- rfc4109: Algorithms for Internet Key Exchange version 1 (IKEv1)
- rfc4120: The Kerberos Network Authentication Service (V5)
- rfc4129: Digital Private Network Signaling System / Digital Access Signaling System 2 Extensions to the IUA Protocol
- rfc4165: Signaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User Peer-to-Peer Adaptation Layer (M2PA)
- rfc4166: Telephony Signalling Transport over Stream Control Transmission Protocol (SCTP) Applicability Statement
- rfc4168: The Stream Control Transmission Protocol (SCTP) as a Transport for the Session Initiation Protocol (SIP)
- rfc4171: Internet Storage Name Service (iSNS)
- rfc4172: iFCP - A Protocol for Internet Fibre Channel Storage Networking
- rfc4233: Integrated Services Digital Network (ISDN) Q.921-User Adaptation Layer
- rfc4248: The telnet URI Scheme
- rfc4250: The Secure Shell (SSH) Protocol Assigned Numbers
- rfc4251: The Secure Shell (SSH) Protocol Architecture
- rfc4252: The Secure Shell (SSH) Authentication Protocol
- rfc4254: The Secure Shell (SSH) Connection Protocol
- rfc4266: The gopher URI Scheme
- rfc4271: A Border Gateway Protocol 4 (BGP-4)
- rfc4301:Security Architecture for the Internet Protocol
- rfc4302: IP Authentication Header
- rfc4303: IP Encapsulating Security Payload (ESP)
- rfc4305: Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentication Header
- rfc4306: Internet Key Exchange (IKEv2) Protocol
- rfc4309: Using Advanced Encryption Standard (AES) CCM Mode with IPsec Encapsulating Security Payload (ESP)
- rfc4320: Actions Addressing Identified Issues with the Session Initiation Protocol's (SIP) Non-INVITE Transaction
- rfc4330: Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI
- rfc4338: Transmission of IPv6, IPv4, and Address Resolution Protocol (ARP) Packets over Fibre Channel
- rfc4346: The Transport Layer Security (TLS) Protocol Version 1.1
- rfc4493: The AES-CMAC Algorithm
- rfc4502: Remote Network Monitoring Management Information Base Version 2
- rfc4506: XDR: External Data Representation Standard
- rfc4510: Lightweight Directory Access Protocol (LDAP):Technical Specification Road Map
- rfc4511: Lightweight Directory Access Protocol (LDAP): The Protocol
- rfc4512: Lightweight Directory Access Protocol (LDAP):Directory Information Models
- rfc4513: Lightweight Directory Access Protocol (LDAP): Authentication Methods and Security Mechanisms
- rfc4515: Lightweight Directory Access Protocol (LDAP):String Representation of Distinguished Names
- rfc4517: Lightweight Directory Access Protocol (LDAP):Syntaxes and Matching Rules
- rfc4518: Lightweight Directory Access Protocol (LDAP):Internationalized String Preparation
- rfc4519: Lightweight Directory Access Protocol (LDAP):Schema for User Applications
- rfc4521: Considerations for Lightweight Directory Access Protocol (LDAP) Extensions
- rfc4523: Lightweight Directory Access Protocol (LDAP)Schema Definitions for X.509 Certificates
- rfc4566: SDP: Session Description Protocol
- rfc4587: RTP Payload Format for H.261 Video Streams
- rfc4601: Protocol Independent Multicast - Sparse Mode (PIM-SM):Protocol Specification (Revised)
- rfc4604: IGMPv3/MLDv2 for SSM
- rfc4615: The Advanced Encryption Standard-Cipher-based Message Authentication Code-Pseudo-Random Function-128 (AES-CMAC-PRF-128)
- rfc4760: Multiprotocol Extensions for BGP-4
- rfc4862: IPv6 Stateless Address Autoconfiguration
- rfc4916: Connected Identity in the Session Initiation Protocol (SIP)
- rfc4960: Stream Control Transmission Protocol