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Ethernet switch classes. Comparison of network devices. Technical parameters of switches Comparison of switches

performance, are:

frame filtering speed;
speed of personnel advancement;
throughput;
transmission delay frame.

Additionally, there are several switch characteristics that have the greatest impact on these performance specifications. These include:

switching type;
frame buffer(s) size;
performance of the switching matrix;
performance of the processor or processors;
size switching tables.

Filtering speed and frame advancement speed

Frame filtering and forwarding speed are two key performance characteristics of a switch. These characteristics are integral indicators and do not depend on how the switch is technically implemented.

Filtration speed

receiving the frame into your buffer;
discarding a frame if an error is detected in it (the checksum does not match, or the frame is less than 64 bytes or more than 1518 bytes);
frame dropping to eliminate loops in the network;
discarding the frame in accordance with the filters configured on the port;
viewing switching tables to find the destination port based on the MAC address of the frame's receiver and discard the frame if the sending and receiving nodes of the frame are connected to the same port.

The filtering speed of almost all switches is non-blocking - the switch manages to discard frames at the rate at which they arrive.

Forwarding speed determines the rate at which the switch performs the following frame processing steps:

receiving the frame into your buffer;
viewing switching tables for the purpose of finding the destination port based on the MAC address of the frame recipient;
transmission of the frame to the network via the found switching table port of destination.

Both filtering speed and forwarding speed are usually measured in frames per second. If the characteristics of the switch do not specify for which protocol and for what frame size the filtering and forwarding speeds are given, then by default it is assumed that these indicators are given for the Ethernet protocol and frames of the minimum size, that is, frames 64 bytes long (without preamble) with data field of 46 bytes. The use of frames of minimum length as the main indicator of the processing speed of a switch is explained by the fact that such frames always create the most difficult operating mode for the switch compared to frames of other formats with equal throughput of transmitted user data. Therefore, when testing a switch, the minimum frame length mode is used as the most difficult test, which should verify the ability of the switch to operate under the worst combination of traffic parameters.

Switch throughput measured by the amount of user data (in megabits or gigabits per second) transmitted per unit of time through its ports. Since the switch operates at the data link layer, its user data is the data that is transferred to the data field of data link layer protocol frames - Ethernet, Fast Ethernet, etc. The maximum value of the switch throughput is always achieved on frames of maximum length, since when In this case, the share of overhead costs for frame service information is much lower than for frames of minimal length, and the time the switch performs frame processing operations per byte of user information is significantly less. Therefore, a switch can be blocking for frames of a minimum length, but still have very good throughput.

Frame transmission delay (forward delay) is measured as the time elapsed from the moment the first byte of the frame arrives at the input port of the switch until the moment this byte appears at its output port. The delay consists of the time spent buffering the frame bytes, as well as the time spent processing the frame by the switch, namely viewing switching tables, making a forwarding decision and gaining access to the output port environment.

The amount of latency introduced by a switch depends on the switching method it uses. If switching is carried out without buffering, then the delays are usually small and range from 5 to 40 μs, and with full frame buffering - from 50 to 200 μs (for frames of minimum length).

Switch table size

Maximum capacity switching tables defines the limit on the number of MAC addresses that the switch can simultaneously operate. IN switching table For each port, both dynamically learned MAC addresses and static MAC addresses that were created by the network administrator can be stored.

The maximum number of MAC addresses that can be stored in switching table, depends on the application of the switch. D-Link workgroup and small office switches typically support 1K to 8K MAC address tables. Large workgroup switches support a MAC address table with a capacity of 8K to 16K, and network backbone switches typically support 16K to 64K addresses or more.

Insufficient capacity switching tables may cause the switch to slow down and the network to become clogged with excess traffic. If the switch table is completely full and the port encounters a new source MAC address in an incoming frame, the switch will not be able to enter it into the table. In this case, the response frame to this MAC address will be sent through all ports (except for the source port), i.e. will cause an avalanche transmission.

Frame Buffer Capacity

To provide temporary storage of frames in cases where they cannot be immediately transmitted to the output port, switches, depending on the implemented architecture, are equipped with buffers on input and output ports or a common buffer for all ports. The buffer size affects both the frame transmission delay and the packet loss rate. Therefore, the larger the buffer memory, the less likely frame loss is.

Typically, switches designed to operate in critical parts of the network have a buffer memory of several tens or hundreds of kilobytes per port. The buffer common to all ports usually has a capacity of several megabytes.

