Optimal mtu size. MTU: value in the Rostelecom network
Having purchased new router, having connected it and configured the connection with the provider, in most cases the user discovers unpleasant feature. Any home or office router slows down the speed, in the worst case reducing it several times. For different models devices is typical different speed routing IP packets. In addition, there are two more parameters that have a finite value - maximum throughput, And greatest number supported connections. The values of all these parameters vary depending on the hardware used, and we will look at how to speed up the operation of the router using software methods.
Average IP packet transmission speed
To make a network harvester work faster, you can overclock its processor, increase the amount of built-in memory, and so on. Most users do not have access to such techniques. Using software methods, considered by us, you can achieve the following results:
- Reduce website opening time (use public DNS)
- Get acceptable torrent speeds
- Increase the speed of data transmission and reception via a Static IP or DHCP Client connection.
Let us immediately explain what we are going to do. Instead of DNS servers issued by the provider, it is recommended to set addresses public DNS. You can increase the communication speed by choosing the right MTU parameter, but a torrent client, if you have a router, needs to limit the number of connections.
The simplest thing is fixed DNS
When setting up a DHCP Client connection (aka Dynamic IP or IPoE), usually the “DNS” parameter is left at “auto”. The provider automatically issues DNS server addresses each time you connect, which ensures that the values of these addresses are correct. But you can set DNS servers explicitly, moreover, on this moment It is recommended to use public services with publicly known addresses. By logging into the router’s web interface, open the connection settings tab with the provider:
Connection settings tab
You will see at least two fields that are for setting DNS addresses. In some firmware, these same fields are contained on a separate tab:
Entering DNS addresses manually
Set the required values, save the settings.
The question remains what these values should be equal to in reality. Here are some of the options:
- 8.8.8.8
- 8.8.4.4
- 208.67.222.222
- 208.67.220.220.
Use any two you like best. Theoretically, any of them can become unemployed with equal probability. But as long as they work, your browser will open sites faster than using automatically obtained DNS servers.
Increase MTU
The connection speed is affected by the value of the “MTU” parameter. There is no need to change it unless necessary. But, as practice shows, a change in value in big side sometimes leads to positive results. Note that owners of SmartTVs, if everything is currently working, are contraindicated in changing the MTU in the router (the parameter value should remain less than 1480).
Dynamic or Static IP
For connections of the form " Dynamic IP address"or "Static IP" MTU value is 1500. Start increasing it in increments of 100, then in increments of 10. As a result, you can select a configuration option that will provide the highest Internet connection speed. You can test the connection to find out the speed of data transmission and reception using free services(http://2ip.ru/speed/ and others). Note that the task under consideration is not for beginners, since in some cases the effect will only appear with large values MTU such as 5000, 10000, etc.
Changing the MTU parameter will be easy. Go to the interface tab containing connection settings. Find the field labeled "MTU":
Correcting the MTU parameter
PPtP and L2TP
For protocols that provide authentication (PPtP and L2TP), two communication interfaces are usually implemented. More precisely, interfaces of two levels are always used, of which lowest level- This is Ethernet. Note that each interface has its own MTU parameter, and both parameters can be changed. Just keep in mind that the MTU of the Ethernet level cannot be less than the MTU of the high level. They also cannot be equal.
On the tab where the connection parameters are located, you can see two configured connections with the provider.
Connections Tab
IN in this case the “WAN” connection will be responsible for the Ethernet layer. You can access its parameters by running double click on the "WAN" line. The same can be said about the line that says “Internet”. Open the parameters of the required connection, look for the field labeled “MTU” (there will be one on each tab).
Sometimes a protocol like “L2TP + Dynamic IP” is configured in the router, which also applies to PPtP. In this case, the parameters tab looks like this:
PPtP Settings Tab
Here, as we see, are available MTU parameters each of the two levels. The question remains what they should be equal to.
The default Ethernet MTU is 1500, as discussed in the previous chapter.
The MTU for L2TP and PPtP is usually set to "1460". But for some providers you need to use other numbers, “1472” or “1474”. Then the communication speed increases. Try changing the number using step 4 or 2. But be aware that if you cross a certain “upper limit”, you can immediately get a broken connection.
Tuning uTorrent
You cannot use a torrent client together with a router if you leave the program settings at their defaults. The important thing is: you need to limit the number simultaneous connections. In the program menu, go to “Settings” -> “Configuration”. Then you need to find the “Speed” tab:
uTorrent connection speed
Leave the “maximum number of connections” between two and three hundred. This should be enough.
The number of distribution slots and the number of peers per torrent, in principle, cannot be explicitly limited (they will already be less than the squared value). But it is better to use the numbers given in the example. And it is possible that they will have to be reduced, and this depends on the model of the equipment used. Happy routing!
