As with the GPON network, the 7360 ISAM FX EPON optical distribution network extends optical access across the “last mile” of the communications network to the subscriber, using fiber optic cabling to provide services from the network to residential or business subscribers.
EPON network elements
The 7360 ISAM FX EPON optical distribution network consists of the following network elements:
• EPON OLT
• EPON
• 10G EPON
• EPON ONU
Figure10-1 shows the EPON network elements deployed in a network topology.
10 — EPON Network Architecture Figure 10-1 EPON network topology
EPON OLT
The optical line termination unit is the equipment located at the network side of the optical distribution network. The OLT performs a network-to-EPON and an EPON-to-network interface function to support the transmission of services and traffic between the network and the EPON ONU.
The P-OLT resides at the central office of the service provider. The EPON OLT provides uplinks to the EMAN and access interfaces for subscribers, and serves two main functions:
• performs conversion between the electrical signals used by the service provider equipment and the fiber optic signals used by the passive optical network
• coordinates the multiplexing between the conversion devices (ONUs) on the other end of the optical network
The EPON OLT supports ONU data configuration preservation using OAM channels to improve service recovery time on end-to-end solutions when the ONU or the OLT power switches off and on.
The EPON OLT supports forwarding of IPv6 UC and MC traffic in the iBridge
Wireless access
Mobile device EMS
PSTN
Video Server
Voice Gateway EMAN
EPON OLT
PC
Splitter EPON
ONU
EPON ONU
PC
STB TV
RGW
Phone STB LAN
10 — EPON Network Architecture
10-4 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02 The EPON OLT supports downstream broadcast flooding. When the secure forwarding mode is disabled in the RB VLAN, the OLT ensures that received ARP packets are forwarded correctly in both the upstream and downstream directions so that there is no need for operator involvement. In the case where RB VLAN flooding is enabled and CVLAN translation is required at the same time, CVLAN translation for flooding packets will not be completed by the OLT resulting in incorrect downstream forwarding behavior. Therefore, CVLAN translation in RB VLAN flooding is not supported.
Lightweight DHCPv6 Relay Agent (LDRA), including Option 18 for Circuit ID and Option 37 for Remote ID, is supported by the EPON OLT in all forwarding models except CC VLAN and S RB VLAN for IPv6 subscriber identification. IPv6 addresses are copied transparently and are not modified or stored. For Option 18, relay agents identify the interface where the client message is received. For Option 37, relay agents that terminate switched or permanent circuits identify the remote hosts. ISAM allows insertion for one or both options to enable LDRA and when both options are disabled, LDRA is disabled.
The EPON OLT supports DHCP Relay Agent Information Object (DHCP Option 82). This is an optional parameter that the relay agent adds to the DHCP request messages to identify the circuit to which a user is connected. In the upstream direction, the EPON OLT adds a relay-tag containing user-port information to the upstream PPPoE discovery packets, depending on the configuration. In the
downstream direction, the EPON OLT does not process the PPPoE proprietary tags therefore it is recommended to follow TR-101 standard.
The EPON OLT is DHCP Option 82 compliant with MII standards. For DHCP and PPPoE Option 82 supports customer ID format for the Remote ID sub-option and physical line ID format for the Circuit ID sub-option, in compliance with the definition of EPON specification v. 2.1 and CCSA “Technical requirements for access network subscriber access loop (port) identification in broadband access networks.”
Serial number inclusion of Option 82 is supported by the EPON OLT. You can specify the type of system identifier added to the header of a DHCP Option 82 message or PPPoE: system, MAC address, or logical ID.
The EPON system supports rogue ONU discovery and closure which means automatic identification of faults or error conditions using alarms and statistics can be used to inform operators of any problems or to have automatic action taken to disable a rogue ONU and avoid any disruption in the PON.
Configuration and retrieval of RSSI thresholds and alarms on optical modules for specific EPON uplink ports on the LT, NT, and NTIO boards is supported and allows the operator to report the operating conditions of the optics module on the ONU and on the PON.
Optical Time-Domain Reflectometry (OTDR) is supported for SFPs and XFPs on EPON interfaces that have an embedded OTDR capability which allows
measurements to be obtained without the requirement for external equipment and without the requirement of an operator on-site.
10 — EPON Network Architecture
The EPON ONU supports the loopback detection in the same Ethernet port or different Ethernet ports. The EPON OLT allows you to enable or disable the function per Ethernet port. When a loopback is detected on the ONU side, the ONU will trigger an alarm and send it to the OLT. The OLT reports the alarm messages to the EMS. The alarm will be cleared by the ONU when the loopback issue is resolved.
The OLT can b configured to enable or disable the action of shutting down the port where the loopback exists. Depending on the configuration, the ONU or the OLT will shutdown the port.
The EPON OLT supports on-board controller (OBC) defense on 1G, 10G EPON LT cards and the NT card in the upstream direction only. Operators can specify the threshold value for each ONU. The following three control level rate limits are supported:
• PON
• LLID
• VP
Two types of rate limits exist in each control level. Each protocol type for each control level and the summation of all protocol types have an independent rate limit threshold value. All alarms are independent with two alarms supported for each level rate limit. A total of six threshold values can be set for the following:
• PON + protocol
• PON + summation of all protocols
• LLID + protocol
• LLID + summation of all protocols
• VP + protocol
• VP + summation of all protocols
The OBC defense features can monitor packets for the following protocols:
• ARP
• DHCP
• PPPoE
• IGMP
• ND
• DHCPv6
Note — The VP control level is currently not supported.
