Types of routes are the main indicators of routing. Routing. general concepts. Depending on the destination, departure routes are:

Or gateway, is a network node with several IP interfaces (containing its own MAC address and IP address) connected to different IP networks, which, based on solving the routing problem, redirects datagrams from one network to another for delivery from the sender to the recipient.

They are either specialized computers or computers with several IP interfaces, the operation of which is controlled by special software.

Routing in IP networks

Routing is used to receive a packet from one device and forward it across a network to another device via other networks. If there are no routers on the network, then routing is not supported. Routers route (forward) traffic to all networks that make up the internetwork.

To route a packet, the router must have the following information:

Destination address
A nearby router from which it can learn about remote networks
Available paths to all remote networks
The best path to each remote network
Methods for maintaining and checking routing information

The router learns about remote networks from neighboring routers or from the network administrator. The router then builds a routing table that describes how to find remote networks.

If the network is connected directly to the router, it already knows how to route the packet to that network. If the network is not directly connected, the router must learn (learn) access paths to the remote network using static routing (the administrator manually enters the location of all networks into the routing table) or using dynamic routing.

Dynamic routing is a routing protocol process that determines how a device communicates with neighboring routers. The router will update information about each network it learns. If a change occurs in the network, the dynamic routing protocol automatically informs all routers of the change. If static routing is used, the system administrator will have to update the routing tables on all devices.

IP routing is a simple process that is the same on networks of any size. For example, the figure shows the process of step-by-step interaction between host A and host B on another network. In the example, the user of host A requests the IP address of host B via ping. Further operations are not so simple, so let’s look at them in more detail:

At the command line, the user enters ping 172.16.20.2. On host A, a packet is generated using network layer protocols and ICMP.

IP calls ARP to find out the destination network for the packet by looking at the IP address and subnet mask of host A. This is a request to the remote host, i.e. the packet is not destined for a host on the local network, so the packet must be forwarded to the router to be forwarded to the desired remote network.
In order for host A to send a packet to the router, the host must know the hardware address of the router interface connected to the local network. The network layer passes the packet and hardware destination address to the data link layer to be divided into frames and forwarded to the local host. To obtain a hardware address, the host looks up the location of the destination in its own memory, called the ARP cache.
If the IP address has not yet been reached and is not present in the ARP cache, the host sends an ARP broadcast to look up the hardware address at IP address 172.16.10.1. This is why the first Ping request will usually time out, but the other four requests will succeed. Once an address is cached, there is usually no timeout.
The router responds and reports the hardware address of the Ethernet interface connected to the local network. Now the host has all the information to forward the packet to the router over the local network. The network layer passes the packet down to generate an ICMP echo request (Ping) at the data link layer, appending the packet with the hardware address to which the host should send the packet. The packet has source and destination IP addresses along with an indication of the packet type (ICMP) in the network layer protocol field.
The data link layer forms a frame that encapsulates the packet along with the control information necessary for forwarding over the local network. This information includes the source and destination hardware addresses, as well as the value in the type field set by the network layer protocol (this will be the type field since IP uses Ethernet_II frames by default). Figure 3 shows a frame generated at the link layer and forwarded over the local media. Figure 3 shows all the information necessary to communicate with the router: source and destination hardware addresses, source and destination IP addresses, data, and the frame CRC checksum located in the FCS (Frame Check Sequence) field.
The link layer of host A forwards the frame to the physical layer. There, zeros and ones are encoded into a digital signal and then transmitted over a local physical network.

