Maximum transmission unit
Encyclopedia
In computer networking, the maximum transmission unit (MTU) of a communications protocol
of a layer
is the size (in byte
s) of the largest protocol data unit
that the layer can pass onwards. MTU parameters usually appear in association with a communications interface (NIC, serial port
, etc.). Standards (Ethernet
, for example) can fix the size of an MTU; or systems (such as point-to-point serial links) may decide MTU at connect time.
A larger MTU brings greater efficiency because each packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means a slight improvement in bulk protocol throughput. A larger MTU also means processing of fewer packets for the same amount of data. In some systems, per-packet-processing can be a critical performance limitation.
Large packets can occupy a slow link for some time, causing greater delays to following packets and increasing lag
and minimum latency. For example, a 1500-byte packet, the largest allowed by Ethernet at the network layer (and hence over most of the Internet
), ties up a 14.4k modem for about one second.
Large packets are also problematic in the presence of communications errors. Corruption of a single bit in a packet requires that the entire packet be retransmitted. At a given bit error rate larger packets are more likely to be corrupted. Retransmissions of larger packets take longer.
size that all hosts must be prepared to accept, which has a value of 576 for IPv4 and of 1280 for IPv6.
to work over many networking technologies, each of which may use packets of different size. While a host will know the MTU of its own interface and possibly that of its peers (from initial handshakes), it will not initially know the lowest MTU in a chain of links to any other peers. Another potential problem is that higher-level protocols may create packets larger than a particular link supports.
To get around this issue, IP allows fragmentation
: dividing the datagram
into pieces, each small enough to pass over the single link that is being fragmented for, using the MTU parameter configured for that interface. This fragmentation process takes place at the IP layer (OSI layer 3
) and marks packets it fragments as such, so that the IP layer of the destination host knows it should reassemble the packets into the original datagram. This method implies a number of possible drawbacks:
The Internet Protocol requires that hosts must be able to process IP datagrams of at least 576 bytes (for IPv4) or 1280 bytes (for IPv6). However, this does not preclude Data Link Layers with an MTU smaller than IP's minimum MTU from conveying IP data. For example, according to IPv6's specification, if a particular Data Link Layer physically cannot deliver an IP datagram of 1280 bytes in a single frame, then the link layer MUST provide its own fragmentation and reassembly mechanism, separate from IP's own fragmentation mechanism, to ensure that a 1280-byte IP datagram can be delivered, intact, to the IP layer.
s of the "path" between a source and destination. Put another way, the path MTU is the largest packet size that can traverse this path without suffering fragmentation.
RFC 1191 (IPv4) and RFC 1981 (IPv6) describe "Path MTU Discovery", a technique for determining the path MTU between two IP hosts. It works by setting the DF (Don't Fragment) option in the IP headers of outgoing packets. Any device along the path whose MTU is smaller than the packet will drop such packets and send back an ICMP
"Destination Unreachable (Datagram Too Big)
" message containing its MTU. This information allows the source host to reduce its assumed path MTU appropriately. The process repeats until the MTU becomes small enough to traverse the entire path without fragmentation.
Unfortunately, increasing numbers of networks drop ICMP traffic
(e.g. to prevent denial-of-service attack
s), which prevents path MTU discovery from working. One often detects such blocking in the cases where a connection works for low-volume data but hangs as soon as a host sends a large block of data. For example, with IRC
a connecting client
might see the initial messages up to and including the initial ping
(sent by the server as an anti spoofing measure), but get no response after that. This is because the large set of welcome messages are sent out in packets bigger than the real MTU. Also, in an IP network, the path from the source address to the destination address often gets modified dynamically, in response to various events (load-balancing
, congestion
, outages
, etc.) - this could result in the path MTU changing (sometimes repeatedly) during a transmission, which may introduce further packet drops before the host finds the new safe MTU.
Most Ethernet
LAN
s use an MTU of 1500 bytes (modern LANs can use Jumbo frames, allowing for an MTU up to 9000 bytes); however, border protocols like PPPoE
will reduce this. The difference between the MTU seen by end-nodes (e.g. 1500) and the Path MTU causes Path MTU Discovery to come into effect, with the possible result of making some sites behind badly-configured firewalls unreachable. One can possibly work around this, depending on which part of the network one controls; for example one can change the MSS (maximum segment size
) in the initial packet that sets up the TCP
connection at one's firewall.
