VLL Services
7705 SAR OS Services Guide Page 189
Targeted LDP and MTU
The extended discovery mechanism for Label Distribution Protocol (LDP) sends LDP
Targeted Hello messages to a specific address. This is known as targeted LDP or TLDP.
Refer to RFC 5036 for detailed information about the extended discovery mechanism.
During the VLL service creation process (that is, using targeted LDP signaling), the MTU or
payload size of a service is signaled to the far-end peer. MTU settings at both ends (near and
far peers) must match in order for the VLL service to operate. Table 30 shows the values that
are expected to match.
Notes:
• In order to accommodate current and future services (including overhead), the MTU
value for Gigabit Ethernet and PPP/MLPPP ports have the default value set to 1572
bytes. For 10/100 Ethernet ports, the MTU value is set to 1514 or 1518 bytes, depending
on the encapsulation setting (null or dot1q).
• The default service MTU value is 1514 bytes; the maximum value is 1522 bytes.
Table 30: Matching MTU or Payload Values for Signaled VLL Services
Apipe Cpipe Epipe Ipipe
Payload size (bytes) Yes
Bit rate Yes
Maximum number of ATM cells Yes
Service MTU Yes Yes
Must match at both ends Yes Yes Yes Yes
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