Table 31: Maximum Transmission Unit Values - Alcatel-Lucent 7705 Service Manual

Description This command configures the service payload (Maximum Transmission Unit – MTU), in octets, for
the service. This MTU value overrides the service-type default MTU.
The service-mtu defines the payload capabilities of the service. It is used by the system to validate
the SAP and SDP binding's operational state within the service.
The service MTU and a SAP's service delineation encapsulation overhead (4 bytes for a dot1q tag) is
used to derive the required MTU of the physical port or channel on which the SAP was created. If the
required payload is larger than the port or channel MTU, then the SAP will be placed in an
inoperative state. If the required MTU is equal to or less than the port or channel MTU, the SAP will
be able to transition to the operative state.
When binding an SDP to a service, the service MTU is compared to the path MTU associated with the
SDP. The path MTU can be administratively defined in the context of the SDP. The default or
administrative path MTU can be dynamically reduced due to the MTU capabilities discovered by the
tunneling mechanism of the SDP or the egress interface MTU capabilities based on the next hop in
the tunnel path. If the service MTU is larger than the path MTU, the SDP binding for the service will
be placed in an inoperative state. If the service MTU is equal to or less than the path MTU, then the
SDP binding will be placed in an operational state.
In the event that a service MTU, port or channel MTU, or path MTU is dynamically or
administratively modified, then all associated SAP and SDP binding operational states are
automatically re-evaluated.
The no form of this command returns the default service-mtu for the indicated service type to the
default value.
Parameters octets — specifies the size of the MTU, expressed as a decimal integer
7705 SAR OS Services Guide
Values 1 to 1514
Default apipe: 1508
cpipe: 1514
epipe: 1514
ipipe: 1500
Table 31
displays MTU values for specific VC types.

Table 31: Maximum Transmission Unit Values

VC-Type
Ethernet
Ethernet (with preserved dot1q)
VLAN (dot1p transparent to MTU value)
VLL Services
Example of Advertised
Service MTU MTU
1514 1500
1518 1504
1514 1500
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