2 * Copyright (c) 1995, Mike Mitchell
3 * Copyright (c) 1982, 1986, 1988, 1993
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39 #ifndef _NETIPX_SPX_TIMER_H_
40 #define _NETIPX_SPX_TIMER_H_
43 * Definitions of the SPX timers. These timers are counted
44 * down PR_SLOWHZ times a second.
46 #define SPXT_REXMT 0 /* retransmit */
47 #define SPXT_PERSIST 1 /* retransmit persistence */
48 #define SPXT_KEEP 2 /* keep alive */
49 #define SPXT_2MSL 3 /* 2*msl quiet time timer */
52 * The SPXT_REXMT timer is used to force retransmissions.
53 * The SPX has the SPXT_REXMT timer set whenever segments
54 * have been sent for which ACKs are expected but not yet
55 * received. If an ACK is received which advances tp->snd_una,
56 * then the retransmit timer is cleared (if there are no more
57 * outstanding segments) or reset to the base value (if there
58 * are more ACKs expected). Whenever the retransmit timer goes off,
59 * we retransmit one unacknowledged segment, and do a backoff
60 * on the retransmit timer.
62 * The SPXT_PERSIST timer is used to keep window size information
63 * flowing even if the window goes shut. If all previous transmissions
64 * have been acknowledged (so that there are no retransmissions in progress),
65 * and the window is too small to bother sending anything, then we start
66 * the SPXT_PERSIST timer. When it expires, if the window is nonzero,
67 * we go to transmit state. Otherwise, at intervals send a single byte
68 * into the peer's window to force him to update our window information.
69 * We do this at most as often as SPXT_PERSMIN time intervals,
70 * but no more frequently than the current estimate of round-trip
71 * packet time. The SPXT_PERSIST timer is cleared whenever we receive
72 * a window update from the peer.
74 * The SPXT_KEEP timer is used to keep connections alive. If an
75 * connection is idle (no segments received) for SPXTV_KEEP amount of time,
76 * but not yet established, then we drop the connection. If the connection
77 * is established, then we force the peer to send us a segment by sending:
78 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
79 * This segment is (deliberately) outside the window, and should elicit
80 * an ack segment in response from the peer. If, despite the SPXT_KEEP
81 * initiated segments we cannot elicit a response from a peer in SPXT_MAXIDLE
82 * amount of time, then we drop the connection.
85 #define SPX_TTL 30 /* default time to live for SPX segs */
89 #define SPXTV_MSL ( 15*PR_SLOWHZ) /* max seg lifetime */
90 #define SPXTV_SRTTBASE 0 /* base roundtrip time;
92 #define SPXTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */
94 #define SPXTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */
95 #define SPXTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
97 #define SPXTV_KEEP ( 75*PR_SLOWHZ) /* keep alive - 75 secs */
98 #define SPXTV_MAXIDLE ( 8*SPXTV_KEEP) /* maximum allowable idle
99 time before drop conn */
101 #define SPXTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */
102 #define SPXTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */
104 #define SPX_LINGERTIME 120 /* linger at most 2 minutes */
106 #define SPX_MAXRXTSHIFT 12 /* maximum retransmits */
110 { "REXMT", "PERSIST", "KEEP", "2MSL" };
114 * Force a time value to be in a certain range.
116 #define SPXT_RANGESET(tv, value, tvmin, tvmax) { \
118 if ((tv) < (tvmin)) \
120 else if ((tv) > (tvmax)) \
124 #endif /* !_NETIPX_SPX_TIMER_H_ */