The signal reaches the router's Ethernet 0 interface, which is synchronized to the digital signal preamble to retrieve the frame. After constructing the frame, the router interface checks the CRC, and at the end of receiving the frame, compares the received value with the contents of the FCS field. In addition, it checks the transfer process for media fragmentation and conflicts.
The destination hardware address is checked. Since it matches the router's address, the frame type field is analyzed to determine what to do next with this data packet. The type field specifies the IP protocol, so the router passes the packet to the IP protocol process running on the router. The frame is deleted. The original packet (generated by host A) is placed in the router's buffer.
The IP protocol looks at the destination IP address in the packet to determine whether the packet is destined for the router itself. Since the destination IP address is 172.16.20.2, the router determines from its routing table that network 172.16.20.0 is directly connected to Ethernet interface 1.
The router forwards the packet from the buffer to Ethernet interface 1. The router needs to frame it to forward the packet to the destination host. The router first checks its ARP cache to determine whether the hardware address has already been resolved during previous interactions with the given network. If the address is not in the ARP cache, the router sends an ARP broadcast request to Ethernet interface 1 to look up the hardware address for IP address 172.16.20.2.
Host B responds with the hardware address of its network adapter to the ARP request. The router's Ethernet 1 interface now has everything it needs to forward the packet to its final destination. The figure shows a frame generated by the router and transmitted over the local physical network.

The frame generated by the router's Ethernet 1 interface has a source hardware address from Ethernet interface 1 and a destination hardware address for the host B network adapter. It is important to note that, despite changes in the source and destination hardware addresses, on each router interface that sent the packet, the IP addresses source and destination never change. The package is not modified in any way, but the frames are changed.

Host B receives the frame and checks the CRC. If the check is successful, the frame is discarded and the packet is transferred to the IP protocol. It analyzes the destination IP address. Since the destination IP address is the same as the address set in Host B, the IP protocol examines the protocol field to determine the destination of the packet.
Our packet contains an ICMP echo request, so Host B generates a new ICMP echo reply with a source IP address equal to Host B and a destination IP address equal to Host A. The process starts again, but in the opposite direction. However, the hardware addresses of all devices along the packet's path are already known, so all devices will be able to obtain the hardware addresses of the interfaces from their own ARP caches.

In large networks, the process is similar, but the packet will have to travel more hops on the way to the destination host.

Routing tables

In the TCP/IP stack, routers and end nodes make decisions about who to pass a packet to in order to successfully deliver it to the destination node, based on so-called routing tables.

The table is a typical example of a route table using network IP addresses for the network shown in the figure.

Routing table for Router 2

The table shows a multi-route routing table, since it contains two routes to network 116.0.0.0. In the case of constructing a single-route routing table, it is necessary to specify only one path to network 116.0.0.0 based on the lowest metric value.

As you can easily see, several routes with different parameters are defined in the table. You need to read each such entry in the routing table as follows:

To deliver a packet to the network with an address from the Network Address field and a mask from the Network Mask field, you need to send a packet from the interface with the IP address from the Interface field to the IP address from the Gateway Address field, and the “cost” of such delivery will be equal to the number from the field Metrics.

In this table, the "Destination Network Address" column indicates the addresses of all networks to which this router can transmit packets. The TCP/IP stack adopts the so-called one-hop approach to optimizing the packet forwarding route (next-hop routing) - each router and end node takes part in choosing only one packet transmission step. Therefore, each line of the routing table does not indicate the entire route as a sequence of IP addresses of the routers through which the packet must pass, but only one IP address - the address of the next router to which the packet must be transmitted. Along with the packet, the responsibility for choosing the next routing hop is transferred to the next router. The one-hop approach to routing means a distributed solution to the route selection problem. This removes the restriction on the maximum number of transit routers along the packet's path.

To send a packet to the next router, knowledge of its local address is required, but in the TCP/IP stack, it is customary to use only IP addresses in routing tables to preserve their universal format, independent of the type of networks on the Internet. To find a local address from a known IP address, you must use the ARP protocol.

One-hop routing has another advantage - it allows you to reduce the size of routing tables in end nodes and routers by using the so-called default route (0.0.0.0), which usually occupies the last line in the routing table, as the destination network number. If there is such an entry in the routing table, then all packets with network numbers that are not in the routing table are sent to the router specified in the default line. Therefore, routers often store limited information about Internet networks in their tables, forwarding packets for other networks to the default port and router. The default router is assumed to forward the packet to the backbone, and routers connected to the backbone have full knowledge of the Internet's composition.

