Datasheet

____________________________________________________ DS34S101, DS34S102, DS34S104, DS34S108
Rev: 032609 38 of 198
Figure 10-10. TDM-over-Packet Encapsulation Formats
4 BYTES 4 BYTES
PREAMBLE
7 BYTES
START OF FRAME
DELIMITER
1 BYTE 6 BYTES 6 BYTES 2 BYTES
DATA AND
PADDING
46-1500 BYTES 4 BYTES
OPTIONAL
DESTINATION
ADDRESS
SOURCE
ADDRESS
VLAN
TAG 1
TYPE
FRAME CHECK
SEQUENCE
TDMoIP
CONTROL WORD
TDMoIP
PAYLOAD
UDP / IPv4
HEADER
or
28 BYTES
MPLS
HEADER
4, 8 or 12 BYTES
4 BYTES
MEF
HEADER
4 BYTES
L2TPv3 / IPv4
HEADER
24, 28 or 32
BYTES
TDMoIP
CONTROL WORD
TDMoIP
PAYLOAD
4 BYTES
RTP
HEADER
RTP
HEADER
OPTIONAL
OPTIONAL
VLAN
TAG 2
OPTIONAL
or
or
L2TPv3 / IPv6
HEADER
44, 48 or 52
BYTES
48 BYTES
UDP / IPv6
HEADER
or
12 BYTES
12 BYTES
or
Table 10-6. Ethernet Packet Fields
Field
Description
Preamble
A sequence of 56 bits (alternating 1 and 0 values) Gives components in the network time to detect the
presence of a signal and synchronize to the incoming bit stream.
Start of Frame
Delimiter (SFD)
A sequence of 8 bits (10101011) that indicates the start of the packet.
Destination
Address and
Source Address
The Destination Address field identifies the station or stations that are to receive the packet. The
Source Address identifies the station that originated the packet. A Destination Address may specify
either an individual address destined for a single station, or a multicast address destined for a group of
stations. A Destination Address of all 1s refers to all stations on the LAN and is called the broadcast
address.
Type
Ethertype. The type of payload contained in the Ethernet frame.
Data and Padding
This field contains the payload data transferred from the source station to the destination station(s). The
maximum size of this field is 1500 bytes. If the payload to be transported is less than 46 bytes, then
padding is used to bring the packet size up to the minimum length. A minimum-length Ethernet packet
is 64 bytes from the Destination Address field through the Frame Check Sequence.
Frame Check
Sequence (FCS)
This field contains a 4-byte cyclical redundancy check (CRC) value used for error checking. When a
source station assembles a packet, it performs a CRC calculation on all the bits in the packet from the
Destination Address through the Pad fields (that is, all fields except the preamble, start frame delimiter,
and frame check sequence). The source station stores the calculated value in the FCS field and
transmits it as part of the packet. When the packet is received by the destination station, it performs an
identical check. If the calculated value does not match the value in the FCS field, the destination station
assumes an error has occurred during transmission and discards the packet.