# ExaBGP RFC Implementation

This document lists all RFC (Request for Comments) specifications implemented in ExaBGP, organized by functional area.

**Last Updated**: 2025-11-09

## Table of Contents
- [Core BGP Protocol](#core-bgp-protocol)
- [BGP Capabilities](#bgp-capabilities)
- [Multiprotocol Extensions](#multiprotocol-extensions)
- [Communities](#communities)
- [VPN and MPLS](#vpn-and-mpls)
- [EVPN (Ethernet VPN)](#evpn-ethernet-vpn)
- [FlowSpec](#flowspec)
- [BGP-LS (Link State)](#bgp-ls-link-state)
- [Segment Routing](#segment-routing)
- [Error Handling and Administrative](#error-handling-and-administrative)
- [Operational Features](#operational-features)
- [Internet Drafts](#internet-drafts)

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## Core BGP Protocol

### <a name="rfc-4271-bgp-4"></a>RFC 4271 - A Border Gateway Protocol 4 (BGP-4)
**Status**: Fully Implemented

The foundational BGP-4 specification defining:
- BGP finite state machine (FSM)
- Message types (OPEN, UPDATE, NOTIFICATION, KEEPALIVE)
- Path attributes
- Route selection process
- Hold time and keepalive mechanisms

**Implementation**: Core protocol implementation across all modules.

---

## BGP Capabilities

### RFC 2918 - Route Refresh Capability for BGP-4
**Status**: Fully Implemented

Allows BGP speakers to request re-advertisement of routes without tearing down the session.

**Implementation**: `src/exabgp/bgp/message/refresh.py`

### RFC 4724 - Graceful Restart Mechanism for BGP
**Status**: Fully Implemented

Enables BGP sessions to maintain forwarding state during control plane restarts.

**Implementation**: `src/exabgp/bgp/message/open/capability/graceful.py`

### RFC 4893 - BGP Support for Four-octet AS Number Space
**Status**: Fully Implemented

Support for 4-byte Autonomous System Numbers (ASNs), extending the 2-byte ASN space.

**Implementation**:
- `src/exabgp/bgp/message/open/capability/capability.py`
- AS4_PATH attribute support

### RFC 5492 - Capabilities Advertisement with BGP-4
**Status**: Fully Implemented

Framework for advertising optional capabilities during BGP session establishment.

**Implementation**: `src/exabgp/bgp/message/open/capability/`

### RFC 6286 - Autonomous-System-Wide Unique BGP Identifier for BGP-4
**Status**: Fully Implemented

Relaxes BGP identifier requirements for AS-wide uniqueness.

**Implementation**: `src/exabgp/bgp/message/open/capability/negotiated.py`

### RFC 7313 - Enhanced Route Refresh Capability for BGP-4
**Status**: Fully Implemented

Adds Beginning-of-Route-Refresh (BoRR) and End-of-Route-Refresh (EoRR) markers.

**Implementation**: `src/exabgp/bgp/message/refresh.py`

### RFC 7911 - Advertisement of Multiple Paths in BGP (ADD-PATH)
**Status**: Fully Implemented

Allows BGP to advertise multiple paths for the same address prefix without new sessions.

**Supported Address Families**:
- IPv4 Unicast/Multicast
- IPv6 Unicast/Multicast
- VPNv4/VPNv6
- FlowSpec (IPv4/IPv6)
- VPLS

**Not Yet Supported**:
- EVPN
- MVPN
- Route Target Constraint (RTC)
- BGP-LS

**Implementation**:
- `src/exabgp/bgp/message/open/capability/addpath.py`
- Path information encoding/decoding in NLRI modules
- `src/exabgp/bgp/neighbor.py` (addpath configuration)

### RFC 9072 - Extended Optional Parameters Length for BGP OPEN Message
**Status**: Fully Implemented

Extends BGP OPEN message to support longer optional parameters (>255 bytes).

**Implementation**: `src/exabgp/bgp/message/open/capability/capabilities.py`

---

## Multiprotocol Extensions

### RFC 2545 - Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing
**Status**: Fully Implemented

Enables BGP to carry IPv6 routing information.

