Editing Internet Protocol (section)

==Link capacity and capability==
The dynamic nature of the Internet and the diversity of its components provide no guarantee that any particular path is actually capable of, or suitable for, performing the data transmission requested. One of the technical constraints is the size of data packets possible on a given link. Facilities exist to examine the [[maximum transmission unit]] (MTU) size of the local link and [[Path MTU Discovery]] can be used for the entire intended path to the destination.<ref>{{Cite book|last=Rishabh|first=Anand|url=https://books.google.com/books?id=XDJlDwAAQBAJ&q=The+dynamic+nature+of+the+Internet+and+the+diversity+of+its+components+provide+no+guarantee+that+any+particular+path+is+actually+capable+of%2C+or+suitable+for%2C+performing+the+data+transmission+requested.+One+of+the+technical+constraints+is+the+size+of+data+packets+possible+on+a+given+link.+Facilities+exist+to+examine+the+maximum+transmission+unit+%28MTU%29+size+of+the+local+link+and+Path+MTU+Discovery+can+be+used+for+the+entire+intended+path+to+the+destination.&pg=PA332|title=Wireless Communication|date=2012|publisher=S. Chand Publishing|isbn=978-81-219-4055-9|language=en|access-date=2020-12-11|archive-date=2024-06-12|archive-url=https://web.archive.org/web/20240612133919/https://books.google.com/books?id=XDJlDwAAQBAJ&q=The+dynamic+nature+of+the+Internet+and+the+diversity+of+its+components+provide+no+guarantee+that+any+particular+path+is+actually+capable+of%2C+or+suitable+for%2C+performing+the+data+transmission+requested.+One+of+the+technical+constraints+is+the+size+of+data+packets+possible+on+a+given+link.+Facilities+exist+to+examine+the+maximum+transmission+unit+%28MTU%29+size+of+the+local+link+and+Path+MTU+Discovery+can+be+used+for+the+entire+intended+path+to+the+destination.&pg=PA332#v=snippet&q=The%20dynamic%20nature%20of%20the%20Internet%20and%20the%20diversity%20of%20its%20components%20provide%20no%20guarantee%20that%20any%20particular%20path%20is%20actually%20capable%20of%2C%20or%20suitable%20for%2C%20performing%20the%20data%20transmission%20requested.%20One%20of%20the%20technical%20constraints%20is%20the%20size%20of%20data%20packets%20possible%20on%20a%20given%20link.%20Facilities%20exist%20to%20examine%20the%20maximum%20transmission%20unit%20(MTU)%20size%20of%20the%20local%20link%20and%20Path%20MTU%20Discovery%20can%20be%20used%20for%20the%20entire%20intended%20path%20to%20the%20destination.&f=false|url-status=live}}</ref>

The IPv4 internetworking layer automatically [[IP fragmentation|fragments]] a datagram into smaller units for transmission when the link MTU is exceeded. IP provides re-ordering of fragments received out of order.<ref>Siyan, Karanjit. ''Inside TCP/IP'', New Riders Publishing, 1997. {{ISBN|1-56205-714-6}}</ref> An IPv6 network does not perform fragmentation in network elements, but requires end hosts and higher-layer protocols to avoid exceeding the path MTU.<ref>{{cite web |title=IPv6 Fragmentation |author=Bill Cerveny |publisher=[[Arbor Networks]] |url=https://www.arbornetworks.com/blog/asert/ipv6-fragmentation/ |date=2011-07-25 |access-date=2016-09-10 |archive-date=2016-09-16 |archive-url=https://web.archive.org/web/20160916162637/https://www.arbornetworks.com/blog/asert/ipv6-fragmentation/ |url-status=live }}</ref>

The [[Transmission Control Protocol]] (TCP) is an example of a protocol that adjusts its segment size to be smaller than the MTU. The [[User Datagram Protocol]] (UDP) and ICMP disregard MTU size, thereby forcing IP to fragment oversized datagrams.<ref>{{Cite web|url = https://community.broadcom.com/symantecenterprise/communities/community-home/librarydocuments/viewdocument?DocumentKey=03c598ea-e171-47c9-8035-753ccd8bb36e&CommunityKey=1ecf5f55-9545-44d6-b0f4-4e4a7f5f5e68&tab=librarydocuments|title = Basic Journey of a Packet|date = 2 November 2010|access-date = 4 May 2014|website = [[Broadcom#Symantec enterprise security|Symantec]]|publisher = [[NortonLifeLock|Symantec]]|last = Parker|first = Don|archive-date = 20 January 2022|archive-url = https://web.archive.org/web/20220120044011/https://community.broadcom.com/symantecenterprise/communities/community-home/librarydocuments/viewdocument?DocumentKey=03c598ea-e171-47c9-8035-753ccd8bb36e&CommunityKey=1ecf5f55-9545-44d6-b0f4-4e4a7f5f5e68&tab=librarydocuments|url-status = live}}</ref>