VLL Service Configuration Commands
Page 242 7210 SAS M Services Guide
Service Filter and QoS Policy Commands
service-mtu
Syntax service-mtu octets
no service-mtu
Context config>service>cpipe
Description This command configures the service payload (Maximum Transmission Unit – MTU), in bytes, 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 (i.e., 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 minus control word length (if applicable), the SDP
binding for the service will be placed in an inoperative state with sdp-bind oper flag
PathMTUTooSmall.
If the CEM SAP’s packet size is larger than the service MTU then the service will be placed in an
inoperative state with service oper flag ServiceMTUTooSmall . The CEM SAP packet size is defined
as CEM SAP payload-size plus rtp-header size (if applicable).
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.
Default cpipe: 1514
octets — The size of the MTU in octets, expressed as a decimal integer, between 1 — 1514.
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