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// Copyright (c) 2000-2019 Ericsson Telecom AB
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v2.0
// which accompanies this distribution, and is available at
// File: SCTP_Engine_Definition.ttcn
// Description: Component definition of the SCTP Engine
// Rev: <RnXnn>
// Prodnr: CNL 113 840
module SCTP_Engine_Definition {
import from SCTP_Engine_PortTypes all;
import from SCTP_Types all;
modulepar SCTP_Proto_params tsp_proto_params:={ rto_initial := 3.0,
rto_min := 1.0,
rto_max := 60.0,
max_burst := 4,
rto_alpha := 0.125,
rto_beta := 0.25,
valid_cookie_life :=60,
assoc_max_retrans := 10,
path_max_retrans := 5,
max_init_retrans := 8,
hb_interval := 30.0,
hb_max_burst :=1,
// MTU discovery parameters
pmntu_min := 900, // This value is used to calculate the data chunk size
// The maximum data chunk size is
// pmntu_min - SCTP_common_header_size
// This ensures that the data chunk can be delivered every cases
// Normal ethernet frame size - (vpn,DTLS,UDP,IPv4 or IPv6) - something more
pmtu_max := 8960, // For Jumbo frames
pmtu_initial := 1200 // WebRTC draft
modulepar SCTP_Reconfig_config tsp_reconf_params:={
is_supported := true,
stream_reset_allowed:= true,
assoc_reset_allowed:= true,
stream_add_allowed:= true
modulepar boolean tsp_forward_tsn_supported := true
type component SCTP_Engine_CT {
// Test ports
port SCTP_Engine_API_request_PT p_sctp_req_api // the upper side, SCTP test port
port SCTP_Engine_API_indication_PT p_sctp_ind_api // the upper side, SCTP test port
port SCTP_Engine_packet_PT p_packet_port // The lower side test port
// main database
var SCTP_Assoc_DB_t v_assoc_db := c_empty_SCTP_Assoc_DB // The association data base
var octetstring v_secret_key := '11223344556677889900'O // the key used to generate MAC of the state cookie
// time & event queue handling
timer t_run_time // timer used to mesure the time, started once
// with a very-very long timeout
timer t_next_event // expires on the next scheduled event
var SCTP_event_db_t v_event_db:= c_empty_event_db // Event queue database
var SCTP_Assoc_data c_empty_SCTP_Assoc_data:={
state_cookie := ''O,
rem_comp := null,
i_data_supported := false,
proto_params := tsp_proto_params,
retransmit_timer_event := -1,
tx_msg_queues := {},
tx_stream_idx_map_id := -1,
tx_chunk_queue := c_empty_chunk_queue_db,
ssthresh := 0,
scheduled_queue := 0,
remote_last_sack_tsn := -1,
rx_chunk_queue := c_empty_chunk_queue_db,
idx_of_last_acked := -1,
rx_msg_queues := {},
rx_stream_idx_map_id := -1,
hb_event_id := -1,
hb_retrial_counter := 0,
data_chunk_max_size := tsp_proto_params.pmntu_min-12, // 12: SCTP common header size. See up
reconfig_ongoing := false,
reconfig_event_id := -1,
ongoing_incoming_reconf_req_seq := -1,
ongoing_outgoing_reconf_req_seq := -1,
last_reconf_resp := omit,
last_reconf_req := omit,
deffered_reset := omit,
close_timer := -1
// Type for association data base
type record SCTP_Assoc_DB_t{
// the data base realized by the list of the association entries.
// Each entries are not removed from the list, but reused if needed.
// In order to track the free elements, the free entries forms a linked list
// holding the index of the next free entry.
// The index of first & last free entries are stored also.
integer used_entries, // How many entries are used.
