ARP & UDP header

at

 

Acronyms

AH Authentication Header (RFC 2402)

ARP Address Resolution Protocol (RFC 826)

BGP Border Gateway Protocol (RFC 1771)

CWR Congestion Window Reduced (RFC 2481)

DF Do not fragment flag (RFC 791)

DHCP Dynamic Host Configuration Protocol (RFC 2131)

DNS Domain Name System (RFC 1035)

ECN Explicit Congestion Notification (RFC 3168)

ESP Encapsulating Security Payload (RFC 2406)

FTP File Transfer Protocol (RFC 959)

GRE Generic Route Encapsulation (RFC 2784)

HTTP Hypertext Transfer Protocol (RFC 1945)

ICMP Internet Control Message Protocol (RFC 792)

IGMP Internet Group Management Protocol (RFC 2236)

IMAP Internet Message Access Protocol (RFC 2060)

IP Internet Protocol (RFC 791)

ISAKMP Internet Sec. Assoc. & Key Mngm Proto. (RFC 7296)

L2TP Layer 2 Tunneling Protocol (RFC 2661)

OSPF Open Shortest Path First (RFC 1583)

POP3 Post Office Protocol v3 (RFC 1460)

RFC Request for Comments

SMTP Simple Mail Transfer Protocol (RFC 821)

SSH Secure Shell (RFC 4253)

SSL Secure Sockets Layer (RFC 6101)

TCP Transmission Control Protocol (RFC793)

TLS Transport Layer Security (RFC 5246)

TFTP Trivial File Transfer Protocol (RFC 1350)

TOS Type of Service (RFC 2474)

UDP User Datagram Protocol (RFC 768)




UDP Header


UDP Header


Common UDP Ports


7 echo 137 netbios-ns 546 DHCPv6c
19 chargen 138 netbios 547 DHCPv6s
53 domain 161 snmp 1900 SSDP
67 DHCPs 162 snmp-trap 5353 mDNS
68 DHCPc 500 isakmp
69 tftp 514 syslog
123 ntp 520 Rip



Length: number of bytes including UDP header. Minimum value is 8
Checksum includes pseudo-header (IPs, length, protocol), UDP header and payload.


ARP


ARP Header


Hardware Type: 1 - 

Ethernet Protocol Type: 0x0800 - 

IPv4 Address Length: 4=IPv4, 6=Ethernet 

Opcode: 1-request, 2-response


Featured Post

Day 41 — BGP Confederations: Sub-AS Design, External View and Migration

1. Opening Confederations are another way to scale BGP inside a large administrative domain. They divide the domain into member autonomous systems while presenting a single confederation identifier to external peers. They are powerful, but their operational model is more complex than simply 'using private ASNs inside.' The engineering goal is not to memorize another BGP command. It is to understand what information each speaker is allowed to propagate, what path information can be hidden, and what failure domain is created by the chosen control-plane architecture . 2. Concept and standards behavior RFC 5065 defines AS_CONFED_SEQUENCE and AS_CONFED_SET and how member-AS relationships are represented. Confederation external sessions have eBGP-like properties inside the confederation, while the confederation is presented externally as one AS. Modern guidance must also account for the fact that RFC 9774 prohibits new origination of AS_SET/AS_CONFED_SET in ordinary aggregation c...