diff --git a/slp_meta.hpp b/slp_meta.hpp
index 538bf9c..aab2f56 100644
--- a/slp_meta.hpp
+++ b/slp_meta.hpp
@@ -12,6 +12,9 @@
 /** @brief SLP service lifetime */
 constexpr auto LIFETIME = 5;
 
+/** @brief Largest input or output buffer allowed */
+constexpr size_t MAX_LEN = 255;
+
 /** @brief Defines the constants for slp header.
  *  Size and the offsets.
  */