diff --git a/README.md b/README.md
index 2e1a95d..49f42d2 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,7 @@ A single network interface can be associated with the device.
 | **Network** | IPv4 | Datagram delivery, TTL handling | [RFC 791](https://datatracker.ietf.org/doc/html/rfc791) |
 | **Network** | IPv4 Forwarding | Multi-interface routing (optional) | [RFC 1812](https://datatracker.ietf.org/doc/html/rfc1812) |
 | **Network** | ICMP | Echo request/reply, TTL exceeded | [RFC 792](https://datatracker.ietf.org/doc/html/rfc792) |
+| **Network** | IPsec | ESP Transport mode | [RFC 4303](https://datatracker.ietf.org/doc/html/rfc4303) |
 | **Transport** | UDP | Unicast datagrams, checksum | [RFC 768](https://datatracker.ietf.org/doc/html/rfc768) |
 | **Transport** | TCP | Connection management, reliable delivery | [RFC 793](https://datatracker.ietf.org/doc/html/rfc793), [RFC 9293](https://datatracker.ietf.org/doc/html/rfc9293) |
 | **Transport** | TCP | Maximum Segment Size negotiation | [RFC 793](https://datatracker.ietf.org/doc/html/rfc793) |
diff --git a/wolfesp.h b/wolfesp.h
index fbb4b07..6ea42ef 100644
--- a/wolfesp.h
+++ b/wolfesp.h
@@ -2,7 +2,9 @@
 #define WOLFESP_H
 
 /* size of static pool */
-#define WOLFIP_ESP_NUM_SA  3
+#ifndef WOLFIP_ESP_NUM_SA
+#define WOLFIP_ESP_NUM_SA  2
+#endif /* WOLFIP_ESP_NUM_SA */
 /* ESP packet parameters */
 #define ESP_SPI_LEN               4
 #define ESP_SEQ_LEN               4