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1.0.- LSA Format

  

LSA type
This extension makes use of the Opaque LSA type 10, which has an area flooding scope.
LSA ID
One new LSA is defined, the Traffic Engineering LSA (TELSA). TELSA describes routers, point-to-point links, and connections to multi-access networks.
TELSA uses type1 as its LSA ID. The instance field (remaing 24 bits) is an arbitrary value used to maintain multiple TELSAs. The LSA ID has no topological significance.
LSA Header
The TELSA starts with the standard LSA header:

The payload is called TLV as follows.
TLV Header
TLV consists of one or more nested Type/Length/Value (TLV) triplets for extensibility. The format is:

First field defines the type of TLV. This document defines types 1 and 2. The Length field defines the length of the value portion in octects (TLV having no value has a length of zero). TLV is padded to four-octets (32-bit) alignment, but padding is not included in the length field. Nested TLVs are also 32-bit aligned. Unrecognized types are ignored.
Two TLVs are defined as follows:
  1. Router Address
  2. Link
Router Address TLV (RATLV)
RATLV specifies a stable IP address of the advertising router that is always reachable if there is any connectivity to it; this is typically implemented as a "loopback address". The idea is that the address does not become unusable if any interface is down. In some other routing protocols this address is known as the "router ID".
RATLV is type 1, has a length of 4 bytes, and a value that is the four octets router IP address. It must appear in exactly one TELSA originated by the router.
Link TLV (LTLV)
LTLV describes a single link. It is constructed of a set of sub-TLVs without any ordering requeriment. Only one LTLV must be carried in each TELSA, allowing for fine granularity changes in topology.
LTLV is type 2 and its length is variable. The following LTLV's subtypes are defined in this document:
  1. Link Type (1 octet)
  2. Link ID (4 octets)
  3. Local interface IP address (4 octets)
  4. Remote interface IP address (4 octets)
  5. Traffic engineering metric (4 octets)
  6. Maximum bandwidth (4 octets)
  7. Maximum reservable bandwidth (4 octets)
  8. Unreserved bandwidth (32 octets)
  9. Administrative group (4 octets)

 

  

The Link Type and Link ID sub-TLVs are mandatory and must appear exactly once. All other sub-TLVs may occur at most once. Unrecognized sub-TLVs are ignored.
Various values of the indicated types are 32-bit IEEE Floating numbers and use this 32-bit format.
Next the different sub-TLVs are detailed:
  • Link Type
      Defines the type of link:
     
    1. Point-to-Point (P2P)
    2. Multi-access (MA)
    		 
  • Link ID
      Identifies the other end of the link. For P2P links, this is the router ID of the neighbor. For MA links, this is the interface address of the designated router.
         		  
  • Local interface IP address
      Specifies the IP address(es) of the interface corresponding to this link. If there are multiple local addresses, they are listed in this sub-TLV; then it is 4N octets in length, where N is the number of local addresses.
         		  
  • Remote interface IP address
      Specifies the IP address(es) of the neighbor's interface corresponding to this link. This, and the local address are used to discern multiple parallel links between systems. Being the link type multi-access, this field is set to 0.0.0.0; alternatively, an implementation may choose not to send this sub-TLV. Same as local address above, this TLV is 4N octets in length, where N is the number of neighbor addresses.
         		  
  • Traffic engineering metric
      Specifies the link metric for traffic engineering porpose, then it may be different that the standard OSPF link metric. Generally, this metric is assigned by a network administrator.
         		  
  • Maximum bandwidth
      Specifies the maximum bandwidth that can be used on this link, in the direction originating-LSA to its neighbor. It is an IEEE floating point number indicating the true capacity in bytes per second.
         		  
  • Maximum reservable bandwidth
      Specifies the maximum bandwidth that may be reserved on this link (same direction). It is an IEEE floating point number and should be user-configurable in bytes per second.
         		  
  • Unreserved bandwidth
      Specifies the amount of bandwidth not yet reserved classified in eight priority levels (0-7). All numbers are IEEE floating point numbers. The values, corresponding to the bandwidth that can be reserved at each level, are arranged in increasing order with the priority 0 occurring at the start of the sub-TLV, and priority 7 at the end. Initial values are all set to the Maximum reservable bandwidth in bytes per second.
         		  
  • Administrative group
      Specifies a 4-octet bit mask assigned by the network administrator. Each set bit corresponds to one group assigned to the interface. A link may belong to multiple groups. The least significant bit is referred to as "group 0" and the most significant bit is referred to as "group 31". The Administrative Group is also called Resource Class/Color.  
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