Lucent Technologies DEFINITY Enterprise Communications Server Release 5, CallVisor, ASAI Protocol Reference Instructions Manual

The ECS Congestion and Flow Control on ASAI Links
Issue 6 June 1997
6-5
If the adjunct sends a STATUS ENQuiry message to the ECS, on a BRI ASAI 
interface, the ECS treats the STATUS ENQuiry as an unexpected message and 
responds as Chapter 5 describes.
Layer 3 Timers
The only layer 3 BRI Timer that the ECS ASAI uses is T316, the retry timer for 
RESTart. T316 has a value of 120 seconds. None of the BRI Management timers 
are used.
The ECS adjunct routing application also makes use of an application-level...

Maintenance
6-6Issue 6 June 1997 
nWhen the ECS receives an ASAI message that begins a new association 
(for example, REGister message), it is discarded and the ECS responds 
with a RELease COMplete Message containing Q.931 Cause Value 42 
(Coding Standard 0/Network Congestion).
nWhen the ECS receives a FACility message with a Domain Control 
Auto-Dial Request, it is discarded and the ECS responds with a FACility 
Message containing Q.931 Cause Value 42 (Coding Standard 0/Network 
Congestion). 
ASAI...

The ECS Congestion and Flow Control on ASAI Links
Issue 6 June 1997
6-7
For hyperactive ASAI links, the L2 processor takes two actions:
1. It flow controls the link by sending an RNR to the link endpoint each time a 
frame is received from the endpoint.
2. It reports the hyperactivity event to the ECS CPU.
The L2 processor continues to flow control the link until the ECS processor 
notifies it to withdraw hyperactivity control on that link. The ECS waits a 
designated period of time (in seconds) after a...

Maintenance
6-8Issue 6 June 1997 
Controls on Send Traffic
This section discusses the ECS congestion controls for traffic from the ECS 
toward the adjuncts (the transmit direction):
1. Over all links (that is, the ECS congestion).
2. Over a single link (that is, link congestion).
Layer 2 Processor Congestion on Send Traffic
L2 processor congestion in the transmit direction (toward adjuncts) is measured 
by the number of available transmit buffers. A common buffer pool is used by the 
L2 processor for...

Issue  6 June 19977-1
7
TCP Tunnel Protocol
Overview
This chapter describes version 1 of the TCP tunnel protocol.
CallVisor ASAI over the DEFINITY LAN Gateway is a communications interface 
that provides the functionality of the Adjunct/Switch Application Interface (ASAI) 
using an Ethernet transport instead of a Basic Rate Interface (BRI) transport.
DEFINITY LAN Gateway uses a TCP tunnel protocol in addition to the protocols 
defined by ASAI for layer 3 Q.931/2. This tunnel protocol works as follows:...

TCP Tunnel Protocol
7-2Issue  6 June 1997 
ASAI-Ethernet connection is established, and pinging of the client ceases for that 
link. It resumes when the ASAI-Ethernet connection is closed. Since the 
ASAI-Ethernet connection rides on top of the TCP connection, closing the TCP 
connection terminates the ASAI-Ethernet connection.
TCP only insures the reliable delivery of a data stream, yet ASAI protocol expects 
to interact in complete messages. To overcome this mismatch, both the client and 
brouter must...

Overview
Issue  6 June 1997
7-3
Table 7-2 that follows lists the message types. A single asterisk (*) next to a 
message indicates that it is sent only by the server. A double asterisk (**) means 
that it is sent only by the client.
Table 7-2. TCP Tunnel Protocol Message Header Values 
Octet 1 value
Message Type
Value and DescriptionOctet 2 value
Message Cause
Value and DescriptionOctet 3 and 4 value
Additional Octet Count
Value and Description
0
Error Notification
The server will 
immediately close the...

TCP Tunnel Protocol
7-4Issue  6 June 1997 
6
Too much (or little) data
The octet count specified 
exceeds the maximum 
allowable for a particular 
message type/cause, or 
the size was not sufficient 
for the particular message 
type.6
Octet 5 contains the 
offending message type.
Octet 6 contains the 
offending message cause. 
Octets 7 and 8 contain the 
offending octet count as a 
16-bit unsigned integer in 
network byte order.
Octets 9 and 10 contain 
the maximum octet count 
as a 16-bit unsigned...

Overview
Issue  6 June 1997
7-5
255
Server error
The server experienced 
an internal error. 
Reconnecting may 
eliminate the error 
condition.0
No additional data.
1
Connection Request**
A client uses this message 
type to request an 
ASAI-Ethernet connection.0
Not used.2
Octet 5 contains the 
client’s link number.
Octet 6 contains the 
client’s TCP Tunnel 
protocol version number.
2
Connection Accepted*
The server has accepted 
the connection request.10
Link up
ASAI data messages can 
now be...

TCP Tunnel Protocol
7-6Issue  6 June 1997 
3
Connection Rejected*
The server has rejected 
the connection request, 
and will close the TCP 
connection.12
Invalid link
The requesting client’s link 
number is unknown to the 
server.0
No additional data.
2
Out of service
The requested link 
number has been taken 
out of service on the 
brouter.0
No additional data.
13
Unsupported TCP Tunnel 
Protocol version
The client’s TCP Tunnel 
protocol version is not 
supported by the server.1
Octet 5 contains the...