Abiyaco Network Infrastructure: Ensuring Reliability and Resilience through Data Centers, WAN Edge, and Dialup Network.

Abiyaco is a growing financial company that provides insurance services to customers in the European region. The company has a network that spans the entire continent with offices in almost every large European country, and multiple offices in larger cities. To ensure the reliability and quality of their services, Abiyaco has deployed multiple data centers interconnected through its core network. The company also migrated its telephony/video conferencing applications to a new IP infrastructure to achieve cost savings and provide new services such as Unified Messaging.

Abiyaco has over 1000 small offices and 40 large office sites in the UK, Spain, and Germany. The company's private core network consists of 11 points of presence (POPs) that are interconnected by leased circuits or DWDM wavelengths. Abiyaco uses EIGRP with unequal-cost load-balancing to optimally utilize its core network links while balancing QoS requirements. The company uses a mathematical model to periodically update the link metrics based on the updated traffic matrix information.

Small and large office locations are connected to Abiyaco's core network using various connections, including leased lines, metro-ethernet connections, layer 2 circuits, and direct Ethernet connections. Every POP has two backbone routers that provide connectivity to the core enterprise network and uses layer 2 switches for link aggregation from edge router devices.

In the event of a failure, small offices with dual-homed connections can use a backup ISDN connection to dial into a central POP for connectivity. Offices without dual-homed connections feature a backup ISDN connection as well. Two data-centers in London provide dial-in services over ISDN for remote office backup connectivity.

This is the infrastructure and design of Abiyaco's data centers. The company has five data centers located in London, Frankfurt, Madrid, and Amsterdam and connected to local POPs with high-speed links, such as Fast Ethernet or Gigabit Ethernet. The data centers host various applications on UNIX/Windows servers and IBM mainframes, and can be accessed by various offices. The servers are connected to Layer 2 aggregation switches and protected by redundant Layer 2 firewalls, while the DC Edge routers perform IP routing functions and implement other special features, such as DLSw+. The data center design is designed for resilience, with redundant links, RSTP to prevent spanning tree loops, and first-hop redundancy protocol for high-availability. The DC edge routers act as primary gateways for different VLAN groups, and both inject equal-cost prefixes into the core network.

The WAN Edge routers of Abiyaco are dedicated to terminating connections from small offices in the corresponding region. There are two main types of connections used: leased lines in the form of fractional digital Ex circuits and ATM/FR virtual circuits. Abiyaco typically obtains connections from two different ATM/FR service providers to allow for dual-homed office connections, but in some locations where this is not possible, ISDN backup is used. The WAN Edge routers run EIGRP with the remote office routers, with one link being primary and the other being used as a backup.

For the dial-up network, two POPs located in London have digital ISDN connections to terminate incoming ISDN and legacy POTS modem calls. Abiyaco uses L2TPv2 to tunnel PPP sessions to Network Access Servers (NAS). This provides backup connectivity to small and large offices, with the option of dynamic bandwidth aggregation for larger offices. The company runs a dynamic IP routing protocol over the dial-up links and the remote router advertises office networks into the IGP.

Snapshot routing is used over the dial-up circuits to allow for fully dynamic routing while keeping the ISDN link in idle state as much as possible. This involves keeping distance-vector update information learned over the ISDN circuit from aging during quiet periods of time, while allowing for short periodic connections for the purpose of routing table updates. In the event of a failure of the primary link, the ISDN link becomes the primary connection automatically. However, remote offices that utilize snapshot routing cannot benefit from EIGRP's unequal-cost load-balancing.

The enterprise network of Abiyaco provides connectivity and support for various business applications, ranging from legacy mainframe software to modern video conferencing products. The applications used in the network include Terminal Services Application (Tetrix), SNA-based Financial Applications (BankOne Suite), Data Center Backup (HeavyTape), Live Video Conferencing (LetsMeet), IP Telephony and Unified Messaging (U-Comm), Enterprise Resource Management (BIG-MAX), and Internet Access. Each application has different traffic characteristics and requirements, such as short bursts, high throughput, low latency, and constant bit-rate delay sensitivity. The applications are hosted at data-centers and large offices, and some of them are mission-critical and require least possible delay. Internet access is provided to some employees but is considered low priority with no guarantees for reliability or quality of service.

In conclusion, the enterprise network of Abiyaco provides connectivity and support for various business applications, ranging from legacy software to modern video-conferencing products. These applications are hosted at data-centers or server farms deployed at large offices. The applications used in the network include Terminal Services Application (Tetrix), SNA-based Financial Applications (BankOne Suite), Data Center Backup (HeavyTape), Live Video Conferencing (LetsMeet), IP Telephony and Unified Messaging (U-Comm), Enterprise Resource Management (BIG-MAX), and limited Internet Access. These applications vary in their traffic patterns, with some being delay-sensitive while others require low latency, and some consuming high network bandwidth while others having little requirement.