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SERVICE NETWORK TRANSIT TRAFFIC TRANSFER TO A TRANSPORT NETWORK
Tatyana Sergeeva,
FSUE ZNIIS, Moscow, Russia, [email protected]
Anastasia Smolskaia,
FSUE ZNIIS, Moscow, Russia, Keywords: service networks, optical transport
[email protected] network, tunnel, DWDM, OTH/OTN, ODU,
linear programming, multicommodity flow.
In transport networks in contrast to service networks (SN) the link choice is made not for individual messages but for their aggregates or groups, which are usually forwarded through a predetermined route. At service networks such groups which may be SN tunnels can be formed out of the total packet stream, selecting packets with totally or partially coinciding routes. In networks of large capacity and length, which is specific for Russia's backbone networks, traffic tunnels are huge and transit a large number of intermediate network nodes without any treatment and changes in the composition of the flows within the tunnel. So eliminating transit traffic from the tunnel intermediate service network routers proposed in this article will lead to a significant load reduction in channels between the routers and will improve the quality of service due to the transparent traffic forwarding and absence of queues in an optical network. It also will increase security of information transmission in the network. The latter is especially important for special customers' data as the packet service network is more vulnerable to unauthorized access than a synchronous optical network.
Such opportunities arose when OTH/OTN (Optical Transport Hierarchy/ Optical Transport Network) optical networking technologies were used with ITU-T G.709 standard [1]. The article discusses the issues of tunnels design optimization in service network with MPLS-TE technology and with subsequent transfer of transit traffic tunnels into OTH/OTN optical transport network.
Information about authors:
Tatiana Sergeeva, FSUE ZNIIS, Chief Researcher, Ph.D., Moscow, Russia Anastasia Smolskaia, FSUE ZNIIS, Postgraduate student, Moscow, Russia
Для цитирования:
Сергеева Т., Смольская А. Перевод транзитного трафика сервисной сети в транспортную сеть // T-Comm: Телекоммуникации и транспорт. 2017. Том 1 1. №7. С. 53-55.
For citation:
Sergeeva Т., Smolskaia А. (2017). Service network transit traffic transfer to a transport network. T-Comm, vol. 1 1, no.7, рр. 53-55.
New opportunities in optical networks
The functional interaction of optical transport networks with service networks has significantly changed currently. For example, earlier fiber-optic technology on the basis of DWDM optical multiplexers OADM was used only lo obtain high bandwidth between the SN nodes. With the advent of configurable optical multiplexer ROADM with bolli electric and optical (photonic) switching in several links of fiber optic network the optical networks functionality has expanded considerably.
Controllable optical network ASON [2] supporting GMPLS protocol [3J is currently introduced which is an extension of MPLS technology to the optical level. GMPLS provides automatic selection and switching not only of ^.-channels, but also of the boot blocks of lower hierarchy level used to build optical transport modules (OTM) loading optical channels in accordance with the ITU-T G.709 Recommendation 11 J. The structure of the optical transport module OTM consists of synchronous blocks of three levels [4]. The lower level module OTM consists of blocks ODUA, where ¿=1,2,3. Currently, ROADM has the ability of the input-output units ODUA extraction out of OTM spectrum in optical nodes, where ODU1 is the smallest unit corresponding to the STM-16 path with transfer rate of2.5Gbit/s. In latest versions of the OTM structure a minimal hoot module is even smaller in capacity/speed unit 1.25 Gbit/s. It matches two STM-4 SDH paths. Each of these ODU1 blocks can be extracted out of the OTM spectrum by transforming OTM into electric form and by using electronic switch to be switched to I/O interfaces associated with SN routers ports. One of such problems considered in this paper is tunnels organization in a service network with further transfer of their traffic into selected modules of the transport network optical channels.
The optimal organization of tunnels problem solution
As mentioned a modem backbone network consists of a packet service network SN providing users with telecommunications services and an optical transport network with DWDM technology (Fig. 1).
Fig, I. Functional components of the communication network
Let's consider tunnels formation in SN network subject to further tunnels traffic transmission in DWDM transport network.
It is known the MPLS-TE technology uses two types of tunnels - fixed (or rigid) tunnel and free tunnel [5]. We point out that in following methodology the SN network determines fixed tunnel, and a DWDM network operates free tunnel. It is known that in MPLS-TE networks, the creation of fixed tunnels is done on basis of pre-calculated schemes [4]. In this paper the optimization algorithm lo produce fixed tunnel uses LSP paths for all kinds of traffic, except the Video traffic. Let's illustrate the methods with an example. Fig. 2 presents the graph of an MPLS
network fragment where PL are boundary nodes and P - nodes with label switching.
Let all LSP paths between RE nodes with a list of intermediate nodes to be known. Wc present all possible tunnels as additional edges in the graph of the initial network (dotted lines in Fig. 3).
Note that the designer can on the basis of his experience add direct edges or specify the most preferred tunnels. Using the following methods among the added edges those that carry the maximum traffic arc selected. The problem of optimal organization of the tunnels is formulated in the form of known Multi-commodity F!ow Problem with minimum cost in path form [6]. The communication network is represented as undirected graph of the original network G(V,M) that is specified with a set V of nodes, a set M of links connecting the nodes, and a set D of demands (LSP paths in the SN network). We introduce a network graph G*( K.A/*) with added edges and set R - a set of paths in the graph G*. Added edges describe options for a tunnel formation including possible ways for the passage of transit LSP path between the end nodes of the tunnel.
