NAME¶
sap - Service Access Point specification
DESCRIPTION¶
The
text2sap and
sap2text functions use the format described in
this man page. Because all standard ATM tools on Linux use those functions to
convert to or from the textual representation of SAP specifications, they
expect them in the same format too.
The SAP is divided into two parts: the
broadband high layer information
(BHLI) and the
broadband low layer information (BLLI). A SAP can
contain one, both, or none of them. In the latter case, the SAP is usually
considered as a wildcard SAP, i.e. a SAP that is compatible with any other
SAP.
Each part begins with its name (
bhli or
blli), followed by a
colon and a (non-empty) list of attributes, which are of the form
attribute =value. Some attributes have sub-attributes,
which follow them. Everything that isn't separated by a colon or an equal sign
is separated by a comma.
Values which are a number of bytes are specified as the corresponding sequence
of pairs of hex digits. The sequence can be optionally prefixed with
0x. Values with are integers in a given range can be specified in
decimal (no prefix), octal (
0 prefix), and hexadecimal (
0x
prefix).
The following, mutually exclusive attributes are allowed in the
bhli part
(see the corresponding ATM Forum and ITU documents for the semantics):
- iso=1-8 bytes
- ISO
- user=1-8 bytes
- User-specific
- hlp=4 bytes
- High layer profile. Note that this attribute only exists on UNI 3.0.
text2sap only recognizes it if your system is configured to accept
UNI 3.0 message formats.
- oui=3 bytes,id=4 bytes
- Vendor-specific application identifier
The structure of the
bhli part is more complex. It distinguishes three
layers,
l1,
l2, and
l3, of which the first one is
presently unsupported. For layer two, the following (mutually exclusive)
possibilities exist:
- l2=iso1745
- Basic mode ISO 1745
- l2=q291
- ITU-T Q.291 (Rec. I.441)
- l2=lapb
- Extended LAPB, half-duplex (Rec. T.71)
- l2=iso8802
- LAN LLC (ISO/IEC 8802/2)
- l2=x75
- ITU-T X.75, SLP
- l2=x25_ll ...
- ITU-T X.25, link layer. This attribute and the following attributes
through l2=iso7776 can optionally be followed by one or more of the
following sub-attributes: mode=mode (mode of operation,
either norm or ext), and window=window size
(window size in k, 1-127).
- l2=x25_ml ...
- ITU-T X.25, multilink
- l2=hdlc_arm ...
- HDLC ARM (ISO/IEC 4335)
- l2=hdlc_nrm ...
- HDLC NRM (ISO/IEC 4335)
- l2=hdlc_abm ...
- HDLC ABM (ISO/IEC 4335)
- l2=q992 ...
- ITU-T Q.922
- l2=iso7776 ...
- ISO 7776 DTE-DTE
- l2=user,info=information
- User-specified. information is an integer in the range 0 to
255.
For layer three, the following (again, mutually exclusive) possibilities exist:
- l3=iso8473
- ITU-T X.233 | ISO/IEC 8473
- l3=t70
- ITU-T T.70 minimum network layer
- l3=h321
- ITU-T Recommendation H.321
- l3=x25 ...
- ITU-T X.25, packet layer. This attribute and the following attributes
through l3=x223 can optionally be followed by one or more of the
following sub-attributes: mode=mode (see above),
size= default packet size (4-12, corresponding to
16-4096), window=window size (see above).
- l3=iso8208 ...
- ISO/IEC 8208
- l3=x223 ...
- ITU-T X.223 | ISO/IEC 8878
- l3=tr9577,ipi=identifier ...
- ISO/IEC TR 9577. identifier is the initial protocol identifier in
the range 0-255. For SNAP (0x80), the keyword snap can be used, and
the following sub-attributes have to be specified: oui=3
bytes, and pid=2 bytes.
- l2=user,info=information
- User-specified, see above.
- l3=h310 ...
- ITU-T Recommendation H.310. The sub-attribute term=type
(terminal type, rx, tx, or rxtx) is recognized. If
present, it enables the two additional sub-attributes
fw_mpx=capability (forward multiplexing capability,
ts, ts_fec, ps, ps_fec, or h221) and
bw_mpx=capability. Both are optional.
Note that commas must never follow colons or other commas. Also, whitespace is
not allowed inside a SAP specification. SAP specifications are
case-insensitive. On input, items must be written in exactly the order used in
this document.
EXAMPLES¶
- blli:l2=iso8802
- Classical IP over ATM (RFC1577)
- bhli:oui=0x0060D7,id=0x01000001,blli:l2=iso8802
- Arequipa (RFC2170)
- blli:l3=tr9577,ipi=snap,oui=0x00A03E,pid=0x0002
- LAN Emulation
AUTHOR¶
Werner Almesberger, EPFL LRC <werner.almesberger@lrc.di.epfl.ch>