Editing Ethernet (section)

==Error conditions==
===Switching loop===
{{main|Switching loop}}
A switching loop or bridge loop occurs in [[computer network]]s when there is more than one [[Layer 2]] ([[OSI model]]) path between two endpoints (e.g. multiple connections between two [[network switch]]es or two ports on the same switch connected to each other). The loop creates [[broadcast radiation|broadcast storms]] as broadcasts and [[multicast]]s are forwarded by switches out every [[Computer port (hardware)|port]], the switch or switches will repeatedly rebroadcast the broadcast messages flooding the network. Since the Layer 2 header does not support a ''[[time to live]]'' (TTL) value, if a frame is sent into a looped topology, it can loop forever.<ref>{{Cite web|title=Layer 2 Switching Loops in Network Explained|url=https://www.computernetworkingnotes.com/ccna-study-guide/layer-2-switching-loops-in-network-explained.html|access-date=January 8, 2022|website=ComputerNetworkingNotes|language=en-gb|archive-date=January 8, 2022|archive-url=https://web.archive.org/web/20220108032858/https://www.computernetworkingnotes.com/ccna-study-guide/layer-2-switching-loops-in-network-explained.html|url-status=live}}</ref>

A physical topology that contains switching or bridge loops is attractive for redundancy reasons, yet a switched network must not have loops. The solution is to allow physical loops, but create a loop-free logical topology using the SPB protocol or the older STP on the network switches.{{citation needed|date=April 2020}}

===Jabber===
A node that is sending longer than the maximum transmission window for an Ethernet packet is considered to be ''jabbering''. Depending on the physical topology, jabber detection and remedy differ somewhat.
* An [[Medium Attachment Unit|MAU]] is required to detect and stop abnormally long transmission from the [[Data terminal equipment|DTE]] (longer than 20–150&nbsp;ms) in order to prevent permanent network disruption.<ref>IEEE 802.3 ''8.2 MAU functional specifications''</ref>
* On an electrically shared medium (10BASE5, 10BASE2, 1BASE5), jabber can only be detected by each end node, stopping reception. No further remedy is possible.<ref>IEEE 802.3 ''8.2.1.5 Jabber function requirements''</ref>
* A repeater/repeater hub uses a jabber timer that ends retransmission to the other ports when it expires. The timer runs for 25,000 to 50,000 bit times for 1&nbsp;Mbit/s,<ref>IEEE 802.3 ''12.4.3.2.3 Jabber function''</ref> 40,000 to 75,000 bit times for 10 and 100&nbsp;Mbit/s,<ref>IEEE 802.3 ''9.6.5 MAU Jabber Lockup Protection''</ref><ref>IEEE 802.3 ''27.3.2.1.4 Timers''</ref> and 80,000 to 150,000 bit times for 1&nbsp;Gbit/s.<ref>IEEE 802.3 ''41.2.2.1.4 Timers''</ref> Jabbering ports are partitioned off the network until a carrier is no longer detected.<ref>IEEE 802.3 ''27.3.1.7 Receive jabber functional requirements''</ref>
* End nodes utilizing a MAC layer will usually detect an oversized Ethernet frame and cease receiving. A bridge/switch will not forward the frame.<ref>IEEE 802.1 ''Table C-1—Largest frame base values''</ref>
* A non-uniform frame size configuration in the network using [[jumbo frame]]s may be detected as jabber by end nodes.{{citation needed|date=April 2020}} Jumbo frames are not part of the official [[IEEE 802.3]] Ethernet standard.
* A packet detected as jabber by an upstream repeater and subsequently cut off has an invalid [[frame check sequence]] and is dropped.<ref>{{Citation |title=802.3-2012 - IEEE Standard for Ethernet |date=2012-12-28 |url=https://ecfsapi.fcc.gov/file/1050839507018/IEEE%20Standard%20for%20Ethernet.pdf |access-date=2015-07-05 |publisher=[[IEEE Standards Association]] |section=3.1.1 Packet format}}</ref>

===Runt frames===
* [[Ethernet frame#Runt frames|Runts]] are packets or frames smaller than the minimum allowed size. They are dropped and not propagated.<ref>{{Cite web|title=Troubleshooting Ethernet|url=http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html|access-date=May 18, 2021|website=Cisco|language=en|archive-date=March 3, 2021|archive-url=https://web.archive.org/web/20210303071756/https://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html|url-status=live}}</ref>