The environment in which an IXP is housed is very important. Some existing IXPs were established in commercial co-location facilities, either in their own dedicated racks or rooms, (e.g. LINX at Telehouse in London) or in rack space belonging to a member ISP. The latter is a low cost and pragmatic solution, but should only be seen as a short-term solution. Expansion of the IXP, access issues and other potential limitations would suggest an IXP have its own dedicated racks as soon as possible.
A number of existing IXPs, particularly those started by institutions, were initially housed by the institution itself, (e.g. VIX, at the University of Vienna), but have more recently expanded to commercial co-location facilities (usually in addition to the original sites). Whilst IXPs housed by institutions can benefit from low housing costs, and the housing can be perfectly adequate in the short to medium term, a successful IXP is likely to outgrow the space available. Also, access by member ISPs who may have equipment at the IXP may be limited, as may be access by telcos to provide communications circuits.
The original location of existing IXPs has generally been determined by accident of circumstance. This is likely to be the case for most new IXPs, but the experiences of the existing IXPs and the major work involved in moving an established IXP would suggest that new IXPs consider location carefully from the outset. A balance must be made between a pragmatic, low cost solution and a solution providing for the future.
Whatever the type and location of housing available to a new IXP, the following facilities need to be considered.
Initially, the amount of rack space required needs to be determined. A major factor is whether the IXP will allow members to co-locate router equipment at the IXP. (This also affects considerations of telco availability - see below). Where an IXP is located in a commercial co-location facility, members may take (or already have) their own rack space in the facility, and can connect a router in their own rack space to the IXP switch infrastructure with an in-building (or on-campus) LAN connection. In this case the IXP may not need to house member routers. However, it is likely that at some stage there will be prospective members who do not wish to have their own presence in the facility, or the facility may become full. At this point the IXP will need to have adequate space to co-locate member router equipment. However much space the IXP expects it will need, it is common to find that the IXP outgrows it. Some co-lo companies will allow space to be reserved at a relatively low cost; this option is worth considering to accommodate future growth with the minimum initial outlay.
If the facility does not allow member ISPs to have their own rack space, clearly the IXP will have to house the member router equipment, and ensure telco access to terminate member WAN circuits. The problems in providing adequate space and access is perhaps the major reason that most European IXPs have moved or expanded into commercial co-location space.
Another factor for the trend towards siting IXPs in commercial co-location facilities has been the increase in availability of high quality co-lo space across Europe. Many of the organisations providing such space did not exist when the older European IXPs were established but now the choice is quite wide in a reasonable number of European metropolitan centres, and a number of established IXPs have taken advantage of this and expanded into these facilities. It should be noted, however, that the expansion would appear to be largely in countries and regions already well served by IXPs, and not so much in the countries and regions where new IXPs are being formed. Several commercial co-lo companies had planned aggressive expansion into these areas, but the downturn in communications businesses would appear to have forced many of these plans to be shelved.
IXPs often become critical to their members' businesses, so it is important that the site of the IXP is as secure as possible. Commercial co-lo companies usually have sophisticated security systems, some elements to consider when looking for space are: 24x7 security manning, CCTV coverage (inside and out), and multiple level access control (site, building, room, rack/cage). The latter is worthy of particular consideration where the IXP is situated in shared rack space. Whatever security systems are in place, they need to be balanced with ease of access for IXP staff. Ideally, access should be available 24x7, and it worth making some effort to ensure co-lo staff are familiar with IXP staff. Where IXP members have equipment co-located in the IXP consideration should be given as to whether they are allowed unaccompanied access. This may be acceptable and pose little risk in the early days of an IXP, but as members rely more and more on the IXP it is probably wise to limit access to accompanied visits only.
The co-lo space should be adequately cooled, with high quality air conditioning. Additionally, robust fire detection and suppression systems should be in place.
Much modern switching and routing equipment has the capability of redundant PSUs. To take advantage of this feature the co-lo should be able to provide at least two power supplies, preferably from diverse parts of the electric companies supply network. There should also be on site generators, with battery back-up/switch over to protect against total supply failure. The IXP may also wish to consider having it's own non-interuptable power supply, this is probably most important where the co-lo company cannot satisfy the requirements above.
Most existing IXPs allow members to co-locate routers at the IXP or are in a site where members may have their own rack space. It will be important to the members to have access to as many telcos as possible, therefore it is in the interest of the IXP to select a site with access by multiple carriers, even though this is not of direct benefit to the IXP itself. In situations where the telco market has not been opened to competition, it is worth discussing with the co-lo company their capability to allow multiple carries into the site in the future. There are two main factors, the physical - is there or will there be, adequate duct capacity, and commercial, are there any constraints on telcos accessing the site (e.g. local planning controls, ownership of the co-lo facility).
Given that a large IXP is likely to have 100+ members, many with 2 or more connections to the IXP, consideration should be given to the amount of space available for cabling. Also, any conditions or requirements the co-lo company may put on cabling need to be clearly understood.
Most commercial co-lo companies offer various levels of technical support. These services can be useful for the start up IXP that may not have staff available 24x7 to support the IXP. This can be quite an expensive option though, also the technical ability of the staff can be quite limited. If co-lo staff are going to be involved in support it is important that they understand the critical nature of the IXP, and are familiar with the role it plays in the Internet infrastructure.