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RFC 3031, "Multiprotocol Label Switching Architecture", January 2001

Source of RFC: mpls (rtg)

Errata ID: 6450
Status: Reported
Type: Technical
Publication Format(s) : TEXT

Reported By: Duane L. Anderson
Date Reported: 2021-03-03

Throughout the document, when it says:

2.2. Terminology defines the terms

        Layer 2         layer 2 the protocol layer under layer 3 
                        (which therefore offers the services used by layer 3)
        Layer 3         the protocol layer at which IP and its associated 
                        routing protocols operate

2.3. Acronyms and Abbreviations defines 

        L2              Layer 2
        L3              Layer 3

However, in 3.14. Scope and Uniqueness of Labels, 4.3. Label Stacks and Implicit Peering, 4.5. LSP Trees as Multipoint-to-Point Entities, and 4.6. LSP Tunneling between BGP Border Routers, L1, L2 and L3 are used as differentiating names for certain labels attached to packets. 

Of course, in 3.23. Time-to-Live (TTL), L2 is used to refer to layer 2 frame header and to a layer 2 switch, which is correct. 

However, in 4.3. Label Stacks and Implicit Peering, the term level 1 is used to refer to the LIFO (stack) ordinal number of a label then named L1 and given a protocol layer 2 protocol of layer 2 (L2). Furthermore, labels named L2 and then L1 are pushed onto the stack of labels prefixed to the packet. To top it all off the packet's stack attribute as protocol level 2 (L2). 

Of course, in 3.17. LSP Next Hop, 4.1.5. The Implicit NULL Label, 5.1.1.2. PushConditional, 5.1.1.4. PulledConditional, 5.1.2.2. RequestWhenNeeded, 5.1.3. Upstream LSR: NotAvailable Procedure, 5.1.4. Upstream LSR: Release Procedure, 5.1.4.2. NoReleaseOnChange, 5.1.5. Upstream LSR: labelUse Procedure, 5.2.2. Schemes for LSRs that do not Support Label Merging, refer to L3 meaning level 3, which is correct. 

Furthermore, in 3.1. Labels, 3.2. Upstream and Downstream LSRs, 3.4. Label Assignment and Distribution, 3.5. Attributes of a Label Binding, 3.14. Scope and Uniqueness of Labels, 4.1.2.2. Distributing Labels, 5.1.5. Upstream LSR: labelUse Procedure, 5.1.5.2. UseIfLoopNotDetected, 5.1.6. Downstream LSR: Withdraw Procedure

 * L is used as a name for a certain label attached to packet, and 

 * L is used as a arbitrary value assigned to a label attached to a packet

It should say:

I have not provided any corrected text as I've literally "highlighted" 44 places in a pdf format file of RFC 3031 that are ambiguous. 

As there is no facility to attach a file to this Report Errata for RFC3031 form, i will send the file commented pdf file upon request. 

Notes:

My rational for highlighting (no pun intended) these problems is that the overloading of the L2, L3 abbreviations layer 2 and layer 3, with the names L1, L2, L3 and L for labels, plus the use of L1 and L2 as indexed names for the ordinal position of a label prefixed to a payload, then to use L2 and L3 as to actually mean layer 2 and layer is uh ... sloppy.

Honestly, I can't understand how RFC 3031 has been posted for twenty years and that it is on the Standards Track and no one has found these problems.

Its similar to when someone publishes a mathematical treatise and use the same set of variable names {x, y, z, t} over and over again in different contexts spread throughout the paper. Its intractable and practically gibberish.

I apologize if my criticism is harsh regarding this problem but I spent a considerable amount of my time reading this document trying to make sense of it before I realized that the fault is not mine but it is of the document.

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