10 — EPON Network Architecture
10-6 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02 EPON
All services and traffic are transported between the OLT and an ONU over the EPON. The EPON brings optical fiber cabling and signals to the subscriber. The optical fiber network connecting the EPON OLT and the EPON ONU is a passive optical network (PON) with no active or powered elements.
The EPON employs a point-to-multipoint topology. A single strand of fiber extends from the OLT at the central office to a passive optical splitter. The PON supports up to 64 splits or ONU.
The EPON network uses the following wavelengths of light between the P-OLT and the ONUs across the EPON:
• 1310 nm transmit in the upstream
• 1490 nm receive in the downstream
10G EPON
All services and traffic are transported between the OLT and an ONU over the 10G EPON. The 10G EPON brings optical fiber cabling and signals to the subscriber. The optical fiber network connecting the EPON OLT and the EPON ONU is a passive optical network (PON) with no active or powered elements.
The 10G EPON employs a point-to-multipoint topology. A single strand of fiber extends from the OLT at the central office to a passive optical splitter. The PON supports up to 128 ONUs on a PON.
A Neighbor Discovery (ND) proxy is supported on the NT board.
IPv6 anti-spoofing is supported for 10G EPON providing the capability of anti-spoofing towards any received IPv6 traffic from the subscriber side based on DHCPv6 snooping.
The 10G EPON network uses the following wavelengths of light between the P-OLT and the ONUs across the EPON:
• 1310 nm burst transmit in the 1 Gb/s upstream
• 1490 nm a continuous receive in the 1 Gb/s downstream
• 1270 nm a burst transmit in the 10 Gb/s upstream
• 1577 nm continuous receive in the 10 Gb/s downstream In the CATV service, 1550 nm wavelength is used.
Figure 10-2 shows the wavelength and spectral width of the 10G EPON system.
10 — EPON Network Architecture Figure 10-2 Wavelength and Spectral Width of the 10G EPON system
EPON ONU
The optical network unit is a conversion device that is located at the subscriber premises as distributed end-points of the optical distribution network. The ONU performs an EPON-to-subscriber and a subscriber-to-EPON interface function to support the distribution of network services and traffic from the OLT to the subscribers, and the transmission of subscriber traffic to the OLT.
The EPON ONU implements the EPON protocol and adapts EPON Protocol Data Units to subscriber service interfaces.
See chapter “ISAM Support for the EPON ONU” for more information about the EPON ONU.
The EPON ONU supports PB encapsulation mode in the upstream and downstream directions, and PB transport mode in the upstream and downstream directions.
When the EPON LT card is set to DPoE mode, the card supports TPID translation and functionality. Operators can configure one ONU using the following TPID values:
• 0x8100
• 0x88a8
• 0x9100
• 0x9200
The configured values used for DPoE OAM support are dependent on the type of service and hardware being used. See Customer Release Notes for DPoE limitations.
See your Alcatel-Lucent representative for more information.
The EPON OLT enables the following behavior:
1260 1360
10 — EPON Network Architecture
10-8 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX R4.6.02
Standards
The EPON and 10G EPON networks are developed based on the following standards:
• IEEE 802.3ah-2004 (Amendment: Media access control parameters, physical layers and management parameters for subscriber access networks)
• IEEE 802.3-2005 (Carrier sense multiple access with collision detection access method and physical layer specifications)
• EPON access device technical specification of CTC R2.1
• ITU-T G.652 and G.657(Characteristics of a single-mode optical fibre and cable)
• CCSA EPON regulation amendment for PX20+, PR20, PRX20, PR30, and PRX30 sublayer requirement
• YD/T 1475-2006 access technical requirements - EPON
• EPON physical ID format for LDRA Option 18 and Option 37 specification of CTC R3.0 technical requirements for Broadband access network: subscriber access loop (port) identification
• IEEE 802.3av-2009 (Co-existence and simultaneous operation of 1 Gb/s and 10 Gb/s and physical layer specifications
• IEEE 802.3av-2009 (PMD, RS, PCS, PMA, and MPCP Sub-Layer Requirements
• CTC EPON Specification V2.1/V3.0
The IEEE 802.3ah series of standards define how traffic is packetized and
transported over the EPON. As per the IEEE 802.3ah protocol, each EPON optical fiber connection from the P-OLT supports:
• line rates of 1.25 Gb/s upstream
• line rates of 1.25 Gb/s downstream
The IEEE 802.3av series of standards define how traffic is packetized and
transported over the EPON, 10G EPON, or both. As per the IEEE 802.3av protocol, each EPON optical fiber connection from the P-OLT supports:
• symmetric operation with line rates of 10 Gb/s upstream and downstream
• support for TDM and WDM with line rates of 1/1, and 10/10 Gb/s upstream/downstream coexistence
• asymmetric operation with line rates of 1 Gb/s upstream, and 10 Gb/s downstream
• support for TDM and WDM with line rates of 1/1 and 10/1 Gb/s upstream/downstream coexistence
The 10G EPON OLT supports the coexistence of 10G EPON and 1G EPON ONUs on the same PON. In the downstream direction, the OLT transmits both 10 Gb/s and 1Gb/s signals in a WDM manner. In the upstream direction, the OLT receives both 10Gb/s and 1Gb/s signals in a TDMA manner. See Figure 10-3.
In the case where the ONU uses a DFB laser in the upstream direction and the actual variance from the center wavelength of 1310nm is ± 8 nm then the card can support an external WDM implementation. The upstream 1G EPON receiver would be on another card. This allows sharing a fiber with 10G and 1G EPON without having to reprovision the existing 1G EPON customers to a new port or having the 1G customers effect the bandwidth available in the upstream of the 10G services.
10 — EPON Network Architecture Figure 10-3 Coexistence of 10/10G EPON, 10/1G EPON, and 1G EPON ONUs