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VX supports transporting data from serial interfaces over IP network. Data received on serial interfaces is encapsulated into IP packets and sent over the IP network. IP packets destined for serial interfaces are stripped off their headers and the payload is transmitted over serial interfaces.

The table below gives a list of features supported for Serial over IP functionality

Serial Over IP Functionality


Characteristic

Description

Protocols

Serial over IP is supported using SAToP. SAToP using UDP is supported. SAToP using RTP is not supported.
Serial over IP is supported for unstructured data and structured (HDLC) frames.

Card/Port

One serial card containing 4 ports.1

Port speeds

Various speeds are available.

DTE/DCE

Support is provided for both DCE and DTE modes.

Mode combinations

Serial ports can be configured to any mode (IP over Serial, Serial over IP etc.), independent of mode of other ports on the card.

Interfaces

V.35, EIA-449, EIA-530 are supported.

Jitter Management

Jitter buffers are used in the egress direction of serial ports to provide jitter tolerance for unstructured SoIP.

Configuration Parameters

Parameter

Description

DTE/DCE

A serial interface can run either as DCE or DTE. These modes are available for all the types (Raw, Hybrid etc.). This affects the clocking and speed configurations on the interface it doesn't affect the physical cabling.
A serial interface running in DCE mode derives it clock from the system backplane. The system backplane clock is derived from one of the ports. These ports can be on the serial card or the telephony cards.
A DTE derives its clock from DCE to which it is connected. A DTE in turn can feed the system backplane as its clock source.
If this value is modified for an operational port, it resets the port for new parameter to take effect.

Mode

A serial interface can be configured in following additional modes:

  • Unstructured SoIP
  • HDLC SoIPIf this value is modified for an operational port, it resets the port for new parameter to take effect.

Cabling

V.35, EIA-449, and EIA-530 are supported for all the interface types (Raw, Hybrid etc.).

Port Speed

Port speed is always same in both transmit and receive direction. Asymmetric speeds are not supported.
A DTE always derives its speed from the DCE it is connected to.
If this value is modified for an operational DCE port, it resets the port for new parameter to take effect.

Destination IP

IP address of the node to which the data needs to be sent across an IP network.

Circuit Bundle Identifier

Circuit Bundle Identifier (CBID) is associated with a SoIP port.

SAToP Length

This is sum of SAToP header (32 bytes) and its payload. In this document payload is also referred to as frame.
SAToP length can be specified for unstructured serial over IP interfaces. If this value is modified for an operational port, it resets the port for new parameter to take effect.
This can take values between 32 to 1500.

Jitter Tolerance

This is specified in terms of number of segments. This determines the number of packet payloads to be stored before sending out the first byte on the serial interface. This also determines the max amount of delay that can be tolerated for packets received out of sequence.
Jitter tolerance in segments translates to some value in time. Timers in VX have granularity of 30 ms. If user specified jitter tolerance is not a multiple of 30 ms then it will be internally increased to some suitable value.
Higher jitter tolerance compensates better for packet delay variation, but also introduces its own latency equal to the amount of tolerance.
This attribute can be specified for both the SoIP modes. If jitter tolerance is modified for an operational port, it resets the port for new parameter to take effect.
Jitter tolerance segments can't be more than 4096. Product of jitter tolerance and segment size should not exceed 512000 bytes.

DS Byte

This specifies the DiffServ priority of the outgoing IP packets.

Receive control lines processing

VX allows turning on and off the processing of receive control lines.

Protocols

VX supports the following types of traffic across the serial link:

  • Regular IP
  • Raw, proprietary VX protocols (BSP/IBP for signaling, and VTP for audio)
  • Hybrid protocol using raw mode for proprietary VoIP protocols, and IP for other traffic
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