**Implementation**: IPv6 address family support

### RFC 4760 - Multiprotocol Extensions for BGP-4
**Status**: Fully Implemented

Core multiprotocol BGP (MP-BGP) specification enabling BGP to carry multiple address families:
- IPv4/IPv6 Unicast and Multicast
- VPNv4/VPNv6
- EVPN
- BGP-LS
- FlowSpec

**Implementation**:
- `src/exabgp/bgp/message/update/attribute/mprnlri.py` (MP_REACH_NLRI)
- `src/exabgp/bgp/message/update/attribute/mpurnlri.py` (MP_UNREACH_NLRI)
- `src/exabgp/protocol/family.py` (AFI/SAFI definitions)

### RFC 5549 - Advertising IPv4 Network Layer Reachability Information with an IPv6 Next Hop
**Status**: Fully Implemented

Allows IPv4 prefixes to be advertised with IPv6 next hops (extended next-hop capability).

**Implementation**: `src/exabgp/bgp/message/open/capability/capability.py`

---

## Communities

### RFC 1997 - BGP Communities Attribute
**Status**: Fully Implemented

Standard 32-bit BGP communities for route tagging and policy application.

**Format**: AS:Value (16-bit:16-bit)

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/`

### RFC 3765 - NOPEER Community for Border Gateway Protocol (BGP) Route Scope Control
**Status**: Fully Implemented

Well-known community (0xFFFFFF04) indicating routes should not be advertised to peers.

**Implementation**: Community attribute support

### RFC 4360 - BGP Extended Communities Attribute
**Status**: Fully Implemented

64-bit extended communities providing additional route tagging capabilities:
- Route Target (RT)
- Route Origin (RO)
- Traffic engineering
- Layer 2 attributes
- Encapsulation

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/extended/`

### RFC 5668 - 4-Octet AS Specific BGP Extended Community
**Status**: Fully Implemented

Extended communities supporting 4-byte ASNs.

**Implementation**: Extended community modules

### RFC 5701 - IPv6 Address Specific BGP Extended Community Attribute
**Status**: Fully Implemented

Extended communities using IPv6 addresses instead of IPv4.

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/extended/`

### RFC 7153 - IANA Registries for BGP Extended Communities
**Status**: Fully Implemented

Registry management for extended community types.

**Implementation**: Extended community type definitions

### RFC 7999 - BLACKHOLE Community
**Status**: Fully Implemented

Well-known community (0xFFFF029A) for blackhole filtering, commonly used in DDoS mitigation.

**Implementation**: Community attribute support

### RFC 8092 - BGP Large Communities Attribute
**Status**: Fully Implemented

96-bit (12-byte) communities supporting large ASN values and flexible policy application.

**Format**: ASN:Value1:Value2 (32-bit:32-bit:32-bit)

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/large/`

---

## VPN and MPLS

### RFC 2385 - Protection of BGP Sessions via the TCP MD5 Signature Option
**Status**: Fully Implemented

TCP MD5 authentication for BGP sessions (80-byte password limit).

**Implementation**: `src/exabgp/data/check.py`, `src/exabgp/configuration/neighbor/`

### RFC 3107 - Carrying Label Information in BGP-4
**Status**: Fully Implemented

Enables BGP to carry MPLS label information for labeled unicast routes.

**Implementation**: NLRI MPLS label support

### RFC 4364 - BGP/MPLS IP Virtual Private Networks (VPNs)
**Status**: Fully Implemented

Core L3VPN specification including:
- VPNv4/VPNv6 address families
- Route Distinguisher (RD) types: Type 0, Type 1, Type 2
- Route Target extended communities

**Implementation**:
- `src/exabgp/bgp/message/update/nlri/ipvpn.py`
- `src/exabgp/protocol/family.py` (MPLS_VPN SAFI)

### RFC 4659 - BGP-MPLS IP Virtual Private Network (VPN) Extension for IPv6 VPN
**Status**: Fully Implemented

Extends L3VPN to support IPv6 (VPNv6).

**Implementation**: IPv6 VPN NLRI support

### RFC 4761 - Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling
**Status**: Fully Implemented

BGP-based VPLS for Layer 2 VPN services.

**Implementation**:
- `src/exabgp/protocol/family.py` (VPLS SAFI)
- `src/exabgp/bgp/message/update/attribute/community/extended/l2info.py`

### RFC 4762 - Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling
**Status**: Documented

LDP-based VPLS (related to BGP VPLS implementation).

### RFC 5512 - The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute
**Status**: Fully Implemented

Tunnel encapsulation for BGP routes (GRE, IPsec, etc.).

