Diff-Serv Traffic Engineering
Page 110 7450 ESS MPLS Guide
Russian Doll Model
The RDM model is defined using the following equations:
SUM (Reserved (CTc)) <= BCb,
where the SUM is across all values of c in the range b <= c <= (MaxCT - 1), and BCb is the
bandwidth constraint of CTb.
BC0= Max-Reservable-Bandwidth, so that:
SUM (Reserved(CTc)) <= Max-Reservable-Bandwidth,
where the SUM is across all values of c in the range 0 <= c <= (MaxCT - 1)
An LSP of class-type CTc, setup priority p, holding priority h (h=<p), and bandwidth B is
admitted into a link if the following condition is satisfied:
B <= Unreserved Bandwidth for TE-Class[i],
where TE-Class [i] maps to < CTc, p > in the definition of the TE classes on the node. The
bandwidth reservation is effected at the holding priority, i.e., in TE-class [j] = <CTc, h>. Thus, the
reserved bandwidth for CTc and the unreserved bandwidth for the TE classes using CTc are
updated as follows:
Reserved(CTc) = Reserved(CTc) + B
Unreserved TE-Class [j] = Unreserved (CTc, h) = Min [
BCc - SUM (Reserved (CTb, q) for 0<=q <= h, c <= b <= 7,
BC(c-1) – SUM (Reserved (CTb, q) for 0<=q <= h, (c-1) <= b <= 7,
…….
BC0 - SUM (Reserved (CTb, q) for 0<=q <= h, 0 <= b <= 7]
Unreserved TE-Class [i] = Unreserved (CTc, p) = Min [
BCc - SUM (Reserved (CTb, q) for 0<=q <= p, c <= b <= 7,
BC(c-1) – SUM (Reserved (CTb, q) for 0<=q <= p, (c-1) <= b <= 7,
…….
BC0 - SUM (Reserved (CTb, q) for 0<=q <= p, 0 <= b <= 7]
The same is done to update the unreserved bandwidth for any other TE class making use of the
same CTc. These new values are advertised to the rest of the network at the next IGP-TE flooding.
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