DumbTcpStateVariables¶

struct DumbTcpStateVariables

State variables for DumbTcp.

Inheritance diagram¶

Extends¶

Name	Type	Description
TcpStateVariables	struct	Contains state variables (“TCB”) for TCP.

Fields¶

Name	Type	Description
active	bool	set if the connection was initiated by an active open
fork	bool	if passive and in LISTEN: whether to fork on an incoming connection
snd_mss	uint32_t	sender maximum segment size (without headers, i.e. only segment text); see RFC 2581, page 1. This will be set to the minimum of the local smss parameter and the value specified in the MSS option received during connection setup.
snd_una	uint32_t	send unacknowledged
snd_nxt	uint32_t	send next (drops back on retransmission)
snd_max	uint32_t	max seq number sent (needed because snd_nxt is re-set on retransmission)
snd_wnd	uint32_t	send window
snd_up	uint32_t	send urgent pointer
snd_wl1	uint32_t	segment sequence number used for last window update
snd_wl2	uint32_t	segment ack. number used for last window update
iss	uint32_t	initial sequence number (ISS)
rcv_nxt	uint32_t	receive next
rcv_wnd	uint32_t	receive window
rcv_up	uint32_t	receive urgent pointer;
irs	uint32_t	initial receive sequence number
rcv_adv	uint32_t	advertised window
syn_rexmit_count	int	number of SYN/SYN+ACK retransmissions (=1 after first rexmit)
syn_rexmit_timeout	simtime_t	current SYN/SYN+ACK retransmission timeout
fin_ack_rcvd	bool	whether ACK of our FIN has been received. Needed in FIN bit processing to decide between transition to TIME-WAIT and CLOSING (set event code TCP_E_RCV_FIN or TCP_E_RCV_FIN_ACK).
send_fin	bool	true if a user CLOSE command has been “queued”
snd_fin_seq	uint32_t	if send_fin == true: FIN should be sent just before this sequence number
fin_rcvd	bool	whether FIN received or not
rcv_fin_seq	uint32_t	if fin_rcvd: sequence number of received FIN
nagle_enabled	bool	set if Nagle’s algorithm (RFC 896) is enabled
delayed_acks_enabled	bool	set if delayed ACK algorithm (RFC 1122) is enabled
limited_transmit_enabled	bool	set if Limited Transmit algorithm (RFC 3042) is enabled
increased_IW_enabled	bool	set if Increased Initial Window (RFC 3390) is enabled
full_sized_segment_counter	uint32_t	this counter is needed for delayed ACK
ack_now	bool	send ACK immediately, needed if delayed_acks_enabled is set Based on [Stevens, W.R.: TCP/IP Illustrated, Volume 2, page 861]. ack_now should be set when: delayed ACK timer expires; an out-of-order segment is received; SYN is received during the three-way handshake; a persist probe is received; FIN is received
afterRto	bool	set at RTO, reset when snd_nxt == snd_max or snd_una == snd_max
ws_support	bool	set if the host supports Window Scale (header option) (RFC 1323)
ws_enabled	bool	set if the connection uses Window Scale (header option)
ws_manual_scale	int	the value of scale parameter if it was set manually (-1 otherwise)
snd_ws	bool	set if initial WINDOW_SCALE has been sent
rcv_ws	bool	set if initial WINDOW_SCALE has been received
rcv_wnd_scale	unsigned int	RFC 1323, page 31: “Receive window scale power”
snd_wnd_scale	unsigned int	RFC 1323, page 31: “Send window scale power”
ts_support	bool	set if the host supports Timestamps (header option) (RFC 1322)
ts_enabled	bool	set if the connection uses Window Scale (header option)
snd_initial_ts	bool	set if initial TIMESTAMP has been sent
rcv_initial_ts	bool	set if initial TIMESTAMP has been received
ts_recent	uint32_t	RFC 1323, page 31: “Latest received Timestamp”
