The 305-LTE is a fully functional MEF CE2.0 compliant 1Gbps NID, which supports Carrier Ethernet over both a fibre and a 4G/LTE radio.
The 305-LTE is most commonly deployed in 2 scenarios:
- Where Carrier Ethernet Service is required but deployment of fibre is delayed
- To provide a back-up communication path in the event of a failure in the fibre connection.
Like all of the Carrier Ethernet NIDs in the Net2Edge portfolio, the 305-LTE supports Zero Touch Provisioning as well as the expected features in CE2.0 such as:
- Hierarchical QoS
- IETF RFC-2544 / ITU-T Y.1564
- Hardware OAM
- ITU-T G.8032v2 rings
- IEEE-1588v2, (PTP)
The 305-LTE lends itself to 4 applications:
- Rapid Service Delivery
- Back-up / Resilience
- Dynamic Bandwidth Allocation
- Separation of Management and Data Traffic
Rapid Service Delivery
When there is no fibre plant in the ground, it often takes a Service Provider significant time to provision fibre in order to deliver a Carrier Ethernet service – in some instances this can take months. In the meantime, the Enterprise customer will have to make do with whatever connectivity is available – often this may be an xDSL service.
The Service Provider can use a 305-LTE to deliver Carrier Ethernet services using the in-built 4G/LTE radio. The 305-LTE establishes an L2TPv3 tunnel over the 4G radio.
Zero Touch Configuration means that service can be delivered as quickly as it takes for a 305-LTE to arrive by courier/post. Of course, an added benefit is that the Service Provider can earn revenue quickly as well!
When fibre becomes available, service can switch seamlessly from the 4G to the fibre. The 4G service can then be discontinued or it can be used for one of the following:
- Backup / resilience
- Bandwidth top up
- Separation of Management traffic
Back-up / Resilience
Loss of connectivity has far reaching consequences for an enterprise:
- It has been estimated recently that downtime cost businesses in the US about $700bn in 2016.
- A recent British study found that the average worker in the UK loses 38 hours every year through slow internet connectivity and downtime
Fibre optic cables are probably rarely on the mind, in fact the only time you may ever think of these cables is when one actually gets cut resulting in an outage. This is a rarity for sure, but it can happen when construction crews aren’t aware of where the cables are. Of course, a cut fibre isn’t the only reason why a company’s fibre Ethernet connection could fail.
Connectivity failure can be mitigated with a back-up path. The 305-LTE can be deployed as a conventional 1G NID with the 4G/LTE radio configured as a back-up path in the event of fibre connectivity failure.
The 4G radio can be configured to ensure the most important applications continue to run. As soon as fibre connectivity is restored the applications switch seamlessly back to the fibre path.
The 4G back-up is established via an L2TPv3 tunnel. For optimum switch-over to 4G, the L2TPv3 tunnel should remain established at all times.
Dynamic Bandwidth Allocation
In this application, the customer can configure the 305-LTE to use the 4G radio to top up the bandwidth.
The customer can optionally configure a particular application and/or VLAN to use the 4G radio or simply trigger the 4G based on EIR.
The 305-LTE will establish an L2TPv3 tunnel across the 4G radio.
Separation of Management Traffic
Some Service Providers have expressed a desire to separate the management and data traffic. This is particularly useful in a multi-provider environment where the Service Provider does not own the access network.
The 305-LTE will establish an L2TPv3 tunnels across the 4G radio and use this exclusively for the transmission of management traffic. The entire capacity of the fibre can then be used for data traffic.
Customer Deployment Options
Service Providers will fall into 1 of 3 categories when delivering Carrier Ethernet Services using the 305-LTE
- Service Providers who own both a fixed and mobile network
- Service Providers who own a fixed network
- Service providers who own a 4G/LTE mobile network but wish to deliver IP/Ethernet services
Service Providers who own both a fixed and mobile network
In this scenario, when using the 4G / LTE link, the L2TPv3 tunnel can be terminated within the Service Provider’s network with onward transmission across their fixed network under the control of the PE / Core Router.
