Alcatel-Lucent 7750 - Table 28: MTU Configuration Example Values; Figure 33: MTU Configuration Example

MTU Configuration Guidelines
Page 170 7750 SR Interface Configuration Guide
Modifying MTU Defaults
MTU parameters should be modified on the service level as well as the port level.
• The service-level MTU parameters configure the service payload (Maximum
Transmission Unit – MTU) in bytes for the service ID overriding the service-type default
MTU.
• The port-level MTU parameters configure the maximum payload MTU size for an
Ethernet port or SONET/SDH SONET path (sub-port)
or TDM port/channel, or a channel
that is part of a multilink bundle or LAG.
The default MTU values should be modified to ensure that packets are not dropped due to frame
size limitations. The service MTU must be less than or equal to both the SAP port MTU and the
SDP path MTU values. When an SDP is configured on a network port using default port MTU
values, the operational path MTU can be less than the service MTU. In this case, enter the show
service sdp command to check the operational state. If the operational state is down, then modify
the MTU value accordingly.
Configuration Example
In order for the maximum length service frame to successfully travel from a local ingress SAP to a
remote egress SAP, the MTU values configured on the local ingress SAP, the SDP (GRE or
MPLS), and the egress SAP must be coordinated to accept the maximum frame size the service
can forward. For example, the targeted MTU values to configure for a distributed Epipe service
(ALA-A and ALA-B) are displayed in Figure 33.
Figure 33: MTU Configuration Example
OSSG012
SAP
1/1/1
encap:
100
Network
2/1/1
SAP
4/1/1
encap:
null
Network
3/1/1
ALA-A ALA-B
Table 28: MTU Configuration Example Values
ALA-A ALA-B
Access (SAP) Network Network Access (SAP)