(packet_type: PacketType, payload: &'a [u8]) -> Result<Self, Tpm2NetError> {
+        Self::with_payload_and_index(packet_type, payload, 1, 1)
+    }
+
+    pub fn with_payload_and_index(
+        packet_type: PacketType,
+        payload: &'a [u8],
+        index: u8,
+        total: u8,
+    ) -> Result<Self, Tpm2NetError> {
+        if payload.len() > PAYLOAD_SIZE_MAX {
+            return Err(Tpm2NetError::PayloadTooLarge);
+        }
+        if index == 0 {
+            return Err(Tpm2NetError::IndexOutOfBounds);
+        }
+        if total == 0 {
+            return Err(Tpm2NetError::IndexOutOfBounds);
+        }
+        if total < index {
+            return Err(Tpm2NetError::IndexOutOfBounds);
+        }
+
+        Ok(Packet {
+            packet_type,
+            index,
+            total,
+            payload,
+        })
+    }
+
+    pub fn packet_type(&self) -> PacketType {
+        self.packet_type
+    }
+
+    pub fn size(&self) -> usize {
+        self.payload.len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn empty_packet() {
+        let packet = Packet::new(PacketType::Command);
+        assert_eq!(packet.size(), 0);
+    }
+
+    #[test]
+    fn packet_with_payload() {
+        let payload: [u8; 4] = [0xca, 0xfe, 0xba, 0xbe];
+        let result = Packet::with_payload(PacketType::Data, &payload);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn payload_too_large() {
+        let payload = [0u8; PAYLOAD_SIZE_MAX + 1];
+        let result = Packet::with_payload(PacketType::Response, &payload);
+        assert!(result.is_err());
+        assert!(result.err().unwrap() == Tpm2NetError::PayloadTooLarge);
+    }
+
+    #[test]
+    fn index_is_zero() {
+        let payload: [u8; 4] = [0xca, 0xfe, 0xba, 0xbe];
+        let result = Packet::with_payload_and_index(PacketType::Data, &payload, 0, 1);
+        assert!(result.is_err());
+        assert!(result.err().unwrap() == Tpm2NetError::IndexOutOfBounds);
+    }
+
+    #[test]
+    fn total_is_zero() {
+        let payload: [u8; 4] = [0xca, 0xfe, 0xba, 0xbe];
+        let result = Packet::with_payload_and_index(PacketType::Data, &payload, 1, 0);
+        assert!(result.is_err());
+        assert!(result.err().unwrap() == Tpm2NetError::IndexOutOfBounds);
+    }
+
+    #[test]
+    fn total_is_less_than_index() {
+        let payload: [u8; 4] = [0xca, 0xfe, 0xba, 0xbe];
+        let result = Packet::with_payload_and_index(PacketType::Data, &payload, 43, 42);
+        assert!(result.is_err());
+        assert!(result.err().unwrap() == Tpm2NetError::IndexOutOfBounds);
+    }
+}