As the Service Provider owns the mobile network the customer can be provided, easily with a Private APN.
Since packets do not leave the network, the Service Provider is in total control of security / encryption.
Service Providers who own a fixed network
Fixed network service providers who don’t own a mobile network can still deliver a Carrier Ethernet service over 4G / LTE.
The optimum method is to partner with a Mobile Network Operator (MNO), which can enable preferential rates to be negotiated. To enable the L2TPv3 tunnel to be established a private APN should be obtained for each customer.
If the MNO is unwilling or unable to provide private APNs with static IP addresses then an alternative is to use a Linux Server running a proxy program to establish the L2TPv3 tunnel – although not optimal this implementation is often used for PoCs.
Service providers who own a 4G/LTE mobile network and wish to deliver IP/Ethernet services
The 305-LTE can be used to deliver Carrier Ethernet over 4G. Support for Zero Touch Configuration comes as standard, so the Service Provider can simply post the 305-LTE to the end customer, who simply needs to unpack it and switch it on
Layer 2 Tunnelling Over 4G / LTE
The Layer Two Tunnelling Protocol (L2TP) provides a dynamic mechanism for tunnelling Layer 2 (L2) “circuits” across a packet-oriented data network (e.g., over IP). L2TP, as originally defined in IETF RFC 2661 is a standard method for tunnelling Point-to-Point Protocol (PPP) sessions.
The 305-LTE uses L2TPv3 to tunnel Ethernet packets over the 4G / LTE link. The 305-LTE tunnels Ethernet frames to / from an unmanaged L2TPv3 endpoint, including:
- Passing untagged frames.
- Passing VLAN tagged frames with a C-tag.
- Passing VLAN tagged frames with a S-tag.
- Passing L2CP frames for all protocols.
The 305-LTE passes maximum size Ethernet frames (tagged and untagged) as well as ARP and IP frames for IP addresses used internally.
What is L2TPv3 Ethernet Pseudo-wire?
- The Layer 2 Tunnelling Protocol -n 2 (L2TPv2) provides a mechanism for tunnelling layer 2 packets over the Internet. However, L2TPv2 is limited to transporting PPP frames.
- Layer 2 Tunnelling Protocol – version 3 (L2TPv3) adds the ability to carry more layer 2 protocols than just PPP. ISPs and network operators may use L2TPv3 to extend Frame Relay or ATM networks over an IP infrastructure.
- Each L2TPv3 session carries one data frame type which is agreed by both peers when the session is established. A session provides the data channel in L2TP and is effectively a virtual physical wire of that data link type.
- L2TPv3 Ethernet pseudo-wires can be used to transport Ethernet frames across an IP backbone network, which connects Ethernet LANs together. A pseudo-wire is an emulation of a point-to-point connection over a Packet Switched Network (PSN).
- L2TPv3 can also be used to transport IPv6 traffic over an IPv4 network.
- L2TPv3 is described in RFC3931 and the specifications for supported layer 2 protocols are maintained in separate RFCs (Ethernet RFC4719).
“Heavy Duty” choice: RFC 3193 “Securing L2TP with IPsec”
- IPSec operates in Transport Mode, L2TP is responsible for tunnelling
- Gives operator the option of turning security on or off at will, decoupling the tunnelling system from the security method
Light duty options:
- Control Connection Authentication
- L2TPv3 “Cookie field” random 64-bit value in each data packet associated with session to protect against a malicious blind attack, or inadvertent insertion of data into the tunnel stream.
Pseudo-wires enable network convergence by emulating a variety of data links over a common packet switched network. Pseudo-wires may be operated over IP without modification of IP core routers.
L2TPv3 is a tunnelling protocol that has a large base of operational experience and standardization in the IETF that is being used for pseudo-wire tunnelling.