L3DL Upper-Layer Protocol ConfigurationArrcus & IIJ5147 Crystal SpringsBainbridge IslandWA98110USrandy@psg.comArrcus2077 Gateway Place, Suite #400San JoseCA95119United States of Americakeyur@arrcus.comThis document uses the Layer-3 Liveness and Discovery protocol
to communicate the parameters needed to exchange inter-device Upper
Layer Protocol Configuration for upper-layer protocols such as the
BGP family.
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.Massive Data Centers (MDCs) which use upper-layer protocols such
as BGP4, BGP-LS, BGP-SPF, etc. may use the Layer-3 Liveness and
Discovery Protocol, L3DP, to
reveal the inter-device links of the topology. It is desirable for
devices to facilitate the configuration parameters of those upper
layer protocols to enable more hands-free configuration. This
document defines a new L3DP PDU to communicate these Upper-Layer
Protocol Configuration parameters.The reader is assumed to have read Layer-3 Discovery and Liveness
. The terminology and PDUs there
are assumed here.Familiarity with the BGP4 Protocol is
assumed. Familiarity with BGP-SPF, , might be useful. To communicate parameters required to configure peering and
operation of Upper-Layer Protocols at IP layer-3 and above, e.g.,
BGP sessions on a link, a neutral sub-TLV based Upper-Layer Protocol
PDU is defined as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 9 | Payload Length ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ | ULPC Type | AttrCount | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Attribute List ... | Sig Type | Signature Len ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ | Signature ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Type and Payload Length are defined in .ULPC Type: An integer denoting the type of the upper-layer
protocol
ReservedBGPReservedThe AttrCount is the number of attribute sub-TLVs in the
Attribute List.The Attribute List is a, possibly null, set of sub-TLVs
describing the configuration attributes of the specific upper-layer
protocol.An Attribute consists of a one octet Attribute Type, a one octet
Attribute Length of the number of octets in the Attribute, and a
Payload of arbitrary length up to 253 octets.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 1 | Attr Len | Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The parameters needed for BGP peering on a link are exchanged
in sub-TLVs within an Upper-Layer Protocol PDU. The following
describe the various sub-TLVs for BGP.The goal is to provide the minimal set of configuration
parameters needed by BGP OPEN to successfully start a BGP peering.
The goal is specifically not to replace or conflict with data
exchanged during BGP OPEN. Multiple sources of truth are a recipe
for complexity and hence pain.If there are multiple BGP sessions on a link, e.g., IPv4 and
IPv6, then multiple sets of BGP sub-TLVs MAY BE exchanged within
the BGP ULPC PDU or multiple BGP ULPC PDUs may be sent, one for
each address family.A peer receiving BGP ULPC PDUs has only one active BGP ULPC PDU
for an particular address family at any point in time; receipt of
a new BGP ULPC PDU for a particular address family replaces any
previous one.If there are one or more open BGP sessions, receipt of a new
BGP ULPC PDU does not affect these sessions and the PDU SHOULD be
discarded. If a peer wishes to replace an open BGP session, they
must first close the running session and then send a new BGP ULPC
PDU.As a link may have multiple encapsulations and multiple
addresses for an IP encapsulation, which address of which
encapsulation is to be used for the BGP session MUST be
specified.For each BGP peering on a link here MUST be one agreed
encapsulation, and the addresses used MUST be in the corresponding
L3DP IPv4/IPv6 Announcement PDUs. If the choice is ambiguous, an
Attribute may be used to signal preferences.If a peering address has been announced as a loopback,
i.e. MUST BE flagged as such in the L3DL Encapsulation PDU (see
Sec. 13.2), a two or three hop
BGP session will be established. Otherwise a direct one hop
session is used. The BGP session to a loopback will forward to
the peer's address which was marked as Primary in the L3DL
Encapsulation Flags, iff it is in a subnet which is shared with
both BGP speakers. If the primary is not in a common subnet, then
the BGP speaker MAY pick a forwarding next hop that is in a subnet
they share. If there are multiple choices, the BGP speaker SHOULD
have signaled which subnet to choose in an Upper-Layer Protocol
Configuration PDU Attribute.The Autonomous System number MUST be specified. If the AS
Number is less than 32 bits, it is padded with high order
zeros.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 1 | Attr Len = 6 | My ASN ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BGP IPv4 Address sub-TLV announces the sender's IPv4 BGP
peering source address to be used by the receiver. At least one
of IPv4 or IPv6 BGP source addresses MUST be announced.As usual, the BGP OPEN capability negotiation will determine
the AFI/SAFIs to be transported over the peering, see .
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 2 | Attr Len = 7 | My IPv4 Peering Address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ | Prefix Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BGP IPv6 Address sub-TLV announces the sender's IPv6 BGP
peering source address to be used by the receiver. At least one
of IPv4 or IPv6 BGP source addresses MUST be announced.As usual, the BGP OPEN capability negotiation will determine
the AFI/SAFIs to be transported over the peering, see .
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 3 | Attr Len = 19 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| My IPv6 Peering Address |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Prefix Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BGP Authentication sub-TLV provides any authentication
data needed to OPEN the BGP session. Depending on operator
configuration of the environment, it might be a simple MD5 key
(see ), the name of a key chain in a
KARP database (see ), or one of multiple
Authentication sub-TLVs to support hop.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 4 | Attr Len | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ BGP Authentication Data ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BGP session OPEN has extensive, and a bit complex,
capability negotiation facilities. In case one or more extra
attributes might be needed, the BGP Miscellaneous Flags sub-TLV
may be used. No flags are currently defined.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Type = 5 | Attr Len = 4 | Misc Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Misc Attrs:
GTSMMust be zeroThe GTSM flag indicates that the sender wishes to enable the
Generalized TTL Security Mechanism for
the session.All the Security considerations of apply to this PDU.As the ULPC PDU may contain keying material, see , it SHOULD BE signed.Any keying material in the PDU SHOULD BE salted and hashed.The BGP Authentication sub-TLV provides for provisioning MD5,
which is a quite weak hash, horribly out of fashion, and kills
puppies. But, like it or not, it has been sufficient against the
kinds of attacks BGP TCP sessions have endured. Soit is what BGP
deployments use.This document requests the IANA create a new entry in the L3DL PDU
Type registry as follows:
PDU
Code PDU Name
---- -------------------
9 ULPC
This document requests the IANA create a registry for L3DL ULPC
Type, which may range from 0 to 255. The name of the registry
should be L3DL-ULPC-Type. The policy for adding to the registry is
RFC Required per , either standards track or
experimental. The initial entries should be the following:
Value Name
----- -------------------
0 Reserved
1 BGP
2-255 Reserved