From 12f1e3c974ac011334246b3ada607dfd8cc37c87 Mon Sep 17 00:00:00 2001 From: Randy Bush Date: Fri, 19 Apr 2019 14:03:34 -0700 Subject: [PATCH] refs and other russ details --- draft-ietf-lsvr-l3dl.xml | 114 +++++++++++++++++++++++---------------- 1 file changed, 69 insertions(+), 45 deletions(-) diff --git a/draft-ietf-lsvr-l3dl.xml b/draft-ietf-lsvr-l3dl.xml index 0aff603..23bd0d1 100644 --- a/draft-ietf-lsvr-l3dl.xml +++ b/draft-ietf-lsvr-l3dl.xml @@ -56,17 +56,13 @@ - Used in Massive Data Centers (MDCs), BGP-SPF and similar - protocols need IP neighbor discovery, logical link encapsulation - data, and Layer 2 liveness. The Layer 3 Discovery and Liveness - protocol provides discovery of the neighbor on a logical link, - exchanges supported encapsulations (IPv4, IPv6, ...) with neighbors, - discovers encapsulation addresses (Layer 3 / MPLS identifiers), and - provides layer 2 liveness checking. The interface data are pushed - directly to a BGP API (for LSVR), obviating the need for centralized - topology distribution architectures. This protocol is intended to - be more widely applicable to other upper layer routing protocols - which need logical link discovery and characterisation. + In Massive Data Centers (MDCs), BGP-SPF and similar routing + protocols are used to build topology and reachability databases. + These protocols need to discover IP Layer 3 attributes of links, + such as logical link IP encapsulation abilities, IP neighbor address + discovery, and link liveness. The Layer 3 Discovery and Liveness + protocol specified in this document collects these data, which are + then disseminated using BGP-SPF and similar protocols. @@ -93,11 +89,12 @@ deal with scaling, while BGP-SPF provides massive scale-out without centralization using a tried and tested scalable distributed control - plane, offering a scalable routing solution in Clos and similar - environments. But BGP-SPF and similar higher level device-spanning - protocols, e.g. , need - logical link state and addressing data from the network to build the - routing topology. They also need prompt reaction to (logical) link + plane, offering a scalable routing solution in Clos and similar environments. But + BGP-SPF and similar higher level device-spanning protocols, + e.g. , need logical link + state and addressing data from the network to build the routing + topology. They also need prompt reaction to (logical) link failure. Layer 3 Discovery and Liveness (L3DL) provides brutally simple @@ -140,20 +137,21 @@ target="I-D.ietf-lsvr-bgp-spf"/>. A hierarchic subset of a crossbar switch topology commonly used in data centers. - The L3DL content of a single Ethernet + The L3DL content of a single Layer 2 frame. A full L3DL PDU may be packaged in multiple Datagrams. Address Family Indicator and Subsequent Address Family Indicator (AFI/SAFI). I.e. classes of layer 2.5 and 3 addresses such as IPv4, IPv6, MPLS, ... - An Ethernet Layer 2 packet. + A Layer 2 packet. A logical connection between two logical ports on two devices. E.g. two VLANs between the same two ports are two links. Logical Link Endpoint Identifier, the unique identifier of one end of a logical link, see . - Media Access Control Address, - essentially an Ethernet address, six octets. See 48-bit Layer 2 addresses are assumed + since they are used by all widely deployed Layer 2 network + technologies of interest, especially Ethernet. See . Massive Data Center, commonly thousands of TORs. @@ -294,9 +292,9 @@ endpoint(s) reachable from an LLEI. The HELLO and OPEN, , PDUs, which are used - to discover and exchange detailed LLEIs, are mandatory; other PDUs - are optional; though at least one encapsulation MUST be agreed at - some point. + to discover and exchange detailed LLEIs, and the ACK/ERROR PDU, + are mandatory; other PDUs are optional; though at least one + encapsulation MUST be agreed at some point. The following is a ladder-style sketch of the L3DL protocol exchanges: @@ -403,8 +401,9 @@ Datagram, it is set to one. 0..127, a monotonically increasing - value, modulo 128, see . Note that this - does not limit an L3DL PDU to 128 frames. + value, modulo 128, see which starts at 0 + for each PDU. Note that this does not limit an L3DL PDU to 128 + frames. Total number of octets in the Datagram including all payloads and fields. @@ -488,7 +487,7 @@ uint32_t sbox_checksum_32(const uint8_t *b, const size_t n) The basic L3DL application layer PDU is a typical TLV (Type Length Value) PDU. It includes a signature to provide optional integrity and authentication. It may be broken into multiple - Datagrams, see + Datagrams, see .