Let dm be a demand between nodes u and v belonging to the set D, and Rm, is a set of paths for this demand , which pass through the links of the network G( VJM) or added edges *. Let jr,11.r to be a share of demand dm passing through the r-th path of the set R,n„ The minimum value of traffic at the tunnel arranging we'll assign equal to 0.8 B, where B is the ODU1 capacity. LP Task is formulated as follows:
£ Z„ m in, m e u •
Provided that
nve D re Ruv
T-Comm Tom 1 1. #7-20 1 7
y Ytixl -kZm$0, m&M,
m uv m ' *
uv e /) re A„
X C = <iWJ i/„„ e Z),
re n„
r _ J 1, if me r, 'w~{o, else, -C > 0, Zm> 0 (integer).
The solution of the problem above can be obtained by means of standard LP packages, such as LPSOLVE package operating in a UNIX environment for example. In the problem that can be solved by using this package the number of integer variables does not exceed a few dozen, but the solution of the continuous problem, the dimension of which can be several tens of thousands of variables can be of significant value hinting paths with maximum transit traffic
A consecutive method of problem solving can be used when the results of the previous solution is applied as source data for subsequent attempt. However though the task of grouping can be solved using the above LP method for a limited part of the network, the solution for the backbone network of actual size forces
to use the developed heuristic algorithm which is not presented here due to limited size of the paper.
Conclusion. Thus, improving the efficiency of the network can be obtained through the optimal organization of the tunnels in networks with the subsequent transfer of transit traffic tunnels into optical transport network, which currently has the technical ability to organize such transfer.
References
1 ITU-T G.709/Y-1331 Recommendation. Interfaces for the optical transport network, 2003.
2 ITU-T G.8080/Y/1304 Recommendation Architecture for the automatically switched optical network. 2012,
3 RFC 3471. Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description, January 2003.
4 Fokin, V. (2003). Optical systems and transport networks. Moscow: Ecotrendz.
5 Oliier, V., Olifer, N. (2006). Computers networks II 3-nd ed„ Sankt-Peterburg: Piter.
6 Sergeheva. T.P., Tetckin, N.N. (2000). Design of Reliable Transport SDH Networks, Proc. of DRCN-2000 (Design of Reliable Communication Networks workshop), Munich, Germany, April 2000.
ПЕРЕВОД ТРАНЗИТНОГО ТРАФИКА СЕРВИСНОЙ СЕТИ В ТРАНСПОРТНУЮ СЕТЬ
Сергеева Татьяна, ФГУП ЦНИИС, Москва, Россия, [email protected] Смольская Анастасия, ФГУП ЦНИИС, Москва, Россия, [email protected]
Аннотация
В транспортных сетях, в отличие от сервисных сетей (СС), выбор направления передачи производится не для отдельных сообщений, а для их совокупностей или групп, которые обычно направляются по заранее определенному маршруту. Формирование таких групп, которые могут являться туннелями СС, производится из общего потока пакетов, маршруты которых совпадают полностью или частично. В сетях большой емкости и протяженности, которыми отличаются магистральные сети России, трафик туннелей имеет большие размеры и проходит значительное количество промежуточных узлов сети транзитом, без обработки и изменения состава потоков, входящих в туннель. Поэтому исключение транзитного трафика туннелей из промежуточных маршрутизаторов сервисной сети приведет к значительному снижению загрузки каналов между этими маршрутизаторами и позволит повысить качество обслуживания за счет прозрачной передачи трафика и отсутствии очередей в оптической сети, а также повысить безопасность передачи информации в сети. Последнее особенно важно для данных спецпотребителей, так как пакетная сервисная сеть больше подвержена угрозам несанкционированного доступа, чем синхронная оптическая сеть. Такие возможности появились при использовании в оптических сетях технологии OTH/OTN (Optical Transport Hierarchy/ Optical Transport Network) со стандартом G.709 МСЭ-Т [1]. В статье рассматриваются вопросы оптимизации построения туннелей в сервисной сети с технологией MPLS-TE с последующей передачей транзитного трафика туннелей в оптическую транспортную сеть.
Ключевые слова: сервисная сеть, оптическая транспортная сеть, туннель, DWDM, OTH/OTN, ODU, линейное программирование, многопродуктовый поток.
Литература
1. ITU-T G.709/Y-I33I Recommendation. Interfaces for the optical transport network. 2003.
2. ITU-T G.8080/Y/I304 Recommendation Architecture for the automatically switched optical network. 2012.
3. RFC 3471. Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description, January 2003.
4. Фокин В.Г. Оптические системы передачи и транспортные сети. М.: Экотрендз, 2003.
5. Олифер В., Олифер Н., Компьютерные сети. С.-Петербург: Питер, 2006.
6. Сергеева Т.П., Тетекин Н.Н. Проектирование надежных транспортных сетей SDH. Тез. докл. DRCN-2000, Мюнхен, Германия, апрель 2000.
Информация об авторах:
Сергеева Татьяна, ФГУП ЦНИИС, главный научный сотрудник, к.т.н., Москва, Россия Смольская Анастасия, ФГУП ЦНИИС, аспирант, Москва, Россия