In addition to the default route, there may be two types of special entries in the routing table - an entry about a host-specific route and an entry about the addresses of networks directly connected to the router ports.

A host-specific route contains a full IP address instead of a network number, that is, an address that has non-zero information not only in the network number field, but also in the host number field. It is assumed that for such an end node the route should be chosen differently from all other nodes in the network to which it belongs. In the case when the table contains different records about the forwarding of packets for the entire network N and its individual node having the address N,D, when a packet addressed to node N,D arrives, the router will give preference to the record for N,D.

Entries in the routing table related to networks directly connected to the router contain zeros (“connected”) in the “Metrics” field.

Routing Algorithms

Basic requirements for routing algorithms:

accuracy;
simplicity;
reliability;
stability;
justice;
optimality.

There are various algorithms for constructing tables for one-hop routing. They can be divided into three classes:

simple routing algorithms;
fixed routing algorithms;
adaptive routing algorithms.

Regardless of the algorithm used to build the routing table, the result of their work has a single format. Due to this, in the same network, different nodes can build routing tables according to their own algorithms, and then exchange missing data with each other, since the formats of these tables are fixed. Therefore, a router using an adaptive routing algorithm can provide an end node using a fixed routing algorithm with path information to a network that the end node knows nothing about.

Easy routing

This is a routing method that does not change when the topology and state of the data transmission network (DTN) changes.

Simple routing is provided by various algorithms, typical of which are the following:

Random routing is the transmission of a message from a node in any randomly selected direction, with the exception of the directions in which the message was received by the node.
Flooding routing is the transmission of a message from a node in all directions except the direction in which the message arrived at the node. This routing guarantees short packet delivery time, at the expense of throughput degradation.
Routing based on previous experience - each packet has a counter for the number of nodes passed, in each communication node the counter is analyzed and the route that corresponds to the minimum value of the counter is remembered. This algorithm allows you to adapt to changes in network topology, but the adaptation process is slow and ineffective.

In general, simple routing does not provide directional packet transmission and has low efficiency. Its main advantage is to ensure stable operation of the network in the event of failure of various parts of the network.

Fixed Routing

This algorithm is used in networks with a simple connection topology and is based on the manual compilation of a routing table by the network administrator. The algorithm often works effectively also for the backbones of large networks, since the backbone itself can have a simple structure with obvious best paths for packets to follow to the subnets attached to the backbone; the following algorithms are distinguished:

Single-path fixed routing is when a single path is established between two subscribers. A network with such routing is unstable to failures and overloads.
Multi-path fixed routing - several possible paths can be established and a path selection rule is introduced. The efficiency of such routing decreases as the load increases. If any communication line fails, it is necessary to change the routing table; for this purpose, several tables are stored in each communication node.

Adaptive Routing

This is the main type of routing algorithms used by routers in modern networks with complex topologies. Adaptive routing is based on the fact that routers periodically exchange special topological information about the networks available on the Internet, as well as about the connections between routers. Usually, not only the topology of links is taken into account, but also their capacity and state.

Adaptive protocols allow all routers to collect information about the topology of connections in the network, quickly processing all changes in the connection configuration. These protocols have a distributed nature, which is expressed in the fact that there are no dedicated routers in the network that would collect and summarize topological information: this work is distributed among all routers, the following algorithms are distinguished:

Local adaptive routing - each node contains information about the link state, queue length and routing table.
Global adaptive routing is based on the use of information received from neighboring nodes. To do this, each node contains a routing table, which indicates the transit time of messages. Based on information received from neighboring nodes, the table value is recalculated taking into account the queue length in the node itself.
Centralized adaptive routing - there is some central node that collects information about the state of the network. This center generates control packets containing routing tables and sends them to communication nodes.
Hybrid adaptive routing is based on the use of a table periodically sent by the center and on analyzing the queue length from the node itself.

