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