How to choose a switch given the existing variety? The functionality of modern models is very different. You can purchase either a simple unmanaged switch or a multifunctional managed switch, which is not much different from a full-fledged router. An example of the latter is Mikrotik CRS125-24G-1S-2HND-IN from the new Cloud Router Switch line. Accordingly, the price of such models will be much higher.

Therefore, when choosing a switch, first of all, you need to decide which of the functions and parameters of modern switches you need, and which ones you shouldn’t overpay for. But first, a little theory.

Types of switches

However, if previously managed switches differed from unmanaged switches, including a wider range of functions, now the difference can only be in the possibility or impossibility of remote device management. As for the rest, manufacturers add additional functionality to even the simplest models, often increasing their cost.

Therefore, at the moment, the classification of switches by level is more informative.

Switch levels

In order to choose a switch that best suits our needs, we need to know its level. This setting is determined based on what OSI (data transfer) network model the device uses.

Devices first level, using physical data transmission have almost disappeared from the market. If anyone else remembers hubs, then this is just an example of a physical level when information is transmitted in a continuous stream.
Level 2. Almost all unmanaged switches fall into this category. The so-called channel network model. Devices divide incoming information into separate packets (frames), check them and send them to a specific recipient device. The basis for information distribution in second-level switches is MAC addresses. From these, the switch compiles an addressing table, remembering which port corresponds to which MAC address. They don't understand IP addresses.

Level 3. By choosing such a switch, you get a device that already works with IP addresses. It also supports many other possibilities for working with data: converting logical addresses into physical ones, network protocols IPv4, IPv6, IPX, etc., pptp, pppoe, vpn connections and others. On the third, network level of data transmission, almost all routers and the most “advanced” part of switches work.

Level 4. The OSI network model used here is called transport. Not even all routers are released with support for this model. Traffic distribution occurs at an intelligent level - the device can work with applications and, based on the headers of data packets, direct them to the desired address. In addition, transport layer protocols, for example TCP, guarantee the reliability of packet delivery, maintain a certain sequence of their transmission, and are able to optimize traffic.

Select a switch - read the characteristics

How to choose a switch based on parameters and functions? Let's look at what is meant by some of the commonly used symbols in specifications. Basic parameters include:

Number of ports. Their number varies from 5 to 48. When choosing a switch, it is better to provide a reserve for further network expansion.

Basic data rate. Most often we see the designation 10/100/1000 Mbit/s - the speeds that each port of the device supports. That is, the selected switch can operate at a speed of 10 Mbit/s, 100 Mbit/s or 1000 Mbit/s. There are quite a lot of models that are equipped with both gigabit and 10/100 Mb/s ports. Most modern switches operate according to the IEEE 802.3 Nway standard, automatically detecting port speeds.

Bandwidth and Internal Bandwidth. The first value, also called the switching matrix, is the maximum amount of traffic that can be passed through the switch per unit of time. It is calculated very simply: number of ports x port speed x 2 (duplex). For example, an 8-port gigabit switch has a throughput of 16 Gbps.
Internal throughput is usually indicated by the manufacturer and is only needed for comparison with the previous value. If the declared internal bandwidth is less than the maximum, the device will not cope well with heavy loads, slow down and freeze.

Auto MDI/MDI-X detection. This is auto-detection and support for both standards by which the twisted pair was crimped, without the need for manual control of connections.

Expansion slots. Possibility of connecting additional interfaces, for example, optical.

MAC address table size. To select a switch, it is important to calculate in advance the size of the table you need, preferably taking into account future network expansion. If there are not enough entries in the table, the switch will write new ones over the old ones, and this will slow down data transfer.

Form factor. The switches are available in two types of housing: desktop/wall-mounted and rack-mounted. In the latter case, the standard device size is 19 inches. Special ears for rack mounting can be removable.

We select a switch with the functions we need to work with traffic

Flow control ( Flow Control, IEEE 802.3x protocol). Provides coordination of data sending and receiving between the sending device and the switch under high loads, in order to avoid packet loss. The function is supported by almost every switch.

Jumbo Frame- increased packages. Used for speeds from 1 Gbit/sec and higher, it allows you to speed up data transfer by reducing the number of packets and the time for processing them. The function is found in almost every switch.

