Signalling Protocols -- Don't know how useful this is
LDP -- Related to MPLS
Q.17 . What are the routing extensions available for traffic engineering ? Ans . Routing extensions available for traffic engineering are as follows: It is Extensions to the Intermediate System to Intermediate System ( IS- IS ) protocol to support Traffic Engineering ( TE). The IS - IS protocol is specified in ISO 10589 , with extensions for supporting IPv4. Each Intermediate System (IS) ( router) advertises one or more IS -IS Link State Protocol Data Units ( LSPs) with routing information. Each LSP is composed of a fixed header and a number of tuples, each consisting of a Type , a Length and a Value . Such tuples are commonly known as TLVs and are a good way of encoding information in a flexible and extensible format.s The Extended IS Reachability TLV : The existing IS reachability ( TLV type 2 , defind in ISO 10589) contains information about a series of IS neighbors. For each neighbor, there is a structure that contains the default metric, the delay, the monetary cost, the reliability and the 7- octet ID of the adjacent neighbor. Of this information , the default metric is commonly used . The default metric is currently one octet , with one bit used to indicate whether the metric is internal or external and one bit that was originally unused , but which was later defined by [ RFC5302] to be the up /down bit. The remaining 6 bits are used to store the actual metric , resulting in a possible metric range of 0-63 . The remaining three metrics ( delay, monetary cost and reliability ) are not commonly implemented and reflect unused overhead in the TLV. The neighbor is identified by its system ID, typically 6 octets, plus one octet indicating the pseudonode number . Thus , the existing TLV consumes 11 octets per neighbor , with 4 octets for metric and 7 octets for neighbor identification. To indicate multiple adjacencies , this structure is repeated within the IS reachability TLV . Because the TLV is limited to 255 octets of content , a single TLV can describe up to 23 neighbors . The IS reachability TLV can be repeated within the LSP fragments to describe further neighbors . The proposed extended IS reachability TLV contains a new data structure , consisting of: 7 octets system ID ad pseudonode number . IS -IS Extensions for Traffic Engineering;( 1 ) It is Extensions to the Intermediate System to Intermediate System 3 octets of default metric. 1 octet of length of sub -TLVs 0-244 octets of sub -TLVs, where each ub-TLV consists of a sequence of 1 octet of sub-type 1 octet of length of the Value field of the sub-TLV 0-242 octets of value . Thus , if no sub- TLV are used, the new encoding requires 11 octets and can contain up to 23 neighbors . While the encoding allows for 255 octets of sub-TLVs , the maximum value cannot fit in the overall IS reachability TLV . Extensions to the OSPF protocol version 2 : The extensions provide a way of describing the traffic engineering topology (including bandwidth and administrative constraints) and distributing this information within a given OSPF area. This topology does not necessarily match the regular routed topology , through this proposal depends on Network LSAs to describe multi - access links. Furthermore, no changes have been made to the operation of OSPFv2 flooding, in particular, if non - TE capable nodes exist in the topology, they MUST flood TE LSAs as any other type 10 ( area local scope) Opaque LSAS . The information made available by these extensions can be used to build an extended link state database just as router LSAs are used to build a "regular" link state database , the difference is that the extended link state database ( referred to below as the traffic engineering database ) has additional link attributes . Uses of the traffic engineering database include: Monitoring the extended link attributes . Local constraint - based source routing and Global traffic engineering