Algorithm indicators (metrics)

Routing tables contain information that switching programs use to select the best route. What characterizes the construction of routing tables? What is the nature of the information they contain? This section on algorithm metrics attempts to answer the question of how an algorithm determines whether one route is preferable to another.

Routing algorithms use many different metrics. Complex routing algorithms can rely on multiple metrics when selecting a route, combining them in such a way that the result is one hybrid metric. The following are the metrics used in routing algorithms:

Route length.
Reliability.
Delay.
Bandwidth.

Route length.

Route length is the most common routing metric. Some routing protocols allow network administrators to assign arbitrary prices to each network link. In this case, the path length is the sum of the costs associated with each channel that was traversed. Other routing protocols define a "hop count," a metric that describes the number of trips a packet must make on its way from its source to its destination through network aggregation elements (such as routers).

Reliability.

Reliability, in the context of routing algorithms, refers to the reliability of each link in the network (usually described in terms of bit-to-error ratio). Some network links may fail more often than others. Failures of some network links can be resolved more easily or quickly than failures of other links. When assigning reliability ratings, any reliability factors can be taken into account. Reliability ratings are typically assigned to network channels by administrators. As a rule, these are arbitrary digital values.

Delay.

Routing latency typically refers to the length of time it takes for a packet to travel from its source to its destination across an internetwork. Latency depends on many factors, including the bandwidth of the intermediate links in the network, the queues at the port of each router along the packet's path, network congestion on all intermediate links in the network, and the physical distance over which the packet must travel. Because there is a conglomeration of several important variables, latency is the most common and useful metric.

Bandwidth.

Bandwidth refers to the available traffic capacity of any link. All other things being equal, a 10 Mbps Ethernet channel is preferable to any leased line with a 64 KB/s bandwidth. Although bandwidth is an estimate of the maximum achievable capacity of a link, routes passing through higher-bandwidth links are not necessarily better than routes passing through slower links.

Types of routing. Protocol groups.

Implemented at the network level of the network. The routing protocol is responsible for it. When choosing a routing strategy, different goals can be set, for example:

Minimizing package delivery time;

Minimizing the cost of package delivery;

Ensuring maximum network throughput, etc.

The routing problem is solved router, which is defined as a network layer device that uses one or more metrics to determine the optimal path for network traffic based on network layer information.

Under metric some quantitative characteristics of the path are understood, for example, length, travel time, throughput, etc. Routing algorithms can be:

Static or dynamic;

Single-route or multi-route;

Single-level or hierarchical;

Intra-domain or inter-domain;

Unicast or group.

Static(non-adaptive) algorithms involve preliminary selection of routes and manual entry of them into the routing table. Thus, there should already be pre-recorded information about which port to send the packet with the corresponding address to. Examples: DEC LAT protocol, NetBIOS protocol.

In dynamic protocols, the routing table is updated automatically when the network topology or schedule changes.

Single-route protocols offer only one route for transmitting a packet (which is not always optimal).

Multi-route algorithms offer several routes. This allows information to be transmitted to the recipient via several routes simultaneously.

Networks may have single-level or hierarchical architecture. Accordingly, routing protocols are distinguished. In hierarchical networks, upper-level routers form a special layer of the backbone network.

Some routing algorithms operate only within their domains, i.e. used intradomain routing Other algorithms can work with adjacent domains - this is defined as cross-domain routing

Unicast protocols are designed to transmit information (via one or more routes) to only one recipient. Multicast – capable of transmitting data to many subscribers at once.

There are three main groups of routing protocols depending on the type of algorithm used to determine the optimal route:

Distance vector protocols;

Channel state protocols;

Routing Policy Protocols.

Protocols distance vector- the simplest and most common. These are, for example, RIP, RTMP, IGRP.

Such protocols transmit (send out) data from their routing table (addresses and metrics) to neighbors at a certain frequency. Neighbors, having received this data, make the necessary changes to their tables. Disadvantage: These protocols only work well on small networks. As the size increases, service traffic on the network increases and the delay in updating routing tables increases.

