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Distributed Layer 4 Call Processing
Host Managed
The host manages call processing on an CSP with a single service access point. If a connection is made between channels on different nodes, internal call control messaging is automatically sent between the nodes. This strategy allows for answer/release to propagate internally. It also allows for outseizure to initiate on a remote node (with the Connect message) so the host can manage calls as though the multi-node CSP were a single-chassis CSP.
When a connection is being made between two nodes (A, B) the host needs to send only a Connect message (or other connection management message) to Node A. Node A then establishes a connection with Node B using the Ethernet link. For routing messages between nodes like this, each node keeps a record of all Logical Span IDs in the CSP.
Important! When cross connecting spans or channels among nodes in an CSP, a separate message must be sent to each span or channel in the connection.
Example: Message 1: to Node 1, Cross Connect Channel A, B
Message 2: to Node 2, Cross Connect Channel B, A
When cross connecting spans or channels in the same node, only one message is required. But you can still use the two-message internodal method. Having one method (internodal) instead of two simplifies your application.
This example shows the format of a Connect message that connects Span 0/Channel 0 on Node 1 to Span 65/Channel 0 on Node 4:
Table 10-2 API
BYTE |
Field Description |
Value and Indication |
---|---|---|
0 |
0xFE |
|
1, 2 |
0x0010 (16) |
|
3, 4 |
Message Type (MSB, LSB) |
0x0000 (Connect) |
5 |
Reserved |
0x00 |
6 |
Sequence Number |
0xSN |
7 |
Node ID |
0x01 (Node 1) |
8 |
Address Method |
0x10 (Positive ACK) |
9 |
Number of Address Elements |
|
10 |
Address Element 1: Channel A Address Type |
0x0D (Channel) |
11, 12 |
Logical Span (MSB, LSB) |
0x0000 (Span 0) |
13 |
Channel |
0x00 (Channel 0) |
14 |
Address Element 2: Channel B Address Type |
0x0D (Channel) |
15, 16 |
Logical Span (MSB, LSB) |
0x0041 (Span 65) |
17 |
Channel |
0x00 (Channel 0) |
18 |
Checksum |
0xCS |