Full-duplex and Half-duplex modes. Almost all modern switches support auto-negotiation between half-duplex and full-duplex (transmitting data in one direction only, transferring data in both directions at the same time) to avoid problems in the network.

Traffic prioritization (IEEE 802.1p standard)- the device can identify more important packets (for example, VoIP) and send them first. When choosing a switch for a network where a significant portion of the traffic will be audio or video, you should pay attention to this function

Support VLAN(standard IEEE 802.1q). VLAN is a convenient means for delimiting separate sections: the internal network of an enterprise and the public network for clients, various departments, etc.

To ensure security within the network, control or check the performance of network equipment, mirroring (traffic duplication) can be used. For example, all incoming information is sent to one port for checking or recording by certain software.

Port Forwarding. You may need this function to deploy a server with Internet access, or for online games.

Loop protection - STP and LBD functions. Particularly important when choosing unmanaged switches. It is almost impossible to detect the formed loop in them - a looped section of the network, the cause of many glitches and freezes. LoopBack Detection automatically blocks the port where a loop has occurred. The STP protocol (IEEE 802.1d) and its more advanced descendants - IEEE 802.1w, IEEE 802.1s - act a little differently, optimizing the network for a tree structure. Initially, the structure provides for spare, looped branches. They are disabled by default, and the switch only starts them when there is a loss on some of the main lines.

Link aggregation (IEEE 802.3ad). Increases channel throughput by combining multiple physical ports into one logical one. The maximum throughput according to the standard is 8 Gbit/sec.

Stacking. Each manufacturer has its own stacking design, but in general this feature refers to the virtual combination of multiple switches into one logical unit. The purpose of stacking is to obtain a larger number of ports than is possible with a physical switch.

Switch functions for monitoring and troubleshooting

Many switches detect a faulty cable connection, usually when the device is turned on, as well as the type of fault - broken wire, short circuit, etc. For example, D-Link provides special indicators on the body:

Protection against virus traffic (Safeguard Engine). The technique allows you to increase operating stability and protect the central processor from overloads with “garbage” traffic of virus programs.

Power Features

Energy saving.How to choose a switch that will save you energy? Pay attentione for the presence of energy saving functions. Some manufacturers, such as D-Link, produce switches with power consumption regulation. For example, a smart switch monitors the devices connected to it, and if any of them is not working at the moment, the corresponding port is put into “sleep mode”.

Power over Ethernet (PoE, IEEE 802.af standard). A switch using this technology can power devices connected to it over twisted pair cables.

Built-in lightning protection. A very necessary function, but we must remember that such switches must be grounded, otherwise the protection will not work.

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230106

(specialty code)

COURSE WORK

by discipline

Subject:

SGPEC 230106.11.15.

Student group: TO3A08, Korchagin A. G.

Teacher: Chirochkin E.I.

Date of defense: _______________________ Evaluation__________

Saransk

2011

Ministry of Education and Science of the Russian Federation

FGOU SPO "Saransk State Industrial and Economic College"

230106

(specialty code)

ASSIGNMENT FOR COURSE WORK

by discipline Computer networks and telecommunications

student of group TO3A08, Korchagin A. G.

Subject: Switches: features and specifications

The course work is completed on 28 sheets and includes the following sections:

Introduction

1 Features of a network switch

2 Classification of modern switches

3 Switch characteristics

Conclusion

List of sources used

Date of issue: ________________ Manager department: ______________

Due date: ____________ Teacher: _______________

Introduction………………………………………………………………………………...5

Features of the network switch…………………………………………………………………… 10

Switch and its role in network structuring…………………………………10
Operating principle……………………………………………………………… …..11

Classification of modern switches…………………………………….. 14

According to the method of personnel promotion………………………………………………...14

On the fly……………………………………………………………………………… ....14
With intermediate storage………………………………………………………..14

According to the operating principle algorithm…………………………………………………………….15

Transparent switches…………………………………………………………………… 15

Switches that implement the source routing algorithm……………………………………………………………………….15

Switches implementing the spanning tree algorithm…………16

According to the internal logical architecture………………………………………... 16

Switches with switching matrix……………………………...16
Switches with a common bus……………………………………………..17
Shared memory switches……………………………………18
Combined switches………………………………………….19

By area of application……………………………………………………………..20

Switches with a fixed number of ports…………………………20
Modular switches…………………………………………………………….20
Stacked switches…………………………………………………………………… ….21

