Ethernet functionalities are available on IDU Plug-In platform by means of a dedicated Access Card, featuring a mixed TDM and Ethernet interface: 8xE1 and 4x10/100 BaseT, and supporting L2 switching and QoS management.
The selected on-air capacity (trunk port capacity), is shared between Ethernet Traffic and PDH traffic as showed in the diagram below.
The capacity reserved for Ethernet traffic is dynamically shared among the 4 LAN ports according to QoS setting.
Ethernet frames transmitted towards the radio are inserted in a NxE1 channel, with N configurable between 1 and 16, with a resolution of a single E1. N synchronous E1 signals are generated by a framer, according to the configured Trunk side capacity, while a proprietary mapping of the Ethernet frames into the NxE1 channel is performed by a mapper device. On the receiving side, N E1 de-framers and a demapper retrieve the original Ethernet frame transmitted by the remote station.
A block scheme of the Data interface unit is shown in the following figure.
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Each LAN port can be individually enabled/disabled .LAN interface is auto sensing (10 or 100 Mbit/s, half or full duplex); in any case it is possible, via management software, to set half/ full-duplex or auto-sensing mode as well as 10, 100 Mbit/s capacity. Ethernet frames with a length up to 1536 bytes are supported by LAN ports.
5.1.
SwitchingThe DATA Access unit implements an Ethernet bridge that has the function of Ethernet switch and manages the access on Ethernet interface to the BB cross-connection matrix.
The L2 Switching is performed among the following Ethernet ports:
Four LAN ports: input/output ports on LAN network of the traffic Ethernet frames
Trunk port: it is the input/output port of the Ethernet traffic towards the radio link.
Each LAN port can be enabled/disabled and configured by the user, while the Trunk port is always enabled.
The switching can be performed on the basis of the MAC Address or the VLAN ID.
The switching functionalities are subdivided in Filtering the Ethernet frames and Forwarding them among the available ports.
5.1.1. Filtering
Filtering is performed according to the source MAC address of the incoming packets.
Source MAC addresses received from LAN Ports are stored, along with the corresponding port the frame was received from (LAN and Trunk), in a data-base (MAC DB) which is continuously updated (Auto-learning mode). Each entry is stored within a configurable aging-time.
Switching Block
Frames received from a port are discarded if the destination MAC address matches one of the MAC addresses contained in the data-base and the input port is equal to the one contained in the data-base.
Also frames received from or sent to a disabled port are discarded.
In case of VLAN-based switching, filtering rules are based on VLAN ID, too (see following section).
5.1.2. Forwarding
All filtered frames are forwarded among the ports according to the selected forwarding mode:
Fully connected LAN ports:
Each frame in input is routed only on the basis of the destination MAC address. The LAN ports are fully interconnected; this causes that the frame in input from a LAN port can be sent to any other port (LAN and Trunk), without any restriction.
An uplink frame (frame in input from a LAN port):
- is sent to only one LAN port if the destination MAC address is stored in the MAC DB and the corresponding port is a LAN port (LAN and Trunk), different from that in input
-is sent both to the Trunk port and to all the other enabled LAN ports if the destination MAC address is unknown.
A downlink frame (frame in input from the Trunk port):
- is sent to only one LAN port if the destination MAC address is stored in the MAC DB and the corresponding port is a LAN port
- is sent to all the enabled LAN ports in the other cases.
Isolated LAN ports
The LAN ports are isolated; this causes that the frames in input from a LAN port can be sent only to the Trunk port (they cannot be sent to another LAN port).
An uplink frame (frame in input from a LAN port):
- is sent to the Trunk port in all cases.
A downlink frame (frame in input from the Trunk port):
- is sent to only one LAN port if the destination MAC address is stored in the MAC DB and the corresponding port is a LAN port
- is sent to all the enabled LAN ports in the other cases.
Selective VLAN forwarding
In each port only the passage of the frames containing a VLAN tag with the value of VLAN ID included in the list of VLAN ID associated to the port is allowed. The user can configure up to 64 different VLAN IDs, specifying the LAN port associated to each VLAN ID. All the configured VLAN IDs are always automatically associated to the Trunk port.
Each frame in input from a port is discarded:
- if it satisfies the filtering rules - if it does not contain a VLAN tag
- if it contains a VLAN tag that is not included in the list of the VLAN tags associated to the input port
- if the destination MAC address is stored in the MAC DB and the corresponding port is not included within the ports associated to the VLAN ID contained in the frame.
Each received frame containing a VLAN ID associated to the input port is sent:
- to only one of the other ports associated to the VLAN ID contained in the frame, if the destination MAC address is stored in the MAC DB and the corresponding port is included within the ports associated to the VLAN ID contained in the frame
- to all the other ports associated to the VLAN ID contained in the frame, if the destination MAC address is unknown.
Uplink VLAN ID tagging and Replacing
To each LAN port is associated only a unique VLAN ID, which can be configured by the user; it is possible to associate the same VLAN ID to more LAN ports.
The frames in input from a port are managed in the following way:
- if the frame contains a VLAN tag, there is the replacement of the VLAN ID contained in the frame with the VLAN ID associated to the input port
- if the frame does not contain a VLAN tag, there is the insertion, into the frame, of a VLAN ID equal to that associated to the input port.
Frames entering the switch from the Trunk port contain a VLAN tag otherwise they are discarded.
Frames are internally forwarded according to the same rules explained for the selective VLAN forwarding mode. VLAN tag is removed from Ethernet frames exiting from LAN ports, whereas frames exiting from Trunk port keep their VLAN tag.
5.2.
SchedulingQoS management is provided by Scheduling in upstream direction (from User side to Radio side) used to transmit data frames with different priority on the radio channel, according to one of the following criteria or possibly a combination of them:
• first arrived first served (no priority);
• LAN port;
• content of the Ethernet User Priority field in the Ethernet frames (“802.1p”);
• content of the ToS/DiffServ field of IPv4 packets or the Traffic Class field of IPv6 packets (“IP based”).
The last three criteria are separately enabled on a per port basis according to software configurations. In case of more than one criterion enabled, LAN port has the lowest priority, while it is possible to select the priority classification between “802.1p” and “IP based”.
In the scheduler, up to 4 different queues are available, according to the selected criteria and the enabled options.
Selection of the frame to be transmitted from the different queues towards the radio is done according to a fixed priority scheme or using a WFQ algorithm with fixed weights.
If Fixed priority is selected, frames with higher priority are always transmitted first.
WFQ allows to share the channel bandwidth among the four different priority levels. The four weights are fixed and respectively equal to 8, 4, 2 and 1.
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