The given two-port network is a symmetric T-network with series arms \(Z_1 = 1\Omega\), \(Z_3 = 1\Omega\) and shunt arm \(Z_2 = 4\Omega\).
ABCD parameters for a T-network:
\(A = 1 + \frac{Z_1}{Z_2}\)
\(B = Z_1 + Z_3 + \frac{Z_1 Z_3}{Z_2}\)
\(C = \frac{1}{Z_2}\)
\(D = 1 + \frac{Z_3}{Z_2}\)
Here, \(Z_1 = 1\Omega\), \(Z_2 = 4\Omega\), \(Z_3 = 1\Omega\).
\(B = 1 + 1 + \frac{1 \times 1}{4} = 2 + \frac{1}{4} = \frac{8+1}{4} = \frac{9}{4} \Omega\).
\(D = 1 + \frac{1}{4} = \frac{4+1}{4} = \frac{5}{4}\) (dimensionless).
The values are B = 9/4 and D = 5/4.
\[ \boxed{\text{B = 9/4, D = 5/4}} \]