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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.

Example Message

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 | Frame | 0xFE
1, 2 | Length (MSB, LSB) | 0x0010 (16)
3, 4 | Message Type (MSB, LSB) | 0x0000 (Connect)
5 | Reserved | 0x00
6 | Sequence Number | 0xSN
7 | Node ID | 0x01 (Node 1)
8 | AIB 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

A computer, attached to the Excel platform through an RS-232 or Ethernet link, from which you run the telecommunications application that controls the Excel platform.
The protocol used in most local area PC networks. Typically, most Ethernet networks support data transmission speeds up to 10 Mbps, but 100 Mbps is also possible.
Range of channels provided by T1 or E1 transmission service. A physical span is a group of channels taking up a single physical wire. A logical span is a group of channels taking up less than a single logical wire, or carried over more than one physical wire.
A group of data bits in a specific format, with a flag at each end to indicate the beginning and the end of the frame.
Most Significant Bit
Least Significant Bit
See Address Information Block.
Positive acknowledgment to a message
The information in an AIB that follows the header, down to the data field. An AIB can have one or more Address Elements. AEs correspond to Span, Channel, and SS7 Link.