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hellopakete [2009/09/13 14:37] (current)
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 +===== Hello packets  =====
 +
 +
 +
 +In the following chapter the structure of the different IS-IS hello packets will be described. Further more the amount of IS-IS packets will be treated.
 +Hello packets will be used to set up and manage the neighbourhood.
 +
 +===== The different hello packets:  =====
 +
 +In principle we can distinguish IS-IS hello (IIH) PDUs into three types of packets.
 +
 +=== IS-IS: ===
 +
 +We distinguish between
 +
 +  * IS-IS point-to-point hello PDUs
 +  * IS-IS hello PDUs LAN level 1
 +  * IS-IS hello PDUs LAN Level 2
 +
 +----
 +
 +{{pdu_hello_lan_l1l2.jpg}}
 +
 +Table 4: IS-IS hello PDU LAN L1L2
 +
 +----
 +
 +{{pdu_hello_point_to_point.jpg}}
 +
 +Table 5: IS-IS hello point-to-point PDU
 +
 +----
 +__Meaning of the hello PDU-header fields:__
 +
 +{{pdu_hello_description.jpg}}
 +
 +Table 6: Description of the Hello-PDU-header fields
 +----
 +
 +===== ES-IS: =====
 +
 +
 +The hello PDUs are used in ES-IS to communicate between an End-System and an Intermediate-System. These hello packets guarantee the establishment of a connection and the capability of being reached between a host and an Intermediate-System.
 +Hello packets use special multicast network addresses to prevent other systems in a network from getting overloaded. These addresses are "all hosts" and "all routers".     
 +
 +It can be distinguished between ISH and ESH:
 +
 +  * With ISH packets the Intermediate-System transmits messages only to hosts in the same subnetwork. ISHs contain a physical address and the identity number of the IS.
 +  * With ESH packets the host transmits messages only to Intermediate-Systems in the same subnetwork. ESHs contain a NSAP-Address, a physical address and the duration of validity of the information.
 +
 +Hello PDUs are transmitted at regular intervals. As a consequence the network is always up-to-date.
 +
 +----
 + __Sources:__
 +
 +
 +Abe Martey, IS-IS Network Design Solution, Kap. 3
 +
 +CCNP 1 Ver. 3.1 Kap.7
 +
 +
 +
 +
 +
 +
 +
 
hellopakete.txt · Last modified: 2009/09/13 14:37 (external edit)
 
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