  We have simulated QCD using 2+1 flavors of domain wall quarks on a $(2.74
{\rm fm})^3$ volume with an inverse lattice scale of $a^{-1} = 1.729(28)$ GeV.
The up and down (light) quarks are degenerate in our calculations and we have
used four values for the ratio of light quark masses to the strange (heavy)
quark mass in our simulations: 0.217, 0.350, 0.617 and 0.884. We have measured
pseudoscalar meson masses and decay constants, the kaon bag parameter $B_K$ and
vector meson couplings. We have used SU(2) chiral perturbation theory, which
assumes only the up and down quark masses are small, and SU(3) chiral
perturbation theory to extrapolate to the physical values for the light quark
masses. While next-to-leading order formulae from both approaches fit our data
for light quarks, we find the higher order corrections for SU(3) very large,
making such fits unreliable. We also find that SU(3) does not fit our data when
the quark masses are near the physical strange quark mass. Thus, we rely on
SU(2) chiral perturbation theory for accurate results. We use the masses of the
$\Omega$ baryon, and the $\pi$ and $K$ mesons to set the lattice scale and
determine the quark masses. We then find $f_\pi = 124.1(3.6)_{\rm
stat}(6.9)_{\rm syst} {\rm MeV}$, $f_K = 149.6(3.6)_{\rm stat}(6.3)_{\rm syst}
{\rm MeV}$ and $f_K/f_\pi = 1.205(0.018)_{\rm stat}(0.062)_{\rm syst}$. Using
non-perturbative renormalization to relate lattice regularized quark masses to
RI-MOM masses, and perturbation theory to relate these to $\bar{\rm MS}$ we
find $ m_{ud}^{\bar{\rm MS}}(2 {\rm GeV}) = 3.72(0.16)_{\rm stat}(0.33)_{\rm
ren}(0.18)_{\rm syst} {\rm MeV}$ and $m_{s}^{\bar{\rm MS}}(2 {\rm GeV}) =
107.3(4.4)_{\rm stat}(9.7)_{\rm ren}(4.9)_{\rm syst} {\rm MeV}$.
