IS-IS Extensions To Support The IPv6 Compressed
Routing Header (CRH)Juniper NetworksElnath-Exora Business Park SurveyBangaloreKarnataka560103Indiapkaneria@juniper.netJuniper NetworksElnath-Exora Business Park SurveyBangaloreKarnataka560103Indiamrajesh@juniper.netJuniper NetworksElnath-Exora Business Park SurveyBangaloreKarnataka560103Indiashraddha@juniper.netJuniper Networks2251 Corporate Park DriveHerndon20171VirginiaUSArbonica@juniper.net
Routing Area
LSR Working GroupISISDraftSource nodes can use the IPv6 Compressed Routing Header (CRH) to
steer packets through a specified path. This document defines IS-IS
extensions that support the CRH.Source nodes can use the IPv6 Compressed Routing Header
(CRH) to steer packets through a specified path. This document
defines IS-IS extensions that support the CRH.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only
when, they appear in all capitals, as shown here.The Router CAPABILITY TLV MAY contain
exactly one CRH sub-TLV. The CRH sub-TLV indicates that the advertising
node can process the CRH.The CRH sub-TLV MAY contain sub-sub-TLVs. No sub-sub-TLVs are
currently defined. depicts the CRH sub-TLV. The CRH sub-TLV
contains the following fields:Type: 8 bits. CRH (value TBD by IANA. Suggested value is 30.)Length: 8 bits. Length of TLV data excluding the TLV header. MUST
be equal to 2 plus the length of sub-sub-TLVs (if any).Max CRH Len: 8 bits. Maximum CRH length supported by the
advertising node, measured in 8-octet units, not including the first
8 octets. See Note 1.Reserved: 8 bits. SHOULD be set to zero by sender. MUST be
ignored by receiver.Note 1: According to , all IPv6 Routings
header include a "Hdr Ext Len" field. That field specifies the length of
the Routing header in 8-octet units, not including the first 8 octets.
The same unit of measure was chosen for the "Max CRH Len" field in the
CRH sub-TLV.The following TLVs MAY contain one or more Prefix SID sub-TLVs:TLV-236 (IPv6 IP Reachability) .TLV-237 (Multitopology IPv6 IP Reachability) .The Prefix SID sub-TLV is valid only when its parent TLV
specifies a prefix length of 128. In this case, it binds the SID that it
contains to the prefix (i.e., IPv6 address) that its parent TLV
contains. This information is used to construct the mapping table
described in .When the parent TLV is propagated across level boundaries, the Prefix
SID sub-TLV SHOULD be kept. depicts the Prefix SID sub-TLV. It contains
the following fields:Type: 8 bits. Prefix SID sub-TLV (Value TBD by IANA. Suggested
value is 33.)Length: 8 bits. Length of TLV data excluding the TLV header,
measured in bytes.Reserved: 16 bits. SHOULD be set to zero by the sender. MUST be
ignored by the receiver.SID - Variable length. Segment Identifier.The following TLVs can contain one or more Adjacency SID
sub-TLVs:TLV-22 (Extended IS reachability) TLV-222 (Multitopology IS) TLV-23 (IS Neighbor Attribute) TLV-223 (Multitopology IS Neighbor Attribute) TLV-141 (inter-AS reachability information) The Adjacency SID sub-TLV is valid only when its parent TLV also
contains an IPv6 Neighbor Address
sub-TLVs. In this case, the SID contained by the Adjacency SID
sub-TLV is bound to the IPv6 address contained by the IPv6 Neighbor
Address sub-TLV. This information is used to construct the mapping table
described in . depicts the Adjacency SID sub-TLV. It
contains the following fields:Type: 8 bits. Adjacency SID sub-TLV (Value TBD by IANA. Suggested
value is 45.)Length: 8 bits. Length of TLV data excluding the TLV header,
measured in bytes.Flags: 8 bits. See below.Weight: 8 bits. The value represents the SID weight for the
purpose of load balancing.SID - Variable length. Segment Identifier. depicts Adjacency SID Sub-TLV flags. They
include the following:B-Flag: Backup flag. If set, the SID is eligible for
protection.S-Flag:. Set flag. When set, the S-Flag indicates that the SID
refers to a set of adjacencies (and therefore MAY be assigned to
other adjacencies as well).P-Flag: Persistent flag. When set, the P-Flag indicates that the