Protocols channel status were first proposed in 1970 by Edsger Dijkstra. Here, instead of broadcasting the contents of routing tables, each router broadcasts a list of routers with which it has a direct connection and a list of local networks directly connected to it. Such distribution can be carried out either when the state of the channels changes, or periodically. Examples of protocols: OSPF, IS-IS, Novell NLSP.

Protocols politicians(rules) routing most often used on the Internet. They rely on distance vector algorithms. Routing information is obtained from neighboring operators based on specific criteria. Based on this exchange, a list of allowed routes is developed. Examples: BGP and EGP protocols.

Routers. Autonomous systems.

Router is a fairly complex device that is defined as a network layer device that uses one or more metrics to determine the optimal path for network traffic based on network layer information.

When creating them, 3 main architectures are used.

1)Single-processor. Here the processor is assigned the entire range of tasks, including: filtering and transmitting packets; modification of packet headers; updating routing tables; allocation of service packages; formation of control packages; working with the SNMP network management protocol, etc.

However, even powerful RISC processors cannot handle heavy workload processing.

2)Extended single-processor. IN The functional diagram of the router allocates modules responsible for performing a number of tasks (for example, working with service packages). Each such functional module is equipped with its own processor (peripheral).

3)Symmetric multiprocessor architecture. Here the load is evenly distributed across all processor modules. Each of the modules performs all routing tasks and has its own copy of the routing table. This is the most advanced architecture for routers.

IP routers

IP (Internet Protocol) is currently the most common (on the Internet). The protocol operates at the network layer and it is at this layer that routing decisions are made.

There are 2 approaches to choosing a route:

One-step approach;

Source routing.

At one-hop routing Each router takes part in selecting only one datagram transmission step. Therefore, the routing table line does not indicate the entire route (to the recipient), but only one IP address of the next router. For those addresses that are not in the table, the default router address is used.

Algorithms for constructing tables for one-hop routing can be as follows:

Fixed routing (the table is compiled “manually” by the administrator);

Random routing (the packet is transmitted in any random direction except the original one);

Flood routing (the datagram is transmitted in all directions except the original one);

Adaptive routing (the routing table is periodically adjusted based on network topology information from other routers).

Adaptive routing protocols are most widespread in IP networks. These protocols are: RIP, OSPF, IS-IS, EGP, BGP, etc. At source routing The route selection is made by the end node or the first router along the datagram path. This method has not found widespread use in IP networks, but is widely used in ATM networks (for example, the PNNI protocol).

Autonomous systems

Due to the growth of the Internet, the performance of routers has decreased significantly. The volume of traffic to support routing has increased incredibly and the routing tables have grown in size. In this regard, the Internet was divided into a number of Autonomous Systems (AC) (Autonomous System) (Fig. 7.1.). Each such system is a group of networks and routers managed by an authorized person. This allows the router within each AS to use different routing protocols. Here, dynamic routing protocols are used, defined as a class of IGP protocols (IGP - Interior Gateway Protocol - internal gateway protocol). This class includes the protocols RIP, IS-IS, etc.

For interaction between routers belonging to different ASs, an additional protocol called EGP (external gateway protocol) is used.

RIP protocol

The RIP protocol belongs to the IGP class. The protocol appeared in 1982 as part of the TCP/IP protocol stack. Became the standard routing protocol within an autonomous system. Limitation - the protocol does not support long paths containing more than 15 transitions.

The metric used is the number of hops (that is, the number of routers that a datagram must pass through before reaching the recipient). The path with the fewest hops is always chosen.

Periodically, each router sends route update messages to its neighbors. Such a message contains its entire routing table. This table is first filled with the addresses of those networks to which the router has direct access (see Fig. 7.2.).