Switch technologies……………………………………………… ………..21

Ethernet switches…………………………………………………….. .21
Token Ring Switches…………………………………………………………….22
FDDI switches………………………………………………………...23

Characteristics of switches……………………………………………………………… ………24

Bandwidth……………………………………………………………… ………24
Frame transmission delay…………………………………………………….24
Speed of frames moving through the network…………………………………….25
Filtration rate……………………………………………………………..25

Conclusion……………………………………………………………………………….26

List of sources used………………………………………………………………. ..27

Introduction

When the situation changed in the late 80s - early 90s - the advent of fast protocols, high-performance personal computers, multimedia information, and the division of the network into a large number of segments - classic bridges could no longer cope with the job. Serving frame streams between now multiple ports using a single processing unit required a significant increase in processor speed, and this is a rather expensive solution. The solution that “gave birth” to switches turned out to be more effective (Fig. 1): to service the flow arriving at each port, separate specialized processors were installed in the device for each of the ports, which implemented the bridge algorithm.

Figure 1 Switch

Essentially, a switch is a multiprocessor bridge capable of simultaneously forwarding frames between all pairs of its ports at once. But if, when processor units were added, the computer was not stopped being called a computer, but only the adjective “multiprocessor” was added, then a metamorphosis occurred with multiprocessor bridges - they turned into switches. This was facilitated by the method of communication between the individual processors of the switch - they were connected by a switching matrix, similar to the matrices of multiprocessor computers connecting processors with memory blocks. Gradually, switches replaced classic single-processor bridges from local networks. The main reason for this is the very high performance with which switches transmit frames between network segments. If bridges could even slow down the network when their performance was less than the intensity of the intersegment frame flow, then switches are always released with port processors that can transmit frames at the maximum speed for which the protocol is designed. Adding to this the parallel transfer of frames between ports made the performance of switches several orders of magnitude higher than bridges - switches can transfer up to several million frames per second, while bridges typically processed 3-5 thousand frames per second. give me a sec. This predetermined the fate of bridges and switches. The collective use of a common cable system by many computers leads to a significant decrease in network performance under heavy traffic. The shared environment can no longer cope with the flow of transmitted frames and a queue of computers appears on the network waiting for access. This problem can be solved by logical structuring of the network using a switch (Fig. 2). Logical network structuring refers to the division of a common shared environment into logical segments in order to localize the traffic of each individual network segment. In this case, individual network segments are connected by devices such as switches. A network divided into logical segments has higher performance and reliability. The benefits of splitting the shared environment into logical segments:

Simplicity of the network topology, allowing for easy expansion of the number of nodes;

No frame loss due to overflow of buffers of communication devices, since a new frame is not transmitted to the network until the previous one is received - the medium division system itself regulates the flow of frames and suspends stations that generate frames too often, forcing them to wait for access;

Simplicity of protocols, ensuring low cost of switching equipment.

Figure 2 Logical network structure using a switch

Since the network contains groups of computers that primarily exchange information with each other, dividing the network into logical segments improves network performance - traffic is localized within the groups, and the load on their shared cabling systems is significantly reduced.

Relevance The chosen research topic is determined, firstly, by the rapid entry of local networks into almost all aspects of information activity. And network devices that improve network performance are an integral part of local area networks. The organization of local networks using network equipment has become the norm when designing large networks. This norm has replaced networks built solely on cable segments that computers on the network use to transmit information.

Secondly, over the past few years (since 2006), switches have begun to noticeably push routers out of their firmly established positions. Routers occupied a central place in the building network, and switches were allocated a place at the floor network level. In addition, there were usually few switches - they were installed only in very busy network segments or to connect high-performance servers. Switches began to displace routers from the center of the network to the periphery where they were used to connect the local network to the global one. The central place in the building's network was occupied by a modular corporate switch, which united all the networks of floors and departments on its internal, very productive backbone. Switches have replaced routers because their price/performance ratio turned out to be much lower than that of a router. Naturally, the trend towards increasing the role of switches in local networks is not absolute. And routers still have their applications where their use is more rational than switches. Routers remain indispensable when connecting a local network to a global one.

Goal of the work– reveal the essence of the operating principle of the switch, its features and characteristics, and also consider the scope of its application.

Tasks research work:

Explain the concept of a switch, the essence of the operating principle, the purpose and role of its use in the operation of local networks;

Consider the various classifications and characteristics of this device;

Analyze the relevance and prospects for using switches in organizing local networks.

