GE T1000, Техническое руководство

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GE Reason Switches Chapter 4
– Functions
REASON SWITCHES-TM-EN-3 87
Trunk ports are always defined as C-Ports and permit tagged and untagged incoming frames. Allowed and Forbidden VLAN at
the ports and egress tagging is user configurable. When using equipment that allow much VLAN traffic, such as IED receiving
Sampled Values and GOOSE messages at the same network interface, port type of the connection point of the IED to the switch
should be considered trunk port.
Hybrid ports allow the user to configure all parameters at a given port, as ingress
filtering, port VLAN (in case of untagged frame), allowed and forbidden VLAN. Hybrid
ports can permit, if desired, the ingress of packets from a given VLAN that is not a
member nor is a forbidden VLAN.
Hybrid ports allow users to configure all possible treatment the switch will perform in the VLAN, such as Port VLAN, Port type,
Ingress filtering, Ingress Acceptance, Egress Acceptance and Allowed and Forbidden VLAN configurable.

Port Type Concept:
In addition to operation mode, there is the port type concept that must be
understood. Port types can be set to be Unaware, C-Port, S-Port and S-Custom-Port
types.
Unaware port is used for legacy equipment connection. These ports do not consider
incoming frames VLAN information, and all incoming frames are classified at port
VLAN number. On frame’s egress, port VLAN tag is removed.
Customer tag port (C-Port) is a port that deals with C-tagged frames. These are
common tagged frames, such as incoming GOOSE messages. Thus, when using
equipment that sends tagged-frames, this is the port type that needs to be used.
Incoming frames with VLAN information will be directed to the VLAN, and priority-
tagged or untagged frames are directed to Port VLAN.
Service tag port (S-Port) is a port that expects to deal with double-tagged frames.
Double-tagged frames are frames that have a C-tagged frame inside other VLAN tag,
which is the service VLAN tag. S-tag frames are used by switching equipment at the
network to create a VLAN to transport tagged frames. Only switching equipment use
this frames. Thus, if S-tag is required, be sure that the S-port is connected to other
switching equipment, e. g., another switch.
Custom Service tag port (S-Custom-Port) is used in environments that traditional S-
tag does not fulfill the requirements of the network. This port behaviour is much like
S-port, except that the expected Ethertype field in the Ethernet frames of custom S-
port is defined at the switch, that is, the Ethertype field in the frame should be
configured manually at the switch. These ports can be used at applications where
non-conventional switching equipment is used, to allow some interoperability to
them.
There are some concepts on the treatment of untagged frames, ingress and egress
filtering on the switch and the VLAN range that a port can be member as explained
below.
Port VLAN parameter is the VLAN that the switch will use if incoming traffic is
untagged. All frames “inside” the switch are tagged -frames, and untagged incoming
frames will be internally tagged in the VLAN defined at Port VLAN.