RFC 4821, Packetization Layer Path MTU Discovery, describes a Path MTU Discovery technique which responds more robustly to ICMP filtering.
) network carries IP traffic. Some providers, particularly those with a telephony background, use ATM on their internal backbone network.
ATM operates at optimum efficiency when packet length is a multiple of 48 bytes. This is because ATM is sent as a stream of fixed-length packets (known as 'cells'), each of which can carry a payload of 48 bytes of user data with 5 bytes of overhead for a total cost of 53 bytes per cell. So the total length of the transmitted data length is 53 * ncells bytes, where ncells = the number of required cells of = INT((payload_length+47)/48). So in the worst case, where the total length = (48*n+1) bytes, one additional cell is needed to transmit the one last byte of payload, the final cell costing an extra 53 transmitted bytes 47 of which are padding. For this reason, artificially declaring a reduced MTU in software maximises protocol efficiency at the ATM layer by making the ATM AAL5 total payload length a multiple of 48 bytes whenever possible.
For example, 31 completely filled ATM cells carry a payload of 31*48=1488 bytes. Taking this figure of 1488 and subtracting from it any overheads contributed by all relevant higher protocols we can obtain a suggested value for an artificially-reduced optimal MTU. In the case where the user would normally send 1500 byte packets, sending between 1489 and 1536 bytes requires an additional fixed cost of 53 bytes transmitted, in the form of one extra ATM cell.
For the example of IP over DSL
connections using PPPoA/VC-MUX
, again choosing to fill 31 ATM cells as before, we obtain a desired optimal reduced MTU figure of 1478 = 31*48-10 taking into account an overhead of 10 bytes consisting of a Point-to-Point Protocol
overhead of 2 bytes, and an AAL5 overhead of 8 bytes. This gives a total cost of 31*53=1643 bytes transmitted via ATM from a 1478 byte packet passed to PPPoA. In the case of IP sent over ADSL using PPPoA the figure of 1478 would be the total length of the IP packet including IP headers. So in this example, keeping to a self-imposed reduced MTU of 1478 as opposed to sending IP packets of total length 1500 saves 53 bytes per packet at the ATM layer at a cost of a 22 byte reduction of the length of IP packets.
RFC 2516 prescribes a maximum MTU for PPPoE/DSL connections of 1492 bytes: the 1500 byte maximum ethernet payload minus 8 bytes of PPPoE headers (2 bytes for the PPP overhead, and 6 bytes for the PPPoE header). This will not necessarily fill an integer number of ATM cells.
standard, developed by ITU-T
, provides a high-speed (up to 1 Gigabit/s) local area network
using existing home wiring (power lines
, phone lines and coaxial cables
). The G.hn Data Link Layer
accepts data frames of up to 214 bytes (16384 bytes). In order to avoid the problem of long data-frames taking up the medium for long periods of time, G.hn defines a procedure for segmentation
that divides the data frame into smaller segments.
es have a built-in capability to detect when a device is jabbering and block it until it resumes proper operation.
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
of a layer
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
is the size (in byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
s) of the largest protocol data unit
Protocol data unit
In telecommunications, the term protocol data unit has the following meanings:#Information that is delivered as a unit among peer entities of a network and that may contain control information, address information, or data....
that the layer can pass onwards. MTU parameters usually appear in association with a communications interface (NIC, serial port
Serial port
In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
, etc.). Standards (Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
, for example) can fix the size of an MTU; or systems (such as point-to-point serial links) may decide MTU at connect time.
A larger MTU brings greater efficiency because each packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means a slight improvement in bulk protocol throughput. A larger MTU also means processing of fewer packets for the same amount of data. In some systems, per-packet-processing can be a critical performance limitation.
Large packets can occupy a slow link for some time, causing greater delays to following packets and increasing lag
Lag
Lag is a common word meaning to fail to keep up or to fall behind. In real-time applications, the term is used when the application fails to respond in a timely fashion to inputs...
and minimum latency. For example, a 1500-byte packet, the largest allowed by Ethernet at the network layer (and hence over most of the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
), ties up a 14.4k modem for about one second.
Large packets are also problematic in the presence of communications errors. Corruption of a single bit in a packet requires that the entire packet be retransmitted. At a given bit error rate larger packets are more likely to be corrupted. Retransmissions of larger packets take longer.
