Hybrid access
Hybrid Access is a technology that enables different Internet access connections, e.g. B. via landline and cellular network, merged into a common network connection. The aim is to use the bandwidth of several available network connections at the same time and thus to improve the reliability of the Internet connection. It is a technology for strengthening initiatives for broadband expansion, especially in underserved rural areas.
Technology and standardization
In a broad sense, hybrid access solutions can combine any network access technologies such as DSL , cable, LAN , WLAN , LTE , 5G , satellite etc. in one connection. The Broadband Forum describes hybrid access broadband network architectures in the TR-348 standard.
The Broadband Forum distinguishes between two scenarios:
- with only one hybrid connection point (router) in the customer connection area: Hybrid Customer Premises Equipment (HCPE) or
- with two hybrid connection points, the HCPE and the Hybrid Access Gateway (HAG) in the network of the Internet service provider.
Only the second variant enables control in both directions (upstream and downstream), so that the data traffic is split up at the entry point and combined in a coordinated manner at the end point, see figure.
Distribution of traffic
The following procedures and protocols at line, network and transport level can be used to distribute data traffic over different paths and technologies:
- Line level ( Layer 2 ): Multilink Point-to-Point Protocol (MLPPP) and Link Aggregation Control Protocol ( LACP )
- Network level ( Layer 3 ): Traffic distribution via IP tunnel (GRE tunnel, VPN) or Equal Cost Multi Path ( ECMP )
- Transport level ( Layer 4 ): Multipath TCP (MPTCP) for dividing parallel TCP flows, Multipath QUIC (MPQUIC)
The first hybrid access solutions established on the market for the combination of landline and mobile networks use IP tunnels at network level (Vibrinet: via VPN, MagentaZuhause Hybrid: via GRE tunnel), see the following section on the distribution in Germany .
There is also research and development work on the hybrid combination of landline and satellite connections, which is due to an enormous increase in satellite capacities for telecommunications and the like. a. gain in importance over the next few years through the Starlink project.
Hybrid access technologies and protocols are also useful for mobile communication in order to bundle all available transmission capacities in the current environment into the greatest possible connection bandwidth.
There are various options for efficient control of the distribution of the data streams:
Preferred primary connection
A primary connection is preferred, with transmissions over further connections only taking place when the primary connection is overloaded. The connection with the best transmission properties, i. d. Usually fixed network, is suitable as a primary connection (fixed minimum bandwidth, low delay, high availability). Advantage: You can expect the hybrid solution to always deliver the same good transmission quality as the primary connection, as well as higher bandwidth and failure protection via the secondary paths.
Distribution depending on the application
Certain applications are preferably assigned to certain connections, e.g. B. real-time applications (voice, gaming etc.) of the connection with the smallest delay or video streaming via the connection with the largest available bandwidth. This assumes that the application for the division of data units is known. In general, IP data packets can also be marked in a QoS class division and distributed in the hybrid system according to the marking.
Flow-based load balancing
All data of a flow at the transport level (TCP, QUIC flow with uniform 5-tuple) are sent over the same connection. Different flows are distributed in different ways for load balancing. This means that individual applications and the associated transport flows have a uniform delay. Also ECMP ensures a flow-based load balancing. Advantage: All data of a river experience similar transmission properties and do not overtake each other in different ways. Disadvantage: A flow and the associated application can only use one connection. Even for a few rivers with different traffic volumes, the bandwidth of the hybrid solution can usually not be used efficiently.
Packet-based load balancing
IP packets are distributed to the hybrid access connections without reference to flows and applications in such a way that they are about equally well utilized. Advantage: The load distribution can be based exactly on the available capacities. Disadvantage: The data of each application is continuously split into different transport media, which leads to different delays (delay jitter) and to packets in the wrong order when received. This is problematic for real-time services such as voice transmission and can also reduce the data throughput for download and streaming services via TCP, QUIC, etc.