last_ack_sent	uint32_t	RFC 1323, page 31: “Last ACK field sent”
time_last_data_sent	simtime_t	time at which the last data segment was sent (needed to compute the IDLE time for PAWS)
sack_support	bool	set if the host supports selective acknowledgment (header option) (RFC 2018, 2883, 3517)
sack_enabled	bool	set if the connection uses selective acknowledgment (header option)
snd_sack_perm	bool	set if SACK_PERMITTED has been sent
rcv_sack_perm	bool	set if SACK_PERMITTED has been received
start_seqno	uint32_t	start sequence number of last received out-of-order segment
end_seqno	uint32_t	end sequence number of last received out-of-order segment
snd_sack	bool	set if received vaild out-of-order segment or rcv_nxt changed, but receivedQueue is not empty
snd_dsack	bool	set if received duplicated segment (sequenceNo+PLength < rcv_nxt) or (segment is not acceptable)
sacks_array	SackList	MAX_SACK_BLOCKS is set to 60
highRxt	uint32_t	RFC 3517, page 3: “”HighRxt” is the highest sequence number which has been retransmitted during the current loss recovery phase.”
pipe	uint32_t	RFC 3517, page 3: “”Pipe” is a sender’s estimate of the number of bytes outstanding in the network.”
recoveryPoint	uint32_t	RFC 3517
sackedBytes	uint32_t	number of sackedBytes
sackedBytes_old	uint32_t	old number of sackedBytes - needed for RFC 3042 to check if last dupAck contained new sack information
lossRecovery	bool	indicates if algorithm is in loss recovery phase
sendQueueLimit	uint32_t	queue management
queueUpdate	bool
dupacks	uint32_t	current number of received consecutive duplicate ACKs
snd_sacks	uint32_t	number of sent sacks
rcv_sacks	uint32_t	number of received sacks
rcv_oooseg	uint32_t	number of received out-of-order segments
rcv_naseg	uint32_t	number of received not acceptable segments
maxRcvBuffer	uint32_t	maximal amount of bytes in tcp receive queue
usedRcvBuffer	uint32_t	current amount of used bytes in tcp receive queue
freeRcvBuffer	uint32_t	current amount of free bytes in tcp receive queue
tcpRcvQueueDrops	uint32_t	number of drops in tcp receive queue
ecnEchoState	bool	indicates if connection is in echo mode (got CE indication from IP and didn’t get CWR from sender yet)
sndCwr	bool	set if ECE was handled
gotEce	bool	set if packet with ECE arrived
gotCeIndication	bool	set if CE was set in controlInfo from IP
ect	bool	set if this connection is ECN Capable (ECT stands for ECN-Capable transport - rfc-3168)
endPointIsWillingECN	bool	set if the other end-point is willing to use ECN
ecnSynSent	bool	set if ECN-setup SYN packet was sent
ecnWillingness	bool	set if current host is willing to use ECN
sndAck	bool	set if sending Ack packet, used to set relevant info in controlInfo.
rexmit	bool	set if retransmitting data, used to send not-ECT codepoint (rfc3168, p. 20)
eceReactionTime	simtime_t	records the time of the last ECE reaction
dupthresh	uint32_t	used for TcpTahoe, TcpReno and SACK (RFC 3517)
pmtudEnabled	bool	set if Path MTU Discovery is enabled
pmtudOriginalMss	uint32_t	negotiated MSS before any PMTUD reduction
pmtudTimeout	simtime_t	time after which the original MSS is restored to probe for increased path MTU
pmtudLastMssReduction	simtime_t	timestamp of last PMTUD-triggered MSS reduction (-1 = never reduced)

Properties¶

Name	Value	Description
descriptor	readonly
implements	cObject

Source code¶

///
/// State variables for DumbTcp.
///
struct DumbTcpStateVariables extends TcpStateVariables
{
    @descriptor(readonly);
};

File: src/inet/transportlayer/tcp/flavours/DumbTcpState.msg