Before transmitting information to a neighboring router, the table is adjusted - the number of transitions to the recipient increases by one. Upon receiving such a service message from a neighboring router, the router updates its routing table in accordance with the following rules:

a) If the new number of hops is less than the old one (for a specific network address), this entry is entered into the routing table.

b) If the entry came from the router that was the source of the already stored entry, then the new hop count value is entered even if it is greater than the old one.

By default, the interval between sending messages is 30 seconds. If a neighboring router is silent for a long time (more than 180 s), entries related to it are deleted from the routing table (assuming a failure of the line or the router itself).

OSPF protocol

The OSPF (Open Shortest Path First) protocol was adopted in 1991. It is intended for use in large distributed networks. Based on the channel state algorithm. The essence of this1 algorithm is that it must calculate the shortest path. By “shortest” we do not mean the physical length, but the time of information transfer. The router sends queries to its neighbors located in the same routing line to determine the state of the links to and from them. The state of the channel is characterized by several parameters called “metrics”. It could be:

Channel capacity;

Information delay when passing through this channel, etc. Having summarized the information received, the router communicates it to all neighbors. after that, it constructs a directed graph of the routing domain topology. Each edge of the graph is assigned an evaluation parameter (metric) (Fig. 7.3.).

Then Dijkstra's algorithm is used, which traverses two given nodes with a set of edges with the lowest total cost, i.e. the optimal route is selected. In accordance with this, a routing table is built.

The OSPF protocol belongs to the class of IP protocols and replaces the RIP protocol in large and complex networks. Information about channel status is sent every 30 minutes. Based on these messages, a link state database (Link-State 1 Datadase) is created on each router. This base is the same on all routers in the domain.

Based on this database, the router generates a network topology map and a tree of shortest paths to all possible recipients (see figure). Then a routing table is formed (Table 7.1.). For networks directly connected to the router, the metric is set to zero.

When the state of at least one connected channel changes, the router sends messages to its neighbors. The channel database is adjusted, the shortest paths are calculated, and the routing table is regenerated.

In large networks (with hundreds of routers), the protocol generates a lot of routing information, and the link state database can reach several MB.

Routing shipments from loading points is a highly efficient way to organize freight transportation.

Below the origin route means a train composition of a specified weight or length, formed by the shipper on the railway access track of the organization or under an agreement with the railway at the railway station with the mandatory exemption of at least one technical station from processing such a train, provided for by the current plan for the formation of freight trains.

Departure routes pass through one or more sorting stations without processing, therefore, the delivery of cargo is accelerated, the work on reforming trains is reduced, the cost of transportation is reduced, the turnover of wagons is accelerated, the need for wagons is reduced, the safety of transported goods is better ensured, and the competitiveness of manufacturers of goods and railway transport increases.

Stepped routes are formed from wagons loaded by different shippers on the tracks of one or several stations of a section or junction. The rules for the transportation of goods along consignor routes by rail provide that in order to speed up the delivery of goods, reduce transport and operating costs, the transportation of goods can be carried out by consignor routes and be provided for in contracts for the organization of cargo transportation by rail. Sender routing is the basis for creating a network of logistics centers for Russian railways in the future.

The procedure for transporting goods along dispatch routes is established by the Rules for transporting goods along dispatch routes by rail.

Depending on the destination, departure routes are:

direct - when transporting to one destination (transshipment) station to one or more consignees (freight cars addressed to each consignee must be part of a separate group);
to spraying - when transporting by appointment to disbandment stations according to the plan for the formation of freight trains, or by appointment to points (stations) of route spraying announced by JSC Russian Railways, where wagons are addressed (indicating destination stations and consignee) at unloading stations to specific consignees, or by appointment to entry and distribution stations receiving fuel cargo, with further targeting of wagons to the unloading station.

The shipper agrees with the consignee on the possibility of accepting routes of a specified weight or length for unloading. If there is a change in the mass of the train (breaking point) in the direction of the station routes in the direction of reduction, the departure of the routes is organized from the core and the trailer part, which follows as part of the route to the turning point of the mass.

