Subject: Questions on MPLS and Diff-Serv

From: "Wayne W. Szeto" <[email-masked]>
Date: Sun, 20 May 2001 23:57:06 -0400 (EDT)

After reading the Internet draft "Requirement for support of 
Diff-Serv-aware MPLS traffic Engieering", I have some questions about
Diff-Serv in MPLS.  

1.  The Internet draft stated a bandwidth reservation scheme which
reserves bandwidth in a per class-type manner, and it also mentioned a
possible enhancement of the above scheme which allows borrowing of
bandwidths between class types.  The "borrowing" part leads me to think
that only the reserved amount of bandwidth will be used for a certain
class-type packet even though there are available unreserved bandwidth for
other class types.  For example, if a link's capacity is 10Mbps and 3Mbps
has been reserved by class type A, and the rest of the bandwidth is
unreserved, then even if the incoming class type A packet rate is more
than 3Mbps, only 3Mbps of the link bandwidth will be used.  Is this true?  

2. On ch6 (p9) of the draft, it says: "If the Diff-Serv packet scheduling
mechanisms are configured statically, it is possible, however, that the
allocation of resources by Diff-Serv-aware Traffic Engineering for
reservation purposes will not always correspond with the resources
allocated in the packet scheduler."  What does configuring packet
scheduling statiscally mean?  My guess is that the packet scheduler is
configure with a reserved bandwidth value during LSP setup, and this value
will not change unless an LSP modification process is performed.