Datasheet

____________________________________________________ DS34S101, DS34S102, DS34S104, DS34S108
Rev: 032609 57 of 198
10.6.7 HDLC Payload Type Machine
Handling HDLC in TDM-over-Packet ensures efficient transport of CCS (common channel signaling, such as SS7),
embedded in the TDM stream or other HDLC-based traffic, such as Frame Relay, according to IETF RFC 4618
(excluding clause 5.3 – PPP) and RFC 5087 (TDMoIP).
For an E1 interface, each bundle supports the rates of 16 kbps or N × 64 kbps, where N is the number of timeslots
configured to be assigned to a bundle (between 1 to 32). For an T1 interface, each bundle supports the rates of 16
kbps, 56 kbps (not supported for T1 SF interface), full T1 (1.544 Mbps) or N × 64 kbps, where N varies from 1 to
24.
In the TDM-to-Ethernet direction, the HDLC block monitors flags until a frame is detected. It removes bit stuffing,
collects the contents of the frame and checks the correctness of the CRC, alignment and frame length. Valid frame
length is anything greater than 2 bytes and less than Tx_max_frame_size in HDLC_Bundle[n]_cfg[95:64].
Erroneous frames are discarded. Good frames are mapped as-is into the payload of the configured layer 2/3
packet type (without the CRC, flags or transparency zero-insertions).
In the Ethernet-to-TDM direction, when a packet is received, its CRC is calculated, and the original HDLC frame
reconstituted (flags are added, bit stuffing is performed, and CRC is added).
Figure 10-38. HDLC Mapping
HDLC TYPE
TDMoIP PAYLOAD
CONTROL
WORD
L2/L3
HEADER
HDLC FRAME
IN TDM
ETHERNET
PACKET
CRC
FLAGS
CRC-16
DATA
FLAGS
ZERO BIT
DELETION