The core is the main part of the sending route of the established mass, which follows without reorganization to the destination railway station in the event of a change in the mass of the train along the route.

According to the conditions of circulation, sending routes are distinguished:

circular trains with a constant train, which after unloading in the same train return to the same station or department for re-loading;
circular trains with a variable composition, which, after unloading, return to the same station or department, while the number, type of cars and their purpose are maintained, but if necessary, some cars can be replaced by other similar cars.

The organization of circular routes significantly reduces the cost of preparing cars for loading, while reducing downtime of cars at loading points, since cars require minimal preparation for loading.

Routing is the subject of a contract for the organization of cargo transportation by rail, therefore only the parties to the contract have the right to determine its content. It may provide for dispatch routes formed on a railway access track or at a railway station, groups of cars for organizing stepped station or section routes, etc. The originating route means a train composition of a specified weight or length, formed by the shipper on the railway access track of the organization or under an agreement with the railway at the railway station with the mandatory exemption of at least one technical station from processing such a train, provided for by the current plan for the formation of freight trains. Departure routes pass through one or more sorting stations without processing, therefore, the delivery of cargo is accelerated, the work on reforming trains is reduced, the cost of transportation is reduced, the turnover of wagons is accelerated, the need for wagons is reduced, the safety of transported goods is better ensured, and the competitiveness of manufacturers of goods and railway transport increases. Stepped routes are formed from wagons loaded by different shippers on the tracks of one or several stations of a section or junction. The rules for the transportation of goods along consignor routes by rail provide that in order to speed up the delivery of goods, reduce transport and operating costs, the transportation of goods can be carried out by consignor routes and be provided for in contracts for the organization of cargo transportation by rail. Sender routing is the basis for creating a network of logistics centers for Russian railways in the future.

Types of routing from loading points

Routing shipments from loading points is a highly efficient way to organize freight transportation. The procedure for transporting goods on shipping routes is established by the Rules for the transportation of goods on dispatch routes by rail. Depending on the destination, departure routes are:: – straight- when transporting to one destination (transshipment) station to one or more consignees (freight cars addressed to each consignee must be in a separate group); – into spray- when transporting by appointment to disbanding stations according to the plan for the formation of freight trains, or by appointment to route distribution points (stations) announced by the Ministry of Railways of Russia, where wagons are addressed (indicating destination stations and consignee) at unloading stations to specific consignees, or by appointment to entry and distribution stations receiving fuel cargo, with further redirection of wagons to unloading stations. The shipper agrees with the consignee on the possibility of accepting routes of a specified weight or length for unloading. If there is a change in the mass of the train (breaking point) in the direction of the station routes in the direction of decrease, the departure of the routes is organized from the core and the trailer part, which follows as part of the route to the turning point of the mass. Core- this is the main part of the sending route of the established mass, which follows without reorganization to the destination railway station in the event of a change in the mass of the train along the route. According to the conditions of circulation, sending routes are distinguished: – ring with constant composition which, after unloading, return in the same composition to the same station or department for re-loading; – ring with variable composition which, after unloading, return to the same station or department, while the number, type of cars and their purpose are retained, but if necessary, some cars can be replaced by other similar cars.

Organization of circular routes significantly reduces the cost of preparing cars for loading, while reducing downtime of cars at loading points, since cars require minimal preparation for loading.

Planning routing of cargo transportation

Transportation routing, a system for organizing the dispatch of goods by routes (as a whole train) from one or more railway stations with destinations at unloading points located in the same area. It is carried out according to routing plans drawn up by the railways. Routes are divided into: departure organized from wagons loaded by one sender at one station (pier or port); stepped- from wagons loaded by different consignors at one or more stations of one or two sections; formed at specialized route bases, which are created at the exits of mass loading areas . Based on travel distance, departure and step routes are divided into: local(intraroad) - when traveling within the same railway, and network- when traveling within two or more railways. Routes provided with a permanently assigned train of cars for circulation between specific points of departure and destination, are called ring. When planning and routing freight flows, it is important to consider the performance of vehicles depending on the transportation line. In other words, the allocated vehicles must ensure cargo flows along the developed travel routes. In transport logistics, models of problems of this type are formed depending on the degree of detail in taking into account the requirements for the functioning of various modes of transport.