SID is persistently allocated, i.e., the SID value remains
consistent across router restart and/or interface flap.)In LAN subnetworks, the Designated Intermediate System (DIS) is
elected and originates the Pseudonode-LSP (PN-LSP) including all
neighbors of the DIS.When the CRH is used, each router in the LAN MAY advertise its
Adjacency SIDs of each of its neighbors. Since, on LANs, each router
only advertises one adjacency to the DIS (and doesn't advertise any
other adjacency), each router advertises the set of Adjacency SIDs (for
each of its neighbors) inside a newly defined sub-TLV part of the TLV
advertising the adjacency to the DIS (e.g.: TLV-22).The following TLVs can contain one or more LAN Adjacency SID
sub-TLVs:TLV-22 (Extended IS reachability) TLV-222 (Multitopology IS) TLV-23 (IS Neighbor Attribute) TLV-223 (Multitopology IS Neighbor Attribute) The LAN Adjacency SID sub-TLV binds an IPv6 address to a SID. The
sub-TLV contains both the IPv6 address and the SID. This information is
used to construct the mapping table described in . depicts the Adjacency SID sub-TLV. It
contains the following fields:Type: 8 bits. Adjacency SID sub-TLV (Value TBD by IANA. Suggested
value is 46.)Length: 8 bits. Length of TLV data excluding the TLV header,
measured in bytes.Flags: 8 bits. See below.Weight: 8 bits. The value represents the SID weight for the
purpose of load balancing.Neighbor System-ID: 6 bytes. IS-IS System-ID of length "ID
Length" as defined in .SID - Variable length. Segment Identifier. depicts Adjacency SID Sub-TLV flags. They
include the following:B-Flag: Backup flag. If set, the SID is eligible for
protection.S-Flag:. Set flag. When set, the S-Flag indicates that the SID
refers to a set of adjacencies (and therefore MAY be assigned to
other adjacencies as well).P-Flag: Persistent flag. When set, the P-Flag indicates that the
SID is persistently allocated, i.e., the SID value remains
consistent across router restart and/or interface flap.)IANA is requested to add a new sub-TLV in the Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY TLV)
Registry .Value - TBD by IANA. (Suggested value is 30).Description - CRHThis document requests the creation of a new IANA managed
registry for sub-sub-TLVs of the CRH sub-TLV. The registration
procedure is "Expert Review" as defined in .
Suggested registry name is "sub-sub-TLVs for CRH sub-TLV". No sub-
sub-TLVs are defined by this document except for the reserved
value.0 - Reserved1 - 255 UnassignedIANA is requested to add a new entry in the Sub-TLVs for TLVs 135, 235, 236, and 237 (Extended
IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach
TLVs) Registry .Value - TBD by IANA. (Suggested value is 33)Description - Prefix SID135 - N136 - N236 - Y237 - YReference - This document.IANA is requested to add the following entries in the Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223
(Extended IS reachability, IS Neighbor Attribute, L2 Bundle Member
Attributes, inter-AS reachability information, MT-ISN, and MT IS
Neighbor Attribute TLVs) Registry .The first entry follows:Value - TBD by IANA (Suggested value is 45).Description - Adjacency SID22 - Y23 - Y25 - N141 - Y222 - Y223 - YReference - This document.The second entry follows:Value - TBD by IANA (Suggested value is 46)Description - LAN Adjacency SID22 - Y23 - Y25 - N141 - N222 - Y223 - YReference - This document.Security concerns for IS-IS are addressed in , , and .Thanks to Ram Santhanakrishnan for his comments on this document.Intermediate system to Intermediate system routing
information exchange protocol for use in conjunction with the
Protocol for providing the Connectionless-mode Network Service (ISO
8473)IANASub-TLVs for TLV 242 (IS-IS Router CAPABILITY TLV)IANASub-TLVs for TLVs 135, 235, 236, and 237 (Extended IP
reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach
TLVs)IANASub-TLVs for TLVs 22, 23, 25, 141, 222, and 223 (Extended IS
reachability, IS Neighbor Attribute, L2 Bundle Member Attributes,
inter-AS reachability information, MT-ISN, and MT IS Neighbor
Attribute TLVs)IANA