Table of MTUs of common media
Note: the MTUs in this section are given as the maximum size of IP packet that can be transmitted without fragmentation - including IP headers but excluding headers from lower levels in the protocol stack. The MTU must not be confused with the minimum datagramDatagram
A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
size that all hosts must be prepared to accept, which has a value of 576 for IPv4 and of 1280 for IPv6.
| Media | Maximum Transmission Unit (bytes) | Notes |
|---|---|---|
| Internet Internet The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide... IPv4 Path MTU |
At least 68 | Practical path MTUs are generally higher. IPv4 links must be able to forward packets of size up to 68 bytes. Systems may use Path MTU Discovery Path MTU discovery Path MTU Discovery is a standardized technique in computer networking for determining the maximum transmission unit size on the network path between two Internet Protocol hosts, usually with the goal of avoiding IP fragmentation... to find the actual path MTU. This should not be mistaken with the packet size every host must be able to handle, which is 576. |
| Internet Internet The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide... IPv6 Path MTU |
At least 1280 | Practical path MTUs are generally higher. Systems must use Path MTU Discovery to find the actual path MTU. |
| Ethernet v2 | 1500 | Nearly all IP over Ethernet implementations use the Ethernet V2 frame format. |
| Ethernet (802.3) IEEE 802.3 IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications... |
1492 | |
| Ethernet Jumbo Frames Jumbo Frames In computer networking, jumbo frames are Ethernet frames with more than 1500 bytes of payload. Conventionally, jumbo frames can carry up to 9000 bytes of payload, but variations exist and some care must be taken when using the term. Many Gigabit Ethernet switches and Gigabit Ethernet network... |
1500-9000 | The limit varies by vendor. For correct interoperation, the whole Ethernet network must have the same MTU. Jumbo frames are usually only seen in special purpose networks. |
| WLAN (802.11) IEEE 802.11 IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent... |
2272 | |
| Token Ring (802.5) | 4464 | |
| FDDI | 4352 |
IP (Internet protocol)
DARPA designed the Internet protocol suiteInternet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
to work over many networking technologies, each of which may use packets of different size. While a host will know the MTU of its own interface and possibly that of its peers (from initial handshakes), it will not initially know the lowest MTU in a chain of links to any other peers. Another potential problem is that higher-level protocols may create packets larger than a particular link supports.
To get around this issue, IP allows fragmentation
IP fragmentation
The Internet Protocol implements datagram fragmentation, so that packets may be formed that can pass through a link with a smaller maximum transmission unit than the original datagram size....
: dividing the datagram
Datagram
A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
into pieces, each small enough to pass over the single link that is being fragmented for, using the MTU parameter configured for that interface. This fragmentation process takes place at the IP layer (OSI layer 3
Network layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
) and marks packets it fragments as such, so that the IP layer of the destination host knows it should reassemble the packets into the original datagram. This method implies a number of possible drawbacks:
- All fragments of a packet must arrive for the packet to be considered received. If the network drops any fragment, the entire packet is lost.
- When the size of most or all packets exceed the MTU of a particular link that has to carry those packets, almost everything has to be fragmented. In certain cases the overhead this causes can be considered unreasonable or unnecessary. For example, various tunneling situations cross the MTU by very little as they add just a header's worth of data. The addition is small, but each packet now has to be sent in two fragments, the second of which carries very little payload. The same amount of payload is being moved, but every intermediate router has to do double the work in terms of header parsing and routing decisions.
- As it is normal to maximize the payload in every fragment, in general as well as when fragmenting, any further fragmentation that turns out to be necessary will increase the overhead even more.
- There is no simple method to discover the MTU of links beyond a node's direct peers.
The Internet Protocol requires that hosts must be able to process IP datagrams of at least 576 bytes (for IPv4) or 1280 bytes (for IPv6). However, this does not preclude Data Link Layers with an MTU smaller than IP's minimum MTU from conveying IP data. For example, according to IPv6's specification, if a particular Data Link Layer physically cannot deliver an IP datagram of 1280 bytes in a single frame, then the link layer MUST provide its own fragmentation and reassembly mechanism, separate from IP's own fragmentation mechanism, to ensure that a 1280-byte IP datagram can be delivered, intact, to the IP layer.
Path MTU Discovery
The Internet Protocol defines the "Path MTU" of an Internet transmission path as the smallest MTU of any of the IP hopHop (telecommunications)
In telecommunication, the term hop has the following meanings:#The excursion of a radio wave from the Earth to the ionosphere and back to the Earth...
s of the "path" between a source and destination. Put another way, the path MTU is the largest packet size that can traverse this path without suffering fragmentation.