Should never be neglected simple rule: best the enemy of the good. Using the equipment's capabilities to the maximum, you must remember that the router is a universal device, and its resources are distributed between several tasks. Therefore, it is not surprising that by setting up one of the services (torrent), you may end up with the absence of something else (IPTV). Using 50% of the maximum is what you need to reliable operation. For the “home” equipment class, where there are not many tasks, this figure can be adjusted to 75.
Changing MTU for PPPoE
If you specify the MTU size incorrectly for PPPoE connections from Rostelecom, problems may arise when opening some resources. Before you determine the required setup configuration for your connection, it's worth learning more about what this option is.
TCP MTU option for Rostelecom and other providers
As a protocol network layer in the TCP/IP set, the latter is intended to be implemented potentially large systems local networks. From our time with IP, we have become accustomed to the concept of hosts that can send information back and forth, even though they are located quite far apart and the data may have to travel across multiple devices. Even though we typically think of the Internet's TCP/IP protocol suite as an abstract "virtual network," we must always remember that at the network layer, data flows over one or more physical lines.
How is data sent?
In order to transmit information over the IP protocol, data is encapsulated (packed) into datagrams ( information blocks). They, in turn, must be sent by physical channel directly to the destination or indirectly to the next intermediate stage of the journey to the recipient. The size of such data packets is called MTU (Maximum Transmission Unit), used in PPPoE connections x Rostelecom and other providers.
The link layer implementation places the transported message and headers in single package data - IP datagram. This immediately raises a potential question about whether the datagram fits within the supported packet size of the underlying data link.
Matching IP datagrams to block size in the core network
The underlying network that is used to connect to other devices can be:
- local (Ethernet);
- wireless (Wi-Fi 11);
- switched;
- telephone (DSL);
- fiber optic (FDDI).
Each physical network usually uses own format transmission, which has restrictions on the amount of data in one block. If an IP datagram is too large for the link layer section of a particular network format, we have a problem.
For example, consider FDDI. The maximum data field size in FDDI is approximately 4470 bytes, depending on the use of SNAP (SubNetwork Access Protocol). This means that FDDI can handle IP datagrams up to 4470 bytes. In contrast, Ethernet uses a format that is limited to a packet size of 1500 bytes and will not be able to interoperate with a larger IP datagram.
So, remember that the transmission of a datagram in an internetwork can be carried out through more than one physical line. In order to access a resource on the Internet, we typically send a request through our local router, which then connects to other devices that forward it to the Internet site. Each section in this chain can use its own primary packet size.
The idea of a network layer protocol to implement the concept of " virtual network"is to transfer data between devices, even if they are far from each other. This means that more high levels don't have to worry about details like size limitations basic technologies channel. However, someone has to take care of this, which is what IP (Internet Protocol) does.
IP limit: MTU settings for Rostelecom
All IP devices on the Internet must receive information about the quality of the technology used to implement the current level of communication channel. This criterion is Network MTU Rostelecom, which is configured on network equipment user. This term is also sometimes seen as maximum size block for transmission.
Interesting: There are two ways to change the MTU: in the operating system itself or in the router settings. The second one will be optimal, since with its help all devices on your network will be able to obtain information about the required value.
When a device receives a message sent over Internet networks, it looks at its size and then calculates how large the datagram will be after adding the 20 or more bytes required for the IP header. If the total length exceeds the Rostelecom MTU for PPPoE connection in specific network, Internet Protocol will split the message into several fragments. So when the host connects TCP level via Ethernet LAN to your local network, he will be able to use the MTU option specified by Rostelecom equipment.
You can find out what MTU Rostelecom has for your type of connection and equipment directly from the provider by calling. The value of this option for most networks in Russia does not exceed 1492 bytes. To figure out best option for your own Internet you can personally, based on the specified value.
To accurately determine the MTU, you need to specify the default value - 1500.
Exists great amount utilities that allow you to do this and not only that. The most common - Internet Tweak 2001 http://www.magellass.com/, NetBoost 99 http://www.download.ru/, iSpeed http://www.hms.com/, MTUSpeed http://www.mjs.u-net.com/, BlazeNET http://www.indeavour.com/html_about_blazenet.htm. If you haven't. opportunity to run one of the above programs, do it manually - using the Windows registry.
In chapter
HKEY_LOCAL_MACHINE\System\CurrentControlSet\ Services\Class \NetTrans\OOOx.
If there is a MaxMTU parameter there, delete it. Next, in the Control Panel, run the utility Net, on the tab Configuration select list item Remote Access Controller and press the button Properties. A dialog box will open Properties: Remote access controller. On the tab Additionally in the parameter group Property select list item IP packet size, and in the parameter group Value - big(Fig. 8.1).
Rice. 8.1. Dialog window Properties: Remote Access Controller
This makes the MTU equal to 1500. For the changes to take effect, restart the computer.
To check whether packets will be fragmented, you need to establish a connection to the Internet. To do this, you can use the Ping program, which is included in any operating system Windows family.
In it. you need to set the following parameters:
ping -f -1 1500 xxx.xxx.xxx.xxx
where is xxx. xxx. xxx. xxx - IP address of the server being tested.