Hybrid Access quality and efficiency
Even if incorrect packet sequences are corrected again in multipath transmissions at the transport level by TCP , QUIC , long and variable packet delays must be expected depending on the combined transmission media. Real-time applications should therefore run without being split over the channel with the least delay. Even for delay-tolerant streaming and data transmissions, error and load control is made more difficult if it has to include paths with different characteristics. A load control for each transport medium involved, e.g. B. by means of MPTCP, in order to achieve a good utilization in adaptation to its respective delay and susceptibility to errors. Otherwise, a hybrid access solution can introduce its own protocol for load control of the overall traffic if the usual protocols TCP and QUIC are not efficient enough at the transport level to utilize the available bandwidths.
Precursors and Developments
One of the origins of hybrid access can be seen in the channel bundling of access media, as it was already implemented between ISDN and modem access before 2000. Network operators have been dealing with multihoming network transitions since 2005 in order to connect routers via several separate access points, see LISP. The availability of heterogeneous network connections on routers and end devices has increased with increasing bandwidth using different wireless transmission technologies from Bluetooth to WiFi, cellular networks and satellite channels. Correspondingly, procedures and protocols have also been developed in order to use an optimal connection via several transmission media in a heterogeneous network environment at the same time. The IETF has protocol developments u. a. in working groups for Multi Path TCP (MPTCP) and BANdwidth Aggregation for Network Access (BANANA).
Distribution in Germany
Business customer market
Controlware GmbH, founded in 1980, has been offering ISDN backup systems (IBS) since 1999 and launched the IBS Cirus 100 commercially in 2007 , which can automatically switch access technologies and also distribute the load for IP access via T1, ISDN , UMTS and xDSL . The company Viprinet has patented a process since 2007 that bundles several landline and mobile phone connections from different network providers to form a VPN multichannel. According to its own information, Viprinet supplied more than 3,000 customers with 8,000 installations of their hybrid access solution in 2019.
Private customers
Since 2015, Deutsche Telekom has offered Hybrid Access as a MagentaZuhause hybrid product for private customers that combines a DSL and LTE connection. According to information in Telekom's annual reports, the hybrid access product is used by over 500,000 customers. The solution relies on DSL as the primary connection and switches to LTE if the DSL bandwidth is insufficient, or switches to LTE if DSL fails, whereby telephony is then continued via LTE. Information on further marketing offers in Europe can be found under Hybrid Access Networks .
Individual evidence
- ↑ Guiu Fabregas: Hybrid Access Broadband Network Architecture . In: Broadband Forum Technical Report . TR 348, 2016 ( broadband-forum.org [PDF]).
- ^ M. Li et al .: Multipath Transmission for the Internet: A Survey . In: IEEE COMMUNICATIONS SURVEYS & TUTORIALS . tape 18/4 , 2016.
- ↑ K. Sklower et al .: The PPP Multilink Protocol . In: IETF, RFC 1990 . 1996.
- ↑ a b c N. Leymann et al .: Huawei's GRE Tunnel Bonding Protocol . In: IETF, RFC 8157 . 2017.
- ↑ a b IETF Working Group MPTCP: Multi Path TCP . ( [1] ).
- ^ Q. de Coninck and O. Bonaventure: Multipath QUIC: Desgin and Evaluation . In: Proc. ACM CoNEXT, Incheon, Korea . 2017.
- ^ A b S. Kissel, Vibrinet Europe GmbH: arrangement for transmitting a data stream over bundled network access lines, as well as sending and receiving auxiliary device for it . In: Europ. Patent Office EP1976202A3 . 2007.
- ↑ a b Viprinet Innovations GmbH. Accessed in 2020 .
- ↑ J. Deutschmann, K.-S. Hielscher and R. German: An ns-3 Model for Multipath Communication with Terrestrial and Satellite Links . In: Proc. MMB Conference, Springer LNCS 12040 . 2020, p. 65-81 ( fau.de ).
- ^ IETF Working Group LISP: Locator / ID Separation Protocol . ( [2] ).
- ↑ IETF Working Group BANANA: Bandwidth aggregation for interNet Access . ( [3] ).
- ↑ OD Ramos-Cantor et al .: A Network Simulation Tool for User Traffic Modeling and Quality of Experience Analysis in a Hybrid Access Architecture . In: Proc. World Telecommunications Congress . 2014, p. 1-6 .