Object of study The switch is one of the most promising network devices used in organizing local networks.

Subject of research are the features and characteristics of the switches.

Work structure.

The first chapter describes the features of a network switch, its concept, role in network structuring and operating principle.

The second chapter describes the classification of modern switches:

By the method of personnel promotion;

According to the operating principle algorithm;

By internal logical architecture;

By area of application;

Switch technologies.

The third chapter describes the characteristics of switches.

1 Features of a network switch

In this chapter, we will look at the concept of a switch, the purpose of its use and the principle of operation.

Switch and its role in network structuring

A switch or switch is a device designed to connect several nodes of a computer network within one segment. The switch transmits data only directly to the recipient. This improves network performance and security by freeing other network segments from having to (and being able to) process data that was not intended for them. The switch can unite hosts on the same network by their MAC addresses. The switch divides the overall data transmission medium into logical segments. A logical segment is formed by combining several physical segments (cable sections). Each logical segment is connected to a separate switch port (Fig. 3). When a frame arrives on any of the ports, the switch repeats this frame only on the port to which the segment is connected. The switch transmits frames in parallel. Content

Introduction………………………………………………………………………………...5
Features of the network switch……………………………………………………………10
Switch and its role in network structuring…………………………………10
Operating principle…………………………………………………………………………………..11
Classification of modern switches……………………………………..14
According to the method of personnel promotion………………………………………………...14
On the fly………………………………………………………………………………....14
With intermediate storage………………………………………………………..14
According to the operating principle algorithm…………………………………………………………….15
Transparent switches……………………………………………………………15
Switches that implement the source routing algorithm……………………………………………………………………………………….15
Switches implementing the spanning tree algorithm…………16
On internal logical architecture……………………………………...16
Switches with switching matrix……………………………...16
Switches with a common bus……………………………………………..17
Shared memory switches……………………………………18
Combined switches………………………………………….19
By area of application……………………………………………………..20
Switches with a fixed number of ports…………………………20
Modular switches…………………………………………………………….20
Stacked switches…………………………………………………….21
Switch technologies………………………………………………………..21
Ethernet switches……………………………………………………...21
Token Ring Switches…………………………………………………………….22
FDDI switches………………………………………………………...23
Characteristics of switches………………………………………………………24
Bandwidth………………………………………………………24
Frame transmission delay…………………………………………………….24
Speed of frames moving through the network…………………………………….25
Filtration rate……………………………………………………………..25
Conclusion……………………………………………………………………………….26
List of sources used……………………………………………………………...27

The topic of gigabit access is becoming more and more relevant, especially now, when competition is growing, ARPU is falling, and tariffs of even 100 Mbit will not surprise anyone. We have been considering the issue of switching to gigabit access for a long time. I was put off by the price of the equipment and commercial feasibility. But competitors are not asleep, and when even Rostelecom began to provide tariffs of more than 100 Mbit, we realized that we could not wait any longer. In addition, the price for a gigabit port has dropped significantly and installing a FastEthernet switch, which in a couple of years will still have to be replaced with a gigabit one, has simply become unprofitable. That’s why we started choosing a gigabit switch for use at the access level.

We looked at various models of gigabit switches and settled on two that were most suitable in terms of parameters and, at the same time, met our budgetary expectations. These are Dlink DGS-1210-28ME and .

Frame

The SNR's body is made of thick, durable metal, which makes it heavier than its "competitor". The D-link is made of thin steel, which gives it a weight advantage. However, it makes it more susceptible to external influences due to its lower strength.

D-link is more compact: its depth is 14 cm, while that of SNR is 23 cm. The SNR power connector is located on the front, which undoubtedly facilitates installation.

Power supplies

D-link power supply

Power supply SNR

Despite the fact that the power supplies are very similar, we still found differences. The D-link power supply is made economically, perhaps even too economically - there is no varnish coating on the board, and the protection from interference at the input and output is minimal. As a result, according to Dlink, there are concerns that these nuances will affect the sensitivity of the switch to power surges, and operation in variable humidity, and in dusty conditions.

Switch board

Both boards are made carefully, there are no complaints about the installation, however, SNR has a higher quality textolite, and the board is made using lead-free soldering technology. The point, of course, is not that SNR contains less lead (which won’t scare anyone in Russia), but that these switches are produced on a more modern line.