For MTU testing it is much more convenient to use modern programs With graphical interface. There are a huge number of such programs. For example, IP Tools. First, you need to determine the IP address of the server you are testing to avoid wasting time allotted to the DNS query.
To do this, use the Traceroute command. Click the button Start in the lower left corner of the screen, select the command Execute and in the window that appears, type
ping -f -I 1500 xxx.xxx.xxx.xxx
where xxx.xxx.xxx.xxx is the IP address of the server being tested. The best time to check the MTU for a dial-up connection is at night. Then the load on the communication line is minimal.
If no response is received, the packet is lost. Moreover, because we forbade it to fragment, and the size is too large for the provider’s equipment. Start gradually reducing the package size. For example, instead of an MTU value of 1500, set it to 1480, etc., until a response is received.
Your ISP may use a lower value. For example, 1524, 1152, 1024, 1006, 576, 568, 560, 552, 548, 536, 528, 520, 512.
This experiment confirmed our guess - the Internet provider can use any packet size, up to 1500. If you are not tired of experimenting yet, try downloading a 500 KB file from the same server at different MTU values.
You will likely find that the speed is greater when using larger
packages. Again, this is only if your provider can accept them without fragmenting them. Also, if you ping many of your favorite sites with a non-fragmentable packet, you will see that almost all accept packets of size 1500 just fine.
And what? You may ask: "Where is that recommended MTU of 576?" But, as it turns out, he is almost nowhere to be found. That's why best advice may become - do not follow other people's recommendations, conduct your own research that can give real results.
Indeed, the quality and speed of the Internet is greatly influenced by packet fragmentation, which occurs if a large packet passes through a network that has an MTU less than the length of your packet.
You can, of course, play it safe and choose the most minimum size An MTU at which packets will most likely not be fragmented, but this may have an even more detrimental effect on the performance of your system than using large packets. In fact, the main thing is that your MTU does not exceed the MTU of the provider, even if the function is enabled
The PMTU system itself will find a path for your packets on the Network in which they will not be fragmented.
By the way, if you find that your provider has an MTU of 512 or less, then it makes sense to think about changing it - too much slag will be transferred along with your data.
The MTU number represents the maximum transferable data packet that is sent from the server to the equipment. It is used in the Internet connection and directly affects its speed. How does MTU work? To ensure connection transfer is fast and efficient, data is transferred not one byte at a time, but in whole packets. The computer unpacks the package and downloads information, for example, a web page, a game, etc.
Few of them ordinary users wondered what MTU is and why it is indicated in the settings
Why is it worth checking and changing such a parameter? It often happens that a user connects to the Internet, and although the stated connection speed should be high, the browser loads the site or game slowly, or does not want to access some pages at all. At the same time, the Internet does not disappear entirely, but poor loading affects individual sites or applications.
To deal with the problem, it is recommended to change DNS settings. This can be done through the Control Panel. Open the Internet connections section, select your network and view its properties. In them you will find components, among which you should select the TCP/IP Internet protocol and manually enter DNS addresses- 8.8.8.8 and in the second line 8.8.4.4.
If you tried changing the DNS value, but it did not help, you should refer to the data packet size settings. When the provider has one number for this parameter, and your router has another number, then the speed drops and connection is not working well. There is no need to change it on your computer, since latest versions Windows system itself determines the optimal value for network operation.
How do you know what MTU to set on your router?
There are standard values for this parameter for routers. In most cases, the number 1500 is used - it is the base default, used for dynamic and static IP addresses.
For an L2TP connection, the number 1460 is selected, and for PPPoE - 1420. It is worth trying the combination 1476 - it is set by default for 3G networks.
Another option you can use to find out the correct size combination packet transmission for router, call to service center your provider. They will provide you with accurate data, but may not be able to answer your request, so it is worth learning how to determine this number yourself.
This can be done by checking set value MTU on computer and router. If they don't match, that's the reason bad speed connections. To find out the combination on your computer, do the following:
- Enter in Total Commander PING string-f -l 1472 xxx.xxx.xxx.xxx, where instead of crosses, enter your IP address.
- If the result is the text “Reply from...”, then the correct MTU number is 1500, as it should be by default. Why 1472? The remaining kilobytes are system ones and are automatically added to this number for a total of 1500.
- If the text “Packet needs to be fragmented but DF set” appears in response to the command, you need to manually search for the correct value by decreasing the number 1472 by tens until you have the line “Reply from...”. Then to final value you need to add 28 system kilobytes to get the correct number.
Setting up MTU in the router
After figuring out the required combination for maximum transmitted packet data, enter it into the router parameters.
This is done as follows:
- Go to your router settings. In the browser line, enter the IP address of the equipment, in the window that appears, enter the login and password (if you have not changed them, use the word Admin in both lines).
- Select the Network section, open the WAN menu.
- Enter the required number in the MTU Size line, save the changes and reboot the equipment.
