diff --git a/README.rst b/README.rst
index 447eb5c..6bc68d4 100644
--- a/README.rst
+++ b/README.rst
@@ -138,9 +138,11 @@ select additional or substitute Maintainers, per `consensus agreements
 -  `Chris Lenk <mailto:clenk@mitre.org>`__; GitHub ID:
    https://github.com/clenk/; WWW: `MITRE Corporation <http://www.mitre.org/>`__
 
--  `Emmanuelle Vargas-Gonzalez <mailto:emmanuelle@mitre.org>`__; GitHub ID:
-   https://github.com/emmanvg/; WWW: `MITRE
-   Corporation <https://www.mitre.org/>`__
+-  `Rich Piazza <mailto:rpiazza@mitre.org>`__; GitHub ID:
+   https://github.com/rpiazza/; WWW: `MITRE Corporation <https://www.mitre.org/>`__
+
+-  `Andy Chisholm <mailto:chisholm@mitre.org>`__; GitHub ID:
+   https://github.com/chisholm/; WWW: `MITRE Corporation <https://www.mitre.org/>`__
 
 -  `Jason Keirstead <mailto:Jason.Keirstead@ca.ibm.com>`__; GitHub ID:
    https://github.com/JasonKeirstead; WWW: `IBM <http://www.ibm.com/>`__
diff --git a/stix2/v21/observables.py b/stix2/v21/observables.py
index 44b346c..9a02150 100644
--- a/stix2/v21/observables.py
+++ b/stix2/v21/observables.py
@@ -561,7 +561,7 @@ class NetworkTraffic(_Observable):
         ('defanged', BooleanProperty(default=lambda: False)),
         ('extensions', ExtensionsProperty(spec_version='2.1')),
     ])
-    _id_contributing_properties = ["start", "src_ref", "dst_ref", "src_port", "dst_port", "protocols"]
+    _id_contributing_properties = ["start", "end", "src_ref", "dst_ref", "src_port", "dst_port", "protocols", "extensions"]
 
     def _check_object_constraints(self):
         super(NetworkTraffic, self)._check_object_constraints()
@@ -579,8 +579,8 @@ class NetworkTraffic(_Observable):
             msg = "{0.id} if 'is_active' is True, 'end' must not be included"
             raise ValueError(msg.format(self))
 
-        if start and end and end <= start:
-            msg = "{0.id} 'end' must be greater than 'start'"
+        if start and end and end < start:
+            msg = "{0.id} 'end' must be greater than or equal to 'start'"
             raise ValueError(msg.format(self))
 
 
diff --git a/stix2/v21/sro.py b/stix2/v21/sro.py
index bfe3f6d..291f507 100644
--- a/stix2/v21/sro.py
+++ b/stix2/v21/sro.py
@@ -89,7 +89,7 @@ class Sighting(_RelationshipObject):
         ('sighting_of_ref', ReferenceProperty(valid_types="SDO", spec_version='2.1', required=True)),
         ('observed_data_refs', ListProperty(ReferenceProperty(valid_types='observed-data', spec_version='2.1'))),
         ('where_sighted_refs', ListProperty(ReferenceProperty(valid_types=['identity', 'location'], spec_version='2.1'))),
-        ('summary', BooleanProperty()),
+        ('summary', BooleanProperty(default=lambda: False)),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
         ('confidence', IntegerProperty()),
diff --git a/stix2/v21/vocab.py b/stix2/v21/vocab.py
index 303692e..2644da5 100644
--- a/stix2/v21/vocab.py
+++ b/stix2/v21/vocab.py
@@ -301,12 +301,16 @@ INFRASTRUCTURE_TYPE_AMPLIFICATION = "amplification"
 INFRASTRUCTURE_TYPE_ANONYMIZATION = "anonymization"
 INFRASTRUCTURE_TYPE_BOTNET = "botnet"
 INFRASTRUCTURE_TYPE_COMMAND_AND_CONTROL = "command-and-control"
+INFRASTRUCTURE_TYPE_CONTROL_SYSTEM = "control-system"
 INFRASTRUCTURE_TYPE_EXFILTRATION = "exfiltration"
+INFRASTRUCTURE_TYPE_FIREWALL = "firewall"
 INFRASTRUCTURE_TYPE_HOSTING_MALWARE = "hosting-malware"
 INFRASTRUCTURE_TYPE_HOSTING_TARGET_LISTS = "hosting-target-lists"
 INFRASTRUCTURE_TYPE_PHISHING = "phishing"
 INFRASTRUCTURE_TYPE_RECONNAISSANCE = "reconnaissance"
+INFRASTRUCTURE_TYPE_ROUTERS_SWITCHES = "routers-switches"
 INFRASTRUCTURE_TYPE_STAGING = "staging"
+INFRASTRUCTURE_TYPE_WORKSTATION = "workstation"
 INFRASTRUCTURE_TYPE_UNKNOWN = "unknown"
 
 
@@ -315,12 +319,16 @@ INFRASTRUCTURE_TYPE = [
     INFRASTRUCTURE_TYPE_ANONYMIZATION,
     INFRASTRUCTURE_TYPE_BOTNET,
     INFRASTRUCTURE_TYPE_COMMAND_AND_CONTROL,
+    INFRASTRUCTURE_TYPE_CONTROL_SYSTEM,
     INFRASTRUCTURE_TYPE_EXFILTRATION,
+    INFRASTRUCTURE_TYPE_FIREWALL,
     INFRASTRUCTURE_TYPE_HOSTING_MALWARE,
     INFRASTRUCTURE_TYPE_HOSTING_TARGET_LISTS,
     INFRASTRUCTURE_TYPE_PHISHING,
     INFRASTRUCTURE_TYPE_RECONNAISSANCE,
+    INFRASTRUCTURE_TYPE_ROUTERS_SWITCHES,
     INFRASTRUCTURE_TYPE_STAGING,
+    INFRASTRUCTURE_TYPE_WORKSTATION,
     INFRASTRUCTURE_TYPE_UNKNOWN,
 ]