The debate of TCP MSS (most section ), and

[Background]
MTU: Maxitum Transmission Unit MTU
MSS: Maxitum Segment Size Maximum segment size (even a literal translation, the translation is not agreeable, do not play
I PP)
PPPoE: PPP Over Ethernet (PPP over Ethernet protocol load)
[analysis]
1st to give it the maximum transmission unit MTU, the maximum transmission unit and the link layer protocol is really closely related, let us 1st recollect EthernetII cautiously frame the architecture of DMAC + SMAC + Type + Data + CRC
as Ethernet transmission electrical limitations, each Ethernet frame has a minimum size of 64bytes is a restrict of 1518bytes, for less than or greater than the restrict of the Ethernet frame we can regarded as wrong data frame, the general Ethernet forwarding device will discard the data frame.
(Note: the data skeleton is generally less than 64Bytes Ethernet conflicts appear due to the frame, this is generally due to line ruckus or a bad Ethernet port generation)
as the largest Ethernet data frame is EthernetII 1518Bytes so planing to the Ethernet frame header (DMAC Destination MAC residence 48bit = 6Bytes + SMAC Source MAC address 48bit = 6Bytes + Type field 2bytes) 14Bytes and end of frame CRC is part of the 4Bytes (The division periodically we call it FCS), then area the remaining upper-layer protocols carry the Data field is the maximum you can only have the value we put it 1500Bytes called MTU. This is the network layer protocol is very concerned about the area, because the network layer protocol such as IP protocol based on this value to determine whether the data passed down to the upper fraction. Is like a carton can not install the next chunk of bread, slice the bread we need, packed in several boxes inside the same reason.
When two remote PC when interlocked, their data needs through a lot of routers and a kind of media to approach the remote network, the network MTU of assorted media varied, like a long segment of water pipes, water pipes of different thickness of the composition (MTU different) the maximum measure of water through this water will start from the middle of the finest pipe determination.
for the upper network layer protocol in terms of (our TCP / IP protocol suite, case in point) they do not attention about the thickness of the water they meditation this is something the network layer. Network layer IP protocol checks each down from the upper protocol packet size and MTU size according to the machine to judge whether to Fragmentation is the biggest drawback
depress transmission performance, had one object you can obtain, numerous get into, so a higher level in the network layer (that is, the transport layer) implementation will often must pay consideration! Some high-level requirements fknow next to nothing ofme reason it will not slice my bread, I want to complete bread, it will be inside the IP packet header plus a
tags: DF (Donot Fragment). So that when the IP packet in a large partition of the network (inside pipe) transmission, if the meet is fewer than the MTU of the IP packet forwarding appliance will reject the packet as necessitated. Then returns an error message to the sender. This tends to cause some communication issues,Lacoste Radiate Croc Trainers, merely fortunately most of the network links are MTU1500 or greater than 1500.
for the UDP protocol, the protocol itself is a connectionless protocol, the arrival of data packets to reach the correct order and not very concerned about, it is generally fragmented UDP applications are not special requirements.
not the same in terms of the TCP protocol, this protocol is connection-oriented protocol, TCP protocol for the purposes it is very cared about the appearance of file packets transmitted in the array, and whether an error happened. Therefore, some TCP applications have requirements --- can not slice slice (DF).
two flowers, with each 1, so much the article of MTU today we talk about the so-called second piglet --- PPPoE PPPoE is PPP over Ethernet protocol to run upon, it was strange, PPP protocol and Ethernet interlock layer protocol is not it? How a link layer upon the link layer to work another work, do not upgrade to the network layer protocol of fragmentation. In truth,Lacoste Zepher MR2 Trainers, this is a misunderstanding: that is, a layer protocol can merely carry an even higher class protocol.
Why would such a strange claim? This is for with broadband way (such as broadband way is generally xDSL or Cable Modem or Ethernet way) because Ethernet lack of authentication and accounting mechanisms and orthodox carriers by PPP protocol for dial-up access, etc. into the service authentication and accounting, and so on out of such a freak: PPPoE. (See detailed specification about PPPoE and V large site story about some of the additional members, I will not instigate the inside of the)
PPPoE brought benefits, it also brings some disadvantages, such as: secondary packaging resource-intensive,Lacoste Camden Trainers, reducing the transportation efficiency, etc. These are not wrong I say, the biggest disadvantage is that PPPoE MTU guide to smaller Ethernet MTU is 1500, minus the end of the PPP packet header on the head of (8Bytes),Lacoste Trainers, becomes 1492.
certain if the network between two hosts using PPPoE it will lead to some fragmentation of the application can not communicate.
this time we need to adjust the host's MTU, the host by reducing the MTU, so that we can smoothly communicate.
way, as TCP applications, there namely variant solution.
immediately call out today,New Lacoste Trainers High Top, the third pig: MSS.
MSS maximum migrate size of the acronym, is a conception which the TCP protocol.
MSS is the TCP packet transmissiin time to the maximum data segment. In order to achieve the best transmission extravaganza of TCP protocol when the connection is commonly talk either MSS value that the TCP protocol is often used in the comprehension of the time instead of the MTU value (with minus the size of IP packet header and TCP data segments 20Bytes Baotou 20Bytes) so often MSS to 1460. Communication invested by both sides according to MSS for this connection ought be the minimum to determine the maximum MSS value.
presentation to the 3 pig s
we look behind inside the prelude that, we imagine, if we are in the middle of each TCP linkage on the router to adjust the maximum MSS makes this fetter via PPPoE Road MSS amount and the maximum end of the data packet header over the PPPoE MTU size is not 1492 so it will not occasion the problem can not communicate, so the above problems can be ip tcp adjust-mss 1452 to resolve.
problem,Lacoste Arixia FD Trainers, of course you tin also adjust the PC's MTU to determination.
[Postscript]
Cisco's TCP Adjust MSS Feature:
The TCP MSS Adjustment function enables the configuration of the
highest section size (MSS) for transient parcels namely traverse a router,
specifically TCP segments in the SYN bit set, while Point apt Point Protocol ;
over Ethernet (PPPoE) is creature accustom in the network. PPPoE truncates the
Ethernet maximum transmission unit (MTU) 1492, and if the efficacious MTU
above the hosts (PCs) is no changed , the router in among the host and the
waiter can abort the TCP conferences. The ip tcp adjust-mss directive
specifies the MSS value on the intermediate router of the SYN packets to
avoid truncation .