Mirror Services - Alcatel-Lucent 7750 SR OS Service Manual

Local and Remote Mirroring
Mirrored frames can be copied and sent to a specific local destination or service on the 7750 SR
router (local mirroring) or copies can be encapsulated and sent to a different 7750 SR router
(remote mirroring). This functionality allows network operators to centralize not only network
analyzer (sniffer) resources, but also the technical staff who operate them.
The 7750 SR allows multiple concurrent mirroring sessions so traffic from more than one ingress
mirror source can be mirrored to the same or different egress mirror destinations.
Remote mirroring uses a service distribution path (SDP) which acts as a logical way of directing
traffic from one 7750 SR-Series router to another through a uni-directional (one-way) service
tunnel. The SDP terminates at the far-end 7750 SR which directs packets to the correct destination
on that device.
The SDP configuration from the mirrored device to a far-end 7750 SR requires a return path SDP
from the far-end 7750 SR back to the mirrored router. Each device must have an SDP defined for
every remote router to which it wants to provide mirroring services. SDPs must be created first,
before services can be configured.
Slicing
A further service mirroring refinement is 'slicing' which copies a specified packet size of each
frame. This is useful to monitor network usage without having to copy the actual data. Slicing
enables mirroring larger frames than the destination packet decode equipment can handle. It also
allows conservation of mirroring resources by limiting the size of the stream of packet through the
7750 SR and the core network.
When a mirror
size is created. For example, if the value of 256 bytes is defined, up to the first 256 bytes of the
frame are transmitted to the mirror destination. The original frame is not affected by the
truncation. Mirrored frames, most likely, will grow larger as encapsulations are added when
packets are transmitted through the network core or out the mirror destination SAP to the packet/
protocol decode equipment.
The transmission of a sliced or non-sliced frame is also dependent on the mirror destination SDP
path MTU and/or the mirror destination SAP physical MTU. Packets that require a larger MTU
than the mirroring destination supports are discarded if the defined slice size does not truncate the
packet to an acceptable size.
7750 SR OS Services Guide
is defined, a threshold that truncates a mirrored frame to a specific
slice-size

Mirror Services

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