TCP 's MSS and MTU

MTU: Maxitum Transmission Unit MTU
MSS: Maxitum Segment Size Maximum segment size (even a literal translation is not agreeable, do not blow
I PP)
PPPoE: PPP Over Ethernet (in the ether Web hosting PPP protocol)
[analysis]
1st to give it the highest displacement element MTU, the maximum transmission unit of the practical and link layer protocol
near relationship, let us recollection cautiously EthernetII border framework
DMAC + SMAC + Type + Data + CRC
the Ethernet transmission of electrical limitations, each Ethernet frame has a minimum size of 64bytes
maximum can not exceed 1518bytes, for small to or greater than the limit of the Ethernet frame we can entire watch it as bad
data frame, the general Ethernet forwarding device will reject the data frame.
(Note: less than 64Bytes the Ethernet frame generally due to the conflicts of the It's called
Giant frame, which is due to line interference usually a wrong Ethernet port or generated)
EthernetII the Ethernet data frame is the largest 1518Bytes so planing to Ethernet frame header
(DMAC purpose of MAC addresses 48bit = 6Bytes + SMAC Source MAC address 48bit = 6Bytes + Type field
2bytes) 14Bytes end of CRC, and frame some of 4Bytes (everybody in this sector it is occasionally called
FCS) , then left the place carrying the upper layer protocol is the maximum Data field can only have 1500Bytes
we'll cry it the worth MTU. This is the web wafer protocol is very cared about the place, for the web floor protocol such as IP protocol
based on this value to make sure whether the data passed down from the top slice.
Like a carton can not install more than the afterward chunk of bread, we need to Cut the bread into pieces, packaged in several boxes inside a
kind of truth.
When two remote PC when joined,Lacoste R75 P2 Trainers, their data needs through a lot of routers and various network
to obtain on the end of the medium, the network MTU in the different medium are different, favor a long segment of the pipes,Lacoste Zepher MR2 Trainers, the pipes from the
essay of another thickness (MTU different) the maximum value of water through this water ought the water pipes from the navel of the smallest determination.
the upper network layer protocol for the purposes of (our TCP / IP protocol apartment case in point) they do not concern about the thickness of water
they calculate this is something the network layer. Network layer IP protocols will check off each of the data from the upper layer protocol
packet size, MTU according to the size of the machine to resolve whether to Fragmentation is the biggest drawback
diluted transmission performance, 1 can get the entities have been divided into several times to get, so the network layer
higher level (that is, the transport layer) is to be effected in this constantly Attention! Some high-level requirements fjust aboutme cause, I will
can not slice the bread, I want to complete the bread, it will be inside the IP packet header and a
tags: DF (Donot Fragment). So that when the IP packet in a large partition of the network (in
water surface) transmission, if there is fewer than the IP MTU packet case, the forwarding apparatus will be necessitated
drop the packet. And then returns an error message to the sender. This will often cause some communication problems on the
, but fortunately most of the network links are MTU1500 or greater than 1500.
for the UDP accession, the agreement itself is a connectionless protocol, the arrival of the packet has the correct order and is
get mini attention,Lacoste Running Trainers, it is generally fragmented UDP applications are no special requirements.
not the same for the purposes of TCP protocol, this protocol is connection-oriented protocol, TCP protocol for the purposes of
it is very concerned about the appearance of file packets transmitted in the order and if the peccadillo happened. Therefore, some TCP petitions
requirements --- tin not slice a slice (DF).
flowers two, with each one, so many the fable of MTU today we talk about the second knuckle --- PPPoE
above the so-called fleeing PPPoE is PPP over Ethernet protocol, it was curious , PPP protocol and Ethernet link layer protocol does not
is it? How a link layer above the link layer to go to another, do not they upgrade a network layer protocol
fragmentation. In fact, this is a misunderstanding: that of a layer protocol can only prop to the next level protocol.
Why would such a strange claim? This is because with broadband access (such as broadband access generally
Cable Modem or xDSL or Ethernet access) because the lack of authentication and accounting machinery
Ethernet and traditional carriers by PPP protocol for dial-up access services such as authentication and accounting, so apt
out such a freak: PPPoE. (For details see V PPPoE, a large and site of some other members introduced into
treatise, I ambition not instigate the inside out)
PPPoE sent benefits, it also brings some disadvantages, such as : secondary pack priceless, reducing the transmission
extravaganza, etc., not many of these disadvantages I said, the biggest downside is the PPPoE MTU smaller lead
Ethernet MTU is 1500, minus the end of the PPP's header packet overhead (8Bytes),Lacoste Gravitate Trainers, it becomes
1492.
definite whether the network among two hosts using PPPoE it will lead to some fragmentation of the application can not be
inability to communicate.
this time we need to accommodate to the host's MTU,Lacoste Radiate Croc Trainers, by reducing the host's MTU, so that we can smoothly
communicating. For TCP applications
lesson there is another solution.
third place today,Lacoste Tourelle Trainers, instantly requested a pig: MSS.
MSS maximum convey size of the acronym is a conception inside the TCP protocol.
MSS is the TCP packet transmissiin season to the maximum data segment. In order to achieve the best transmission performance
TCP protocol when a articulation is normally two sides to be refereed MSS value, the value accomplished
TCP protocol often accustomed when the MTU value instead of (need to subtract the IP packet header TCP data segment size 20Bytes and the
header 20Bytes) so often MSS to 1460. Communicating parties will be catered based on either the value of MSS should be identified as the smallest connection
maximum MSS value.
introduction to the three piglet s
we see behind inside the foreword, we imagine, if we in the middle of the router to each TCP connection
MSS correction which makes the largest MSS by the maximum value of PPPoE link with
header trailer will not exceed the PPPoE MTU size of 1492 so as not to cause no communication problems
So the above issues can be ip tcp adjust-mss 1452 to solution.
problem, of course can also modify the MTU PC-to solve.