diff --git a/v2/session/grpc/service.pb.go b/v2/session/grpc/service.pb.go
index e18b8f3..223c38b 100644
--- a/v2/session/grpc/service.pb.go
+++ b/v2/session/grpc/service.pb.go
@@ -176,7 +176,7 @@ type CreateRequest_Body struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	// Dession initiating user's or node's key derived `OwnerID`.
+	// Session initiating user's or node's key derived `OwnerID`
 	OwnerId *grpc.OwnerID `protobuf:"bytes,1,opt,name=owner_id,json=ownerId,proto3" json:"owner_id,omitempty"`
 	// Session expiration `Epoch`
 	Expiration uint64 `protobuf:"varint,2,opt,name=expiration,proto3" json:"expiration,omitempty"`
diff --git a/v2/session/grpc/types.pb.go b/v2/session/grpc/types.pb.go
index fe557fd..aba3ceb 100644
--- a/v2/session/grpc/types.pb.go
+++ b/v2/session/grpc/types.pb.go
@@ -218,7 +218,25 @@ func (x *SessionToken) GetSignature() *grpc.Signature {
 	return nil
 }
 
-// Extended headers for Request/Response.
+// Extended headers for Request/Response. May contain any user-defined headers
+// to be interpreted on application level.
+//
+// Key name must be unique valid UTF-8 string. Value can't be empty. Requests or
+// Responses with duplicated header names or headers with empty values will be
+// considered invalid.
+//
+// There are some "well-known" headers starting with `__NEOFS__` prefix that
+// affect system behaviour:
+//
+// * __NEOFS__NETMAP_EPOCH \
+//   Netmap epoch to use for object placement calculation. The `value` is string
+//   encoded `uint64` in decimal presentation. If set to '0' or not set, the
+//   current epoch only will be used.
+// * __NEOFS__NETMAP_LOOKUP_DEPTH \
+//   If object can't be found using current epoch's netmap, this header limits
+//   how many past epochs back the node can lookup. The `value` is string
+//   encoded `uint64` in decimal presentation. If set to '0' or not set, the
+//   current epoch only will be used.
 type XHeader struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
diff --git a/v2/session/xheaders.go b/v2/session/xheaders.go
new file mode 100644
index 0000000..64b16de
--- /dev/null
+++ b/v2/session/xheaders.go
@@ -0,0 +1,16 @@
+package session
+
+// ReservedXHeaderPrefix is a prefix of keys to "well-known" X-headers.
+const ReservedXHeaderPrefix = "__NEOFS__"
+
+const (
+	// XHeaderNetmapEpoch is a key to the reserved X-header that specifies netmap epoch
+	// to use for object placement calculation. If set to '0' or not set, the current
+	// epoch only will be used.
+	XHeaderNetmapEpoch = ReservedXHeaderPrefix + "NETMAP_EPOCH"
+
+	// XHeaderNetmapLookupDepth is a key to the reserved X-header that limits
+	// how many past epochs back the node will can lookup. If set to '0' or not
+	// set, the current epoch only will be used.
+	XHeaderNetmapLookupDepth = ReservedXHeaderPrefix + "NETMAP_LOOKUP_DEPTH"
+)