public class SREROSubobject
extends EROSubobject
An SR-ERO subobject consists of a 32-bit header followed by the SID
and the NAI associated with the SID. The SID is a 32-bit number.
The size of the NAI depends on its respective type, as described in
the following sections.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | ST | Flags |F|S|C|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NAI (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: SR-ERO Subobject format
The fields in the ERO Subobject are as follows:
Sivabalan, et al. Expires April 19, 2014 [Page 10]
Internet-Draft PCEP Extensions for Segment Routing October 2013
The 'L' Flag indicates whether the subobject represents a loose-hop
in the explicit route [RFC3209]. If this flag is unset, a PCC
MUST not overwrite the SID value present in the SR-ERO subobject.
Otherwise, a PCC MAY expand or replace one or more SID value(s) in
the received SR-ERO based on its local policy.
Type is the type of the SR-ERO Subobject. This document defines the
SR-ERO Subobject type. A new code point will be requested for the
SR-ERO Subobject from IANA.
Length contains the total length of the subobject in octets,
including the L, Type and Length fields. Length MUST be at least
4, and MUST be a multiple of 4.
SID Type (ST) indicates the type of information associated with the
SID contained in the object body. The SID-Type values are
described later in this document.
Flags is used to carry any additional information pertaining to SID.
Currently, the following flag bits are defined:
M: When this bit is set, the SID value represents an MPLS label
stack entry as specified in [RFC5462] where only the label
value is specified by the PCE. Other fields (TC, S, and TTL)
fields MUST be considered invalid, and PCC MUST set these
fields according to its local policy and MPLS forwarding rules.
C: When this bit as well as the M bit are set, then the SID
value represents an MPLS label stack entry as specified in
[RFC5462], where all the entry's fields (Label, TC, S, and TTL)
are specified by the PCE. However, a PCC MAY choose to
override TC, S, and TTL values according its local policy and
MPLS forwarding rules.
S: When this bit is set, the SID value in the subobject body is
null. In this case, the PCC is responsible for choosing the
SID value, e.g., by looking up its Traffic Engineering Database
(TED) using node/adjacency identifier in the subobject body.
F: When this bit is set, the NAI value in the subobject body is
null.
SID is the Segment Identifier.
NAI contains the NAI associated with the SID. Depending on the
value of ST, the NAI can have different format as described in the
following section.
- Author:
- Ayk