RFC 1191 (IPv4) and RFC 1981 (IPv6) describe "Path MTU Discovery", a technique for determining the path MTU between two IP hosts. It works by setting the DF (Don't Fragment) option in the IP headers of outgoing packets. Any device along the path whose MTU is smaller than the packet will drop such packets and send back an ICMP
Internet Control Message Protocol
The Internet Control Message Protocol is one of the core protocols of the Internet Protocol Suite. It is chiefly used by the operating systems of networked computers to send error messages indicating, for example, that a requested service is not available or that a host or router could not be...
"Destination Unreachable (Datagram Too Big)
ICMP Destination Unreachable
The Destination Unreachable message is an ICMP message which is generated by the host or its inbound gateway to inform the client that the destination is unreachable for some reason. A Destination Unreachable message may be generated as a result of a TCP, UDP or another ICMP transmission...
" message containing its MTU. This information allows the source host to reduce its assumed path MTU appropriately. The process repeats until the MTU becomes small enough to traverse the entire path without fragmentation.
Unfortunately, increasing numbers of networks drop ICMP traffic
Black hole (networking)
In networking, black holes refer to places in the network where incoming traffic is silently discarded , without informing the source that the data did not reach its intended recipient....
(e.g. to prevent denial-of-service attack
Denial-of-service attack
A denial-of-service attack or distributed denial-of-service attack is an attempt to make a computer resource unavailable to its intended users...
s), which prevents path MTU discovery from working. One often detects such blocking in the cases where a connection works for low-volume data but hangs as soon as a host sends a large block of data. For example, with IRC
Internet Relay Chat
Internet Relay Chat is a protocol for real-time Internet text messaging or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file...
a connecting client
Client (computing)
A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....
might see the initial messages up to and including the initial ping
Ping
Ping is a computer network administration utility used to test the reachability of a host on an Internet Protocol network and to measure the round-trip time for messages sent from the originating host to a destination computer...
(sent by the server as an anti spoofing measure), but get no response after that. This is because the large set of welcome messages are sent out in packets bigger than the real MTU. Also, in an IP network, the path from the source address to the destination address often gets modified dynamically, in response to various events (load-balancing
Load balancing (computing)
Load balancing is a computer networking methodology to distribute workload across multiple computers or a computer cluster, network links, central processing units, disk drives, or other resources, to achieve optimal resource utilization, maximize throughput, minimize response time, and avoid...
, congestion
Network congestion
In data networking and queueing theory, network congestion occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss or the blocking of new connections...
, outages
Downtime
The term downtime is used to refer to periods when a system is unavailable.Downtime or outage duration refers to a period of time that a system fails to provide or perform its primary function...
, etc.) - this could result in the path MTU changing (sometimes repeatedly) during a transmission, which may introduce further packet drops before the host finds the new safe MTU.
Most Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
LAN
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s use an MTU of 1500 bytes (modern LANs can use Jumbo frames, allowing for an MTU up to 9000 bytes); however, border protocols like PPPoE
Point-to-Point Protocol over Ethernet
The Point-to-Point Protocol over Ethernet is a network protocol for encapsulating Point-to-Point Protocol frames inside Ethernet frames. It is used mainly with DSL services where individual users connect to the DSL modem over Ethernet and in plain Metro Ethernet networks...
will reduce this. The difference between the MTU seen by end-nodes (e.g. 1500) and the Path MTU causes Path MTU Discovery to come into effect, with the possible result of making some sites behind badly-configured firewalls unreachable. One can possibly work around this, depending on which part of the network one controls; for example one can change the MSS (maximum segment size
Maximum segment size
The maximum segment size is a parameter of the TCP protocol that specifies the largest amount of data, specified in octets, that a computer or communications device can receive in a single TCP segment, and therefore in a single IP datagram. It does not count the TCP header or the IP header...
) in the initial packet that sets up the TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
connection at one's firewall.
RFC 4821, Packetization Layer Path MTU Discovery, describes a Path MTU Discovery technique which responds more robustly to ICMP filtering.
ATM backbones, an example of MTU tuning
Sometimes the demands of efficiency encourage artificially declaring a reduced MTU in software below the true maximum possible length supported - for example: where an ATM (Asynchronous Transfer ModeAsynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
) network carries IP traffic. Some providers, particularly those with a telephony background, use ATM on their internal backbone network.