integer first_free, // points to the first free
integer last_free, // points to the last free
SCTP_Assoc_entry_list associations // The list of the entries
// constant used to initialize the v_assoc_db
const SCTP_Assoc_DB_t c_empty_SCTP_Assoc_DB:={
used_entries := 0,
first_free :=-1,
last_free :=-1,
associations :={}
type record of SCTP_Assoc_entry SCTP_Assoc_entry_list
type record SCTP_Assoc_entry {
integer next_free, // points to the next free entry if not used
SCTP_Assoc_data assoc_data optional // holds the data of the association
// if the entry is not used, the data
// is ommited in order to free the
// memory
const SCTP_Assoc_entry c_empty_SCTP_Assoc_entry:={
next_free := -1,
assoc_data := omit
// The value of the enumeration is ordered, so a range can be specified
type enumerated SCTP_Assoc_state { SCTP_ASSOC_LISTEN(0),
// holds the data belongs to the association
type record SCTP_Assoc_data {
SCTP_Assoc_state state,
integer transport_id, // The transport id
integer local_port, // Local sctp port number
integer remote_port, // Remote sctp port number
integer own_tag, // Own verification tag, The incoming message should come with this
integer remote_tag, // Remotes verification tag, set in the outgoing message
integer cookie_validity, // 0 - Cookie ok, 1- Cokkie expired. See the return value of SCTP_check_state_cookie
integer remote_tsn, // remote initial tsn, last sent SACK tsn + 1
integer own_tsn, // own next tsn/ initial tsn
integer remote_os, // remote outgoing sream number
integer remote_mis, // remote's max incoming stream number
integer remote_a_rwnd, // remote advertised receive window
integer cookie_lifespan, // The lifespan of our state cookie
octetstring state_cookie, // the stored received state cookie, used for retransmission
SCTP_Engine_CT rem_comp, // The component id of sctp user component
boolean i_data_supported, // Support I-DATA chunk
SCTP_Proto_params proto_params, // SCTP protocol parameters of the association
integer retransmit_counter, // the messages was retransmitted that many time without answer
integer retransmit_timer_event, // The event id of the retransmitt timer
float rto, // RTO
float srtt, // SRTT
float rttvar, // RTTVAR see: RFC 4960 6.3. Management of Retransmission Timer
integer pmtu, // The Path MTU
// Message queues
SCTP_msg_queue_list_t tx_msg_queues, // The queues of the TX messages, every stream has an own queue
// the Nth queue is the ordered msg queue, that idx is stored in the map below
// the N+1 th is for the unordered
integer tx_stream_idx_map_id, // The ID of the stream -> queue idx map, tells which stream belongs to which queue
SCTP_Chunk_queue_db_t tx_chunk_queue, // the TX DATA chunk queue
// Congestion control data see the rfc 4690
integer cwnd, // congestion window
integer flight_size, // sent but not acked bytes
integer partially_acked_bytes, // partially acknowledged bytes
integer ssthresh, // Slow start treshold
integer scheduled_queue, // the message from that queue will be sent
integer remote_last_sack_tsn, // The latest TSN acked by the remote
SCTP_Chunk_queue_db_t rx_chunk_queue, // the RX DATA chunk queue, used for reassembly
// How the queue is used: When a data chunk is received, it will be inserted into the queue
// If there are missing data chunk, a dummy placeholder is inserted into the queue
// The chunk field of the queue element is omited in that case
integer idx_of_last_acked, // the index of the last acked chunk in the queue
SCTP_msg_queue_list_t rx_msg_queues, // The queues of the RX messages, every stream has an own queue
// the Nth queue is the ordered msg queue, that idx is stored in the map below
// the N+1 th is for the unordered
integer rx_stream_idx_map_id, // The ID of the stream -> rx queue idx map, tells which stream belongs to which queue
integer hb_event_id, // The event id of the scheduled heartbeat event
integer hb_retrial_counter, // The heatbeat retrial counter
integer data_chunk_max_size, // the maximum size of the data chunk
SCTP_Reconfig_config reconf_params, // reconfiguration extension RFC6525
integer reconf_own_seq_num, // our next seq number/ initial one
integer reconf_remote_seq_num , // our next expected
boolean reconfig_ongoing,
boolean forward_tsn_supported, // indicates the support of RFC3758
integer reconfig_event_id,
integer ongoing_incoming_reconf_req_seq, // store the initiated "incomig type request": Incoming SSN Reset, Add Incoming Streams
integer ongoing_outgoing_reconf_req_seq, // store the initiated "outgoing type request": Outgoing SSN Reset, Add Outgoing Streams, SSN/TSN Reset Request
SCTP_Re_Config_chunk last_reconf_resp optional, // stores the last reconf response chunk for retransmission
SCTP_Re_Config_chunk last_reconf_req optional, // stores the last reconf request chunk for retransmission
SCTP_Out_SSN_Reset_req_parameter deffered_reset optional, // stores the reconf request for "deferred reset processing"
integer reconfig_retransmit_counter,
integer close_timer
// Parameters for reconfiguration extension RFC6525
/*type record SCTP_Reconf_data {
boolean is_supported,
boolean stream_reset_allowed,
boolean assoc_reset_allowed,
boolean stream_add_allowed
// The type holds the SCTP Protocol Parameters
// See RFC4960 chapter 15
type record SCTP_Proto_params{
float rto_initial,
float rto_min,
float rto_max,
integer max_burst,
float rto_alpha,
float rto_beta,
integer valid_cookie_life,
integer assoc_max_retrans,
integer path_max_retrans,
integer max_init_retrans,
float hb_interval,
integer hb_max_burst,
integer pmntu_min,
integer pmtu_max,
integer pmtu_initial
// Event handling database
// All of the scheduled events are stored in the event DB
// One event DB entry stores the <assoc_id, timer_id>
// the t_next_event timer is sceduled for the earliest event
// in the case of timeout, adding or deleting event, the timer is recalculated
// The events are stored in the same way as the assoc DB
// The order of the events are stored & maintained in an external ordered std::map
type record SCTP_event_db_t{
integer used_entries, // How many entries are used.
