Technical data

TraverseEdge 2020 Applications and Engineering Guide, Chapter 3: System Applications
Release 5.0.x Turin Networks Page 3-55
tags can be “nested” (Q in Q).
In cases where customer traffic does not contain VLANs then a VLAN tag can be added to incoming traf-
fic on a specific port allowing it to be routed through a TE-206 or TE-2020 packet engine while maintain-
ing full traffic segregation. At the egress point in the network the VLAN tag can either be stripped (placing
“native” Ethernet frames onto the remote Ethernet port), or VLAN tags can be preserved allowing an
attached device (such as an edge router) to maintain traffic segregation.
3.10.8 Ethernet Switching
In shared ring configurations, MAC address-based Ethernet switching can be used in conjunction with
VLAN ID to route a packet from the ingress port to the egress port of a network. The VLAN ID is used to
define a closed group, and within this group MAC addresses are used for routing. Ethernet switching per-
mits multiple packet sources, or customers, to share a common pipe or common path around a network (ex.
shared rings).
Generic Framing Procedure
Generic Framing Procedure (GFP) provides a generic mechanism to adapt traffic from higher-layer client
signals over a transport network. Currently, two modes of client signal adaptation are defined for GFP:
• A PDU-oriented adaptation mode, referred to a Frame Mapped GFP (GFP-F)
• A block-code oriented adaptation mode, referred to as Transparent GFP (GFP-T).
Only GFP-F is supported in Turin Networks products as of this release.
In the ingress direction, the GbE PLM uses GFP-F to encapsulate valid Ethernet frames and insert them in
the payload of the STS-Nc-Xv SONET connection. Figure 3-50 illustrates the GFP-F mapping of an Ether-
net frame into a GFP frame. The GFP frame carries as its payload the entire Ethernet MAC frame (this
does not include the Preamble, Start of Frame Delimiter, or Inter-Frame Gap). The GFP frame adds a four
octet Core Header and a Payload Header. The GbE PLM uses the eight octet Payload Header for a Linear
frame. The GFP frame concludes with a four octet Payload Frame Check Sequence (FCS).
Figure 3-50 Ethernet Mapping into GFP
Note that all fields of the Ethernet MAC frame are carried unchanged by the GFP frame. Note also that the
GFP frame can support transport of Ethernet jumbo frames.
In the egress direction, the GbE PLM performs the reverse process: It checks each received GFP frame
and, if the GFP frame is valid, the GbE PLM extracts the Ethernet frame from the GFP frame Payload Info.