Kazohi Blog

SDN (Software Defined Networking) Networking devices have two functional planes of operation Control plane Data plane Direct programmable Configuration is different than forwarding Agile Changes can be made dynamically Centrally managed - Global view, single pane of glass Programmatically configured Orchestration - No human intervention Open standards / vendor neutral A standard interface to the network Distributed switching Remove the physical segmentation A virtual network distributed across all physical platforms When a VM moves, the network doesn't change Servers will always connect to the right VLAN

Circuit Switching Circuit is established between endpoints before data passes Like a phone call Nobody else can use the circuit when it's idle Inefficient use of resources Connection is always there It's mine. You can't use it. Capacity is guaranteed You'd better use it, you paid for it. POTS (plain old telephone service) and PSTN (public switched telephone network) T1/E1/T3/E3 Create a circuit between two sites ISDN Use a phone number to call another ISDN modern Packet switching Data is grouped into packets Voice, data, video, etc. like a network The media is usually shared Someone else can use it, even when you don't One connection may have more bandwidth allocated than another How much money would you like to spend? SONET, ATM DSL Frame relay MPLS Cable modem Satellite Wireless

Packet filtering Used to allow or deny traffic Also used for NAT, QoS, etc. Defined on the ingress or egress of an interface Incoming or outgoing ACLs can evaluate on certain criteria Source IP, Destination IP, TCP port numbers, UDP port numbers, ICMP Deny or permit What happens when an ACL matches the traffic? ACLs have evolved through the years More options and features available for traffic filtering Firewall rules Access control lists (ACLs) Allow or disallow traffic based on tuples Groupings of categories Source IP, Destination IP, port number, time of day, application, etc. A logical path Usually top-to-bottom Can be very general or very specific Specific rules are usually at the top Implicit deny Most firewalls include a deny at the bottom Even if you didn't put one

NAT (Network Address Translation) It is estimated that there are over 20 billion devices connected to the Internet (and growing) IPv4 supports around 4.29 billion addresses The address space for IPv4 is exhausted There are no available addresses to assign How does it all work? Network Address Translation This isn't the only use of NAT NAT is handy in many situations Port Forwarding 24x7 access to a service hosted internally Web server, gaming server, security system, etc. External IP/port number maps to an internal IP/port Does not have to be the same port number Also called Destination NAT or Static NAT Destination address is translated from a public IP to a private IP Does not expire or timeout RFC 1918 Private IPv4 Addresses

Managing Network Traffic Many different devices Desktop, laptop, VoIP phone, mobile devices Many different applications Mission critical applications, streaming video, streaming audio Different apps have different network requirements Voice is real-time Recorded streaming video has a buffer Database application is interactive Some applications are "more important" than others Voice traffic needs to have priority over YouTube Packet shaping Packet shaping, traffic shaping Control by bandwidth usage or data rates Set important applications to have higher priorities than other apps QoS (Quality of Service) Prioritize traffic performance Voice over IP traffic has priority over web-browsing Prioritize by maximum bandwidth, traffic rate, VLAN, etc. Quality of Service Describes the process of controlling traffic flows Many different methods - Across many different topologies Managing Q0S CoS (Class of Service) OSI Layer2 Ethernet frame header in an 802.1q trunk Usually applied in th...

Dual-stack routing Dual-stack IPv4 and IPv6 Run both at the same time Interfaces will be assigned multiple address types IPv4 Configured with IPv4 addresses Maintains an IPv4 routing table Uses IPv4 dynamic routing protocols IPv6 Configured with IPv6 addresses Maintains a separate IPv6 routing table Uses IPv6 dynamic routing protocols Tunneling IPv6 6 to 4 addressing Send IPv6 over an existing IPv4 network Creates an IPv6 based on the IPv4 address Requires relay routers IP protocol 41 - a transition technology No support for NAT 4in6 Tunnel IPv4 traffic on an IPv6 network Teredo/Miredo Tunnel IPv6 through NATed IPv4 End-to-end IPv6 through an IPv4 network No special IPv6 router needed Temporary use We'll have IPv6 native networks soon (?) Miredo - Open-source Teredo for Linux, BSD Unix, and Mac OS X Full functionality NDP (Neighbor Discovery Protocol) No broadcasts! Operates using multicast over ICMPv6 Neighbor MAC Discovery Replaces the IPv4 ARP SLAAC (Stateless Address Auto Confi...

The IP address of a device IP Address, e.g., 192.168.1.165 Every device needs a unique IP address Subnet mask, e.g., 255.255.255.0 Used by the local workstation to determine what subnet it's on The subnet mask isn't (usually) transmitted across the network You'll ask for the subnet mask all the time What's the subnet mask of this network? The secret behind the IP address The IP address isn't really a single address. An IP address is a combination of a network ID and a host ID The subnet mask determines what part of the IP address is the network and which part is the host The subnet mask is just as important as your address! The best way to see this work is in binary This is the (very easy) math part IPv4 addresses - Internet Protocol version 4 OSI layer 3 address Since one byte is 8 bits, the maximum decimal value for each byte is 255 IPv6 addresses Internet Protocol v6 - 128-bit address 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses ...