HP's E-Series ZL Ethernet Modules Sip Power

Hewlett-Packard's new E-Series ZL v2 modules for the HP 8200 and 5400 switch chassis, which are targeted at the campus LAN, sport increased port density and support for the IEEE 802.3az Energy Efficient Ethernet standard. This standard defines how an Ethernet port can switch to a sleep mode when not being used, which leads to less energy consumption. HP is also changing its licensing models with the 8200 and 5400, doing away with the premium license for advanced features such as advanced routing.

The 802.3az standard was ratified in September and allows a switch port to go into a Low Power Idle (LPI) conserving power. While in LPI, the port remains active and the physical layer remains in an up state.

The standard allows for as much as 16.5 microseconds of latency to return to full power, which would hardly be noticeable in campus LANs. LPI can be disabled on a per-port basis in cases where the delay coming out of LPI is unacceptable.

802.3az does require both ends of the physical connection to support the feature. Both ends of the physical links negotiate LPI. When in LPI mode, if a peer wants to send traffic, it sends a wake-up signal to the other side before sending traffic. Currently, only interswitch links between 8200 and 5400 switches support 802.3az; it will work only between HP 8200 and 5400 chassis.

Support for end nodes with servers, laptops, printers and wireless access points will have to wait until vendors ship NICs with 802.3az. 802.3az is supported on HP copper interfaces on the ZL v2 modules. Support for 8-2.3az on fiber ports is planned and will require new ZL modules with support built in.802.3az operates independently of PoE and PoE+ interfaces. There is no power budget to manage and no schedule to define, unlike with PoE, 802.3af, PoE+ and 802.3at. Ports that are using PoE and PoE+ continue to provide power regardless of the ports' LPI mode.

HP's new ASIC modules also conserve power using features such as Smart Clock Gating, which allows the switch to turn off unused processing modules to conserve power. For example, if the switch doesn't have any access control lists, the ACL processing can be powered down until needed.

Whether 802.3az will have an impact on power costs remains to be seen. Given the amount of broadcast traffic on the network due to everything from Spanning Tree data units to Windows file sharing, there is hardly ever a time when a NIC isn't preparing to send some data. In some rare cases where network devices don't use any broadcast services, like network cameras or VoIP phones, there might be some savings if network broadcast traffic is curtailed.

The new ZL modules can be used in both new and existing 8200s and 5400s and are hot-swappable. The switch must be running the HP K15 operating system to enable 802.3az. In terms of licensing, HP is removing the premium license. Advanced Layer 3 features such as PIM, OSPF and EIGRP are now part of the base price. Now, all features are available for the same price. The 5400 base price increased only $100, to $4,299, and the 8200 price dropped slightly.