ATM operates at optimum efficiency when packet length is a multiple of 48 bytes. This is because ATM is sent as a stream of fixed-length packets (known as 'cells'), each of which can carry a payload of 48 bytes of user data with 5 bytes of overhead for a total cost of 53 bytes per cell. So the total length of the transmitted data length is 53 * ncells bytes, where ncells = the number of required cells of = INT((payload_length+47)/48). So in the worst case, where the total length = (48*n+1) bytes, one additional cell is needed to transmit the one last byte of payload, the final cell costing an extra 53 transmitted bytes 47 of which are padding. For this reason, artificially declaring a reduced MTU in software maximises protocol efficiency at the ATM layer by making the ATM AAL5 total payload length a multiple of 48 bytes whenever possible.
For example, 31 completely filled ATM cells carry a payload of 31*48=1488 bytes. Taking this figure of 1488 and subtracting from it any overheads contributed by all relevant higher protocols we can obtain a suggested value for an artificially-reduced optimal MTU. In the case where the user would normally send 1500 byte packets, sending between 1489 and 1536 bytes requires an additional fixed cost of 53 bytes transmitted, in the form of one extra ATM cell.
For the example of IP over DSL
Digital Subscriber Line
Digital subscriber line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line ,...
connections using PPPoA/VC-MUX
VC-MUX
Virtual circuit multiplexing or VC-MUX is one of the two mechanisms for identifying the protocol carried in ATM Adaptation Layer 5 frames specified by RFC 2684, Multiprotocol Encapsulation over ATM....
, again choosing to fill 31 ATM cells as before, we obtain a desired optimal reduced MTU figure of 1478 = 31*48-10 taking into account an overhead of 10 bytes consisting of a Point-to-Point Protocol
Point-to-Point Protocol
In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
overhead of 2 bytes, and an AAL5 overhead of 8 bytes. This gives a total cost of 31*53=1643 bytes transmitted via ATM from a 1478 byte packet passed to PPPoA. In the case of IP sent over ADSL using PPPoA the figure of 1478 would be the total length of the IP packet including IP headers. So in this example, keeping to a self-imposed reduced MTU of 1478 as opposed to sending IP packets of total length 1500 saves 53 bytes per packet at the ATM layer at a cost of a 22 byte reduction of the length of IP packets.
RFC 2516 prescribes a maximum MTU for PPPoE/DSL connections of 1492 bytes: the 1500 byte maximum ethernet payload minus 8 bytes of PPPoE headers (2 bytes for the PPP overhead, and 6 bytes for the PPPoE header). This will not necessarily fill an integer number of ATM cells.
MTU in other standards
The G.hnG.hn
G.hn is the common name for a home network technology family of standards developed under the International Telecommunication Union's Standardization arm and promoted by the HomeGrid Forum...
standard, developed by ITU-T
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
, provides a high-speed (up to 1 Gigabit/s) local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
using existing home wiring (power lines
Power line communication
Power line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...
, phone lines and coaxial cables
Ethernet over coax
Ethernet over Coax is a family of technologies that supports the transmission of Ethernet frames over coaxial cable.- History :The first Ethernet standard, known as 10BASE5 in the family of IEEE 802.3, specified baseband operation over coaxial cable...
). The G.hn Data Link Layer
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
accepts data frames of up to 214 bytes (16384 bytes). In order to avoid the problem of long data-frames taking up the medium for long periods of time, G.hn defines a procedure for segmentation
Segmentation
Segmentation may mean:*Market segmentation, in economics and marketingBiology*A process of morphogenesis that divides a metazoan body into a series of semi-repetitive segments*Segmentation , a series of semi-repetitive segments...
that divides the data frame into smaller segments.
Disruption
The transmission of a packet on a physical network segment that is larger than the segment's MTU is known as jabber. This is almost always caused by faulty devices. Many network switchNetwork switch
A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
es have a built-in capability to detect when a device is jabbering and block it until it resumes proper operation.
External links
- Tweaking your MTU / RWin for Orange Broadband Users
- How to set the TCP MSS value using iptables
- Discovering of MTU value via pingPingPing is a computer network administration utility used to test the reachability of a host on an Internet Protocol network and to measure the round-trip time for messages sent from the originating host to a destination computer...
and setting it in Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal... - DrTCP – a utility for optimizing MTU under Microsoft Windows
- mturoute – a console utility for debugging mtu problems
- MSS Initiative
- MTU Path MTU discovery tool for IPv4 and IPv6 networks