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NAME

scspd — SCSP daemon

SYNOPSIS

scspd [−f ⟨ cfg−file⟩ ] [−d] [−T⟨ options⟩ ]

DESCRIPTION

The scspd utility is an implementation of the Server Cache Synchronization Protocol (SCSP) for the Host ATM Research Platform (HARP) networking software. The scspd utility synchronizes the cache(s) of server(s) running on a host with the caches of servers on remote hosts. SCSP is defined for a number of different protocols, but the present version of scspd only supports ATMARP.

By using scspd and atmarpd(8), one can provide multiple ATMARP servers in a single ATM LIS. This might be useful, for example, when a LIS consists of a number of local-area ATM networks connected by long-distance links. Each local-area network could have its own ATMARP server, with all the servers’ caches being synchronized by SCSP. Then, if a long-distance link fails, hosts on a local-area network will still have connectivity to other local hosts (since they all use the local ATMARP server); when the long-distance link is restored, SCSP will re-synchronize the servers’ caches, restoring connectivity to remote hosts. Both scspd and atmarpd(8) must be running before any ATMARP cache synchronization can take place.

The scspd utility implements SCSP as specified in RFC 2334, Server Cache Synchronization Protocol (SCSP) and draft−ietf−ion−scspd−atmarpd−00.txt, A Distributed ATMARP Service using SCSP.

When scspd starts, it parses its command line and puts itself into the background.

TERMINOLOGY

Some of the vocabulary associated with SCSP can be confusing. In this document, the following definitions are used:

Client server or local server means the server running on the same host as scspd whose cache is to be synchronized with that of one or more remote servers. When the word server is used alone, it means client server.

Remote server means a server running on some host other than the one where scspd is running.

Directly Connected Server (DCS) means a remote server that scspd communicates with directly. The remote server will also be running an implementation of SCSP.

Cache Alignment (CA) has two meanings. The Cache Alignment protocol is a part of the SCSP protocol specification, and the Cache Alignment finite state machine (FSM) is a finite state machine that implements the Cache Alignment protocol.

OPTIONS

The command-line options are:

−f ⟨ cfg−file⟩

Specifies the name of the configuration file. If this option is not specified, scspd looks for the file /etc/scspd.conf.

−d

Specifies that scspd is to be run in debug mode. In debug mode, the daemon is not put into the background. Log messages are written to standard output instead of to the log file specified in the configuration file.

−T⟨ options⟩

Specifies that scspd will trace specified events and messages as it executes. The −T flag is followed by one or more of the following options:

c

trace scspd’s CA Finite State Machine (FSM),

h

trace scspd’s Hello FSM,

i

trace scspd’s Client Interface FSM,

C

trace CA, CSUS, CSU Request, and CSU Reply messages,

H

trace Hello messages,

I

trace interface messages to and from scspd’s clients.

CONFIGURATION

The configuration file consists of a sequence of configuration statements. These statements specify information about the servers, both local and remote, whose caches are to be synchronized by scspd. RFC 2334, Server Cache Synchronization Protocol (SCSP) and draft−ietf−ion−scspd−atmarpd−00.txt, A Distributed ATMARP Service using SCSP will be valuable in understanding how to configure scspd.

A configuration statement other than a comment is terminated by a semicolon. Some statements contain blocks, delimited by braces (’’{’’ and ’’}’’). Configuration statement keywords are not case-sensitive, but some parameters (e.g. interface names) are. Configuration statements can span multiple lines.

Comments
Three types of comments are allowed:

# comments:

any characters from ’’#’’ to the end of the line are ignored.

C comments:

any characters between ’’/*’’ and ’’*/’’ are ignored.

C++ comments:

any characters from ’’//’’ to the end of the line are ignored.

Statements
The configuration statements recognized by scspd are:

Server <name> {

};

Log {

};

Where a host address needs to be specified in the configuration file, either a DNS name or an IP address in dotted decimal format can be used.

ATM addresses are specified as strings of hex digits, with an optional leading ’’0x’’. Fields within the address may be separated by periods, but periods are for readability only and are ignored. ATM addresses are 20 bytes long. The full address, including any leading zeroes, must be given. For example:

0x47.0005.80.ffe100.0000.f21a.0170.0020481a0170.00

Server Statement
The server statement specifies a client server whose cache to be synchronized with the caches of other servers running on remote hosts. There will be one server statement in the configuration file for each client server whose cache is to be synchronized by scspd. The format of the server statement is:

Server ⟨ name⟩ { ⟨ statements⟩ };

A name must be specified on the server statement, but it is not used by scspd. It is expected to give a brief description of the server’s purpose.

The server statement has several sub-statements that specify the details of the scspd’s configuration. They are:

Protocol ATMARP;

The only protocol supported by the current version of scspd is ATMARP. The protocol statement must always be specified.

Netif ⟨ intf⟩ ;

The netif statement specifies the name of the ATM network interface on which a client server is providing service. The netif statement must always be specified.

ServerGroupID ⟨ ID⟩ ;

The ServerGroupID statement specifies an identifier for the group of servers being synchronized by scspd. The ID is specified as a decimal number in the range 0 - 65,535. The server group ID must be the same for all servers whose caches are being synchronized by an SCSP session. That is, the server group ID for a host must be the same for all Directly Connected Servers (DCSs) pointed to within a server statement. The ServerGroupID statement must always be specified.

FamilyID ⟨ ID⟩ ;

The familyID statement specifies an identifier for a family of parallel SCSP sessions running between a group of hosts (i.e., a set of SCSP sessions with different protocol IDs but the same set of servers). The ID is specified as a decimal number in the range 0 - 65,535. The family ID is currently not used by scspd.

