SAP
Section: Miscellaneous (7)
Updated: November 6, 1997
Page Index
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>