RFC1582 - Extensions to RIP to Support Demand Circuits(11)

Packet Exchange (IPX) protocol using socket number 452h.
SAP operates on similar principals to running RIP. Routers act as
SAP agents, collecting service information from different networks
and relay it to interested parties.
To support the triggered update mechanism outlined in this proposal
the packet format for Netware SAP is modified as shown in Figure 4.
Every Service Advertising Protocol datagram contains the following:
SAP OPERATION
Operations supported in standard Netware SAP are: general
service query (1), general service response (2), nearest
service query (3) and nearest service response (4).
The fields sequence number, fragment number and number of
fragments MUST NOT be included in packets with these
operation values.
The following new operations are required:
TRIGGERED GENERAL SERVICE QUERY (6)
A request for the responding system to send the
identities of all servers of all types.
Only the first 2 octets of the packet format shown in
figure 4 are sent, since all service types are
implied by this request type.
0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
- - - - - - - - - - - - - - - -
operation (2)
--------------- ---------------
The following new fields are inserted for some operations
0 1 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
sequence number (2)fragment (1) no of frags (1)
------------------------------- -------------------------------
Followed by up to 8 service entries (each 66 octets)
0 1 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Service Type (4)
---------------------------------------------------------------
Service Name (48)
.
.
---------------------------------------------------------------
Network Address (4)
---------------------------------------------------------------
Node Address (6)
-------------------------------
Socket Address (2)
---------------------------------------------------------------
Hops to Server (2)
-------------------------------
.
.
The format of a Netware SAP datagram in octets, with each tick
mark representing one bit. All fields are in network order.
The four octets: sequence number (2), fragment number (1) and
number of fragments (1) are not present in the original SAP
specification. They are only present if operation takes the
values 7 or 8.
Figure 4. Netware Service Advertising Protocol packet format
TRIGGERED GENERAL SERVICE RESPONSE (7)
A message containing all of the sender"s services
table, excluding those entries learned from the
interface to which the service advertising
information is being sent out.
This message may be sent in response to a triggered
general service query, or it may be an update message
resulting from a change in the service advertising
database.
A triggered general service response message MUST be
sent in response to a triggered general request
message even if there are no services to advertise.
This would be the case for a router with a LAN
network which had work stations but no servers on it.
TRIGGERED GENERAL SERVICE ACKNOWLEDGEMENT (8)
A message sent in response to every triggered general
service response packet received.
Only the first 6 octets of the packet format shown in
figure 4 are sent.
SEQUENCE NUMBER
This is a new field inserted if operation takes the values
7 or 8.
The sequence number MUST be incremented every time updated