integer first_free, // points to the first free
integer last_free, // points to the last free
integer the_sceduled_event, // That event is used to start the t_next_event timer
SCTP_event_entry_list events // The list of the events
const SCTP_event_db_t c_empty_event_db:={
used_entries := 0,
first_free :=-1,
last_free :=-1,
the_sceduled_event := -1,
events :={}
type record of SCTP_event_entry SCTP_event_entry_list
type record SCTP_event_entry {
integer next_free, // points to the next free entry if not used
integer assoc_id, // the event is scheduled by this assoc
integer timer_id, // the id of the assoc timer
float timeout_time // The absulute time of the timeout
// calculated as 'time_since_start' + 'timeout_val'
const SCTP_event_entry c_empty_event_entry:={
// Data types for queues
// Chunk queue
// Simple linked list, with free queue
type record SCTP_Chunk_queue_db_t{
integer used_entries, // How many entries are used.
integer first_free, // points to the first free
integer last_free, // points to the last free
integer first_element, // points to the head of the chunk queue
integer last_element, // points to the tail of the chunk queue
SCTP_Chunk_queue_element_list_t chunk_queue
const SCTP_Chunk_queue_db_t c_empty_chunk_queue_db:={
used_entries := 0,
first_free :=-1,
last_free :=-1,
first_element :=-1,
last_element := -1,
chunk_queue :={}
type record of SCTP_Chunk_queue_element_t SCTP_Chunk_queue_element_list_t
type record SCTP_Chunk_queue_element_t {
integer next_element,
boolean mark_flag, // used to mark the chunk in the queue:
// tx chunk queue: mark for retransmit
// rx chunk queue: added to the rx stream queue
float lifetime, // Used on sender side, partial reliability feature
integer counter, // Used on sender side, partial reliability feature
boolean unmark_flag, // tx queues: mark for abandon
integer tsn,
SCTP_Chunk chunk optional
const SCTP_Chunk_queue_element_t c_empty_Chunk_queue_element:={
next_element := -1,
mark_flag := false,
lifetime := -1.0,
counter := -1,
unmark_flag := false,
tsn := -1,
chunk := omit
// TX message queue types
// Every outgoing stream has its own queue
// represents one msg queue
type record SCTP_msg_queue_t {
integer next_ssn, // the next SSN for the stream
integer num_of_queued_octets, // The number of the octets of the first message already put into the TX queue
boolean flag,
SCTP_Chunk_queue_db_t messages // Each message is represented by a DATA chunk
const SCTP_msg_queue_t c_empty_msg_queue:={
next_ssn := 0,
num_of_queued_octets := 0,
messages := c_empty_chunk_queue_db
type record of SCTP_msg_queue_t SCTP_msg_queue_list_t
type record of integer integer_list
// Timer constants
const integer c_timer_T1 := 0;
const integer c_timer_T1_cookie := 1;
const integer c_timer_T3_rtx := 2;
const integer c_timer_T2_shutdown := 3;
const integer c_timer_heartbeat := 4;
const integer c_timer_reconfig := 5;
const integer c_timer_close := 6;
const integer c_min_chunk_size := 24 // The minimum data chunk size we use