38. Key indicators of the implementation of the transportation routing plan

To analyze and evaluate the implementation of transportation routing tasks, the following main indicators have been established: 1) the number of wagons sent during the reporting period on routes in general and by type of cargo on average per day; 2) routing level (routing percentage) by type of cargo - determined by the ratio of the number of wagons loaded and sent on routes U Mrsh, to the total number of loaded wagons U total, in percentage: 3) the average travel distance of all routes and wagons in their trains and by type of cargo: , where is the sum of route kilometers; - total number of routes; 4) distribution of cars sent on routes by distance zones and their percentage in the total number of loaded cars (range zones: up to 400 km, from 401 to 1000 km, from 1001 to 1500 km and over 1500 km); 5) the number of wagons sent on direct routes in general and by type of cargo and their percentage in the total number of loaded wagons; 6) average composition of routes (in cars) - determined by dividing the number of routed cars by the number of routes sent; 7) fulfillment of a task for the transportation of goods by routes - the ratio of the number of cars sent on routes and provided for by the task (in percentage).

Magnitude (and in calculations the following can be accepted:

■ for automated and mechanized hump sorting
stations 1.5-2.2 hours;

■ for non-mechanized stations 2.1-2.8 hours; „|____________ ;:_,___ , t ________ „„..

■ for humpless stations 4.0-5.0 hours.

In addition, when passing jets without processing, it must be taken into account that recycling carriages at stations and pass them without processing The costs are far from the same. Recycling requires sorting tracks, humps, hoods, locomotives, and a large staff of station workers.

Therefore, in order to take into account the economic costs of the options, the concept of equivalent recycling of wagons was introduced. Savings from railcar recycling are expressed by the equivalent h in= 1.5-2.5, savings in locomotive hours and crew hours are expressed by h = 0.4-1.5.

Thus, the final formula for calculating the reduced car-hour savings per car is:

All calculations by definition T are conducted at the Ministry of Railways of Russia using electronic computer technology.

3.2. Organization of car flows from loading points

Types of routes, basic routing indicators

On railway networks are allocated several hundred main, decisive stations, at which 70 % loading, and about the same number of stations - 70 % unloading. At loading stations, powerful cargo flows are formed, which are included in the top ten most important cargoes: oil, forestry, coal, ore, construction, chemical and mineral fertilizers, grain, etc. The most effective way to organize car flows is transportation routing. It allows you to speed up the delivery of goods, reduce the need for a working fleet of cars, free passing stations from expensive work on processing cars, and therefore reduce operating costs in the transportation process.

The routes are distinguished:

According to the terms of the organization from the loading points;
■ for its intended purpose;

According to the terms of the application.

According to the conditions of the organization, the following routes are distinguished from the loading points:

Routes are distinguished by destination:

According to the terms of application, the routes are:

A high percentage of coverage by sender routing has such cargo as ore (more than 90%), coal and oil (about 70%), chemical and mineral fertilizers (more than 50%). Grain cargo is poorly routed (about 3 %).

If we analyze the range, more than 57% of routes travel short distances (up to 400 km). And routes traveling over distances of more than 1,500 km make up only 10%. The indicated percentages cannot fully characterize the level of routing on the network, because one third of the routes go only to route bases, i.e. into spraying, which is less efficient compared to pure sender routing to the unloading station.

The quality of routing organization is assessed by the following indicator:

as routing level ^, where () m is the mass of goods sent on routes; 0, - total weight of shipped goods.

But it is much more expedient to take the ratio ^-p as the main indicator of the routing level, where 1 M is the average route distance

volume of cargo on shipping routes, km; I is the average distance of cargo, km.