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/extended/encapsulation.py`

### RFC 6514 - BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs
**Status**: Fully Implemented

Multicast VPN (MVPN) support including:
- MVPN NLRI types
- PMSI (Provider Multicast Service Interface) tunnel attribute

**Implementation**:
- `src/exabgp/protocol/family.py` (MCAST_VPN SAFI)
- `src/exabgp/bgp/message/update/attribute/pmsi.py`

---

## EVPN (Ethernet VPN)

### RFC 7432 - BGP MPLS-Based Ethernet VPN
**Status**: Fully Implemented

Complete EVPN implementation for Layer 2 VPN services:
- EVPN route types (1-5)
- Ethernet Segment Identifier (ESI)
- MAC/IP advertisement
- Inclusive multicast
- Ethernet auto-discovery

**Implementation**:
- `src/exabgp/bgp/message/update/nlri/evpn/`
- `src/exabgp/bgp/message/update/attribute/community/extended/mac_mobility.py`

---

## FlowSpec

### RFC 5575 - Dissemination of Flow Specification Rules
**Status**: Fully Implemented

BGP FlowSpec for distributing traffic filtering rules:
- IPv4/IPv6 FlowSpec
- Flow component matching (destination, source, protocol, port, etc.)
- Traffic filtering actions (rate-limit, redirect, mark, discard)

**Implementation**:
- `src/exabgp/bgp/message/update/nlri/flow.py`
- `src/exabgp/protocol/family.py` (FLOW_IP, FLOW_VPN SAFIs)
- `src/exabgp/bgp/message/update/attribute/community/extended/traffic.py`

### RFC 7674 - Clarification of the Flowspec Redirect Extended Community
**Status**: Fully Implemented

Redirect to VRF using 4-octet AS numbers for FlowSpec.

**Implementation**: `src/exabgp/bgp/message/update/attribute/community/extended/traffic.py`

---

## BGP-LS (Link State)

### RFC 7752 - North-Bound Distribution of Link-State and Traffic Engineering Information Using BGP
**Status**: Fully Implemented

BGP-LS for distributing IGP topology and TE information:
- Node descriptors and attributes
- Link descriptors and attributes
- Prefix descriptors and attributes
- OSPF and IS-IS topology information

**Implementation**:
- `src/exabgp/bgp/message/update/nlri/bgpls/`
- `src/exabgp/bgp/message/update/attribute/bgpls/`
- `src/exabgp/protocol/family.py` (BGPLS, BGPLS_VPN SAFIs)

**Note**: Current implementation supports receive-only mode for BGP-LS advertisements.

**Related Support RFCs** (via BGP-LS):
- **RFC 2328** - OSPF Version 2
- **RFC 4915** - Multi-Topology Routing in OSPF
- **RFC 5120** - M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-IS)
- **RFC 5130** - A Policy Control Mechanism in IS-IS Using Administrative Tags
- **RFC 5305** - IS-IS Extensions for Traffic Engineering
- **RFC 5307** - IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
- **RFC 5340** - OSPF for IPv6
- **RFC 6119** - IPv6 Traffic Engineering in IS-IS
- **RFC 7794** - IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability

---

## Segment Routing

### RFC 9514 - Border Gateway Protocol - Link State (BGP-LS) Extensions for Segment Routing over IPv6 (SRv6)
**Status**: Fully Implemented

Comprehensive SRv6 support via BGP-LS including:
- SRv6 SID Information TLV
- SRv6 Capabilities TLV
- SRv6 End.X SID TLV
- SRv6 LAN End.X SID TLV
- SRv6 Locator TLV
- SRv6 Endpoint Behavior
- SRv6 SID Structure

**Implementation**: `src/exabgp/bgp/message/update/attribute/bgpls/link/srv6*.py` and related SRv6 modules

**Related Support** (via Segment Routing):
- **RFC 3209** - RSVP-TE: Extensions to RSVP for LSP Tunnels (MPLS protocol mask)
- **RFC 5036** - LDP Specification (MPLS protocol mask)

---

## Error Handling and Administrative

### RFC 4456 - BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)
**Status**: Fully Implemented

Route reflection for scalable iBGP deployments.

**Implementation**: `src/exabgp/bgp/message/update/attribute/` (ORIGINATOR_ID, CLUSTER_LIST)

### RFC 4486 - Subcodes for BGP Cease Notification Message
**Status**: Fully Implemented

Detailed subcodes for BGP Cease notifications.

**Implementation**: `src/exabgp/bgp/message/notification.py`

### RFC 6608 - Subcodes for BGP Finite State Machine Error
**Status**: Fully Implemented

Specific error subcodes for BGP FSM errors.

**Implementation**: `src/exabgp/bgp/message/notification.py`

### RFC 7606 - Revised Error Handling for BGP UPDATE Messages
**Status**: Fully Implemented

Improved error handling using "treat-as-withdraw" approach instead of session reset.

**Implementation**: UPDATE message processing

### RFC 8203 - BGP Administrative Shutdown Communication
**Status**: Fully Implemented

Allows graceful shutdown with human-readable reason (128-byte limit for legacy).