In addition, again, as in the case of power supplies, D-link saved on the varnish coating. SNR has a varnish coating on the board.

Apparently, it is assumed that the operating conditions of D-link access switches should be a priori excellent - clean, dry, cool... well, like everyone else. ;)

Cooling

Both switches have a passive cooling system. D-link has larger radiators, and this is a definite plus. However, SNR has free space between the board and the back wall, which has a positive effect on heat dissipation. An additional nuance is the presence of heat-dissipating plates located under the chip, which transfer heat to the switch body.

We conducted a small test - we measured the temperature of the heatsink on the chip under normal conditions:

The switch is placed on a table at room temperature 22C,
2 SFP modules installed,
We wait 8-10 minutes.

The test results were surprising - D-link heated up to 72C, while SNR - only up to 63C. It’s better not to think about what will happen to D-link in a tightly packed box in the summer heat.

Temperature on D-link 72 degrees

At SNR 61 C, flight is normal

Lightning protection

The switches are equipped with various lightning protection systems. D-link uses gas dischargers. SNR has varistors. Each of them has its pros and cons. However, the response time of varistors is better, and this provides better protection for the switch itself and the subscriber devices connected to it.

Summary

D-link leaves a feeling of savings on all components - on the power supply, board, case. Therefore, in this case it seems like a more preferable product for us.

Frame filtering and forwarding speeds are two key performance characteristics of a switch. These characteristics are integral; they do not depend on how the switch is technically implemented.

The filtering rate is the speed at which the switch performs the following frame processing steps:

1. Receive the frame into your buffer.

3. Frame destruction, since its destination port and source port belong to a single-logical segment.

The filtering speed of almost all switches is not a blocking factor - the switch manages to discard frames at the rate at which they arrive.

The forwarding rate is the speed at which the switch performs the next stages of frame processing.

1. Receive the frame into your buffer.

2. Look through the address table to find the port for the frame's destination address.

3. Transmitting the frame to the network through the destination port found in the address table.

Frame transmission latency is measured as the time elapsed from the moment the first byte of the frame arrives at the input port of the switch until the moment this byte appears at its output port. Latency is the sum of the time spent buffering the bytes of the frame and the time spent processing the frame by the switch - looking through the address table, making filtering or forwarding decisions, gaining access to the egress port environment. The amount of delay introduced by the switch depends on its operating mode. If switching is carried out “on the fly”, then the delays are usually small and range from 5 to 40 μs, and with full frame buffering - from 50 to 200 μs for frames of minimum length when transmitting at a speed of 10 Mbit/s. Switches that support faster versions of Ethernet introduce less latency in the frame forwarding process.

The performance of a switch is determined by the amount of user data transferred per unit of time through its ports, and is measured in megabits per second (Mbps). Since the switch operates at the data link layer, its user data is the data that is carried in the data field of Ethernet frames.

The maximum value of switch performance is always achieved on frames of maximum length, since in this case the share of overhead costs for frame overhead is minimal. A switch is a multiport device, so it is customary to characterize it as having maximum overall performance while simultaneously transmitting traffic across all of its ports.

To perform the operations of each port, switches most often use a dedicated processing unit with its own memory to store its own copy of the address table. Each port stores only those sets of addresses with which it has recently worked, so the copies of the address table of different processor modules, as a rule, do not match.

The maximum number of MAC addresses that the port processor can remember depends on the application of the switch. Workgroup switches typically support only a few addresses per port because they are designed to form microsegments. Department switches must support several hundred addresses, and network backbone switches must support up to several thousand (usually 4000-8000 addresses).

Insufficient address table capacity can cause the switch to slow down and the network to become clogged with excess traffic. If the port processor's address table is completely full and it encounters a new source address in an incoming frame, the processor must remove any old address from the table and place a new one in its place. This operation itself takes up some of the processor's time, but the main performance loss is observed when a frame arrives with a destination address that had to be removed from the address table. Since the frame's destination address is unknown, the switch must forward the frame to all other ports. Some switch manufacturers solve this problem by changing the algorithm for handling frames with an unknown destination address. One of the switch ports is configured as a trunk port, to which all frames with an unknown address are sent by default. A frame is transmitted to a trunk port on the assumption that this port is connected to a higher-level switch (in a hierarchical connection of switches in a large network), which has sufficient address table capacity and “knows” where any frame can be sent.