IGP Routing Protocol Extensions 257
• Support for identiﬁcation of the ER-LSP-based TE tunnel—New types of
Filter_Spec and Sender_Template objects are used to carry the tunnel identiﬁer. The
Session Object is also allowed to carry a null IP protocol number because an LSP
tunnel is likely to carry IP packets of many different protocol numbers.
• Support for new reservation removal algorithm—A new RSVP message, RESV
Tear Conﬁrm, is added. This message is added to reliably tear down an established TE
A summary of the RSVP objects that were added or modiﬁed to support TE is tabulated in
IGP Routing Protocol Extensions
The OSPF and IS-IS interior routing protocols have been extended to distribute link
resource attributes along with IP reachability information. IS-IS uses a new tuple,
consisting of a Type, a Length, and a Value commonly known as TLV
, and OSPF uses
Opaque Link State Advertisement (LSA)
to carry the link resource information. Note that
the existing dynamics of IS-IS and OSPF remain the same. Only now, OSPF and IS-IS send
the current constraint information whenever it needs to ﬂood the IP reachability
information. TE link admission control on a router requests reﬂooding of the constraint
information when it sees signiﬁcant changes in the available resource information, as
determined by the conﬁgured threshold values.
Table 10-3 New or Modiﬁed RSVP Objects for TE and Their Functions
RSVP Object RSVP Message Purpose
Label RESV Performs label distribution.
Label Request PATH Used to request label
Source Route PATH Speciﬁes the explicit source
Record Route PATH, RESV Used for diagnosis. This object
is used to record the path taken
by the RSVP message.
Session Attribute PATH Speciﬁes the holding priority
and setup priority.
Session PATH Can carry a null IP protocol
Sender_Template PATH Sender_Template and
Filter_Spec RESV Filter_Spec can carry a tunnel
identiﬁer to enable ER-LSP