DCS Statement
The DCS statement is a sub-statement of the server statement that specifies the characteristics of a Directly Connected Server (DCS). The server statement will have one DCS statement for each DCS that scspd is to exchange information with. The DCS statement has a number of sub-statements that specify the details of the configuration for the DCS. They are:

ATMaddr ⟨ ATM address⟩ ;

The ATMaddr statement specifies the ATM address of the DCS. The ATMaddr statement must always be specified.

ID ⟨ host⟩ ;

The ID statement specifies the SCSP identifier of the DCS. For ATMARP, the ID is the IP address or DNS name associated with the ATM interface of the DCS. The ID statement must always be specified.

CAReXmitInt ⟨ int⟩ ;

The CAReXmitInt statement specifies the interval that is allowed to elapse between retransmissions of CA messages. If a CA message is sent and an acknowledgement is not received within CAReXmitInt seconds, the message will be retransmitted. The default value for CAReXmitInt is 3 seconds.

CSUSReXmitInt ⟨ int⟩ ;

The CSUSReXmitInt statement specifies the interval that is allowed to elapse between retransmissions of CSU Solicit messages. When a CSUS message is sent, any Cache State Advertisements (CSAs) requested by the CSUS that have not been received within CSUSReXmitInt seconds will be requested again by another CSUS message. The default value for CSUSReXmitInt is 3 seconds. Be careful not to confuse CSUSReXmitInt and CSUReXmitInt.

CSUReXmitInt ⟨ int⟩ ;

The CSUReXmitInt statement specifies the interval that is allowed to elapse between retransmissions of CSU Request messages. When a CSU Request message is sent, any CSAs that are not acknowledged by a CSU Reply message within CSUReXmitInt seconds will be retransmitted. The default value for CSUReXmitInt is 2 seconds. Be careful not to confuse CSUReXmitInt and CSUSReXmitInt.

CSUReXmitMax ⟨ cnt⟩ ;

The CSUReXmitMax statement specifies the number of times that a CSA will be retransmitted as described above before SCSP gives up on the CSA and discards it. The default value for CSUReXmitMax is 5.

HelloDead ⟨ cnt⟩ ;

The HelloDead statement specifies the Hello Dead Factor that will be sent to the DCS in Hello messages. A ’’DCS down’’ condition will be detected when nothing is received from a DCS in HelloDead * HelloInt seconds. The default value for HelloDead is 3.

HelloInt ⟨ int⟩ ;

The HelloInt statement specifies the Hello Interval that will be sent to the DCS in Hello messages. The default value for HelloInt is 3 seconds.

Hops ⟨ cnt⟩ ;

The Hops statement specifies the number of hops (DCS to DCS) that will be specified in CSAs originating from the local server. This number must be at least as large as the diameter of the server group. That is, it must be large enough for a CSA to be propagated from server to server all the way across the server group. The default value for Hops is 3.

Log Statement
The log statement specifies how scspd is to log information about its operation. The scspd utility can write log information to a file, to the system log, or both.

File ⟨ file name⟩ ;

The file statement specifies that scspd is to write its log messages to the named file. Log messages will be appended to the end of the file if it already exists.

Syslog;

The syslog statement specifies that scspd is to write its log messages to the syslog facility. The scspd utility writes its messages to syslog with a facility code of LOG_DAEMON.

If no log statement is specified, scspd writes log messages to the system log. If both file and syslog are specified, scspd will write log messages to both the named file and the system log.

Examples
An example of a simple configuration file for scspd might be:

server atmarp_ni0 {
protocol ATMARP;
netif ni0;
ServerGroupID 23;
DCS {
ID 10.1.1.2;
ATMaddr 0x47.0005.80.ffdc00.0000.0002.0001.002048061de7.00;
hops 2;
};
};

This configuration would synchronize the cache of the ATMARP server operating on network interface ni0 with the cache of a second server running on a host whose IP address is 10.1.1.2. Log messages would be written to the system log.

SIGNAL PROCESSING

The following signals can be used to control scspd:

SIGHUP

Reread the configuration file and restart scspd.

SIGINT

Dump debugging information to a file. When it receives a SIGINT signal, scspd dumps a summary of its control blocks to a text file (see FILES).

FILES
/etc/scspd.conf

scspd default configuration file name. A different file name can be specified with the −f command-line option.

/tmp/scspd.⟨ pid⟩ .⟨ seq⟩ .out

debugging information dump file name. The scspd utility writes a summary of its control blocks to this file when it receives a SIGINT signal. ⟨ pid⟩ is the process ID of the daemon and ⟨ seq⟩ is a sequence number which is incremented every time a dump is taken.

/tmp/scspd.⟨ pid⟩ .trace

trace file. The scspd utility writes trace information to this file if the −T option is specified on the command line.

SEE ALSO

atm(8), atmarpd(8)

Server Cache Synchronization Protocol (SCSP)

,

RFC 2334 .

A Distributed ATMARP Service Using SCSP

,

draft−ietf−ion−scsp−atmarpd−00.txt .

BUGS

If scspd terminates and is restarted, there will be a period of instability while previously-synchronized cache entries time out and are refreshed.

Please report any bugs to ⟨ harp−bugs [AT] magic.net⟩ .

COPYRIGHT

Copyright (c) 1994-1998, Network Computing Services, Inc.

AUTHORS

John Cavanaugh, Network Computing Services, Inc.
Mike Spengler, Network Computing Services, Inc.
Joe Thomas, Network Computing Services, Inc.

ACKNOWLEDGMENTS

This software was developed with the support of the Defense Advanced Research Projects Agency (DARPA).

BSD August 21, 1998 BSD