**Implementation**:
- `src/exabgp/reactor/api/transcoder.py`
- `src/exabgp/bgp/message/notification.py`

### RFC 9003 - Extended BGP Administrative Shutdown Communication
**Status**: Fully Implemented

Extended shutdown communication supporting 255-byte messages (UTF-8 multibyte characters).

**Implementation**: `src/exabgp/bgp/message/notification.py`

---

## Operational Features

### RFC 5396 - Textual Representation of Autonomous System (AS) Numbers
**Status**: Fully Implemented

Standard textual format for AS numbers (asplain and asdot formats).

**Implementation**: AS number parsing and display

### RFC 7311 - The Accumulated IGP Metric Attribute for BGP
**Status**: Fully Implemented

AIGP (Accumulated IGP) metric attribute for maintaining IGP metrics across AS boundaries.

**Implementation**: `src/exabgp/bgp/message/update/attribute/aigp.py`

---

## Internet Drafts

### draft-ietf-idr-operational-message-00 - BGP OPERATIONAL Message
**Status**: Partially Implemented

Experimental operational messages for BGP state and statistics exchange.

**Implementation**: `src/exabgp/bgp/message/open/capability/operational.py`

### draft-walton-bgp-hostname-capability - BGP Hostname Capability
**Status**: Implemented

Allows BGP speakers to exchange hostname information (capability code 0x49).

**Implementation**: `src/exabgp/bgp/message/open/capability/hostname.py`

### draft-abraitis-bgp-version-capability - BGP Software Version Capability
**Status**: Implemented

Allows BGP speakers to exchange software version information (capability code 0x4B).

**Implementation**: `src/exabgp/bgp/message/open/capability/software.py`

### draft-ietf-idr-bgp-extended-messages - Extended Message Support for BGP
**Status**: Implemented

Support for BGP messages larger than 4096 bytes (capability code 0x06).

**Implementation**: `src/exabgp/bgp/message/open/capability/capability.py`

### draft-mpmz-bess-mup-safi - BGP Extensions for MUP
**Status**: Implemented

Mobile User Plane (MUP) SAFI support for 5G networks (SAFI 85).

**Implementation**: `src/exabgp/protocol/family.py`

---

## Implementation Statistics

- **Total RFCs Implemented**: 55+
- **Core BGP RFCs**: 8
- **Capability RFCs**: 8
- **Community RFCs**: 7
- **VPN/MPLS RFCs**: 9
- **Advanced Features**: EVPN, FlowSpec, BGP-LS, SRv6, MVPN
- **Internet Drafts**: 5+

---

## Implementation Notes

### Key Design Features

1. **No FIB Manipulation**: ExaBGP implements the BGP protocol and provides APIs for external process communication, but does not manipulate the Forwarding Information Base.

2. **Comprehensive Address Family Support**:
   - IPv4/IPv6 Unicast and Multicast
   - VPNv4/VPNv6 (L3VPN)
   - EVPN (Layer 2 VPN)
   - FlowSpec (IPv4/IPv6/VPN variants)
   - BGP-LS (topology distribution)
   - VPLS
   - MVPN
   - MUP

3. **Modern BGP Extensions**:
   - 4-byte ASN support
   - ADD-PATH capability
   - Graceful restart
   - Enhanced route refresh
   - Extended message support
   - SRv6 for segment routing

4. **Production-Ready Error Handling**:
   - RFC 7606 treat-as-withdraw
   - Detailed notification subcodes
   - Graceful shutdown with communication

### Testing and Validation

ExaBGP's RFC compliance is validated through:
- Functional tests for BGP message encoding/decoding (`qa/bin/functional`)
- Configuration parsing tests (`qa/bin/parsing`)
- Unit tests with coverage (`pytest`)
- Real-world deployments in production networks

### Future Enhancements

The ExaBGP team continues to track and implement new BGP specifications as they are standardized by the IETF. For the latest developments, see the [CHANGELOG](https://github.com/Exa-Networks/exabgp/blob/main/CHANGELOG).

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## Contributing

Found an RFC that should be listed or noticed incorrect information? Please open an issue or pull request on the [ExaBGP GitHub repository](https://github.com/Exa-Networks/exabgp).

## References

- [IETF BGP Working Group](https://datatracker.ietf.org/wg/idr/)
- [BGP Parameters - IANA Registry](https://www.iana.org/assignments/bgp-parameters/)
- [ExaBGP Documentation](https://github.com/Exa-Networks/exabgp/wiki)

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